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Ohm cooking 101: understanding amps, speakers and impedance


If you’re a gigging guitarist, chances are you’ve turned up at a show with your amp head and the hopes of using someone else’s cabs. And chances are you’ve then had problems trying to understand the equipment’s various impedance levels, when really you should’ve been focusing on playing a great show instead. Here, we break the topic down into layman terms so you can rock on stage without having to worry about that troublesome little Ω symbol ever again!

Most guitarists would probably not consider themselves experts when it comes to the subject of natural sciences. Although you may have a vague idea of the different scientific phenomena that hide behind every note you play, your main focus as a player – quite naturally – is usually on the music itself, and the instrument. Boring science is just something that would get in the way.

And yet, consider this: the everyday electric guitar player probably namechecks a bunch of famous physicists regularly, even though they might not be overly au fait with the scientific laws associated with these long-dead genii in white coats. Hertz, Ohm, Volt, Ampere – these are all familiar names that belong in the basic vocabulary of any slightly technically-minded guitarist.

These things duly considered, it can be highly insightful for you to get to know the stories – and the theories – behind those names in a bit more detail. One particularly important physicist for guitar players is the German Georg Simon Ohm (1789-1854), who gave the world of electricity the eponymous Ohm’s law.

Some amps, like the one pictured, have multiple connections for speakers. This can give you more flexibility in finding a matching setup.

Some amps, like the one pictured, have multiple connections for speakers. This can give you more flexibility in finding a matching setup.

Every guitarist who has stood in front of a tube amp wondering which speaker output it’s best to hook his or her cab (or cabs) up to has inevitably come face to face with Ohms. And it’s that universally recognised – but not usually understood – Greek letter, Ω, that causes confusion. Referred to in English as Omega, Ω is the symbol of a unit of electrical resistance, and when you see it written on your all-tube amp, you’ll probably start asking questions like these ones:

Why does a “load” – that is, a loudspeaker – have to be connected?

Can I use a 4 ohm speaker with a 16 ohm output?

Can I run two cabs with different impedances in parallel?

These are just some of the questions we often get asked about tube amps, so let’s try and unravel some of the mysteries surrounding the murky world of impedance. The physics behind all this are pretty darn complex at times, so we’ll try and stay as practical and understandable as possible here! Now, lab coats on, and let’s get started.

A guitar amp’s tube power amp works on the principle of matching impedance. In practice, this means using corresponding speakers and amps. For example, if you connect an 8 ohm speaker to the 8 ohm output on a tube amp, the internal resistance of the source (that is, the tube output stage) is exactly that of the load, or speaker. In this way, and only in this way, can the amp unleash its full power on your unsuspecting audience. This is also the only way you will get your amp to sound exactly like the designers intended it to sound.

Of course, you can still experiment and try out new things if you like – and if you stick to a few basic rules, you won’t be in danger of breaking anything. In some cases, you might not be able to match your impedance – for example, you might be playing a stage where only an 8 ohm output is available, but the cab has an impedance of 16 ohms – and in this case, you’ll have no option but to rock a mismatched combination.

But what are the consequences of doing this: can it damage your equipment, or can it have a negative influence on your all-important tone?

First of you all, you should commit this critical ground rule to memory: never – really, NEVER! – operate your tube amp without a load/speaker(s). If you do, the result will be a high level of induction voltage that could damage – or even destroy – your amp’s output transformer and tubes. As long as you remember this, you should be on the safe side, even with a mismatched setup.

But what happens exactly when you use the various impedance combinations? Here are a few examples:

How to connect your mismatched speakers and amps successfully. For more detail, read the three cases below!

How to connect your mismatched speakers and amps successfully. For more detail, read the three cases below!

Case 1: running a 16 ohm speaker with an 8 ohm amp output

With this combination, the voltage at the speaker output will rise, while the current will almost halve. The power will drop, although you probably won’t notice it too much, as this combination will likely increase the mids in your tone. So long as you don’t overdo it – make it a rule of thumb not to connect a speaker with more than double the output impedance of that of the amp – this method can be quite useful, as you can effectively boost the mids in a cab that might otherwise be lacking in this department.

Case 2: running a 4 ohm speaker with a 16 ohm amp output

Here, the complete opposite to Case 1 occurs: while the speaker output voltage significantly falls, the flowing current only marginally increases. This will alter your tone too, but in the exact opposite way from before – you’ll get a drop in your mids! If you’ve got a cab that is way too mids-heavy, then, this can be the perfect method to better balance your overall tone. Because this combination can help lessen the self-induction effect that might occur in your tubes, it is generally safer to use than the example in Case 1. In terms of the amount of mismatching you can get away with here, we’d go with the 25% rule: so, for instance, don’t connect a speaker with less than a 4 ohm output to a 16 ohm amp output!

Case 3: the exotic combination of 16 and 8 ohms together, and how to hook them up together…

Almost every gigging guitarist will have experienced this before: you’ve got one cab with 8 ohms, and one with 16 – and you want to connect them both to a speaker output at the same time. Is that even possible?

To put it simply, yes. You just need to know the total impedance you’ll have if you’re running the two speakers in parallel. This can be surprisingly easy to calculate. Another ground rule here: if you’re connecting resistors in parallel, then the total resistance is always going to be smaller than the smallest partial resistance. In this case, that would mean we will end up with a total resistance somewhere south of 8 ohms. To be more exact, we can calculate the precise figure using the following formula (which, by the way, only works in cases where you have two parallel resistors!):

Use this handy formula to calculate impedances when you're hooking your amp up to more than one speaker.

Use this handy formula to calculate impedances when you’re hooking your amp up to more than one speaker.

Or, in our case, that’s (8×16) / (8+16) = 128/24 = 5.333 Ω

Simple, right? Well, you’ll get used to it!

Based on these variables and peculiarities, you can start to think about whether you would prefer to use this combination with a tube amp output of 4 or 8 ohms. It’s certainly technically feasible, and the difference in volume between the two speakers will also be less than most people would think. And by the way, you should avoid combining 4 ohm cabs if you can, because you’ll end up in a red zone of under four ohms in total (for example if you go for the following ohm combinations: 4+4, 4+8, 4+16). Most amps aren’t designed to go this low, and you could cause serious damage.

As a final point, and just like with another of our recent posts – When could, would and should you replace tubes? – don’t be afraid of what’s written above! If you pay attention to those few ground rules, chances are you won’t blow your amp up by accident. In return, checking out the various options you have with your amps and cabs could give you way more options to improve your tone.

And by the way, we’ve put all the combinations mentioned above to the live test many times – sometimes for years on end! To date, we’ve never managed to even bring a tube amp out of its comfort zone, let alone leave one a smoking wreck!

What about you?


First published: June 20 2014. Most recent update: October 16 2015.

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Leave a comment

Zlatko on February 3, 2020 Reply

DV Mark Little 40 L34
… amplifier with three different outputs of 4_8_16 ohms

can i connect all three outputs “at the same time” to 3 boxes of appropriate ohms for each

or only one output must be used

    Hughes & Kettner Hughes & Kettner on February 4, 2020 Reply

    We checked the manual on the DV site and it has a pretty good answer for you Zlatko:

    13) SPEAKER OUTS One 4 ohm, one 8 ohm and one 16 ohm jack are provided for connecting the head to a speaker cabinet.
    Verify the impedance of your speaker so you know which jack to use. If you want to use the amp with two 8 ohm cabs (a 4 ohm load) connect
    one cabinet to the 4 ohm jack, and connect the two cabinets together with another speaker cable. For two 16 ohm cabinets, connect to the 8
    ohm jack and connect the two cabinets together.

    We’d go with that 🙂

    Team H&K

Grady Douglas on January 28, 2020 Reply

What about what not to do? Any common mistakes that you know that can really screw things up? Speaker blowouts, Amp blowouts, poopy tone?

    Hughes & Kettner Hughes & Kettner on February 4, 2020 Reply

    That’s a top idea Grady, we’ll have to do something on those topics in future for sure! Watch out for that 🙂

Vivek on December 30, 2019 Reply

Thank you so much for this great article!

    Hughes & Kettner Hughes & Kettner on January 6, 2020 Reply

    No problem Vivek, glad you got something good out of it!

Johannes Kingma on December 28, 2019 Reply

This is really valuable information. Thank you so much!
I was searching all day long to find an appropriate answer to the question since I want to upgrade my 1 x 10″speaker cab which is 16 Ohms.

Most amplifiers I have are 8 Ohms, but once upon a time I had a small amp which had a 16 Ohms output. After selling it the cab is dusting away so I want to re-use it again.

Regards, Johannes Kingma
FWS Pedals – North Rhine-Westphalia

    Hughes & Kettner Hughes & Kettner on January 6, 2020 Reply

    No problem Johannes, glad to have helped!

    Rock on,

    Team H&K

Bill crispano on December 24, 2019 Reply

I just purchased a 2×12 cab with 2 8 ohm speakers. What is the actual ohm jack I should use?

    Hughes & Kettner Hughes & Kettner on January 6, 2020 Reply

    Hi Bill, the cab will say what its impedance is on the back – just go with that figure 🙂

    Team H&K

William on December 22, 2019 Reply

Kinda confused on all this impedance stuff! I have a 20 watt tube amp, 8ohm speaker output jack! My 1 12 cab says 8ohms too. But why is there a LINK jack right beside it? If 8 goes into 8 why another jack? It’s like the Jack’s there to put another cab, make a full stack, but 2 8ohm connected is 4 ohms, which your not suspose to do, I don’t get it?

    Hughes & Kettner Hughes & Kettner on January 6, 2020 Reply

    Hmm, don’t worry, impedance is a confusing beast 😉 What cab do you have anyway?

    Team H&K

Thomas on December 17, 2019 Reply

first off, there’s a genuine THANK YOU below…

Q: My PRS Sonzera 20w 1X12 Combo Amp and PRS 2×12 cabinet (john mayer signature) are an “ohm matching” nightmare.

It has 5 output jacks:
16 ohm
8 ohm
8 ohm ext
4 ohm
4 ohm ext

Despite a 16 ohm output jack (connected to this combo amp at purchase) the speaker is a Celestion G12 V Type, which I’ve only seen to be spec’d at 8 ohms.

The Cabinet is marked as 8 ohms. Especially after verifying its celestion G-65’s are available in 8 ohms and 16 ohms I’m about certain the company is trying to avoid the ohm matching rabbit hole by simplifying the total load for the two speakers run in parallel.

My research all but proves the combo speaker is 8 ohm, and the cabinet total load is 8 ohms. Sounds to me like I should be able to use the 4 ohm and 4 ohm ext jacks, but PRS will not confirm. If a 8 ohm speaker is running from a COMBO AMP’s 16 ohm amp output, the load is 8, end of story…right?

Why would PRS’ “default” setting for it’s combo amp then be the 16 ohm jack (with no matching 16 ohm ext jack, keep in mind).

Thank You guys for the most helpful, thoughtful moderation of this topic I’ve found. Everyone on this topic – as I understand best from you guys is incredibly subjective – thinks they’re an expert and everyone else is an idiot. And the most self identified knowledgeable people contradict one another, leaving people like me who live to actually PLAY MUSIC more confused each time I’m dumb enough to try to learn more.

I’d so appreciate a response, and thanks again.


    Hughes & Kettner Hughes & Kettner on December 17, 2019 Reply

    Hey there Thomas,

    That’s a very interesting little story! Our first thoughts are: yes, PRS are making things very complicated for themselves by doing it like that! And why aren’t they answering your questions properly? Weird.

    Ultimately, they should be officially telling you that plugging the cab into the “8 ohm ext” socket should be fine.

    But the question is: should the combo be treated as 16 ohms, or as 8 ohms? We’ve seen G12 V Types as 8 or 16 ohms (here’s one example of a 16 ohms one: but the only way you’ll know for sure what’s in your combo will be by taking it apart and looking. Which we wouldn’t recommend, as that can get messy. We reckon it’s probably 16 ohms, and that’s what PRS list on their site in the specs, but that’s pure guesswork.

    And the next thing is: is plugging an 8-ohm cab into that OK? (And by the way, we’re sure you’re right on the cab thing: two 16-ohm speakers running in parallel for a total of 8 ohms.) Well, by our experience, it would be. And presumably by PRS’s too. They wouldn’t give you so many options if that wasn’t the case. So that’s how we see it. Of course, it’d be a lot easier if they just made the combo a certain 8 ohms, and gave an extension cab option as such.

    We hope those general musings help a bit. As you’ve noticed, everyone here seems to think they are the one and only source of unlimited knowledge on this issue. Hell, even we’re just saying what has worked for us in the past, from experience. And that’s probably the key takeaway – experience. Have you tried plugging the cab into the different jacks to see what results you get? It’s something we’d do, just out of curiosity. We’d start with the “8 ohm ext”, then unplug the combo speaker and see how the combo runs with just the cab at 8 ohms, then move down to the “4 ohm ext” and so on. But that’s just us 😉

    Let us know how you get on with it, and if you do ever get official clarification from the guys at PRS 😉

    Rock on,

    Team H&K in Germany

Giovanni on December 15, 2019 Reply

I am a bit confused about the impedance mismatch with 4Ohm speaker and 16Ohm Amp. If I correctly remember the math, impedance matching halves the power supplied by the amp between the load and the output impedance of the amp ((Vout^2)/(4*Z_load). If the load gets lower, the power dissipated by the output impedance increases. Is not that a possible issue for the amp? Is it a possible cause of overheating?
Thank you in advance.

    Hughes & Kettner Hughes & Kettner on December 17, 2019 Reply

    Hi Giovanni. We know what you mean, and a 4-ohm cab with a 16-ohm head is certainly our limit – we wouldn’t go lower than that (1/4 is generally our rule!). We’ve tested this with a number of amps over the years and never blown anything up or had problems, but we obviously cannot promise that every amp will be OK with it, as some are much more sensitive than others 😉 So for best results, a ‘perfect’ match is always best.

    Team H&K

Jeff Dees on December 13, 2019 Reply

Hi . I have a marshall dsl40c combo. It comes with a 16 ohm speaker attached. It has 2 more 8 ohm outputs. My question is can I plug in an 8 ohm 1×12 cab along with the internal 16 to give it a little more thump and be okay?

    Hughes & Kettner Hughes & Kettner on December 17, 2019 Reply

    Hmm, we checked in the DSL40C manual Jeff, and it says this about the 16-ohm speaker output: “It should be noted that when this Speaker Output is in use the remaining Speaker Outputs are not operational.”

    So that wouldn’t work, unfortunately! You’d need to two separate cabs to have two speakers working, and disconnect the combo’s built-in speaker.

    Team H&K

John R. Hunt on December 3, 2019 Reply

very good im a musician and an electronic teacher this is great

    Hughes & Kettner Hughes & Kettner on December 4, 2019 Reply

    Thanks John, glad you enjoyed it!

Cristian on November 1, 2019 Reply

Sorry but I have doubts

I have the tubemaister deluxe 40 (8/16 ohm)

Can i connect TWO h&K TC 412 A60 cabinets (8 ohm)?


    Hughes & Kettner Hughes & Kettner on November 5, 2019 Reply

    Hi Christian. As we said in the blog, this is something we’d be happy to do, and if you’Re worried about doing it in parallel – why not hook the speakers up in series for a total impedance of 16 Ohms?

    Team H&K

Steve on October 25, 2019 Reply

Quick follow-up on the note below.

Thanks for the info, I was surprised too, as the mesa cabinet I traded for did have 8 and 4 jacks.

What I wanted to be clear off is that starting slow and low would be OK for the amp. I’m more concerned about damaging the head than the cab.


    Hughes & Kettner Hughes & Kettner on November 5, 2019 Reply

    Ah OK, good to know! So yes, just go for it 🙂 We might have to look into acquiring one of those cabs at some point, see how it works 😉

    Team H&K

steve on October 25, 2019 Reply

Hi, this is a bit simpler than some of the others, but backwards to what’s in the chart.

I have a tubemeister 36 head with the 8-16 ohm out jack, and a 2×12 mesa California tweed that only has a 4 ohm jack. Is that one OK?


    Hughes & Kettner Hughes & Kettner on October 25, 2019 Reply

    Hmm, it’s weird that that cab would only have one 4-ohm connection point, but we Googled it and it’s true! Strange, and unusual (you don’t see 4-ohm cabs that often these days). We’d normally say stuff like that we’d be happy to try – just take it easy and start quiet, and go from there 😉

    That said, if you’re really doubtful about it drop Mesa themselves a line and see what they say. You never know, they may have a different opinion on the matter!

    Hope that helps!

    Team H&K

Beau on October 25, 2019 Reply

Good day H&K,

Thankyou guys for helping and spreading the light alas I’m still confused .
I’ve got a Fender Hot Rod Deville 4×10 around a 2012 model
I believe it’s in series/parallel but could be wrong
I want to pull out three of the speakers if possible, the speakers are 30W /8ohm
What’s your thoughts?
Any help will be greatly appreciated

Thankyou Beau

    Hughes & Kettner Hughes & Kettner on October 25, 2019 Reply

    Hey Beau,

    Hmm, that’s a tough one! We’ve not got any experience with that exact amp (don’t even know if it’s series/parallel, and there’s not much info online to go on!), so we’d recommend you ask the guys at Fender. Pulling out speakers is not something we’d recommend if you’ve not got experience doing stuff like that – a tech should do it. Whether it’ll work or not is another question 😉 That’s probably best for the guys at Fender to answer! Sorry we can’t help more directly there.

    Team H&K

mark on October 15, 2019 Reply

I’m new to tube amps. I’m hearing different things from different people.
My head is 8ohm and I have two 8ohm cabs daisy chained making them 4ohm (if I’m correct).
From your diagram my 8ohm into 4ohm should be ok.
Am I correct in this thinking?

Than you for your time


    Hughes & Kettner Hughes & Kettner on October 16, 2019 Reply

    Hi Mark,

    Well, what you write there is something we’ve done many times happily with H&K amps and cabs. You don’t say what gear you’re using exactly, but if you do have any doubts just drop the manufacturer a line and see what they’d say. We’re adventurous types, though, and we’d just test it – gently at first, and take it from there!

    Hope this helps, and enjoy your tube amp adventure!

    Team H&K

James on September 15, 2019 Reply

Hi, I have an ashdown lil bastard 30w bass amp with 4 and 8 ohm outputs.
I want to connect it to my orange 212 which only has 16ohm outputs.

From Your article it seems 8>16 should be fine. I’m just unsure because every tech I have asked has said never to mismatch and I want to try this but I’m worried out breaking my gear.

    Hughes & Kettner Hughes & Kettner on October 16, 2019 Reply

    Hi James,

    Well, that’s the kind of thing we’d be willing to try with H&K gear, so we’d do it… but if you have any doubts you might want to ask Ashdown and/or Orange for their thoughts, just in case 😉 As we’ve written here, we’ve had many experiences of using mismatched rigs without issue over the years! If you start gentle and work from there, generally nothing is going to break.

    Team H&K

Tom on September 4, 2019 Reply

I have a 2 yr old tube meister. I am doing solo shows and the digital processor to the FOH is lacking that tube crunch. I have used the DI out on the HK to the FOH but am not really happy with it. Question: I was thinking on hooking up the HK 110 and miking it to the FOH for that tube sound, is this a good choice or should I go with the 112. Keep in mind this is an augmentation to the digital processor.

    Hughes & Kettner Hughes & Kettner on September 5, 2019 Reply

    Hi Tom!

    Hmm, the real thing here is… what kind of music do you play? We’d generally say go with a 1×12 (you’ll have a ‘bigger’ sound, and more low-end if needed, etc.) but if you’re playing music that doesn’t require that, the 1×10 will be totally fine! If you can, we’d say try both out first, and go with the one that sounds best to your ears!

