Matching Speakers To Amps

This is a beginners guide to matching speakers and amps and what you can do without stressing or breaking them.

Ultimate Guitar
There are a lot of threads running in the forums about using extra speakers cabinets to increase your sound or improve your tone and it seems that half the guitar world won't do simple things because they are worrying too much about breaking their stuff whilst others are fearlessly trashing their gear through too much experimentation. As a crap musician but competent technician I'll try to lay out some basics as simply as I can. If this gets a reasonable reception I'll try to build this up into a series of hopefully helpful articles. Please let me know if you think I've made any mistakes and ask any extra questions if I've not covered something or failed to explain it clearly. I'll leave it a while and then try to update my article to include all your ideas. This first article is about the ohm thing; how do I match speakers to amplifiers, will it improve the sound and will it destroy my amplifier? How can you get to be really loud?

The Ohm Thing

Ohms are about resistance. How easily will electricity flow through something and how much current will it draw. Everything electrical has a resistance, light bulbs have ohms, electric ovens have ohms and even drummers have ohms. Lots of ohms means that electricity has trouble getting through and less ohms mean that electricity storms through. Sweaty drummers have fewer ohms and are easier to electrocute. Single loudspeakers usually have eight ohms, though you can buy them with four or with sixteen. (Just in case of confusion I ought to explain about impedance. Speakers are often described as having an impedance of eight ohms, this is because some of their ohms come from speakers being electromagnets. This is more complicated than you need in a musicians guide so for us ohms , resistance and impedance are the same thing.)

How Many Speakers Can I Safely Connect

OK if you connect two speakers in parallel (more on this later) then there are two routes that the electricity from the amplifier can go through and there will be twice as much power right? Three speakers and three times as much, four speakers, five Actually this is pretty much what can happen but before you get carried away you should think about the poor amplifier. A 100W amplifier is still only a 100W amplifier. If it is a solid state (transistor) amp it will bravely try to go on pushing more and more power through your speakers Transistor amps will try to deliver double the power every time you halve the ohms. Eventually they will run out of steam. What happens next depends upon the detailed design. Most will have protection and will just limit their own power/distort or blow a fuse. (never go to a gig without spare fuses) With many of them the power supply will be inadequate for the power demand so they only develop their max power into a speaker with the right number of ohms. This means you are wasting your time trying to squeeze more power out. The worst case if you try to add too many speakers is that the output transistors will overheat and fry. FET,s are less likely than silicon transistors to do this, but if you understood that sentence you don't need me to explain. If you have a valve amp then the situation is that you must match the output to the speaker and fortunately you have a transformer inside the amp to do this. The deadly thing for valve amps is too high an impedance, too many ohms. Well designed valve amps should have multiple tappings on the output transformer and you really should try to match the ohms on the amp and the speakers. As a general rule most amplifiers will deal with four ohms with no bother although depending on the power supply they may be happier with eight. If you have two speaker cabinets of eight ohms then wiring them up in parallel will give you four ohms and your amp should deal with this happily. The problem would come if you tried to plug in three cabs. Now you have three speakers with only two and a bit ohms, you could be demanding three times the power from your poor amp. Don't do this unless you have calculated the overall impedance and are happy that your amp can cope. If in doubt contact the manufacturer and find out if the amp will cope with low impedances (anything less than four ohms). If you have a combo amp with a built in speaker and an outlet socket for an extension speaker things can get a little more complex. On some combos the socket has a switch so that the internal speaker is disconnected (my Peavey does this). This means I can ignore the ohms of that speaker and just use the Peavey as if it were a head. If your combo leaves the speaker connected when you plug in a lead (which you can tell as the sound will still come out of that speaker) then any speaker will be in parallel with the internal speaker and you need to work out the ohms of the two speakers combined to make sure it doesn,t go too low. Fortunately manufacturers don't usually provide a socket for an extension speaker if the amp won't take it so you can be pretty confident about plugging in your extra speaker. Just like with a head amp don't just plug in in two extra speakers as with the internal speaker this makes three and you could damage some amps. Having too many speakers will only damage amps at high volumes. In any practical situation the damage is almost always caused by too much power. Turn the volume right down at first until you know everything is working and turn the volume up a little at a time listening for any distortion you are not expecting. There are ways of connecting more than two cabs to an amp by using series connection though you will need special leads to do this. Before you try this you should read the section on series and parallel. In any case you should ask yourself why you want to do this for an instrument amp.

Will This Be Louder

Yes probably. But it is not completely straightforward. Loudness is subjective because we are more sensitive to some frequencies of sound than others. New speakers may give a smoother sound and seem quieter. Secondly speakers vary quite a lot in their efficiency, that is in how well they turn the electricity from your amp into sound. In practice it is quite possible for the most efficient speakers to make 10 watts sound like 100 watts do from less efficient speakers.

How Loud Can I Go

If you play gigs then you only need to match the volume of the other instruments if your band is to sound balanced. The best band in the world will sound rubbish if they are not properly mixed. In practice the critical point for most bands comes when your sound matches the drummer. Any louder and the drums will need to be miked through the PA to match you. If your PA can deal with this then you are in a whole new ball game. You might as well get the extra sound for all of the instruments through the PA which will give you the chance of having someone mix you properly and achieving a balanced sound. Keeping the onstage sound down to manageable levels and letting the PA do the work makes sense at every level Even fairly modest combos will produce over 100dB of sound which is more than enough to damage your hearing. Do you really need to be louder? Is hearing important to musicians? I think you know that one. Adding extra speakers should be about the quality of sound for most of us not just a mad pursuit of power.

How Safe Are The Speakers.

So far this has all been about protecting the amp from too few ohms (too many speakers). Now I want to look at matching the speakers to the amp. There are many ways to damage a speaker but the amp only has two ways. It can cook the speaker by passing too much power for too long or it can pop the speaker by pushing it right out of its frame. Most instrument speakers and professional PA speakers are designed so that they can not be pushed out of their frames but hi-fi speakers often aren't. Don't play guitar through your hi-fi unless you want an excuse to buy new speakers. Very low notes do demand that the speaker cones have to move further though, so using bass or keyboards with guitar speakers at high volumes can also cause problems. Burning out your speakers is much more likely. You have to match the power output of your amplifier to the maximum power handled by the speakers. Power is measured in watts and you need to make sure that you are dealing with real watts. Real watts are RMS watts, ignore anything which says music power, peak watts, PMPO or anything other than RMS. RMS measures the maximum output your amp will produce without distortion. Being a guitarist of course means you will want distortion or overdrive. This effectively adds to the power your amp is generating in fact with distortion your amp will generate up to 1.414 times the RMS output. If you want your speakers safe then it means you need at least one and a half times the power handling in your speakers. This means that a thirty watt amp should have speakers that can handle at least 45Watts and a 100w amp should be matched with at least 150W speakers. In practice I