    Hope that helps,

    Team H&K in Germany

Ormonde O'Carroll on August 29, 2019 Reply

I have a Crate Blue Voodoo 150 watt tube amp head that I intend to use for a bass amp (I play a 1968 Fender Telecaster bass that I bought brand new when I was a kid), the amp has four output jacks and a choice of 4, 8, or 16 Ohm impedance. I currently have an Ampeg bottom (B Series) with 4 10″s, an SWR bass reflex cab with a single 15″ , and a Gallien Krueger bass reflex cab with a single 15″ speaker also. I’m assuming that all of these cabs are 8 Ohm impedance, none of them are marked otherwise. I would think setting the Blue Voodoo on 4 Ohm output and just plugging in all three speaker cabs would probably be alright but I’m not sure. If all the cabs were 8 Ohms I think the result would be the amp set for 4 Ohm load pushing onto a 2.66 impedance load, Would that hurt anything?

    Hughes & Kettner Hughes & Kettner on August 30, 2019 Reply

    We wouldn’t really want to go that low Ormonde (2.66 Ohms). The best thing you can do first though is find out what the exact impedances of each cab are before you do anything. You never know, one of them might be something other than 8 ohms… The other question is: will the Crate amp like being used for that? It’s an amp we’re not sure about, but start quietly and go from there and you shouldn’t blow anything 😉 Either way it sounds like an intriguing and unique setup!

    Rock on,

    Team H&K

David Sodee on August 4, 2019 Reply

So I own a Switchblade and I have the 2-12 H&K bottom. I am fine running them both in 16 ohms or should I use 4 ohms on the combo amp (1-12) ? I am thinking the dual 16 is fine but just checking.

    Hughes & Kettner Hughes & Kettner on August 6, 2019 Reply

    Hi David, you’re fine as you are – a 16-ohm match is ideal 🙂

    Team H&K

Jeremy on July 18, 2019 Reply

This is exactly what I was looking for! I had an older 16ohm 2×12” cab I was using until I recently replaced it with an 8ohm 4×12”. Been trying to find a way to use both of them in a safe manner, as I didn’t want to leave my 2×12” cab to settle in dust. Thanks for this article.

    Hughes & Kettner Hughes & Kettner on July 18, 2019 Reply

    No worries, and glad you’re now able to rock both your cabs together!

    Team H&K

Mike on June 15, 2019 Reply

Hey there!

It was a very useful article, I have learnt a lot, but I still have doubts about my setup.

My question is simple:

16 Ohm amp (50 W) ——-> into ——> 8 Ohm (4×12) cab?

It will cause any damage?

Thank you for your answer.

    Hughes & Kettner Hughes & Kettner on July 18, 2019 Reply

    Hi Mike! Well, ultimately it depends on the amp/cab too, but that’s an impedance mismatch we’ve rocked many times with H&K amps without issue 🙂 You might want to contact the amp maker themselves first to double check their thoughts on the issue, but if it’s an H&K, start gently and build up from there and you’ll be all good!

    Team H&K

Lennon on June 3, 2019 Reply

Hey there! I have a epiphone valve standard and was wonder can I run the combo amp and an extension speaker cab that’s at 8 ohms at the same time? It says 8 ohms min on the back. I know playing them both would result in the ohms being cut to 4 ohm, but on the epiphone site it says “ just plug in an 8ohm extension for more volume” . Or do I have to unplug the main speaker and run the cab separately?

    Hughes & Kettner Hughes & Kettner on June 3, 2019 Reply

    Hey there Lennon! Hmm, we googled the amp and it seems to be exactly as you said – we reckon you’d be safe plugging in that extra 8-ohm cab (otherwise we’re sure they’d warn you about unplugging the built-in speaker on the amp itself). You could try asking Epiphone themselves to be 100% sure, but we reckon you’re good to go!

    Team H&K

Lee Shields on March 11, 2019 Reply


I recently bought a second hand statesman 50w head and 2×12 cab. Is there any advantage to running at either 4 or 16 ohms matched into the cab?

Also at the end of the first gig i lost output, we were trying a few things to get it working (cables, pedals etc) and after a few minutes i found it was the input socket on the cab. Swapped the speaker connection over and it was fine for the last couple of songs. When i later checked, the socket was loose (although not sure why that would cause the problem) so i tightened it up and went over the solder joints on the board just in case. It seems fine now though hasnt been used in anger since.

Should I be concerned the amp was running no load during the time trying to find the issue? Amp volume was about half way or less.


    Hughes & Kettner Hughes & Kettner on April 25, 2019 Reply

    Hi Lee,

    On the first point, it’s obviously ideal to have an impedance match, so it depends on the cab. Then try out the options and see which sounds best to you tonally, kind of like in the cases in the blog here – you’ll notice volume and tonal shifts depending on which impedance value you go for.

    And about the gig situation, we think you may have got away with that one, and there’s seemingly no lasting damage – the only way to be 100% sure though would be for a tech to have a thorough look around the amp and see if anything bad did happen (seems like you know your way around amps too though?). Is there any local tech you’d entrust to do that?

    All the best,

    Team H&K

George Thompson on March 9, 2019 Reply

Interesting article I came across it while looking for a yes/no answer to my question on Google?.
I have a green board 15W 8ohm output Fender Blues Junior amp with the original 12″ Eminence special design speaker. I also had in my toolbox figuratively speaking a 20W 4ohm Eminence Patriot 820H speaker. Being an avid DIY’er I decided to buy another 820H and build a pine extension cab for them, wire them in series which would also give an output of 8 ohms and use this as an alternative tone to the 12″ built in speaker. I did this and found that it works really well.
I understand a little about ohms etc and am competent with a soldering iron but cannot find an answer to my question which is, If I for example did away with the two input jacks and cut off say the 1/4″ inch input jack on the extension cab and re-soldered the wires to the 12″ speaker input jack this I believe would give me a combined output of 4ohms but with the BJr’ being an 8ohm amp I am unsure whether this would or would not damage the amp?.
If it makes any difference I am not a gigging musician but an elderly gent playing at home at neighbour friendly volume. Do you have any advice or an opinion on this which would solve it for me?.

Chris on March 6, 2019 Reply

I like your knowledgeable answers.. Q. Can I replace a 4 ohm speaker with an 8 ohm speaker & what can I expect performance wise with the 8 ohm compared to the 4 ohm that the amp came with?

    Hughes & Kettner Hughes & Kettner on April 25, 2019 Reply

    Cheers Chris! Hmm, it depends on the amp/cab… what setup are you using?

Verne on February 3, 2019 Reply

I recently got a Tubemeister 5 and a Tubemeister 112. I now know after reading here that this is definitely a safe match, maybe not ideal, but safe. I also have another cab with an 8ohm speaker that would obviously work better with the TM5, but the TM112 sounds better with the TM5. I can run the the 8ohm cab off the 16ohm TM112, but am not entirely sure this is a “safe” mismatch. Can you let me know if this is a bad idea entirely? I don’t jam, I don’t gig and I never leave the basement, so volume is never that high. Maybe volume at 12 o’clock and gain at 9 o’clock.
I don’t know electronics in any way, so to say all this is confusing is an understatement.

    Hughes & Kettner Hughes & Kettner on February 14, 2019 Reply

    Hi Verne. Well, the good news is the TM5 and the TM112 are indeed a perfect match – the TM5 is perfect with any cab between 8 and 16 ohms, which is what the TM112 is (16 ohms).

    The 8-ohm cab is also a perfect match for the amp. Without knowing the identity of this other cab, the reason the TM112 sounds better is because the TubeMeister amps and cabs have all been designed to fit with one another – so they’re always a great match.

    You could run both cabs simultaneously, too, and this would be the same scenario as Case 3 in the blog. Just take it easy at first if you’re worried, but we think you’ll be pleased with the results.

    Ultimately, though, tone is a personal thing – so just choose the speaker (or speakers) that you think sound best for your home application, and that’s all there is to it.

    Hope this helps, and enjoy your TM5!

    Team H&K

Jorge Bolanos-Shaw on January 12, 2019 Reply

Great info!!
my situation is like example #2
tubemeister 36 output 8 to 16ohms single connection
to 2 x 8omhs cabs (4ohms total)


Cubics on December 9, 2018 Reply

Hi there,

Thanks for the explanation of things where i was constantly crashed on.
However, I have one question. If I would want to combine the signals from the guitar and return from the looper to one input in mey Guitar Amp, how to do it?
There are many merger and audio combiner, but they are all balanced or line. The guitar amplifier has a different impedance at the input.
Is there any way to combine 2 unbalanced (guitar) singnals without switching A/B ?


newbornALIEN on November 23, 2018 Reply

I just bought an amp head with speaker cab but I was wondering how can I connect it to a pa mixer? I used to do this with my fender combo amp but that one had a headphones jack out. The amp with speaker cab doesn’t have such a thing. How can I safely connect the amp to my pa without damaging anything? I can’t use a microphone because I live in an apartment.

    Hughes & Kettner Hughes & Kettner on November 23, 2018 Reply

    Hi there! What amp is it? Let us know (a link to a photo with all the connections on the amp would be really helpful) and we can maybe advise you further 🙂

painkiller84 on November 15, 2018 Reply

I own a tubemeister 18 head(great amp) and I want to connect it to two 1×12 cabinets, 8 ohm each,so I have to connect them in series.Thought of building a box like this :
Would it be safe? and if so, should I isolate the socket jacks of the box,or simply use a plastic box? Thank you..

    Hughes & Kettner Hughes & Kettner on November 23, 2018 Reply

    Hey there! Glad you’re liking your TM18 so far 🙂 We’d resist building anything like that unless you really know what you’re doing. But if you’re handy with a soldering iron, go for it: there’s plenty of other sites where people have described exactly how they’ve built boxes exactly like this. Follow one of those plans and you’ll hopefully end up with a decent result 🙂

John on November 6, 2018 Reply

I have a Hughes and Kettner Grandmeister 40 Deluxe where the Speaker out states 8 – 16 Ohm. So if I am hooking it up to an 8 Ohm plus a 4 Ohm cabinet I would be best off hooking them up isn series 8 + 4 = 12 Ohm – is that correct?
I want to be sure as the first valves in the amp needed changing after 6 months (where I only used either or of the above cabinets depending on the gig) and although it states in your article above that this shouldn’t have been a problem, I have never had to change tubes so early before and I want to be sure.
I have just purchased a Palmer CAB M cab Merger (on its way to me) as an interface for this connection/purpose.

    Hughes & Kettner Hughes & Kettner on November 6, 2018 Reply

    Hi John! Yep, all looks right to us. Hmm, valves/tubes are very unstable things by nature – we’ve had some that needed changing after 10 seconds, and some that’d easily have lasted 10 years! So hopefully it wasn’t a case of you doing anything wrong with yours, but just these ones that reached the end of their natural life fairly quickly… Either way, we hope you’re enjoying your new setup and you’re getting some great tones out of the dual cab method!

    Rock on,

    Team H&K

Douglas on October 10, 2018 Reply

So I have a emperor 4×15 that is 4 8 ohm eminence bass lite speakers that are wired for 2 separate 4 ohm loads. I have an ampeg svt2 pro that has 2 and 4 ohm capability. I ran the head at 4ohms. My just kicked saying I blew a tube. I should’ve been running at 2ohm per speaker duo because of it being in parallel right?

    Hughes & Kettner Hughes & Kettner on November 23, 2018 Reply

    Hi Douglas. Hmm, if you connect two 4 ohm speakers in parallel, the overall resistance will be 2 ohms. So in that case we’d recommend running the head at 2 ohms too.

Matthew on September 24, 2018 Reply

How many H&K cabs can I safely run with a TM 20 Deluxe? I have a 1X12 and a 2X12 now, which I know is ok, but want to add more. Can I add a third cab, another 2X12 safely? Can I use 4? And connect all through the out on the cab (daisy chain them)?


    Hughes & Kettner Hughes & Kettner on November 23, 2018 Reply

    Hi Matthew! Well, the amp’s happy between 8 and 16 ohms, so if you’re hooking up cabs, you just need to try and keep your total impedance within that total. If you keep it there, no matter how many cabs are connected (within reason!) you’ll be OK. We have to say, though, that we’ve never heard of anything running four with the TM20! You might struggle for power there. We recently ran four 4x12s with the Black Spirit 200, though, and we needed a special cable to hook them all up simultaneously.

Dave on August 20, 2018 Reply

Hi all,
I recently purchased a GM40. Beautiful amp and sounds great through a 4×12. Problem with the 4×12 is it’s ponderous size, and I play some small rooms (and getting too old to carry the thing). I have 2 Mesa Boogie Rectifier 1×12 cabinets. They are 8ohm with v30s and have parallel outs. If I understand this article correctly that will give me 4 ohms?
The manual for the GM40 states to only use 8 or 16 ohm cabs…If I try hooking up both Mesa cabs, will I damage the head?

    Hughes & Kettner Hughes & Kettner on September 27, 2018 Reply

    Hi Dave. Yep, we’d try and avoid that if possible, although it’s certainly something you could test just to see. It’s probably not going to break anything, but we can’t make any promises there! We’ve gone down to 4 ohms before with our amps without issue, but we wouldn’t go lower, and we’d always try and get an impedance match if possible. Would it be at all possible to try hooking them up in serial though?

    Team H&K

Paul on August 10, 2018 Reply

Hi guys,
Interesting article, but I am still a little nervous about mis-matching speakers to amp outputs.
I have read conflicting articles on the web, some saying that you can use a higher impedance speaker okay, some saying you should only ever use a matched or lower speaker impedance on a tube amp, and some saying that you should never use a higher speaker impedance due to the possibility of “blowback” voltage damaging your amp.
I am trying to replace the speaker on a Peavey Encore 65 combo that has a min 4 ohm output, and since 4 ohm speakers are harder to get hold of, I was thinking I would be okay using an 8 ohm. But after reading articles by amp techs warning about “blowback “ voltage I am now not sure.
What are they actually talking about? And is it a real concern?

    Hughes & Kettner Hughes & Kettner on November 23, 2018 Reply

    Hi Paul. This is a very legitimate concern, and as with everything these days, there really is a mass of conflicting situation on the subject available online. And everyone thinks their opinion is correct 😉 So we’re just one voice in the crowd, and on this blog we explain what we’re comfortable doing. Others may disagree 🙂 We just Googled blowback, and we’ve seen a bunch of different meanings attributed to it.

    To be absolutely sure with a Peavey amp, the one thing you can do is ask Peavey themselves. We’re sure they have their own line of thinking on stuff like this. They’ll also be able to hook you up with a decent replacement, as necessary.

    However, we also note that you say your amp has a “min 4 ohm output”. The term minimum suggests an 8-ohm speaker would be fine… If you have a photo you can share with us that might help us give you a little more advice on the subject.

    Team H&K

G Holden on August 3, 2018 Reply

I am trying to get a handle on the single 8 – 16 ohm speaker tap on the GrandMeister 40. In an earlier post you stated: “the GrandMeister’s output has an impedance setting that equalizes the range between 8 and 16 ohms”.

Does the amp fully drive all 4 speakers of say a Marshall 1960B at 16 ohms mono? Or, is this an under-current situation?

Thanks in advance.

Alex on July 13, 2018 Reply

First of all – great article!

And a quick question: in case if I use 16 Ohm cab + 16 Ohm resistor in parallel will it make an impedance match for 8 Ohm rated amp and if yes what are consequences (power output, tone change, etc)?


stephen D Lederle on July 3, 2018 Reply

ok Ive got a 2×12 cabinet loaded with 2 16 ohm speakers and it’s wired in series. I have an amp that say “8 ohm minimum”. am I good or should i make changes?

    Hughes & Kettner Hughes & Kettner on November 23, 2018 Reply

    Hmm, it depends. “8 ohm minimum” could mean more is OK! Check that with the amp maker and make your decision based on that 🙂

Jason Saathoff on May 4, 2018 Reply

Hello there this is a very informative article but I have a question on case number three. In this instance how do you propose connecting the two cabs to the amp? If you’re using either the four or eight Ohm selector from the amp would you use a Y cable to hook to the cabinets or would you go to one cabinet from the amp and then attach that cabinet to the other cabinet? In the latter, wouldn’t that be a series connection, not parallel? Or, do you hook one cabinet to the eight home source on the amp and the other cabinet to the floor him source on the app? It seems there is quite a bit left to be curious her or, do you hook one cabinet to the eight home source on the amp and the other cabinet to the floor am source on the app? Some clarification on how you would make these connections properly would be very very much appreciated.

bo huggabee on April 28, 2018 Reply

take a voltmeter and find the resistance of each speaker, then if it parallel or series wired will tell you what resistance to use. most speakers will be 13 ohms or 6 ohms and they are rated at 16 or 8. always assume the higher number in cases like that.

MattSA on April 5, 2018 Reply

Quick question – I have been playing guitar for a number of years. I always held to the belief that when I had the cash I would go out and buy an amp head (yes, H&K 🙂 ). I was also under the impression that I could connect my guitar to the amp head, and then wire the output of the amp head into my Fender Frontman 212R, thinking I would have the tone controls of both devices. After reading this article I see that most amp heads are hooked up to cabinets. My question is, is it ever safe to hook an amp head to a regular amplifier? Are there safe combinations for this type of rig (like the rules above for ohm ouput? I looked at the specs on the Fender Frontman and its list a bunch of different properties – Power Output, Poweramp Input, etc., but I cannot make sense of these values.

    Hughes & Kettner Hughes & Kettner on June 4, 2018 Reply

    Hi Matt!

    Well, while it’s most common to hook amp heads up to dedicated cabinets, there are certain combo amps that have the necessary inputs/outputs to connect a head too. You’d need to check with Fender themselves about whether this would be possible with the 212R, as unfortunately we’ve not used that amp (and a Google image search doesn’t show much – you’d probably need to look under the hood to see if there’s a speaker connection jack you can get to). The simplest way might actually be to take the amp to your local music store and have their tech advise you on whether it’ll work.

    By the way, here’s a handy video by our good friend Colin Scott of CS Guitars fame where he shows how you can also do this yourself, if you feel confident:

    It’s a simple thing, really – it’s just a case of finding out if your 212R has the necessary jacks to let you connect its speakers to your amp head of choice, H&K or otherwise 😉

    Hope this helps,

    Team H&K in Germany

Darien Lux on March 30, 2018 Reply

I have a old Vintage Series cab and I’m not sure what Ohm it is. It’s a 2×12.

    Hughes & Kettner Hughes & Kettner on April 3, 2018 Reply

    Got any more info or pictures you could share with us Darien? Maybe we can help you identify it 🙂

Mason Dixon on March 16, 2018 Reply

Excellent article… I was worried after having played my home setup for months with my amp set to 16 ohms into my attenuator which was set at 8 ohms from a previous setup. It’s good to know that this was okay, and now that I have committed this formula to memory, I should be good to go in the future for any setup that comes my way.

    Hughes & Kettner Hughes & Kettner on April 3, 2018 Reply

    Glad to be of help Mason, and happy to hear nothing bad happened because of your mismatch! You’ll always be good to go now with that formula committed to memory 🙂

    Rock on,

    Team H&K

Greg on March 12, 2018 Reply

I’m currently in the scenario of wiring a 2×12 cab with 8ohm speakers. I can’t decide whether to do it in series and get 16ohms or parallel and get 4ohms. The problem is two of my three amps only do 8ohms. The other amp has a switch between 4/8ohms. But this switchable amp does get rather dark and muted in the 2nd channel. And, after reading this article, it gives the idea of boosting the mids by doing the cab at 16ohms and switching the amp to 8ohms.

Decisions, decisions. Really I just wish I had two 16ohm or two 4ohm speakers for the 2×12 cab.

Nathan on March 8, 2018 Reply

I read this blog hoping to figure out how to break my ohms down on my bass rig for a lower (more reggae sounding) tone. I have an orange terror bass 500 and a orange 4×10 cabinet. I was looking into adding an orange 15” cab onto it as I was told when I add a 2nd 8ohm cabinet that I would flip the switch on the back of the amp from 8 to 4 ohms and the sound will be beefy and low! My question is: Is this correct and if so is this a good way to get a deep bass tone? Or should I not buy another cabinet and get my lower tone out of eq and playing the bass towards the neck pickups?

    Hughes & Kettner Hughes & Kettner on March 9, 2018 Reply

    Hi Nathan. Well, we’ll start this by saying we’re guitarists, not bass players… but anyway, we’ll have a go at this 😉

    We checked out the Terror Bass 500 manual and it suggests you’ll be fine if you hook up the two 8-ohm cabs and have the amp’s impedance selector switch set to 4 ohms. Page 11, it’s all here:

    Anyway, as to the sound, we’d imagine the extra speakers will give you more extra low-end, sure! In terms of experimenting with other methods though, we’re all for that too! Although in the guitar world, if you really need that deepest low-end, you need a 4×12 or a full-stack – you can only get so close to the real thing using creative EQing and other techniques. So our advice to you is, try as many little things as you can, and if nothing gets you the tone you want, then go for the extra cab option!

    Hope this helps,

    Team H&K

Jason on March 3, 2018 Reply

I have a 120w solid state head with 2 16ohm output and 2 1×12 (both have horns, they ara Traynor cs-122h) 8ohm with 4 imputs: normal, “bi-amp” low gain and High gain. Should I wire them in paralle or series and wich inputs should I wire the head to? Thanks

Rex on March 1, 2018 Reply

How does the multiple cab formula work with 3 16 ohm cabs(2- H&K 112..1- EVH 212). I have a H&K Tubmeister 18.

    Hughes & Kettner Hughes & Kettner on April 3, 2018 Reply

    Hi Rex. Yep, three 16 ohm cabs you can connect in parallel. You divide the total impedance by three, so 16 divided by 3 gives

Vino on February 28, 2018 Reply

Each cab are 8ohm

Don on February 25, 2018 Reply

I just got a H&K Tubemeister 18 with a single H&K 1/12(16ohms ) cab and I am adding another H&K 1/2 and a EVH 2/12(16 ohms) cab.Since the H&K doesn’t have a ohm switch I take it can see the load and act accordingly if I go out of the H&K TM18, IN to H&K cab#1 then OUT of H&K #1 to IN of HK #2 then OUT of HK #2 into EVH (whew!!)

Does that mean 16+16+16=48 or is the parallel out of the H&K cabs now just 16 for both and the EVH still 16 for 32 total?

Frank on February 22, 2018 Reply

I have the grand meister deluxe 40 with one output 8 or 16 ohms and i Want to connect my 2 cab 4×12 laney modèle Gs412ps 4-8 or 16 ohms ( total 8 speakers) i Want to no if its dangerous for my grand meister and if i cant do that its in parallèle or in série tanks

Francis on February 21, 2018 Reply

2 cab 16 ohms

    Hughes & Kettner Hughes & Kettner on February 21, 2018 Reply

    Hi Francis. Sorry, we had problems understanding your comment! OK, so if you have two cabs, each with 16 ohms’ resistance, wire them in parallel – then you will have a total of 8 ohms’ resistance, which is perfect for GrandMeister 🙂

    Team H&K

Francis on February 21, 2018 Reply

My cab is laney 16 ohms

    Hughes & Kettner Hughes & Kettner on February 21, 2018 Reply

    Hi Francis! That’s totally fine – the GrandMeister is a perfect match for any cab between 8 and 16 ohms, so your Laney will work very well. Just connect it to the cab’s input, and rock on! 🙂

    Team H&K

Francis on February 21, 2018 Reply

I have the grand meister delux 40 and i Want to connect 2 cab 4X12 cant i do in parallèle connections or série and its dangerous for my power ( grand meister deluxe 40) tanks you verry much

    Hughes & Kettner Hughes & Kettner on February 21, 2018 Reply

    Hi Francis. Tell us more about the cabs: what is their impedance rating? The best thing is if you send us a link to them so we can check them out for you 🙂

    Team H&K

Scott on February 11, 2018 Reply

My amp case is just like case 3. I have a switch on the back of my amp for 8ohm or 4 ohms. The 8 ohms switch is for the internal speaker, and a 4 ohm switch is for adding a cabinet. If I’m playing the internal speaker plus adding a 16 ohm cabinet it seems I would switch it from 8 ohms to 4 ohms (on the back of the amp), and play the internal speaker and the external cabinet. The reason I say that is because the final impedance according to case 3 is 5.33 ohms, which seems close enough to the 4 ohm switch. Is this correct?

Also the 16 ohm cabinet is a 140 watt cabinet. My amp is 5 watts with a 25 watt speaker inside. Is this too much wattage to add in regard to volume and tone? Just wondering volume and tone on this question not impedance.


    Hughes & Kettner Hughes & Kettner on February 20, 2018 Reply

    Hi Scott. What amp have you got, and can you link us to a pic of that back panel? We’re not quite sure what’s going on there, or if your amp even lets you use the internal speaker an an external cab together. Seems to be one or the other. Anyway, send us a pic and we’ll have a look.

    About the second part, you just need to make sure the cabs can handle the power of the amp: so a 5-watt amp will be absolutely fine, and nothing will get damaged. A 5-watt tube amp can drive a 4×12, sure! But you won’t get the same natural drive or volumes as a more powerful amp would… Still, we often make quite a racket with our TubeMeister 5s 😉

iain C on February 7, 2018 Reply

I love my tubemeister 18 head. It’s a too loud for practice in my condo paired with the HK 1×12 cabinet. I have a homemade 8 inch 4 ohm cabinet that should be quieter.

Does this fall within the ‘cabinet minimum 1/4 output’ guidelines? The amp output is labelled with a range, 8 to 16 ohms. Is this strict? A low volume test produced with no smoke or flames.

    Hughes & Kettner Hughes & Kettner on February 20, 2018 Reply

    Hi Iain. Well, if you’ve tried it at low volumes, and it’s doing the job OK, exercise with caution and enjoy! Like we say in the article, the 4-ohm thing is kind of a border. We wouldn’t go anywhere under that…

GEORGE BARNAK on January 26, 2018 Reply

One topic not covered is the use of an FRFR passive speaker cabinet with a tube amp. Wanting a Valve Amplifier/ Speaker Cabinet combination to be able to play both Piezo Acoustic and Piezo Electric guitars. Is the limitation of the valve amplifiers tailoring to the specific musical instrument the issue since it is designed a specific frequency range?

    Hughes & Kettner Hughes & Kettner on February 21, 2018 Reply

    Hi George. Tough one. With acoustic instruments, you can use full range cabinets no problem, of course. But as soon any kind of tube overdrive kicks in, it will sound – for want of a better word – weird 😉 This is the reason you don’t often see acoustic players using tube amps. There is the odd amp around, we’ve seen a few online that you can buy in the USA, but we’ve never tried one. So, we’d say that acoustics guitar with clean – really clean – tube amplification will probably work. Anything more than that, and you need to test it first and see if it works for the specific sounds you want to achieve…

Vino on January 25, 2018 Reply

I have a 16ohm 120w SOLID STATE head and 2 1×12 ohm cabs, should I wire them in seried or in parallel? Thanks

    Hughes & Kettner Hughes & Kettner on February 20, 2018 Reply

    Vino, you forgot to tell us what the cabs’ ohmage is! Let us know and we’ll see what we can do to help 🙂

    Team H&K

Tim on January 19, 2018 Reply

I would like to ask you for your take on it.

I’d like to buy a TubeMeister 20 deluxe and run it over a pair of Marshall cabinets (each 1×10″ / 16 Ohm / 25 Watt). Using a mono Y-cable to split the signal from the 16 Ohm amp output (that is parallel, I guess), would this be like having two 8 Ohm speakers?

How would I have to expect the tone, would it be loud enough or rather dimmed when running the amp cranked up – compared to a single 16 Ohm cabinet

Thanks a lot.

david on December 27, 2017 Reply

great info. but was hoping for a sort of ‘rule of thumb’ to quickly figure things out – like: for for a 4ohm amp use a 4ohm cab with 1 spkr / an 8ohm cab with 2 spkrs….etc…or whatever it is.
(had splits in the 80’s…but had combo amps ever since, & been thinking i’d like to have an amp/cab again…and i’m too old to have to learn new science – but definitely NOT too old to keep rocking.
so…thanks again for all your effort to try to help. if you have a minute & the patience to help – much appreciated.

Matt Wellendorf on December 17, 2017 Reply

Fender Bassman 4ohm head…..can it run two separate 8 ohm cabs safely?

    Hughes & Kettner Hughes & Kettner on December 18, 2017 Reply

    Hi Matt. Which Bassman model? Show us a pic or send us a link and we’ll have a look 🙂

    Team H&K

John M on November 20, 2017 Reply

Hi there and thanks for the great article. I have a much better understanding of ohm cooking.

I have two combo amps. One is a Fender Superchamp X2. The one speaker out jack (that the internal speaker is connected to) says Minimum 8 ohms. The other amp is a Vox AC10 with a speaker out jack of 16 ohm.

I’m looking for a 2×12 cab that could be used for either amp. I found the Bugera TS212. On the back it has a 4ohm mono jack and a 16ohm mono jack. It also has a stereo switch so it can also handle 2×8 ohm stereo.

I know the Vox will work best through the 16 ohm mono jack.

I think the Fender would work fine going to one of the jacks with the stereo switch engaged knowing that the output would only come through one of the speakers. I think…

Could I reasonably connect the Minimum 8 ohm out from the Fender to one of the mono 4 or 16 ohm jacks. The article intimated that it would be ok. Which would be better and why?

Also, you mentioned several times in comments that folks should be careful or to take it easy when trying mismatched options. Can you elaborate on what you mean by that?

Thanks for continuing to answer comments.


    Hughes & Kettner Hughes & Kettner on December 4, 2017 Reply

    Hi John, thanks for writing, and we’re glad you enjoyed the blog! We’re huge advocates of ohm cooking, you know 😉

    You ask some good questions, and we imagine you know what our advice is going to be… that’s right, we’d be all for trying this. Especially with an H&K setup, which would certainly handle it. With the Vox and the Fender it should be a total no-brainer too, although you could always ask the other companies what they think, and whether they’d recommend it. But we imagine it’d be all good. In terms of what would sound best, that’s totally subjective – what we’d do is try both options with our guitar(s) of choice and then decide which would be best for us.

    What we mean by taking it easy at first is – don’t just hook it up and blast it straight everything on ten! Let the amp warm up as usual, and start quietly and gently first. This should be self-explanatory, of course, but the last thing we’d want to happen is that someone takes our advice too excitedly and causes some damage to their precious amp. So that’s why we reiterate this point over and over 😉

    We hope this helps a bit, and let us know how you get on 🙂

    Team H&K

Eric on November 13, 2017 Reply


I have a 1×12 combo with a 16 ohm output. Can I safely run this through my 8 ohm 4×12 cab?

    Hughes & Kettner Hughes & Kettner on December 4, 2017 Reply

    That’s like Case 2 in the blog Eric. With an H&K setup, we’d be happy to try it… if you’re rocking a different brand though, and you’Re not sure, ask them what they’d recommend. Or, if you trust yourself, just give it a go, starting very gently, and see how it sounds… 🙂 We love experimentation like this, but we wouldn’t want any damage to your amp!

    Hope that helps a bit,

    Team H&K

Sean on November 5, 2017 Reply

So, question here. I am looking into buying an amp head with 3 speaker outputs: 2 8ohm, and 1 16ohm. My 2×12 cab (2 8ohm speakers wired parallel) is 4 ohms. What would be the best way to plug the amp into my cab. through the 16ohm or would one of the 8ohms work?

    Hughes & Kettner Hughes & Kettner on November 9, 2017 Reply

    Hi Sean. That would depend on how comfortable you are with using a mismatched setup, as written about in the article. For these purposes, your cab is 4 ohms… and we know we’d happily try that with an H&K amp and cab, but if it’s a different brand and you’re worried about it, ask the maker of the head first! They should be able to help you put your mind at rest 🙂

Dave on November 1, 2017 Reply


I have a Vox amp with a switchable 8ohm or 16ohm output. Can I run this into a 4ohm 1×12 speaker without blowing the amp?

Thanks 🙂

    Hughes & Kettner Hughes & Kettner on November 9, 2017 Reply

    Hi Dave. It’s something we’d happily try with an H&K amp, gently at first, as mentioned in the article. As for the Vox, we’re not as sure how happy it will be – so try asking Vox directly if you’re worried about it. We wouldn’t want to be responsible for you damaging your amp 😉

Hank on September 26, 2017 Reply

I have a silver face 1968 (drip edge) Super Reverb, same era Deluxe Reverb, and a reissue Marshall 1974x. I’m wondering about using an attenuator DI box (looking into the Red Box 5) but I’m reading forums and people mention making sure you have the right Ohms between your amp and your DI/attenuator. Particularly when reading about attenuators for the Super Reverb, people recommend finding one that works for 2 Ohms. Apparently the Dr. Z Airbrake which is advertised to work with any Ohm load, isn’t recommended (by Dr. Z) to use with a Super Reverb. I started looking into DI boxes when I found I couldn’t get a full enough tone live with mics. An attenuator in addition to running direct sounds great! Just trying not to blow up my stuff.

    Hughes & Kettner Hughes & Kettner on October 19, 2017 Reply

    Hi Hank. That’s quite a cool collection you’ve got there!

    One thing we must mention: the Red Box 5 is NOT an attenuator. It’s just a DI. It’s only our Power Soak-equipped amps (TubeMeisters and GrandMeisters) which have the attenuation built in. So you would need to find an external attenuator in your case anyway. We’ve heard many good things about the THD Hot Plate, but we’d recommend you getting to a store where you could try a couple out in advance, to see which works for you – because they can significantly change your tone!

John McConnell on September 24, 2017 Reply

I have a crate GT 212 2×12 combo amp and can’t seem to find the optimal extension cabinet for it. I’ve read the manual and (not sure) but l think. it’s 16 ohms and the amps speakers are active along with the extension cabs l have a 2×12 mess boogie that is 8 ohms . But l think l need a 16 ohm 2×12 please help .

    Hughes & Kettner Hughes & Kettner on October 19, 2017 Reply

    Hi John. Have you got any pics of the amp? Or a link to the manual? Let us know and we’ll have a look, see if we can find something. If not, try contacting Crate themselves and they should be able to help you out too!

Norm Salisbury on September 16, 2017 Reply

Awesome article. I had been sitting here trying to figure out how to connect up 2 x 8 ohm cabinets in parallel to connect to a new amp that only has 1 x 8 ohm or a 1 x 16 ohm connection. I built the (ported) cabinets and they contain 1 x 10″ Alnico Jensen (8 ohm) speaker each with an additional parallel 6mm socket in one of the cabs so I can link between with a standard speaker cable.Works great with my 2 x15″ speaker cabinet (switchable single/parallel) as I can hook up 3 cabs to my big amp as a 8 ohm load in total.After reading this article I won’t have to change anything but might have to boost the mids on the new baby amp.Thanks.

    Hughes & Kettner Hughes & Kettner on September 20, 2017 Reply

    Sounds like a great setup you’ve built yourself there Norm, very impressive! And glad the article was able to help out a bit as well. Now all that’s left to do is get playing and adjust your tones to taste 🙂 Enjoy!

    Team H&K in Germany

Grant Willem on August 29, 2017 Reply

Please for the love of everything holy do this for bass rigs! then shoot me a link! thanks

    Hughes & Kettner Hughes & Kettner on September 20, 2017 Reply

    Ha ha, if we ever get round to that we will indeed let you know 🙂

Ry on July 23, 2017 Reply

Thanks for the Article, I think I have a fourth scenario for you if you wouldn’t mind answering. I recently watched a video on someone using a small 1×8 style combo amp as a head by bypassing the speaker and connecting the little amp (head) to a 2×12 cab, I realized I had a long forgotten 1×8 Roland Cube amp I haven’t touched in years and went to check to see if I could make this work somehow, I noticed a headphones/recording out jack on the Roland Cube-15 and decided to plug a mono cable to it and run that to my Tube Amp 2×12 Combo. I plugged it into my Tube amp’s return loop, thinking it would bypass the Amp’s Pre-Amp tubes and go straight for the Power Tubes. It worked to my Surprise but it left me wondering if I could damage the amp in the process. Here’s what I know, The Roland Cube-15 ohm output is unknown to me. My Tube Amp is a Peavey Valveking 212 100watt Combo, the switch is set to 8ohm (can be 4/8/16) because I have two 16ohm 12″ speakers wired in parallel. (Whichever one halves the impedence 2×16=8ohm etc.). So let’s say for giggles if the Roland Cube-15 amp is set to 4ohm or 16ohm, would this be trouble for my precious tube amp? Does this even matter since one is solid state and the other is all tube?

or is the Roland Recording out a line level connection making the Ohm difference negligible between amps? Can anyone explain that one to me? I know Amp to speaker resistance matching is proper, but what if you’re feeding an amp another amp’s signal, does it still matter? Thanks!!!

what about vice versa? I have a rack mount preamp and power amp, if i run the signal from the power amp to the cube’s aux input will it smoke the little amp? or should i just send the signal from the pre-amp to the aux input?

Erwin on July 16, 2017 Reply

Can I have the complete electronic scheme of the Basskick 101 40 Watts bassamplifier?

    Hughes & Kettner Hughes & Kettner on July 17, 2017 Reply

    Hi Erwin, you’d need to ask our techs for that – they’re on – shoot them an email any time.

    Hope this helps,

    Team H&K

Brian Mato on June 25, 2017 Reply

Thank you for this great info!!! i have a question about my setup.
Have a 2 head, 1 stereo cab setup. Heads are Peavy Roadmaster and Randall RH200 and both just say “4 Ohm min”. The Cab is a Fender HM4-12A and is 8 ohm. If i understand everything from the article, this should be fine, but i wanted a second opinion!

    Hughes & Kettner Hughes & Kettner on June 26, 2017 Reply

    Hi Brian, and thanks for the kind words about our blog! Hmm, we googled that cab of yours and it looks like it has two 8-ohm mono inputs… plug into them and you should be just fine 🙂

    Hope this helps,

    Team H&K in Germany

Aaron Gardea on June 14, 2017 Reply

Thank you for the article.

Cabinets are often referred to as “x” ohm cabinet, such as a 4ohm cabinet, or an 8ohm cabinet” what does the number 4 or 8 apply to? Is it the sum of impedance offered by all speakers in the cabinet, or is it something different?

Thank you much


    Hughes & Kettner Hughes & Kettner on July 10, 2017 Reply

    Hi Aaron, good question! And you’re right in your summary – a cab’s listed impedance will indeed be a result of the wiring of the speaker(s) inside. There’s a few decent blogs around that explain in a little more detail (for example why some 4x12s have different impedance ratings, and it’s all down to how the speakers inside are wired together):×12-speaker-cabinet

    Hope this helps,

    Team H&K 🙂

Ohmrider on May 18, 2017 Reply

but why? going by the rules in the article 4Ohms would be fine on a 12Ohm output (1/4 of 12 is 3 so 4 is higher than the minimum) or did I misunderstand the article?

    Hughes & Kettner Hughes & Kettner on May 19, 2017 Reply

    We can’t find your original question Ohmrider! There’s too many comments here to see what you originally asked and what we answered 😉 Can you copy us the original question?

tim on May 18, 2017 Reply

Would like to know, on my 1974 Peavey 212 Classic, what the four inputs do? “High”, “Series”, “Paralel” and “Normal”. When and how to use them for what purpose. Appreciate any feedback (Pun) Tim

    Hughes & Kettner Hughes & Kettner on May 18, 2017 Reply

    Interesting, got any pics of that amp’s front panel Tim? We googled around for it but couldn’t find anything…

tom on May 13, 2017 Reply

very helpful! is there a newsletter or any lit. that i can sign up for? i have my eye on a few of your products,please keep me in the loop. thank you/

Sagar Choudhary on February 21, 2017 Reply

Sir,l have soundstandard ca20 amp. 8ohm stereo 2000w/channel.and I setup 18″,8ohm 1500w×3/channel in parallel.whats right?

    Hughes & Kettner Hughes & Kettner on March 10, 2017 Reply

    Hi Sagar. We actually make electric guitar amplifiers, not power amps in the sense you want. Please ask Sound Standard directly, and hopefully they can help you with your question 🙂

Brent Phelps on February 17, 2017 Reply

I have a Super Reverb with a 2, 4, and 8 ohm output transformer installed. I plugged into an 8 ohm Celestion Seventy 80 single 12 cabinet and the amp breaks up around 4-5 volume, less headroom but more sweet spot with enough stage volume with a moderate volume drummer. However at 7-10 volume I heard strange distortion and ghost after-tones. Is that ok? will something blow up?
Then I plugged into a single 1 12 Celestion G12T-100 4 ohm speaker, the headroom increased and the amp is clean up to 6-7 on the volume. More headroom for clean tones but overdrive at 8-10 is now too loud, but no more ghost tones and smother distortion. I use a Mooer Rumble Drive for overdrive with the volume at 4-5 now.
Which is the best way to go and safest for the amp?

    Hughes & Kettner Hughes & Kettner on March 10, 2017 Reply

    Hi Brent. Hmm, it mostly depends on the sound you want. If you want more distortion in your sound (and quicker), use your single 8-ohm Celestion speaker. If not, use your 4-ohm cab. If your amp is OK from a technical standpoint (which we obviously don’t know from here, so we’ll have to take your word on) either option will be safe, and it’s down to your ears as to what sounds better. Just take it easy at first and crank as required!

Steve Browning on February 11, 2017 Reply

Just read your article “Ohm cooking 101″ regarding external cab with 16 ohm speaker, and a tube amp output designed for 8 ohm. I have a similar situation but not a tube amp. I have a Marshall mg50fx SOLID STATE amp with output to one internal 12″ 8 ohm speaker . I have a 15″ 16 ohm speaker that I took out of an old Leslie 147 cab (with a large permanent magnet). Marshall has the internal speaker plugged into the external speaker port, so that the internal speaker has to be disconnected to plug in the external speaker. Will it damage the solid state amp to drive the external 15” 16 ohm speaker? Thank you.

    Hughes & Kettner Hughes & Kettner on March 8, 2017 Reply

    Hi Steve! With a solid state amp, you don’t face the same impedance issues as with tube amps, so what you’re proposing there should be just fine 🙂

MARK on February 8, 2017 Reply


    Hughes & Kettner Hughes & Kettner on March 8, 2017 Reply

    Hi there. Hmm, we’d ask Peavey what they think about that too. Also, what guitar amp are you using? In guitar amp theory, if you have two 4-ohm cabs hooked up in parallel you’d end up with 2 ohms’ impedance…

John on February 6, 2017 Reply

1974 Marshall JMP (4 speaker outs) with 3 4×12 16 ohm cabs

    Hughes & Kettner Hughes & Kettner on February 7, 2017 Reply

    Damn, we can’t find any pics of one with four speaker outs. Any chance you could share a pic of that with us? Is it a special customised one or something? What is written around the speaker outs? Any mention of ohmage?

John on February 4, 2017 Reply

Great info! Thank you!

What would i set my impedance to if I were to run 3 16 ohm cabinets – each plugged directly into the amplifier?

    Hughes & Kettner Hughes & Kettner on February 6, 2017 Reply

    Thanks John, we aim to please 😉

    What’s the exact amp setup – what speaker outs does it have?

Nathan on January 10, 2017 Reply

I have a 112 valve combo, with an internal 8ohm speaker. It has an impedance switch, so you can select 4, 8 or 16ohms. And has parallel speaker outputs.

I have a 412 cab. Two 8ohm stereo inputs or a 16ohm mono input or a 4ohm mono input.

I want to keep the internal 112 speaker connected to one of the parallel outputs and connect the other to my 412.

What is the best way to do this?

At the minute I have been using one of the 8ohm stereo inputs on my 412 (so running it like a 212).

    Hughes & Kettner Hughes & Kettner on February 7, 2017 Reply

    Hi Nathan. Hmm, we’d switch the combo’s impedance to 4 ohms, then plug the 4×12 in through its 16-ohm input, and that’d be a fairly close match! Of course, it would not be a perfect impedance match, so you’ll have to choose whether you feel confident plugging in that way… but we would and do 😉

Jason on January 8, 2017 Reply

I have an Orange CR120C and two 8ohm 4×12 cabs. Is there any way to configure this setup in order to play the amp through one or ideally both cabs?

Thanks guys

    Hughes & Kettner Hughes & Kettner on January 10, 2017 Reply

    Hey Jason. Well, you can try running it mismatched if you feel it’ll be safe: running one of the cabs into the amp’s speaker extension port (which is intended for 16 ohms – you might want to ask Orange if they’d feel confident doing this! We would with an H&K amp/cab for sure, as it’s mentioned in Case 2 here).

    The second option would be two run the two cabs in serial together, which would give you a total of 8 + 8 = 16 ohms 🙂

Oli on January 6, 2017 Reply

What is it that actually changes when you switch your impedance setting on your amp? The thing that is confusing is in example 1: when you say the current halves and voltage increases, how can that be, to satisfy ohms law/watts law? If you have a 50W amp with a 16ohm load at 16ohm setting, voltage is 28.28V and current is 1.768A at full blast. If you switch that setting to 8ohm with the same load, the example says current should be 0.884A, wouldn’t that mean voltage decreases to 14.14V. There’s obviously a missing piece of the puzzle that I don’t have. Please help.

    Hughes & Kettner Hughes & Kettner on May 19, 2017 Reply

    Hi Oli,

    We were cleaning up the Blog comments section and saw we never answered this: we’re very sorry about that! Anyway, we had to ask our tech boffins about your issue, and they came back with this (well, we’ve translated from the German, hopefully nothing gets lost in translation):

    If you connect the correct load (4/4, 8/8, 16/16) to a tube amp/current source with different output impedances, this is called power adjustment. In your example, this means that the amp always delivers 50 watts, despite different loads, assuming it’s connected correctly. With a classic transistor amplifier (voltage source), this is not the case. Here you halve the power if you connect a 16-ohm cab instead of an 8-ohm cab. So, working on the premise that we’re using a transistor amp (see below as to why):

    With regards your calculations, the first bit you got right. With a 50W amp with a 16ohm load at 16ohm setting, voltage is indeed 28.28V and current is 1.768A at full blast.

    If we switch to 8 ohms’ impedance, we have a power adjustment and consequently slightly lower voltage.

    For 50 watts at 8 ohms, it’s 20V and 2.5A. This winding thus supplies 20V in contrast to the 16-ohm winding, which supplied 28.28V.

    And with a 16-ohm load through an 8-ohm output, you have 20V at 16 Ohms = 25W = 1.25A.

    What you did wrong here was halve both the voltage and the current. The current is halved, but not the voltage.

    This is more strictly true for transistor amps, because with tube amps things are a little different. As we know, a tube watt is louder than a transistor watt – this has something to do with the operation of the output stage and the output power over the impedance. So the above calculations are only of a simple theoretical nature.

    In the case of a mismatch of 16-ohm loudspeakers with an 8-ohm output impedance, the output power for a tube amplifier decreases only to about 89% and not to 50%, as in the above calculation.

    And this again applies only to fixed ohmic impedances. A guitar speaker has no fixed impedance over the frequency range. It increases at higher frequencies. Since a tube amp can delivers its power better there than a transistor amp does, a tube amplifier with the same power sounds louder than a transistor amplifier.

    So, there’s something of an answer. It’s basically impossible to provide a clear-cut, 100% foolproof answer to something like this, but we tried.


    Team H&K

frank on December 28, 2016 Reply

I recently bought a crate Excalibur which has a 2ohm output. I have a b-52 cab and a bringer bottom cab that are 8 to 16 ohms will this work and who would I hook it up from amp to cad to cab or from the outputs to each cab


    Hughes & Kettner Hughes & Kettner on January 5, 2017 Reply

    Hey Frank! Hmm, we had a look in the Crate manual and you should be be fine with this. Look at their advice:

    We’re not sure what Crate themselves would say about a mis-matched setup, but their manual/amp display implies it wouldn’t be an issue (it says 2 ohms minimum load, implying more is OK!). To be 100% certain about that you’d need to ask them though.

    About connections, yes: just hook one cab to one of the speaker outs, and the other to the other, as Crate suggest in the manual…

John Reist on December 18, 2016 Reply

I learned a lot from this. I have a big CBS Fender 400 PS Bass amp I just restored. Has six 6550 tube and a lot of power. Supposed to run three big concert 4 ohm speaker cabinets. I only have a big Kustom 200 cabinet with two 8 ohm 15″ speakers. Get a outstanding sound. But don’t want blow the speakers.

    Hughes & Kettner Hughes & Kettner on December 22, 2016 Reply

    Glad it was informative for you, John! Interesting rig you’ve got there, bet it sounds massive… enjoy it! 🙂

Eric on December 13, 2016 Reply

I have a H&K Triamp MKII that I normally run at half power (50 watts instead of 100 watts). I read somewhere online that when using half power switches like this, the amp’s ohm output should be adjusted. For example, if running 100 watts at 8 ohms, 50 watts should be run at 4 ohms for optimal results. Is this correct? In my case I’m running it into a 1×12 with an 8 ohm speaker, however I use the amp’s 8 ohm output regardless of whether it’s 100 or 50 watts. Should I switch to the 4 ohm output?


    Hughes & Kettner Hughes & Kettner on December 23, 2016 Reply

    Hi Eric! Hmm, interesting. This might be the case with some other amps, but with the TriAmp MKII it’s not, so you’re totally fine sticking with what you’re doing right now 🙂

qaw on December 4, 2016 Reply

thank you for explaining OHMs in a way that even i, a drummer posing as a guitar player, can understand!!!!

    Hughes & Kettner Hughes & Kettner on December 6, 2016 Reply

    Ha ha, that’s a real seal of approval for us: “Blog Of Toine – Understood By Drummers!” 😉 On a serious note, happy we were able to break it down in a way that was understandable for you, as we always try and do on here. There’s plenty of guitarists out there who don’t understand the impedance/ohms thing, though they’d never admit it to you 😉 Happy playing!

Hans Frønes on November 28, 2016 Reply

It’s an old tube amp pulled from a Kodak 16mm projector.
Tubes; 12ay7, 12sl7GT, 2x 35L6GT
The enclosed speaker is labelled 6 Ohms, so I presume that the amp outpur is the same

    Hughes & Kettner Hughes & Kettner on November 29, 2016 Reply

    Oh wow, that sounds pretty cool! We’d be careful with it, but we reckon it’ll be just fine. We have a colleague here who’s tried the same thing in the past and he loves the idea 😉 If you’ve got any pictures of the rig to share that’d be lovely!

hans frønes on November 28, 2016 Reply

Would it be safe to run a 6 ohm output amp into a 8 ohm speaker?

    Hughes & Kettner Hughes & Kettner on November 28, 2016 Reply

    Hi Hans, that’s generally be something we’d consider, but what exactly are you using here? A 6-ohm output is not that common…

Rob on November 22, 2016 Reply

Excellent thank you, another question i have a 100wt triple rectifier amp that is switchble between 4, 8, and 16 ohms could i run both parallel and non parallel and if so which ohm would be most ideal?

Thanks Rob.

    Hughes & Kettner Hughes & Kettner on November 22, 2016 Reply

    Hi again Rob. This is the same as the other one. Think of it like this: when you wire in parallel, the total decreases. Wired in serial, it increases. So again with parallel you’d be at 8 ohms’ total resistance. With serial, you’d be going up above 16 and it’d not be a perfect match…

Rob on November 21, 2016 Reply

Sorry for the confusion it’s the krank rev jr pro thats switchable from 8 to 16 ohms and two 1×12 cabs each with a 16ohm celestion speaker, the amp has 2 out puts one for each cab and each cab has 2 inputs, so i guess my question is, if i run in parallel do i set it at 8 or 16 ohms and if i run non parallel which ohm setting do i use?

    Hughes & Kettner Hughes & Kettner on November 21, 2016 Reply

    Aha, OK! If you run in parallel (which you do want to!), the total impedance will be 8 ohms. And you just go into one cab from the amp’s input, then go from one cab into the other. With these figures, you don’t want to run serial…

joe on November 14, 2016 Reply


So if I hook up a 4 10″ cabinet with a
1 15″ cabinet and both are 8 ohms I am good?

    Hughes & Kettner Hughes & Kettner on November 15, 2016 Reply

    Depends on what your head is rated at Joe – depending on how you hook those cabs up they’ll be either 4 or 16 ohms. If that fits, then you’re good to go… 🙂

megacreon on November 2, 2016 Reply

Great article. Do the rules change for combos with external jacks? Commenters on some forums I’ve read have different advice for matching impedance. They want me to believe that I cannot connect an 8ohm cab to my peavy classic 20. The jack on the back says “16 ohm minimum.” Am I therefore in a nothing under 16 ohm situation?

    Hughes & Kettner Hughes & Kettner on November 4, 2016 Reply

    Thanks! Hmm, are you meaning you’d disconnect the amp’s standard 16-ohm speaker, or does the combo offer the option to run the built-in speaker aloing with an extra cab connected? Because that could change things 😉 But generally speaking, most tube amp companies don’t recommend you run ‘mismatched’ setups.

Alexander on October 28, 2016 Reply

Hey guys,
just bought a Tubemeister 5 head (great tone!). I have a 4 ohm 10″ cabinet which i can use following your rules on the 8-16ohm Output.
BUT: there are so much different informations in the WWW that I’m not sure if i should try… 🙁

Maybe important: I would play with this combination only at low bedroom level!

Thank you for reply,

    Hughes & Kettner Hughes & Kettner on October 28, 2016 Reply

    Hi Alexander, and thanks for your question! Yep, there’s loads of conflicting info out there online, but you’ve come to the right place here 🙂 You can try that setup, yes, it’s the same as our Case 2 scenario. Actually, starting quiet is always our recommendation, so the fact that you just want bedroom volumes is maybe even a good one 😉 Happy playing!

Ryan on October 25, 2016 Reply

My biggest concern is if this article is applicable to just H&K’s or universally. I’d hate to blow up my Marshall if I used info that was only intended for H&K owners.

    Hughes & Kettner Hughes & Kettner on October 28, 2016 Reply

    Hi Ryan. That’s an interesting point. All our blogs are written from general perspectives, and our guys have all played many different amp/guitar/gear types. Our guy who wrote this blog has played every amp under the sun (so you can assume he’s had his fair share of Marshall experience too!) and he’s never blown an amp up in all the time he’s been playing.

    That said… if you have any concerns, don’t try the stuff in the blog. And, if you’re playing another brand, they might make different recommendations to us. You can always try asking Marshall. We’d try it, of course, because we like trying stuff, but you never know.

    And, another point is that our amps are generally very forgiving when it comes to unmatched setups – others might be different.

    Bottom line: if you want to try anything mentioned in this article with your Marshall, ask them first what they think. We’re pretty sure they’ve got some decent advice on the subject too!

beau on October 25, 2016 Reply ive been reading the comments and replys along with the article above. would just like to clarify: H&K attax 100 head says MIN 4 ohms, while i have a 4X12 cab at 8ohms. is this ok?

    Hughes & Kettner Hughes & Kettner on October 28, 2016 Reply

    Hi Beau. Yep, if your head says MIN 4 ohms (i.e. minimum four ohms), an 8-ohm cab is just fine 🙂 You can rock away in peace with that!

Ivan on October 18, 2016 Reply

Thanks for your time.
Yeah a real shame, cuz i wanna play right now! hehehe. But i guess is better to wait. And i didn´t know that some amps have that Direct connection, Must be awesome for night recordings!!

Again, thanks for your help, and for this great site. We learn more and more each day.


    Hughes & Kettner Hughes & Kettner on October 28, 2016 Reply

    No worries, that’s what we’re here for 🙂 Yeah, that’s exactly why we make them! Our slogan is “Rock on Stage. Play at Home. Record at Night.” Because that’s what our amps let you do 😉

    All the best, and enjoy your new setup when you finally get it!

Ivan on October 11, 2016 Reply

Guys here’s the manual for the Peavey KB/a 100
Im totally noob about charts and impedances or so…

Thanks again

    Hughes & Kettner Hughes & Kettner on October 17, 2016 Reply

    Hi Ivan! Good news: your English is awesome, we understood everything you asked 🙂 Bad news: we wouldn’t recommend you connect your DSL amp head to the Peavey. You could try asking the Marshall guys what they think, but we’re pretty sure they’ll also say it won’t work. It’s a shame that amp doesn’t have Red Box DI like our amps do, or you’d be able tp plug into your computer very easily! Hmm, and on the other question: the DSL has thrree speaker outs on the back, so you can easily connect cabs with different ohm ratings (8 ohms or 16 ohms). You can also switch the power from 100 watts to 50 watts, but that’s by using the Triode/Pentode switch 🙂

    Hope this helps a bit, and we hope you can be patient until your cab arrives in December! (Looks like a cool cab by the way…)

Ivan on October 11, 2016 Reply

Awesome blog, ive read a lot of questions and answers, but i have a big question. Hope you can help me.
Recently i´ve bought a Marshall DSL100H,
but i cannot buy my cab until december.
I own a Peavey KB/A100 which is for Keyboard and acoustic guitar,
(i was playing my electric guitar here/with some pedalboard).
My question is: Can i link my Marshall to the Peavey via power amp?
Or is there any way to connect it? I cannot wait till i get my new Cab.
Sorry for my bad English.
BTW my new cab will be a Randall 4×12
which i think will match my Marshall head.
Oh and one more thing, the Marshall has a switch for changing 8ohm-4ohm. Someone said from 100w to 50w… is that true?


MARK PEARL on October 5, 2016 Reply

I have a two part question
#1 can I change a 4 ohm bass guitar cabinet into an 8 ohm cabinet? Does it have something to do with the crossover???
#2 I am using 8 ohm bass speakers in a cabinet that is rated at for ohms, how can I wire them up to match the 8 ohms of my Bugera Veyron tube head rated at 2000 watts? Do you have a schematic on how to wire them up in parallel?

    Hughes & Kettner Hughes & Kettner on November 4, 2016 Reply

    Hi Mark. Hmm, we don’t have any relevant schematics that could help you – you would need to go to the maker of your cab for that. Unless it’s an H&K one, then we can help, so let us know 😉 Work like that can be done, but it’s of course complex and something for an experienced tech…

Ryan on September 15, 2016 Reply

So silly question, I have yet to buy an amp and I’m doing all the homework I can to find what is best for me. Now I do have an old Crate 4×12 cab and the speakers and wires are blown, so I am planning on buying Celestions due to I know the quality and sound is great. So how should I match these? I don’t need a huge amount of sound but I do want Grade-A tone. I am going to buy a Marshall head so should I try to find a head I like with around 100 whats and 16 Ohm? And if I went with that head then how should I do the speakers? 4×4 ohms in series? or 2 sets of 16s in series and run those in parellal? Any suggestions needed!

    Hughes & Kettner Hughes & Kettner on November 21, 2016 Reply

    The best thing to do Ryan is take the head to a store and find the cab that sounds the best for you. YOu can then model your own custom cab on that 🙂

Atrend USA on September 14, 2016 Reply

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Shayne on September 11, 2016 Reply

I have 2 4 Ohm 2×15 cabs, can I wire one somehow so that instead of taking it down to a 2 Ohm load that I would somehow get a 8 or 16 Ohm load? Thanks for the help!

    Hughes & Kettner Hughes & Kettner on October 28, 2016 Reply

    Hi Shayne. Yep, you could wire them in series to get a total of 8 ohms together, and that would work just fine. Just Google around and there’s plenty of guides telling you how to do just that 🙂

Malcolm Bates on September 5, 2016 Reply

Hey, so I have a Vox AC10 amplifier with a 16ohm speaker output, and a 4ohm 4×10 cab. If I were to use it, would that be unsafe for the amp?

    Hughes & Kettner Hughes & Kettner on October 17, 2016 Reply

    Hi Malcolm, you’re sort of on our limit there. We’d do that with an H&K setup, albeit starting by proceeding with caution. To be 100% sure on this one though, you might try asking Vox themselves what they think 🙂

Rob on September 2, 2016 Reply

Hey! Thanks for the reply the amp is a krank rev jr pro and it is switchable between 8 and 16 ohms and my other amp is a b52 AT 100 and it’s switch able between 4, 8. And 16 ohms both would be plugged into a 2×12 cab with 75wt 16 ohm speakers. I’m new to all this, all my previous amps were solid state. So I’m trying to learn all this.

Thanks again!

    Hughes & Kettner Hughes & Kettner on November 21, 2016 Reply

    No worries Rob, but we’re confused now 🙁 Do you have one amp head and two cabinets, or two amps and one cab as you say in this last email?

Al on August 22, 2016 Reply

Hey, guys. This has been the most informative (and fun) article I’ve read on the subject. I notice a lot of people asking questions about this amp or that speaker. I have a different kind of question.
I’m currently building a 212 cab, using 2 Celestion Greenbacks (16ohm, 25w each). Since I have multiple amps I might use and two 1/4 inch jacks on the back, I’d like to make one 8 and one 16 ohm. Then, depending on which amp I’m using, I simply plug into one or the other jack.
My question is this. If I leave ALL the wires plugged into the speakers at all times, will the audio signal travel back over the wiring (parallel/series) and cause problems? Would I then need some kind of switch/break in the circuit I am NOT using? For the record, I would prefer my speaker and amp impedances to match.
Thanks for some great input and (hopefully) an answer to my own question.

Rob on August 20, 2016 Reply

I have a amp that is switchable from 16 to 8 ohms, it’s plugged into 2 1×12 cabs, each with a 16 ohm speaker. I run a cable from each output on the amp to each cab. So should i run the amp at 16 ohms or 8ohms? I’m afraid to turn it up loud.

    Hughes & Kettner Hughes & Kettner on September 2, 2016 Reply

    Hi Rob, most likely run the amp at 16 ohms, but do us a favor and let us know the model/make first so we can check it out 🙂

Stefan on August 19, 2016 Reply

Wait…I’m confused. How can a 16 ohm cab potentially harm a 4 ohm output from an old Fender Twin? I thought more ohms on the load end would just pull less current from the amp? Is that incorrect? Please clarify…

Thank you and awesome article!!

    Hughes & Kettner Hughes & Kettner on August 30, 2016 Reply

    Thanks for the kind words Stefan! You’re right about the current. The thing is though, most amps and cabs work best when the impedances are matched, and you can run into issues with certain setups if they’re mismatched. Like we say in the blog, we’d be happy running an 8-ohm amp into a 16-ohm cab, but more than double is pushing things a little… And we’d never recommend people try stuff with amps from other brands than H&K if they’re not sure, as we don’t want anyone to attempt anything potentially dangerous or damaging their amp after reading this blog 😉

Nando Vieira on August 10, 2016 Reply

Having a Marshall MG15CF (8 ohms), can I use with a Marshall MX412A cab (16 ohms) safely? As per case 1, I think so. Is it going to be any louder?

    Hughes & Kettner Hughes & Kettner on August 11, 2016 Reply

    Hi Nando. Hmm, we Googled that amp and it doesn’t appear to have any option to attach an extra speaker cab! So in that case, you can’t use it like that unfortunately 🙁

Logan on August 7, 2016 Reply

Great article, but I just want to make 100% sure…I have a Peavey 5150 combo that says 16 oh for the external speaker Jack. But all I have is an 8 on cab. I’m okay right?

    Hughes & Kettner Hughes & Kettner on August 8, 2016 Reply

    Hi Logan. Hmm, this is like Case 2 in the blog, so it’s something we’d happily try with an H&K amp. We checked the manual for the 5150 combo though, and it says you shouldn’t use any cab with less than 16 ohms… So make of that what you will 😉 You could try asking Peavey themselves to be 110% sure.

Glen Kimura on August 5, 2016 Reply

Ok, I have a peavey VTM 60. 4 16 ohm outputs or 16,8,4 ohms. I have 2 8ohm cabs,can I hook both to the vtm at the same time? Thanks!!!

    Hughes & Kettner Hughes & Kettner on August 8, 2016 Reply

    Hi Glen, sure: just run the two cabs in parallel for a total impedance of 4 ohms 🙂

Eian Lopez on July 26, 2016 Reply

I have a peavy vyper 15w combo. It puts out 4 ohms, and I want to put a 12″ speaker that puts out 16 ohms. Would that be possible?

    Hughes & Kettner Hughes & Kettner on August 8, 2016 Reply

    Hi Eian, you mean a cab with 16-ohms impedance? That’s a no-no, we’d say – for an amp with a 4-ohm output, we’d not use a cab with more than 8 ohms, like we mention in Case 1 of the blog here…

Ian on July 16, 2016 Reply

Hey people, I am a clueless HiFi wannabe, but I recently bought some cool Grundig + Metz equipment and want to try to set them up but I need a little help from someone who knows what they’re doing. Anyone care to take a look? Thanks in advance.

Guitar Sound Guru on July 8, 2016 Reply

Great Blog! Very useful!

sainuddeen sp on June 8, 2016 Reply

i have a amplifier with two output terminals one out terminal with 16 ohms aother with100 ohms and two speaker box with 16 ohms each now how i can connect these two speakers box with terminal 16ohm or terminal100ohms? please

    Hughes & Kettner Hughes & Kettner on June 15, 2016 Reply

    Hi Sainudden, we’re not 100% sure what you mean. Do you have pictures of the amp/speakers you can show us?

papatom on May 20, 2016 Reply

I need amp load 102.. I want to put an 8 ohm JBL 2225H 8 Ohm, ,400W 15 inch Low Frequency Transducer Speaker and change the existing copied JBL D130F 15 inch 4 Ohm speaker made by or copied by Eminence, the one they are putting into the latest Black Face 1965 Twin Reverb Custom 15 Fender Tube Amplifier that is a 4 OHM Load, 85 watt rating. The rule of thumb I remember was as long as the impedience was more it would be ok, that is an 8 ohm into a 4 ohm output transformer but I’m old guy now I forget and this is tube as well. can it be done. I believe the output transformer is not a varible type and says 4 ohm output.. or I was thinking of using two 4 ohm Alesis 200 watt Dome Tweeters and wiring them in series to 8 ohm and installing the JBL 2225H 8 ohm 15 400 watt speaker and then paralleling them together to make the load 4 ohm.. can this be done? and with a 85 watt Fender twin reverb custom 15 amp.. thank you..

    Hughes & Kettner Hughes & Kettner on June 15, 2016 Reply

    Hi papatom. Hmm, like we said before, it would really be best in this situation if Fender themselves give you guidance – it’s a call we can’t make with their newer tube amps. If it was an H&K setup, we’d be more comfortable, that’s for sure 😉 Did you shoot an email to the guys from Fender yet. and have you heard back from them? We’d be interested to know their thoughts on the matter…

JL on May 18, 2016 Reply

Regarding your chart, a 16 Ohm output into a 4 Ohm load sounds dangerous as the differential is to high. maybe into 8 at best? Can that really safely be done?


    Hughes & Kettner Hughes & Kettner on May 19, 2016 Reply

    Hi JL. You’re right, you’re defintitely on the border there, and some amps might not like it at all (and going under 4 ohms is something we wouldn’t do!). Of course it’s optimal to have a perfect match for things like this, but we’ve tried and tested these situations with H&K amps and have been OK…

papatom on May 5, 2016 Reply

I was disappointed to see you didn’t use a 4 ohm with 8 ohm speaker. I’m getting old I use to know this stuff. But I don’t know how the newer Fender Tube Amps. Here’s my question. I have a NOS JBL 2225 H/J 15 inch 8 ohm 300 watt speaker. The Fender Twin Reverb Custom has the remake by Eminence JBL 130 copy that is 4 ohms. I don’t like Eminence.. I use to know as long as the ohm rating was higher then the amp ohm output, it wouldn’t harm the amp..however with age, well you know.. If I put the 8 ohm JBL 2225 H/J in the Fender Twin Amp.. will the common adjust to taking that speaker without over heating the output transformer and tubes. I know if you put a 4 ohm speaker in an 8 ohm speaker that would cause a problem. because of wattage draw. I’m not sure if the new amps.. even though they say the Fender Twin Reverb Custom 15 amp is supposed to be an exact copy of the 65 black face. I’m not sure. Your help would be greatly appreciated..

    Hughes & Kettner Hughes & Kettner on May 19, 2016 Reply

    Hi papatom, this is a tough one (your specific case), and we wouldn’t want to say with certain what the situation would be with regards the Fender amps. Have you tried asking them directly? We wouldn’t want to give you any advice that could potentially cause damage to your amp 🙂

    Anyway, as we say in Case 1 in the blog, we’d be happy to run a 4-ohm output H&K amp into an 8-ohnm speaker (it’s double, so borderline, but doable). In fact, we tested all this stuff with our amps before we wrote this blog. Our rule here is generally don’t go more than double or halves! Stay within those boundaries with H&K amps and we’re sure you’ll be just fine, especially if you take it easy at first, and if necessary get a qualified tech to make the alts and check over the amp for you before you play it.

Rick Verlander on April 29, 2016 Reply

I have a Blackstar HT Club 50. I has speaker outs that allow for running one 8 ohm cabinet alone, two 16 ohm cabinets in parallel, or one 16 ohm cabinet alone. It specifically states “The output marked ‘1×16 Ohm’ should never be used at the same time as any of the outputs marked ‘1×8 Ohm or 2×16 Ohm’. Failure to correctly match the impedance of the amplifier and speakers will damage the amplifier.” I presently own a Blackstar HTV 212 cabinet that allows for 8 ohm mono usage or 16 ohm stereo usage. I wanted to get a Hughes & Kettner closed back 2×12 to stack with the Blackstar, but it is rated at 16 ohms. It would appear that attaching the H&K cab to the 16 ohm mono out and the HTV 212 to the 8 ohm mono is not acceptable…the warning states that. What about attaching the 16 ohm H&K to one 16 ohm “stereo” out on the amp and the 8 ohm Blackstar to the other 16 ohm “stereo” out on the amp? I gather that the over ohms would be 5.3333 {16×8 divided by 16+8}, but one 16 ohm out would be running into an 8 ohm speaker and the other 16 ohm out would be running into a 16 ohm speaker. Is that a problem? Would the closed back H&K 16 ohm speaker be significantly less in volume? Would the amp be overworked ? Thanks for any help on this.

    Hughes & Kettner Hughes & Kettner on May 2, 2016 Reply

    Hi Rick. Hmm, your amp doesn’t actually have a stereo out, as far as we understand (the 2 x 16 ohm inputs are not for stereo, they’re for two separate 16-ohm cabs). Just because your cab is able to work in stereo, doesn’t mean the head also is. And we’re also concerned about Blackstar’s warnings. With some amp makers, mismatching is a defninite no-no. You’d have to ask them about that, but their warnings look pretty clear to us.

    As we wrote in the blog, we’re fairly open to the idea, if it’s approached carefully and sensibly. And indeed, with an H&K amp you’d probably be alright in this position (see Case 3 in th blog). But, just to be safe, we’d recommend you ask the guys at Blackstar and see what their opinion is on the matter. When you get an answer, we’d be interested to hear what they have to say, so please let us know 🙂

Mike on April 11, 2016 Reply


I need some hand holding here. I have a Fender Blues Junior NOS, it is 15 watts into 8ohms and the speaker in it is a Jensen C12-N 50 watts 8 ohms. I want to add a second exact speaker, separate cabinet. Can you use a Y Cable or the Power Y Box? If so, should it be series or parallel? Or, if I want to run 2 speakers, do I need to buy 2 speakers with a different ohm rating?

Thanks – Mike

    Hughes & Kettner Hughes & Kettner on April 26, 2016 Reply

    Hi Mike, and thanks for your questions. OK, so with that setup you’re going to run into issues – the two 8-ohm cabs together are either going to be 4 ohms or 16 ohms in total. We know that you’d get away with the 16-ohm figure with an H&K amp, because we’ve tried and tested it a lot 😉 BUt with a Fender, we don’t feel confident to mkae that call, and we suspect Fender would tell you not to do that.

    So, you’re either stuck with the one 8-ohm cab, or, if you desperately want to use two cabs, get two which are both rated at 4 ohms (and wire them in serial to get a total of 8 ohms) or two both rated at 16 ohms (and hook them up in parallel to end up at 8 ohms).

    We hope this is helpful, but just let us know if you have any more quedtions 🙂

doug on April 11, 2016 Reply

I have a tubemeister 36 can i run 2 16 ohm single 12 cabs into a mono spliter into the 8 ohm jack

    Hughes & Kettner Hughes & Kettner on April 26, 2016 Reply

    You sure can, Doug 🙂 This would be like Case 3 in the blog: running in parallel, you’d end up with 8 ohms’ total impedance.

Kent on April 10, 2016 Reply

Since my Grandmeister has only 1 output ( 8-16 ohms) is there a circuit actually recognizing the different impedance of which cab I plug into it?
Example: I have a Jet City 2×12 8 ohm cab (mono). I have a Carvin 4×12 16 ohm cab (mono). Is the GM maximized using the 2×12 and losing output using the 4×12? Or does the GM recognize the 4×12’s 16 ohms and adjust to match it for maximum efficiency?

    Hughes & Kettner Hughes & Kettner on April 26, 2016 Reply

    Hi Kent, and thanks for your questions. We had to ask some of the techier techs about this one 😉

    In your case, the impedance of the cabinets is not actually an important factor. Reagrding the amp itself, the GrandMeister’s output has an impedance setting that equalizes the range between 8 and 16 ohms. So, what you should be thinking about is how many working speakers you have (i.e. two or four) and choosing your favorite sounds based off which sounds better to you. The 4×12 is probasbly going to sound a little louder to your ears, but whether that’s better or not is down to you 🙂 Tone is subjective, after all!

kevin on March 22, 2016 Reply

This is a little off topic but….when I received my tubemeister18 one of the four black clips that are attached to the glass faceplate broke off during shipping. Do you know who in the USA can get me parts for my amp?

    Hughes & Kettner Hughes & Kettner on March 23, 2016 Reply

    Hi Kevin, no worries 🙂 Hmm, in America it would be our distribution partners, Yorkville. Here’s their contact details:

    Yorkville Sound, Inc
    4625 Witmer Industrial Estates
    14305 Niagara Falls
    Tel.: +1 7162972920

    Give them a call or shoot them a message and they’ll be able to put you right!

Peter on March 19, 2016 Reply

Hello! I have two amps. A Bassman Head and an Orange Tiny Terror. Im willing to buy a Tubemeister Combo.
My Bassman Head has two taps: 4ohm and 8ohm.
Can i run a 16ohm cab and a 8ohm cab at the same time in the two taps, like 16ohm speaker in 4 tap and 8ohm speaker in 8 tap or 8ohm speaker in 4tap and 16ohm speaker in 8tap?

    Hughes & Kettner Hughes & Kettner on March 22, 2016 Reply

    Hi Peter. Hmm, we don’t know how the two taps on the Bassman Head are wired (you’ll have to ask Fender about that!).

    But anyway, we wouldn’t recommend you plug them in separately like this. Instead, we’d just recommend you go from the 4-ohm out on the Bassman and connect the two cabs to that in parallel – then you’re safe 🙂

Ivan on March 19, 2016 Reply

Good information, but awfully wordy. Just the facts, ma’am!

    Hughes & Kettner Hughes & Kettner on March 22, 2016 Reply

    Ha, thanks for the feedback 😉

Kevin on March 14, 2016 Reply

I have a new tubemeister 18 head and one H&K TM112 cab. My question is…Can I add a second TM112 and run both TM112’s at the same time? I guess that would essentially bring my 16ohm load down to 8?

    Hughes & Kettner Hughes & Kettner on March 17, 2016 Reply

    Hi Kevin, you’re absolutely right – you can do this no problem, and connected in parallel you’ll end up at 8 ohms! Hope the helps 🙂

chris charlong on March 12, 2016 Reply

hi,i just bought a new h&k tube meister 36head and i have two 10 inch 50 watt 8 ohms marshall speakers ,that i want to install into a cab,this is the first time i ever had a tube amp and was just wondering if the would be good to use

    Hughes & Kettner Hughes & Kettner on March 17, 2016 Reply

    Hi Chris, if the speakers were to be connected in series, you’d end up with 16 ohms, which would work just fine with the TubeMeister 🙂 Are you doing the work yourself, or is a tech going to do it?

Igor on March 12, 2016 Reply

Hey there!

Not a lot of talk about 2 ohm cabs on here. I own a Acoustic 4×15 rated at 2 ohms, I recently purchased an Orange ad200b rated 200 watts at 4 ohms. Would this work? Wouldn’t this increase the power of the Orange and run the risk of frying the amp?


    Hughes & Kettner Hughes & Kettner on March 17, 2016 Reply

    Hi Igor, 2-ohm cabs are fairly rare! We’re not familiar with that cab, unfortunately, so you should ask Orange what they think about this. If it was an H&K amp, we’d say you could give it a gentle try, but we can’t make that call for Orange, so it’s safest to check with them 😉

Jérôme BASSEVILLE on March 9, 2016 Reply

I have a Grandmeister 36 running into a Tubemeister 112. I would like to buy another Tubemeister 112 and put these 2 in parallele. If I understand correctly what you explained in this post I will get an impedance of 8 ohm which match perfectly with the Grandmeister 8 ohm output. But my question is, is this the same thing to plug the Grandmeister into 2 Tubemeister 112 and plug the Grandmeister into the Tubemeister 212 ? Another question is will I get a stereo sound whith this set up ?
The fact that the Grandmeister gets only one output, can we get true stereo sound ?

Kind regards,

    Hughes & Kettner Hughes & Kettner on March 17, 2016 Reply

    Hi Jerome, and thanks for your questions! OK, so let’s answer them one at a time. Firstly, yes: running the 2 16-ohm cabs in parallel will give you a total impedance of 8 ohms.

    Running two TM112s is different to running one TM212 – two 1x12s sound different to a single 2×12, and the impedance is different. But the result is not all that far away from each other – so we’d advise you try both options and see what works for you. The third option – where you mix a TM112 and a TM212 – is similar again, but you’ll get more low end thump with this, and a little more volume and power. Again though, you’ll end up with a total of 8 ohms impedance.

    You can’t get true stereo sound by doing this, no. For that, you need two power amps to be in operation.

    We hope this is helpful, but just let us know if you have any more questions! 🙂

    Team H&K

J J on February 24, 2016 Reply

Randomly found this blog, still trying to figure out impedance..clearest explanations I’ve found yet, by the way.
But what really struck me was even when the question is clearly related to another company’s gear, you still give a decent answer where possible..

Super classy!

That’s all..


    Hughes & Kettner Hughes & Kettner on February 26, 2016 Reply

    Thanks JJ – we always try our best to help people out no matter what they’re playing! We’re all guitarists at the end of the day, after all 🙂 And we’re glad you found the blog useful! If you ever have any questions on impedance or anything else guitar-related, feel free to ask us any time…

Jeff on February 21, 2016 Reply

Thanks for the reply.

I sold the Line6 cab before being brave enough to try it with the TM18……but then managed to get a good deal on two TM212 cabs. That is working perfectly. One cab stays at home to practice there. The other stays at band practice so I only need to take guitar and TM18 between the two.

For small gigs I just take the one TM212, and take both for a convenient 4 x 12 setup to larger venues.

    Hughes & Kettner Hughes & Kettner on February 23, 2016 Reply

    Aha, good to know that the TM212 pair is doing the business for you then! You’ve got the perfect solution for every situation now 🙂

Scot on February 20, 2016 Reply

I am considering to purchase a Bugera 333XL Infinium which has ohm selections for 4/8/16 which is great. I already own a B52 AT412A cabinet and understand 100% how to hook it up in mono using 4 or 16 ohms. However I am curious about using the cabinet in stereo given the two outputs of the guitar amp are in parallel? The cabinet is rated at 8 ohms per channel in stereo so which ohm setting on the amp would work best since I would be using both outputs? Thanks in advance!

    Hughes & Kettner Hughes & Kettner on February 26, 2016 Reply

    Hi Scot, without having any experience with this amp ourselves (or the cab, for that matter!) we’d say that the best thing to try would be to switch the head to 8 ohms and connect both outputs and inputs. However, to be 100% sure you should ask the guys at Bugera – they’re sure to know this one slightly better than us 😉

alex on February 5, 2016 Reply

Can i hook up my carvin v3 100 watt tube amp with an output of 16 ohm to my carvin 412v 300 watt cab set to 16 ohm? or would my amp need to have an output of 8 ohm to run a 16 ohm cab? i have a option of 4, 8, and 16 ohm on my head but, only 8, and 16 ohm choice on my cab? what is the safest way to hook this up without losing tone?

    Hughes & Kettner Hughes & Kettner on February 9, 2016 Reply

    Hi Alex, a 16-ohm amp to a 16-ohm cab is a perfect match, and an ideal setup 🙂 Go with that, as that’s clearly how Carvin designed them to be operated!

Dennis on January 11, 2016 Reply

I have a peavy 6505+112 combo, which is 16ohm
Which on the back has a switch I can go from 4-8-16 ohm paralleled
I have a Marshall 4×12 8ohm 120watt cab,
to run the cab I just switch it to 8ohm on the head?
And just out of curiosity can I run combo n cab both together or is it smoke time for the amp cheers

    Hughes & Kettner Hughes & Kettner on February 17, 2016 Reply

    Hi Dennis. Yep, to run the cab through the combo, just switch it to 8 ohms and you’ll be fine. You can’t run the combo’s built-in speaker and the cab together really. If you were to have two cabinets like this, though, it’d be a case of one 8-ohm and one 16-ohm cab giving you a total impedance of 5.333 ohms – so you’d use the 4-ohm switch 🙂

JonMc on January 6, 2016 Reply

Hi, great article but I have a question. I have a solid state head with two 8 ohm outputs one of which is driving a 8 ohm 2×10 cab. If I decided to run another cab off the same amp what resistance cab would I be looking at?

Thank you.

    Hughes & Kettner Hughes & Kettner on February 17, 2016 Reply

    Hi JonMc, thanks for the kind words! OK, so if you’Re running two 8-ohm cabs off the one amp like this, you’d end up with a total resistance of 4 ohms – meaning it’d be just fine to do 🙂

Jeff on January 3, 2016 Reply

This is the best article I have read on this subject. I really understood it with the clear reference chart and case examples. With support like this it makes me even more confident in my Tubemeister 18 purchase. However, some of your replies really confused me. May 7 – 4ohm head into 16ohm cab advised as OK, but case 1 says keep to the double rule as more dangerous than case 2. But here the cab is 4 times the head?

This next confusion is even important to me as I have a Tubemeister 18 NOS arriving in a couple days and I don’t want to risk any damage:

April 23 2015 – TM5 8/16ohm into 4ohm cab advised as OK. This keeps to the case 2 1/4 rule and not lower than 4ohm so I agree should be ok. Contradicted by:

July 10 – TM18 8/16ohm into 4ohm cab advised as not ok, but this also keeps to case 2 1/4 rule and above 4ohm?

This is important to me as I have Line6 Spider 4×12 cab which has a 4ohm mono connection, which I thought should be ok with the TM18. If it auto selects 8ohm the cab is 1/2 so ok. If it selects 16ohm I am also ok as the cab it 1/4. I wonder which option to TM18 would auto select? I guess 1/2 is a better match then 1/4?

The spider cab also has two 8ohm stereo inputs, so is there a magical cable that will plug into the single TM18 output but then split into 2 in series for 16ohm matched head/cab heaven? Or is it already wired in parallel inside the cab hence the 4ohm mono connection option???…….I think I now need to find a Hughes and Kettner article on cable/wiring options showing parallel/series and mono/stereo configuration.

Thanks for the article and comment responses.

    Hughes & Kettner Hughes & Kettner on February 17, 2016 Reply

    Hi Jeff, thanks for your comments and feedback! Yep, there’s so many questions and answers in here it can be hard for us to keep track, especially when there’s a couiple of people answering stuff 😉

    Anyway, let’s look at your issues on their own. Disregard everything else for now 😉 The Line 6 cab with a 4-ohm connection will be just fine – it matches Case 2 in the blog, and you’re easy either way. All the fancy gubbins in those Line 6 cabs is apprently there because their cabs are built and matched to workj best with their heads. So apparently you’ll get a flatter sound than you would with a more standard 4×12, although we’ve not tried it so don’t know! It’d actually be really cool if you could plug in and let us know your experiences with this 🙂

Shawn on December 31, 2015 Reply

Yes I just want to use the redbox signal on my tubemeister 18. Do I have to have a cab connected if I have it set to silent mode?

    Hughes & Kettner Hughes & Kettner on January 6, 2016 Reply

    Hi Shawn. No, with the built-in Red Box on the TubeMeister amps (and the GrandMeister!) you don’t need a cab connected at all! Just plug and play…

Shawn on December 27, 2015 Reply

Hello maybe someone here can help me, I have a Marshall Vintage Modern 2466 100 watt head, and Im having trouble, I recently purchased a Mojotone 2×12 Bluesbreaker cab with 2 – Celestion Heritage 30’s at 8ohm wired to 16 ohm. for some reason Im not getting any output out of this new cab, the head is switched to 16ohm setting. I know its not the Marshall and I tried another Marshall Head with this cab and still no output, the only thing I can think of is the wiring in this Mojotone cab is messed up. if anyone has any suggestions please let me know thank you.

    Hughes & Kettner Hughes & Kettner on February 17, 2016 Reply

    Hi Shawn, this is confusing and we think the wirting must have something wrong somewhere. Take it to a tech and see what the issue is! Anyone else on here have experiences or suggestions with this kind of thing?

Rob on December 24, 2015 Reply

… a whole lot of speedtyping errors in my last post 😉

I didnt notice the application in the text were tube amps.
It should be noted, because of the difference.

You can erase my post before of you like.

I should have put a little more in that example.
Had a hurry because of the christmas and all.

Rob on December 24, 2015 Reply

Utter B.S – typical when musicians boasts about how fidelity works.

It can be said and explained right in much simpler ways.

In short, no tone will be altered. Just output from the amp, and sound spl overall.
If you paralel the speakers versus connect them in series, the load (Ohm) the amplifier will “see” doubles or halves. Therefore you could mix and match to be best for the amp.
And the load (ohm) fluctuates with low or high frequensies – and ZERO ohm is literally a short-out – so if not a really powerhouse of an engine (google “power cube” in relation to amps to get a clue) you should never get under 4 ohms. Because of the fluctuation.

If an amp outputs, say 250W in 8 ohm, and it got a really unusual “power cube” it should double the output in 4 ohm, and you get half of that 250W in 16 ohm – thats 125W.

And what will actually happen? – well, most guitar elements has a high spl output with just 1W, compared to most home-speakers.
97-99dB is not unusual.
That is the output with just 1W.

So, in my 250W example, you got quite a lot more juice to crank the element with.
The elements can take different amounts of wattage before it give up.
But more is less bad than to little.
Distorsion because of to little is what kill them, usually.

The can
binet (bass reflex, closed etc.) will affect the lot, though…

And also google what it takes in W to double the sound pressure and what it takes to really hear that doubled difference.
Then just calculate upwards from your speced spl/1m output and amp in your element resistance, and the max power rating for the element.

Simple as that.

Tone can be affected, but nut scientificly in the matter described in the above article.
Its is too generalized.

Mox on December 20, 2015 Reply

nice … so i read all article .. and for me its me most complete article i found about this .

So i have a question.

I have a Randall Rd100 with a back panel with one 16ohms output , and two paralels outputs ( swichable in 8 or 4 ) ohms , cab be used at same time , but the 16 ohms can just used alone .
Rear :

and i use my blackstar HTV 212 – with 2 celestions seventy 80 inside at 16 ohms . i plug every time this cab in mono output ( 160 rms ) with 8 ohms .
in a paralel output of the amp

now i buy a nem cab , with a amazing sound with a 2 celestions ( one k100 and other v30 8 ohms each ) inside in 16 ohms in serie i think . ( the cab have just one plug )

I like it to plug the two cabs ant the amp , in the two paralels outputs .
Can i do it ?
Its possible ?
How i can do it ?

the sound of the cabs are amazing , to play live its the best for me .. but …

    Hughes & Kettner Hughes & Kettner on February 17, 2016 Reply

    Hi Mox, and thanks for the cool feedback! We’re glad the article could help. 🙂

    OK, so in your case here, you should be able to use both cabs together. With a 16-ohm cab and an 8-ohm cab together in parallel, you have a total of 5.333 ohms. So just use the 4-ohm output on the back of the head and you’re good! Hope this helps some more 🙂

Jay on December 17, 2015 Reply

So, I’ve got an Albion TCT 50 head, rated for 8 or 16 ohm output.

I stumbled across a great deal on an 4 x 8 mini cabinet, but it’s only rated at 4 ohms.

That being said, should I go for the deal? Or will I risk damage to the amp by trying that setup?

Thanks! Great article.

    Hughes & Kettner Hughes & Kettner on December 18, 2015 Reply

    Hi Jay, and thanks for the kind words! Hmm, this is a tricky one – 4 ohms is on the border of not being good for the head. Because it’s such a good deal and an usual cab you’Re not likely to find anywhere else, you could give it a gentle try in the store though, and perhaps ask the tech there for their thoughts too…

Wes on December 14, 2015 Reply

Hi, I have a guitar head with 3 outputs 1x16ohm and 2x8ohm I want to connect 2 1×12 cabinets. Which is the best way to do? (both cabinets are 16ohm and have NOT option for series connection)

    Hughes & Kettner Hughes & Kettner on February 17, 2016 Reply

    Hi Wes, use the parallel out 🙂

Alan on December 10, 2015 Reply

what should i expect if i use an HK 8in pa full range speaker cab with a EV 15in pa full range cab,on each side.I am putting very loud backing tracks, 2 vocals and very loud gary moore style guitar,in full pub and club idea is to enhance the female vocal with out messing anything else up,any surgestions of help please.

    Hughes & Kettner Hughes & Kettner on January 6, 2016 Reply

    Hi Alan. What speakers exactly would you be using there? In theory the setups you mention should work just fine – just tinker them to fit each venue, and make sure your guitar is not killing everything else 😉

    Hughes & Kettner Hughes & Kettner on December 7, 2015 Reply

    Hi David. A quick Google search shows up that this cab has a mono 4-ohm input and stereo 8-ohm inputs – so there’s your answer! Hope this helps, but let us know if you have any more questions 🙂

Bob on November 26, 2015 Reply

So I have a Tubemeister 36 and a Laney IRT Studio (at home) that I’ve been using with the TM112 cab. I’m not a huge fan of the v30, I find it too treble-y. I was considering getting the TM212 and switching out either both or one of the v30’s for g12h30’s. How is the TM212 wired, series or parallel? I’m guessing it’s series with the v30’s @8ohms for a total 16ohms.

Since both of my amps only have 8 and 16 ohm outputs, I’m stuck with either two 8ohm speakers in series or two 16ohm speakers in parallel. As of now, I’m leaning towards parallel, will I be able to do that when I swap out the speakers in the TM212?

    Hughes & Kettner Hughes & Kettner on January 7, 2016 Reply

    Hi Bob, the TM212 is wired in series, as you suspected… 🙂

Zacc on November 25, 2015 Reply

Hi, what would happen if i used my 4ohm output with a 16ohm cab?

    Hughes & Kettner Hughes & Kettner on November 25, 2015 Reply

    Hi Zacc, this is similar to Case 1 in the article, and it should be OK. Start off taking it easy and then gradually build up to where you want it. Our colleague who wrote this article used a 4-ohm head/16-ohm cab combination for years and it never blew up on him 🙂

Gordon on November 9, 2015 Reply

So would it be safe to connect up an 8ohm cab to a 16 ohm valve amp?

    Hughes & Kettner Hughes & Kettner on November 16, 2015 Reply

    Hi Gordon, this would be a mismatch like me mention in Case 2. Always check and see what your amp/cabn manufacturers say too, but generally this is something we would consider! Just take it easy at first and then crank it a bit more once you know it’s going to be OK 🙂

Chris on November 6, 2015 Reply

Hey! I have a Peavey Valveking 212 with an ohm selector switch (4,8,16) on the rear. I am trying to run the combo + an Orange 2×12 (16ohm).. I believe in parallel it would be 5.333 ohms so would I just set the amp @ 4ohms? Is that safe? the speakers in the peavey are 16ohms each, and the orange cabinet is 16ohm. So right now the peavey is set at 8ohms for just the peavey, if I add the Orange 16ohm cabinet into the parallel speaker jack on the back of the amp would that make the total 5.333 and would I set the switch to 4ohms? Or would it be better to daisy chain the two or something? Thanks for any help!!!

    Hughes & Kettner Hughes & Kettner on November 18, 2015 Reply

    Hi Chris. Yes, you’re all good: 8 Ohms and 16 Ohms in parallel are 5.3 Ohms, so you should set the amp to 4 Ohms. Hope this helps! 🙂

Steve hoas on November 2, 2015 Reply

Hello again. In regards to my previous post, I have a Behringer bxl3000 amp that is 300w at 4ohms and has both line out and an effects loop but no speaker out. I was recently fortunate to acquire a Randall 4\12 slant cab with 4 Celestion 8ohm 65w speakers wired for 8ohms. It has become apparent that I cannot use both the built in 15in speaker and the cab as I would be under the safe limmit for the amp. I could use a switching jack and just run the cab butt I am now thinking that maybe I should buy either a power amp or just another amp with effects in forum the cab and forget about trying to run both speakers from the combo amp. Your thoughts please. Cheers,Steve.

    Hughes & Kettner Hughes & Kettner on November 18, 2015 Reply

    Hi Steve. We asked our techs about this, and their first question was: why is Steve wanting to run a bass signal through a guitar cab? 😉

    But then they cheered up and said both of your suggestions would be workable. Their opinion is that you would be better off ditching the guitar-specific cab and just focusing on a kickass bass amp! And our head tech’s actually a bass player, so this is most definitely good advice 😉

danchi on October 31, 2015 Reply

🙂 ok – 2x speaker 4ohm in series wiring = 8ohm

solution is than: get two 8ohm speakers in parallel wiring and you got 4ohm cab, which is than conected to head out 4 ohm.

I think this is best solution. Is it enough two 10″ speakers (200W each) to handle 200W Bass head?

When you go parallel and your 200W 8ohm speaker turn out 4ohm, do you also loose Watt power (200W to 100W) or power stays the same…so, you still have 2 x 200W speakers ?

I am not a el. technician, but I can make my self cables 🙂

thanx !

    Hughes & Kettner Hughes & Kettner on November 2, 2015 Reply

    Hi again danchi! So yes, you’ve got it: 2 x 8 Ohms speakers in parallel will be 4 Ohms. Every speaker can handle 200W, so in total it’s 400W. There you go! We hope this helps, and yes, maybe it will also be useful for some of our other readers 🙂

danchi on October 30, 2015 Reply

So, I need to buy
– two speakers 8ohm -> parallel wiring = into 4ohm out on amp.
– two 4 ohm speakers -> series wiring = into 4ohm out on amp.

Is this right?

big thanx Hughes & Kettner ! 🙂

hope that this info also helps some other guys here

danchi on October 30, 2015 Reply

…looking for ohm info and found you guys. I will try to make my own speaker cab for bass. I read some stuff but, am I right if:
Head speaker output:
– 1x 4ohm 2oow
– 1x 8ohm 150w
I will use 4 ohm out 200w rms

speakers solution 1:
– 2x 4ohm 10″
– 1x 8ohm 8″ or 12″
Am I right 4+4+8=16ohm and I am good to go in 4ohm Head out and get 200w power ?

speakers solution 2:
– 2x 8ohm 10″
Am I right 8+8=16ohm and I am good to go in 4ohm Head out and get 200w power ?

If not, please, can you give me advice what to do , because I am going to get amp and if I want to get those 200w power, I need to buy 4ohm 4×10 box which is alot of money if you want good speakers inside. In other side, idea to get svt 210 which is good speaker for money, but I can put it only in 8ohm and get if I want 200w power from head, than I need to buy another svt210 cab which is no much money. So If I did it my self… I get good eminence speakers with 8ohm per speaker + wood and I will not land over the 350€ at the and I will get 200w rms … if I am right.

Thanx for reply

    Hughes & Kettner Hughes & Kettner on October 30, 2015 Reply

    Hi Danchi, and thanks for your questions. OK, so we had to consult our technical wizards about this, and here is what they said:

    For your speaker solution 1: “No, 16Ohms on a 4Ohms output will be less power. If you connect the 4 Ohm speakers in series it’s 8 Ohms. If you connect these two speakers parallel to the 8 Ohms speaker, you will have 4 Ohms in total. The amp will run on 200W. It’s difficult to use speakers with different impedances in the same cabinet. The 8 Ohm speaker will get less power than the 4 Ohms and the volume will be lower.”

    And for your solution 2: “No, same as above. Connect the speakers in parallel and you will get 4 Ohms total, which means 200W.”

    So there you go, hope this helps! Good luck building your bass rig 🙂

David Lodge on October 30, 2015 Reply

Hi, I have just bought the Red Box 5 and am very impressed with the sound. I am using it in the extension speaker out of an Egnater Tweaker 40. The extension does not turn off the internal speaker. The amp has variable impedance obviously based on what speaker combinations you use. The amp has a 16ohm speaker. My question is, with the Red Box set up in this way (extension speaker) do I need to change the impedance on the amp?

    Hughes & Kettner Hughes & Kettner on October 30, 2015 Reply

    Hi David, glad to hear you’re enjoying the sound of the Red Box! The simple answer to your question is: no. The Red Box has no influence on the speaker impedance, and the amp doesn’t even ‘recognize’ that there’s a Red Box involved. So, just carry on as normal 🙂

steve hoas on October 22, 2015 Reply

Hi y’all.I need some info I haven’t been able to find so far. I have a Behringer 300w combo with a 4ohm speaker. I also have 4/12 cab at 8ohms and would like to run both together.there is no speaker out so would I be better off putting a straight RCA jack in parallel or a shorting jack to take the built in speaker out of the equasion. Back in the sixties we did not care about impeadance we just plugged whatever into whatever and never had a problem. Thanks for any help you can provide Steve.

    Hughes & Kettner Hughes & Kettner on October 26, 2015 Reply

    Hi Steve. Hmm, without knowing exactly which amp you’ve got there… Normally amps like this can handle a minimum load of 4 Ohms so it’s not possible to connect a 8 Ohm cab in parallel – but it’s possible to connect it in series. There are little helper boxes you can get to facilitate things like this, like this one:

    Hope this helps a bit, and that it doens’t go against your 60s philosophy too much! 🙂

Mark on October 19, 2015 Reply

Thx! That was the final piece of the puzzle for me right now.
Thx H&K for the service even though it’s about an older model. Great stuff!

    Hughes & Kettner Hughes & Kettner on October 19, 2015 Reply

    No worries Mark – we always try our best to help out, even if it’s with our older gear! Happy rocking 🙂

Mark on October 19, 2015 Reply

Thx for the reply!
I didn’t mind the wait as it turns out you went out of your way to get me a good answer to my question.

Up until now I have been using both outputs of the head and plugged them into both inputs of the cab. That probably meant I have been playing with a mismatch of 2:1.

That is also the last question I have left. Does plugging in both outputs of the head into both inputs of the cab get me the full 100 watts power?

Fact is that it has not damaged my setup yet. I have no idea whether or not that has something to do with the fact that the cab is a 200 watts cab and the head is only 100 watts. Since I am doing quite a lot of loud gigs with this setup playing in a symphonic metal band that requires some volume at times I was (and am) quite interested in utilising the full power of my setup. And since the second ax412 cab is nowhere to be found for sale (I live in the Netherlands) I wanted to try getting the most out of what I have since the sound still works well for me and right now I just don’t have the money for a new one…

Thx again for the responses. Maybe I will keep on playing with the mismatch (it worked for so long, it probably won’t break down any time soon), maybe I won’t…

    Hughes & Kettner Hughes & Kettner on October 19, 2015 Reply

    Hi Mark. Hmm, using two cables will not make any difference, because 2 x 8 ohms is the same as using 1 x 4 ohms. If you wanted to get the full power out of this rig, you’d need a cab that is switchable to 4 ohms. Which means, for now, you might have to keep on rocking the mismatch 🙂

Mark on October 2, 2015 Reply

This helps somewhat, but I am stille confused as to WTF (exuse my language) H&K were thinking when building this setup. If I plug my head and cab together like you say it leaves me with a 1:2 safe mismatch which is ok but does not utilise all the potential of the head.

If however I were to use both outputs of the head (2 x 8 Ohms) and plug that into the two inputs aof the cabinet (2 x 4 ohms) I’m left with a 2:1 mismatch which might damage my gear. So the way I see it there is no way that this setup is ever going to work properly which baffles me since the head and cabinet are actually made to be sold together.
The only way to make this work is to get another cabinet and then use both ooutputs on the head to both inputs on the cabs. Then however the question remains why there are two inputs on the cabinets that are in that case useless apart from plugging in a second head which will not happen very often I believe.

So I guess I’m still left with two questions (sorry for the long reply here).
– Is my deduction of the possible ways to wire this setup correct or am I missing something?
– Is there a way to utilise the full power and potential of my head and cabinet together and if so how do I manage that?

Thx again!

    Hughes & Kettner Hughes & Kettner on October 19, 2015 Reply

    Hi Mark. Right, apologies for the delay, but we really had to ask around about this one 🙂 We finally got the H&K senior product manager’s personal take on it, so here it is:

    “With solid state power amps, it always tells you the minimum impedance, so there is no 100% impedance match needed like there is with tube amps. For a solid state amp the rule is: never connect a cab with a lower impedance. If it’s higher, don’t worry. So use the 4 ohms output of the amp to the 8 ohms input of the cab. However, it will cut the power down to 75 watts (Mark: see below for more on this). The amp was designed this way to connect two AX412 cabs (each with 8 ohms) to one Tour Reverb Head (use 2 x 8 ohms outputs). Back at the time the amp was made, guitarists were still asking for full stacks 🙂 But no worries, there is neither a risk of damage nor an audible drop in volume!”

    And our head service tech also said this:

    “It’s true, with an 8 ohm load, the power will be around 75W – with 4 ohms it’ll be about 100W. But normally, nobody will hear the difference unless you want to play with maximum clean headroom on a big stage. It’s possible to use the cab’s 4 ohm stereo input to play with 100W, but only with 2 speakers. But this probably will be as loud as playing into the 8 Ohm input with 4 speakers…”

    So there you go – hope this also helps!

Mark on September 26, 2015 Reply

I have a h&m attachment Tour reverb head with two outputs that say 4 ohms or 2x 8 ohms. I want to connect this to my attax cabinet a which is sold with it but the inputs on that state either 8’ohms mono or 2 x 4 ohms. I am confused as to how to connect the two. It seems that there will be a impedence mismatch however i do it, (even when connecting two attax cabinets a and b, which i don,t OWN by the way). Since the cabs are sold with the amp this makes no sense so i am probably missing something…please help!

Do i use the 4 ohms out to the 8’ohms mono in or do i use the 2 x 8 out to the 2 x 4 ohms in.
Or, last option that i can think of but probably impossible. Can i use the right output on the head and will that provider 8’ohms? And the plug it into the 8 ohms mono on the cabinet.

Thx for the help!

    Hughes & Kettner Hughes & Kettner on October 1, 2015 Reply

    Hi Mark. 4 Ohm is the minimum impedances, so you can use a 4 Ohm, 8 Ohm or 16 Ohm cabinet. Just connect your 8 Ohm Mono Input from the box to one of the two speaker outputs (no matter which one, they’re parallel)! Hope this helps 🙂

Jacob Lewis on September 21, 2015 Reply

Please Help!! If I have a 68 custom Princeton Reverb reissue with an 8 ohm impedance load, is it safe for me to use a Celestion alnico gold 16 ohm speaker?

    Hughes & Kettner Hughes & Kettner on September 21, 2015 Reply

    Hi Jacob, you mean as a replacement speaker for the one already in the combo? For that, we’d recommend you ask Fender, as we’re not sure what their official line would be. We’re guessing they won’t like it 😉 But if you’re looking to add an extension cab to your combo, then this should be OK if you take it easy – the results would be similar to Case 1 in our blog 🙂

Mike on September 19, 2015 Reply

I think this information is very helpful but I have a question:
In the first scenerio of mismatching an 8 ohm amp to a 16 ohm cab you say that it usually results in an increase in midrange response. Does this apply to any 1-2 mismatch? For example would there be a boost in mids if you were to put an 8 ohm load on a 4 ohm amp?

    Hughes & Kettner Hughes & Kettner on October 1, 2015 Reply

    Hi Mike! Yes, this is technically the same. But don’t use a 16 Ohm cab on a 4 Ohm output…

Paul R on September 8, 2015 Reply

I’m playing a Tube Combo 2×12 with 8 ohm celestions that would normally run out of the 16 ohm output. It also has outputs for 8 and 4 ohms. I have an 8 ohm mono extension cab running with the amp’s internal speakers. And I have them hooked up to the 4 ohm outputs. Is this the correct setup to run these speakers?

    Hughes & Kettner Hughes & Kettner on October 1, 2015 Reply

    Hi Paul. We’d need to know what the amp model is to answer this question with real certainty. However, in normal circumstances and with most amps, it’s advisable to only use one output (either 1×4, 1×8 or 1 x 16). So, unless your amp manual says otherwise, don’t. Let us know your amp model if you still have any questions about this! 🙂

Scott on September 6, 2015 Reply

Thanks so much for this article.

Just a few clarifying questions:

1) If I am unsure about the ohms rating of a cabinet, can I detect this by hearing which ohm selection (on the head) results in the loudest output from the speaker?

2) As a general rule, can it be stated that an amp head is safe from danger by running a cab that is equal or higher in ohms, or lower in ohms? (I was told higher by some, but after reading this page, I am wondering!?!)

Thanks so much, as we muso’s sometimes need some guidance from beyond the bench…


    Hughes & Kettner Hughes & Kettner on September 11, 2015 Reply

    Hi Scott, and thanks for your questions! OK, so on the first one, no. You should always be able to find the rating written/printed on the cabinet somewhere. If not, check the manufacturer’s website. Or send us a pic/link and we can try and work it out for you! If you’re going to do that, also let us know what head you’re using, and what output that has.

    Secondly, this is a very, very grey area! Generally, matched speakers and amps are the best and safest way to go. However, as our examples here suggest, going both ways can be safe in moderation. Like our writer says, though: “In terms of the amount of mismatching you can get away with here, we’d go with the 25% rule: so, for instance, don’t connect a speaker with less than a 4 ohm output to a 16 ohm amp output!” We guess the general rule is: experiment if you want to, but always take it easy at first, and ask a tech (or us!) before trying somerthing you’re not sure of. And never use a tube amp without a speaker/load connected 😉 Hope this helps a bit, but just let us know if you’ve got any more questions!

Cameron on August 10, 2015 Reply

I own an 8 ohm 4×10 cab and I’m looking for a head to use with it. The problem is that every single head I’ve looked at says minimum 4 ohms. Does that mean that it’s a 4 ohm head and I would get half power? Or does that mean it can be adjusted to work with different impedance?

    Hughes & Kettner Hughes & Kettner on August 11, 2015 Reply

    Hi Cameron. ‘Minimum four ohms’ is exactly what is stated – the minimum value you can go with. But the vast majority of modern-day amp heads will handle 8 and/or 16 ohm speakers without issue – they just don’t want you to go lower than 4 because it can be unsafe to do so.

    Take the first pic in the blog as an example of a modern head that is flexible with speaker connections: it’s one of our amps, and you can plug in anything from 4 to 16 ohm speakers no problem. If you’re still not comfortable with this, let us know which heads you’re looking at buying, and we can let you know if they should be safe for you or not.

Wayne on August 3, 2015 Reply

I have an Egnater Tweaker 88 head. 4, 8, 16 ohm switch on the back. I have two Fender MH cabs that are 4 ohms each, so 2 ohms in parallel. I always run these together with no issues, but is it technically ok?

I also have a Rivera Knucklehead Tre and in the manual it says it’s fine to run a 2 ohm load into the 4 ohm setting. I don’t have the manual for the Egnater so I’m not sure.

I don’t think this would be an amp by amp situation, correct? It would either be ok or not ok for all of them.


    Hughes & Kettner Hughes & Kettner on August 11, 2015 Reply

    Hi Wayne, we found the Tweaker 88 manual on the Egnater site for you here: Unfortunately there’s no specific info in there that solves your issue though 😉

    But anyway, as we said in the blog, going under 4 ohms can be risky (as some amps are just not designed to go that low), and it could cause damage to your rig. But, if amps like the Rivera specifically state that it’s OK, then carry on! With the Egnater, we’d be more careful. Maybe consider asking them directly if they have thoughts on the issue? Because on your last question, it depends on design – some amps are designed to be able to handle certain mismatches, and others don’t like them at all…

Kenny on July 22, 2015 Reply

What are the effects of using a 16ohm head into an 8ohm speaker? Is that safe?

    Hughes & Kettner Hughes & Kettner on July 23, 2015 Reply

    Hi Kenny, take it easy with this setup and you should be OK! It’s similar to what we describe in Case 2 here, in that you’ll probably notice a drop in your mids.

Zack on July 10, 2015 Reply

I have a Tubemeister 18. I have two 1×12 cabs…both are 8 ohms. If I run them in parallel it would be 4 ohms, right? Is that safe to do with my amp? Does the power soak option (1w, 5w, 18w) make a difference in how safe or unsafe this would be? It would be great to be able to use both cabs together but everything I’ve heard so far makes it sound like a bad idea.

    Hughes & Kettner Hughes & Kettner on July 10, 2015 Reply

    Yep, that’s not a good idea – because when you get down to 4 ohms like that (and you’re right, it does become 4 ohms in parallel), you’re getting close to dangerous territory. We wouldn’t receommend anything less than 8 ohms with the TM18… On the other note: no, your power soak settings don’t make a difference here.

Barry on July 1, 2015 Reply

Finally a voice of reason. You have made me feel much better. I have recently purchased a 16 ohm Leslie speaker and I was paraniod about driving it with an amp rated for an 8 ohm speaker. Thanks!

    Hughes & Kettner Hughes & Kettner on July 9, 2015 Reply

    Thanks Barry! As with the advice in the blog, just take it easy and all should be well 🙂 Now enjoy that Leslie speaker!

Haroon Awan on June 27, 2015 Reply


It was good article, can you suggest me something? the problem is I’m from Pakistan, I am into Sound Reinforcement Manufacturing Unit, so I simply can not take equipment with me all the time so simple to short my question, when ever I attached 4+4+4 ohms speaker in series (12 ohms net impedance) with 4/8/16 ohm impedance output, the amplifier don’t match and speakers are keep getting burn. It’s really annoying as I’m in installation wing also, it’s really annoying, could you like tell me or share something, is it voltage disturbance in amplifier or something, because I simply can not take amplifier here and there on my own and think for 1 amplifier I can not afford to call company van, it’s Ramadan and it’s happening right now, I am really tired, I found your blog and can you give me some quick list to check where could be the problem, is it power amplifier problem.

Right now, 12+12 (mono amplifier) 24 net impedance via 70 line is connected with 70/100 line in amplifier output. It’s 4th time speakers got burn.

I calculated the loads, impedance, voltage, watts, wire resistance and everything, still none of my setting is working, after all I thought of may be Power Amplifier is giving too much voltage or no voltage at all. I need something quick to fix this issue, any hint clue so I can bravely tell company, what is the problem and customer too. Thanks for reading.

    Hughes & Kettner Hughes & Kettner on June 29, 2015 Reply

    Hi Haroon, and thanks for your message. It’s not 100% clear to us what exactly the situation is here, so could you maybe send us some photos and more clear descriptions of the exact amps and speakers involved? Maybe then we can help more 🙂

stephen booker on June 4, 2015 Reply

I’m just using stock gibson pick ups,which is an SG.I was thinking about getting the cab rewired to an 8ohm or getting the 300t,which would give me more head room,but it doesn’t crackle really just breaks up.But was wondering in theory if i got the cab rewired to the right ohms would that create more head room?Also another thing about the bassman’s clean channels tonestack is the same thats in the twin reverb,as i just found out,in theory you should be sweet with a guitar i was thinking.

    Hughes & Kettner Hughes & Kettner on June 15, 2015 Reply

    OK, interesting. In theory yes, they should sound great with a guitar. If you think it’s worth getting the cab rewired, it could solve your problem, yes – but we’re not certain. Perhaps you should get a tech to go over the amp for you, to see if there’s something else not quite right with it… You never know, there could be a simple fix somewhere that we can’t see from here!

stephen booker on June 3, 2015 Reply

brand new one,I’ve also tried two different pedals through it and get the same result.

stephen booker on June 3, 2015 Reply

a hi watt hi gain cab and a fender bassman100t.

    Hughes & Kettner Hughes & Kettner on June 3, 2015 Reply

    Hi Stephen. OK, so this is an interesting one. You’re right in that you’ve got a mismatched setup there, but this probably shouldn’t cause breakup so fast – you should have a lot of clean headroom with that amp, that’s what they’re famous for among guitarists. We’re not actually familiar with the new 100T Bassman model (haven’t had the chance to play one yet) but we checked around in the manual, and there’s no real solution there. If you haven’t seen it, by the way, link here:

    Next we did some internet research and it seems guitars can make Bassman amps crackle – after all, they’re designed for basses. Check out this simialr issue we saw on Premier Guitar. Is it of any help?

    What we would’ve suggested would be getting the tubes checked. Use the Bias feature on the amp or take the amp to a tech, as the Premier Guitar article also recommends. Without having the amp in front of us here, it’s impossible to diagnose the problem with any certainty, but tubes often play a role in things like this.

    The other point off the top of our heads would be pickups – you’re not using super active hot EMGs or anything, are you? Becuase they encourage breakup, of course…

    Hopefully this is of some help!

Tony Vitale on June 2, 2015 Reply

Is he playing and recording to garageband?
I just noticed that this is on a Mac not iPad

How would i connect my GM to do this? Thanks in advance!

    Hughes & Kettner Hughes & Kettner on June 3, 2015 Reply

    Ah, right. No, the second video’s confusing, but the sounds are all direct from GrandMeister, and he’s just recorded the GM36 sound into GarageBand. That’s how it looks anyway. Having the GarageBand FX and amp sims onscreen during the video is a little confusing. You can of course connect GarageBand/your laptop to a normal speaker to hear the sounds like a monitor, but not recommended with the GM cab.

    In that first video, he’s not recording, just playing at the end.

    There is a desktop GM36 editor for Mac and PC (developed by a third party, not us) – you can find it here:

Tony Vitale on June 2, 2015 Reply

Thanks for the info. No I definitely don’t want to control GM with Garageband. 🙂 🙂 🙂

The only thing I was curious about was if I could play with garageband amps and tones and stuff and have it come out of the cabinet

Tony Vitale on June 1, 2015 Reply

Gotcha! I could have sworn i saw a video and someone had grandmeister connected to ipad and the GM was showing up in garageband, and he was playing through garageband.

    Hughes & Kettner Hughes & Kettner on June 2, 2015 Reply

    OK, you got us 😉 So, technically you can control the GrandMeister from GarageBand (if you program controller numbers, etc.), but there’s no inter-app connectivity between the GM36 app and GarageBand. You can also run the two apps simultaneously, of course, but you can’t use the GM36 as an Inter-App Audio App as you can with things like AmpliTube, BIAS, etc. In terms of programming your gear so GarageBand can control the GM36, why you’d want to do this we have no idea. Except to prove that you can, of course 😉 If you ever ifnd that video again, by the way, shoot the link our way and we’ll have a watch. It’s always interesting for us to see stuff like that…

stephen booker on June 1, 2015 Reply

I’ve just bought a 16ohm cab and have been trying out a 100 watt bass head out on the clean channel,which should have a ton of head room as I’m playing guitar through it.when i give the distortion a little more volume the amp breaks up.The heads impedance only goes up to 8ohms,which halves the power,what i was wondering is would this be the cause for the amp breaking up or is that just the design of the amp.


    Hughes & Kettner Hughes & Kettner on June 2, 2015 Reply

    Hi Stephen, what’s the gear involved? Is the bass head in particular an older one?

Will Maxwell on May 28, 2015 Reply

I have a question.
I’m currently working on building a talkbox. I acquired a 40w midrange horn driver. It’s impedance is 16 ohms. I was hoping to use an old Ibanez IBZ10G combo amp to drive it, but it doesn’t have a dedicated speaker output jack. I also haven’t been able to find the amp’s ohms rating. Before I go and gut my amp, I need to know; is this a good combination? If not, would you be able to recommend any fairly inexpensive amps I can try?

    Hughes & Kettner Hughes & Kettner on May 28, 2015 Reply

    Hi Will – cool project idea! OK, so we scouted around and found a store that has the IBZ10G’s manual for download as a PDF. Here’s the link:–IBAIBZ10G

    This is the amp, right? Anyway, the output power is given as 10 watts at 8 ohms on the very last page of the manual, so there’s your answer. If this is true, it’s not a perfect combination, and before you do anything we recommend you ask Ibanez for more info and whether there’s any safety issues with gutting the amp, etc., anyway.

    In terms of other amps, if you’re just looking for something cheap you can gut (and you’re not bothered about the actual amp’s sounds at all), see what you kind find used at your local store. If you can find one with matching impedance, i.e. 16 ohms, that’d instantly be an improvement. Hope this helps a bit, but just shoot if you have any more questions! And make us a video when the talkbox is done, we’re always interested to see mods and projects like this 😉

Craig on May 24, 2015 Reply

Hi There!

I have a Fender 65 Deluxe Reverb reissue amp head that puts out 8-ohms – would it be possible to run two of your (H&K) 16 ohm extension cabs 1×12 (together) from the 8 ohm speaker jack of the amp head?
I believe your cabs are connect through the use of a parallel circuit-

Thank you much-

    Hughes & Kettner Hughes & Kettner on May 27, 2015 Reply

    Hi Craig. Yep, if you’re talking about the TM112 cabs, what you’ve said is correct. They’re 16 ohms, and two wired in parallel would be 8 ohms. And we just checked up on that Deluxe Reverb head – seems to be 8 ohms. Therefore, we’d say you’re good to go with that setup!

Tony Vitale on May 19, 2015 Reply

Yes all is well though GM app. I was trying to tweak some presets without having to plug the cabinet in. Plug headphones into iPad.

I also tried it through garage band, couldn’t get anything there either.

AM i off track with using the headphone out on iPad?

    Hughes & Kettner Hughes & Kettner on May 27, 2015 Reply

    Aha, you can’t record directly in the GM36 app. To record the GrandMeister, you’ll need to go through the RedBox directly into your mixing desk or recording software. (You can still use the iPad app for controlling your sounds, but not for recording into!).

Tony Vitale on May 11, 2015 Reply

Good morning, damn i wish i got an email letting me know you replied. I finally figured out the FX loop button. I pulled my hair out for almost an hour wondering why it wouldn’t work.

Question as far as connecting to iPad for silent recording. I must be completely blind as i cannot find out how to do this. Can i hook up the iRig MIDI in and out to GM MIDI in and out? Didnt work so far. Is there a DI to iPad interface that i need? thanks in advance!

….If you wants to control the Master Volume (which is a non-programmable pot) the best way is indeed to use an analog volume pedal like the Ernie Ball EB6181, yes. And, 25Kohm is the right impedance, the loop is line level.

How to do it? Connect SEND into pedal in, pedal out into RETURN (and don’t forget tho switch FX loop on 🙂 )

Oh, and you can also connect an expression pedal to the FSM and control the preset volume. But this is a differnt thing….

    Hughes & Kettner Hughes & Kettner on May 18, 2015 Reply

    Hi Tony, sounds like you’re doing everything right… You are going through the GrandMeister app, right? Or are you trying to record actually on to your iPad, like with GarageBand or something?

Kai on May 10, 2015 Reply


I have read the blog and I’m a little bit uncertain about:

Can I drive my Hughes&Kettner CC412 A25 (4×12 Greenbacks 25) in 4 Ohm mode with my grandmeister?

Thx for the great amp!


    Hughes & Kettner Hughes & Kettner on May 11, 2015 Reply

    Hi Kai, and glad you’re enjoying the amp! This is like Case 2 in the blog, so take it easy and you should be just fine. But don’t forget, the GrandMeister has an 8-16 ohm speaker output, so you can also go into the cab’s 16 ohm input. Then you’ve got a matching setup…

Christoph Mayer on May 7, 2015 Reply


thank you for your good informing article. I own a Grandmeister 36 and love this cute little thing for small or even bigger gigs. On the output jack there is no defined impedance of the amp but what impedance should i prefer? I also heared something like: “If you have a 4×12, run it stereo with 2x 8ohm and connect the tube amp with 2 cables to the cabinet. It will be more powerfull”. I don’t hear any changes but I’m now on the save way, that the amp is not used without a load (broken cable, jack is not plugged in on the “full” way). What is your experience with that?

Thank you and Best Regards from Germany 🙂

    Hughes & Kettner Hughes & Kettner on May 11, 2015 Reply

    Hey Christoph, and thanks for your message! The GrandMeister speaker out is mark 8-16 ohms, so anything is this range is ideal for you. Our experience of using amps without a load is – you should never use a tube amp without a load! Like we said in the article, it can be dangerous and could result in your gear getting damaged, or even destroyed. (Of course, with the Meister amps and the Red Box for recording/live use, you have another option 😉 ).

The Dude on May 7, 2015 Reply

If I am running a 400w solid state head that runs at 4ohms optimally into a 16ohm cab with 4 vintage 30s, am I at risk of blowing anything (including speakers)?

    Hughes & Kettner Hughes & Kettner on May 11, 2015 Reply

    Hi there! Although this is not a so-called ‘match’, and we don’t know exactly what gear you’re running, if you take it easy at first you should be OK.

DeanIversen on May 6, 2015 Reply

don’t some amps have 4/8/16 outputs or like 4/16?

aren’t the lower the ohms the more bass like 2 ohms for subs and 16 for like horns? for as matching as in separate amps for separate speakers, sub amp/mid amp/tweet-horn amp?

wouldn’t logic dictate something like;

subs 2 ohms
sub mids 4 ohm
mids 8 ohms
tweets/horn 16 ohms

I know guitar amps basically combine it altogether as apposed a separate component powered system like in automobile or home hifi..

also I’ve always noticed that as far as crossover capacitors go the lower the ohm the bigger the passive cap I remember my fosgate sub caps were HUGE basically the same size as the sub speaker magnet where the tweeter caps were the size of a cigarette butt, odd how that works..

like to build my own amps someday, something like the H&K 18 tubemeister in say like an 80 or 120 Watt version, no bells no whistles or EQ. basic;… volume knob, tone knob, channel knob (hi/lo) for that same warm full clean sound you get from the H&K 18 (which just happens to be my favorite amp right now, I’m trying to stay clean as possible to find some tone in my hands) yet big enough to push 8 8 ohm speaks comfortable with plenty of headroom or maybe switchable headroom like I’m seeing in some amps these days… 60/120amp switching, not as in channel but as in PS and tube circuit and perhaps ohm selectable and 2 maybe 3 channel, a clean and naughty channel then a silk zero gain channel, yes 3 channel mo betta…

the tubemeister 18 I play at GC is one of the best tones I’ve heard ever come out of an amp at practice volume and its not even paired with the best speaks out there if I remember correctly..

I sometimes feel they complicate it by more more more and somewhere it loses that WARM full silky responsive tone, I want to build one just like the 18 but like I say in a 60/120 or 80 amp range, maybe even overdo the coils and what not to keep it cool on those hot sunny southwest nights..

playing on a nice clear warm dessert night outside under the stars? yup

    Hughes & Kettner Hughes & Kettner on May 11, 2015 Reply

    Hi Dean. Yep, you’re right: some amp have those outputs (plenty of ours do, for example). Gives you more options when looking at head/cab combinations! You seem to be in a position to start building amps someday (you’ve certainly got the knowledge and know what you want!), so if you do we’d wish you all the best in it 🙂

    Sounds like a few nice ideas for an amp. Some do have too many bells and whistles on them these days, for sure – we really worked on the TM’s clean channel for that reason. The tone’s really in the fingers with our amps! We’ll see you under the stars…

rudy on May 4, 2015 Reply

I was wondering if I have a 2×12 cab that I plug into the 8 ohm input and I’m using a 8 ohm speaker plus a 16 ohm speaker with my amp at 8 ohms will I burn it out?

    Hughes & Kettner Hughes & Kettner on May 4, 2015 Reply

    Hi Rudy, just to be clear: your 2×12 has two different speakers with different impedances? Or do you mean you have two entirely separate speakers? Maybe send us the exact kit list/specs so we can give you a more complete answer 🙂

Tony Vitale on April 29, 2015 Reply

I now understand the volume and gain thing! and yes i would like to control volume while leaving gain alone. I now have GM36 with TM112!!
I picked up the EB6181 25K just to test out. am i correct in understanding that the only way of this to work is to go out of pedal into fx loop, out of fx loop back to pedal? Can this be connected via FSM footswitch?

    Hughes & Kettner Hughes & Kettner on May 4, 2015 Reply

    If you wants to control the Master Volume (which is a non-programmable pot) the best way is indeed to use an analog volume pedal like the Ernie Ball EB6181, yes. And, 25Kohm is the right impedance, the loop is line level.

    How to do it? Connect SEND into pedal in, pedal out into RETURN (and don’t forget tho switch FX loop on 🙂 )

    Oh, and you can also connect an expression pedal to the FSM and control the preset volume. But this is a differnt thing…. 😉

Scott Bailey on April 28, 2015 Reply

After reading all of the above,Am I correct in assuming that I can
run a 16 ohm extension cab from my 8 ohm extension jack on a
Fender 65 Deluxe Reverb reissue amp?

    Hughes & Kettner Hughes & Kettner on April 30, 2015 Reply

    Hi Scott. Yes, this is the scenario we describe in Case 1 in the blog. Be careful with it, and you should be fine. We’d be interested to hear how it affects your tone, so please let us know!

Steven Taylor on April 24, 2015 Reply

ok, I’m trying it out now and the mids seem fine, but I seem to be getting less gain and bite

    Hughes & Kettner Hughes & Kettner on April 24, 2015 Reply

    Hmm, OK. So the thing now is to decide whether you like that or not, whether you can tweak your settings (guitar/amp/pedals – they can all have an effect on this) to make it sound more to your liking… or whether you’ll need a different cab!

Tony Vitale on April 23, 2015 Reply

Here is a link to the info i had found regarding the pedal i was asking about. If you scroll down bout hafl way the user gravydb posted. I’m not quite sure what he is meaning my volume and gain….

    Hughes & Kettner Hughes & Kettner on April 28, 2015 Reply

    OK, read it. What exactly do you want to know? gravydb is speaking sense there, but perhaps we can help explain in clearer terms…

Tony Vitale on April 23, 2015 Reply

Thanks for the feedback. Am i correct in assuming this would plug into the H&K foot-switch then?

    Hughes & Kettner Hughes & Kettner on April 28, 2015 Reply

    Hi Tony, yes you’re right – into the Control ports.

Steven Taylor on April 23, 2015 Reply

I have a 4 ohm cab but I really want a tube miester 5 that runs at 8 or 16 ohms, is this a problem?

    Hughes & Kettner Hughes & Kettner on April 23, 2015 Reply

    Hi Steven. Obviously, it’s not a perfect ‘match’, so not optimum in that sense. But you can use this setup if you’re careful, as we wrote. Just take it easy before you crank it up! Case 2 in the blog explains how it could alter your sound (i.e. less mids, etc.), and the effects it could have on your rig/tubes over time.

Tony Vitale on April 21, 2015 Reply

The yamaha looks kind of cheesy and cheap… Can you recomend something more robust. also have a separate cable is important

Hi Tony. No, you’d need an expression pedal like the Yamaha FC7…

    Hughes & Kettner Hughes & Kettner on April 23, 2015 Reply

    Hmm, you could try Morley pedals – this one’s good:

    But honestly, the FC7 is, and has been, the industry standard since… well, a long time, and we’ve had no problems at all with it! It’s pretty much the chunkiest, most robust pedal out there too.

Tony Vitale on April 21, 2015 Reply

So after reading, its OK to run a grandmeister 36 and a TM112? THe info on the TM112 said its paired for tubemeister.

    Hughes & Kettner Hughes & Kettner on April 21, 2015 Reply

    Hi Tony – yes, that’s absolutely OK! The TM cabs were designed sound-wise to match the Meisters (including the GrandMeister) perfectly…

Darren Gill on April 13, 2015 Reply

I saw someone recently using a Grandmeister with 2 x 112 cabs stacked (looked way cooler than the 212, as the logo’s are the right way up!).
What are the benefits of this set up as I understand you can only do this in series…any audio improvements?

    Hughes & Kettner Hughes & Kettner on April 14, 2015 Reply

    Hi Darren. More cabs will give you more oomph and volume – but whether the tone is improved is entirely up to you! Give it a try and see if it floats your boat 🙂 Oh, and yes, it does look cooler and more ‘rockstar’ too, which is nice!

Paul WR on March 29, 2015 Reply

Great article! There is however a much simpler method for calculating the resulting resistance for exotic combinations:

In the case of combining 8 Ω and 16 Ω cabs, you can regard the 8 Ω cab as two parallel 16 Ω cabs. So, in total three 16 Ω cabs. 16/3 equals 5.333 Ω.

Or, in the case of combining 4 Ω and 8 Ω cabs: 8/3 equals 2.666 Ω.

Easier to remember and doesn’t require a calculator. Just my 2 Ω…errr, cents….

    Hughes & Kettner Hughes & Kettner on March 31, 2015 Reply

    That’s a cool way of doing it Paul, so thanks for sharing your 2Ω with us! 😉 Glad you enjoyed the article, by the way.

Martin on March 19, 2015 Reply

If my Cabinet is 8 OHMS then what does my tube amp need to be on? will i get the best possible sound if its at 8 OHMS? i can change my tube amp from 4,8 or 16 OHMS

    Hughes & Kettner Hughes & Kettner on March 20, 2015 Reply

    Hi Martin, a matched setup will always be the most natural solution – that’s the way the amp/cab are built to sound best together – so that’s what we would recommend you go for. Like we said in the blog, there are different effects to be had from the mismatched setups, but you should always exercise caution if you do anything like that 😉

Andrew Otwell on March 2, 2015 Reply

Many thanks for the reference chart with various configurations and the green check marks. That is the epitome of a user friendly reference guide. Great Job!


    Hughes & Kettner Hughes & Kettner on March 2, 2015 Reply

    Thanks a lot Andrew! Glad the chart was/is useful for you…

Nathan on February 25, 2015 Reply

I just bought a 16ohm 1×12″ Blackstar HTV 112 cab

Could I use a blackstar ht 1rh 1W head (8 ohm) with it?

    Hughes & Kettner Hughes & Kettner on February 27, 2015 Reply

    Hi Nathan. OK, so we just checked out that amp online, and you should be fine. The rear panel says the head can take speakers of between 4 and 16 ohms. In the HT1 manaul, it says: “The output marked ‘4-16 ohms’ is for the connection of an extension speaker cab with an impedance of 4 to 16 ohms.” That means the HTV 112 cab would be good to go with it!

    One thing: if your amp head doesn’t say 4-16 ohms, let us know (send us a pic or something) and we can think again!

michael rigsby on February 20, 2015 Reply

very important stuff i needed to know.thanx!!mike

    Hughes & Kettner Hughes & Kettner on February 20, 2015 Reply

    Glad to be of service, Mike!

Michael D Long on January 17, 2015 Reply

I did the same thing…I’m currently shopping not only for a 16ohm speaker, but one better than the $35.00 Chinese Celestion 30. Looking at the Celestion G10N-40 or the G10 Vintage….

Paul on January 1, 2015 Reply

Hi I have a 1967 fender twin reverb, it has two speaker outputs not labeled for ohms. I think there 4ohm outputs?
I just picked up an old Marshall 4-12 cab at 16 ohms.
Can I plug this can into my ext. speaker jack on my twin?

    Hughes & Kettner Hughes & Kettner on January 7, 2015 Reply

    Hi Paul. You would need to find out for sure before doing anything (the internet or a local tech would surely know), but in any case, a 16-ohm speaker would not be the ideal match for the 4-ohm outputs. The worst case scenario could be damage to the amp, so proceed with exteme caution if you do try it, because that’s one amazing amp that you’ll want to keep in the best state possible! Hope this helps…

Garett O on December 21, 2014 Reply

H&K, please help! I own a Tubemeister 18 head and a Tubemeister 112 cabinet. I just this week bought a Tubemeister 110 cabinet.
Based on these cabs and my head, is it safe to run them in series? Can you please walk me through the math as well?

Thanks in advance I look forward to your response so I can hook them up and hear how great they sound, if it’s safe!

    Hughes & Kettner Hughes & Kettner on January 7, 2015 Reply

    Hi Garett! The two cabs would have a total impedance of 24 ohms in series, and 5.333 ohms in parallel. The TubeMeister 18 has an 8-16 ohms speaker output, which makes this not an ideal match. Like we said in the blog, running a mismatched setup like this can be a risk, but if you’re careful, you shouldn’t blow anything up 😉

    About maths, we’re currently planning another blog on this very subject, and hopefully it’ll be online with all your answers soon!

paul on December 7, 2014 Reply

thanks for the info. i have a 1972 ampeg svt head that is 4 ohms. can i plug it into an 8ohm speaker cabinet without any issues

    Hughes & Kettner Hughes & Kettner on December 12, 2014 Reply

    Hi Paul. Yes, you can plug the 8 ohm cab into your 4 ohm head. Because it’s not perfectly matched, you’ll get a little less power than you would through a 4 ohm cab, plus you’ll probably hear more mids in your tone.

    And this is also worth mentioning, even though the effect is negligible: this could reduce the lifespan of your tubes. Like we said though, it’ll only be by a tiny amount.

Malcolm stilwell on December 5, 2014 Reply

Well I have a combo amp its a b-52 it has two 16 ohm speakers in it then I have a carvin cab with four eight ohm speakers in it can I play them together the amp can be used tube or solid state plus it has a switch on it were I can change it from 4-8-16 ohm speakers I would like to know if I plug the 4×12 cab into amp what to set switch on please help

    Hughes & Kettner Hughes & Kettner on December 12, 2014 Reply

    Cool sounding rig, Malcolm! Do you have any pics you could send us of it? Then we’ll take a look 😉

steven d carrell on November 16, 2014 Reply

Need to know what to set the ohms on the head ?

steven d carrell on November 16, 2014 Reply

I want to know if I can run a 16 ohm peavey 4×12 cab and a 1×12 4ohm cab together thru my peavy viper 120 watt tube head ?

    Hughes & Kettner Hughes & Kettner on November 17, 2014 Reply

    Hi Steven. Have you gotz a picture of that specific head’s back panel anywhere? We can’t find the exact one online, but if you can show us, we might be able to help…

Mark Hossain on November 13, 2014 Reply

Excellent read on the subject, really helpful.
But I have a question here; I ‘ve a Vox night train 50 watts Amp head
with the following :1x8ohm output, 2×16 ohm output and finally a 1x16ohm output.Now I have got two cabinets: VOX 1×12 (16 ohm)65 watts
and a Marshall 4×12 (8 ohm) 200 watts which I would like to connect with the same head. Is it possible to run the 8ohm and 16 ohm outputs from the am to the respective cabinets? can I just run it like that or I need some kind of cabinet merger to do the job?
Also what does a 2×16 ohm connects to? a 32 ohm cabinet??

Many Thanks

Adam Gilleland on November 9, 2014 Reply

i have a 16 ohm head with 2 16 ohm cabs. What’s the best way to add two more of the same cabs?

Neville on October 28, 2014 Reply

“First of you all, you should commit this critical ground rule to memory: never – really, NEVER! – operate your tube amp without a load/speaker(s).*”

*Unless it’s a Grandmeister 36 😉

Got an issue with the chart in the blog – cases 1 & 2 both have a GM36 and show 8ohm and 16ohm output (respectively) – but how is this possible when you are unable to manually select the output ohmage on the GM (it auto selects 8 or 16 to the best of my knowledge?) Cheers

    Hughes & Kettner Hughes & Kettner on October 30, 2014 Reply

    You’re right – with Red Box and DI outs, you’Ve kind of got an exception! We’ve asked our impedance experts about your question, and will report back… 😉

Mike Teodorescu on October 28, 2014 Reply

Great article,…. blog etc…
. If I have an older Peavey Backstage amp listed 20w 8 ohm….
can I replace the speaker with a 16 ohm speaker ? ( I have an extra Celestion 16 ohm)
thank you

    Hughes & Kettner Hughes & Kettner on October 28, 2014 Reply

    Thanks Mike. Hmm, that’s an old amp! We’d recommend you contact Peavey directly about that. We did search around a bit, and found the manual for your amp though – maybe it’ll help:

    In theory, though, of course a qualified tech will be able to make the alts for you!

Mark on October 21, 2014 Reply

I’m curious about the power requirements of the speaker when you connect them in parallel. I have a Tubmeister 18 combo with the 1×10 speaker. I also have the grandmeister 36 with a TM 112. If I plugged my GM into the tm 112 cab and them took the parallel out and plugged in my 10 inch from the combo (would need a female to male adapter), I would like to know if I might damage the 10 inch speaker as it’s rated at 30 watts. Total ohms would be 8 which should be ok for the GM36, but how is power distributed between the speakers. If I run the GM at 36 watts what would go to each speaker?

I’d like to try because I think the difference in the sound of the two speakers might be cool

    Hughes & Kettner Hughes & Kettner on October 22, 2014 Reply

    Hi Mark. OK, so the total impedance of your speakers would be under 8 ohms (it’s round about 6, if you use the formula in the blog above). All you need to do, then, is wire the speakers in series, and you’ll be fine!

Rob on August 19, 2014 Reply

A question please, I have 2 x 8 ohm speakers in parallel. That makes the cab 16 ohms. Which is OK with my H&K Grand Meister (8-16Ohms) what happens to the tone in theory with this set up as is, versus a straight 8 ohm cab? Does it even matter since the head can be 8 or 16 ohms? Best regards and TY, Rob

    Hughes & Kettner Hughes & Kettner on August 26, 2014 Reply

    Hi Rob. Caution: 2 x 8 ohms in parallel results in 4 ohms! The speakers have to be wired in series to achieve 16 ohms. The impedance match of the GrandMeister is 12 ohms, so both 8 and 16 ohms are fine. With 4 ohms, you’ve got to be much more careful 😉

Christian Terjesen on June 23, 2014 Reply

Thanks so much for this info! I had no idea that different impedance outputs could effect the midrange in my cab. Awesome article and please post more!

Andy Johnson on June 21, 2014 Reply

That’s useful to know! Personally I use a 16ohm cab connected to 16ohm o/p of H&K amp and it all sounds good. I have tried wiring same speakers in 4ohm configuration and connecting to 4ohm o/p but really preferred the sound and sensitivity of 16 to my taste. Seemed to “feel” better to me.

    Hughes & Kettner Hughes & Kettner on June 23, 2014 Reply

    Hi Andy,

    That’s the beauty of experimentation. If you stick to the safety rules, you won’t blow your amp up and you’ll be able to play around until you find that sound that just feels right for you – as you’ve done!

    All the best!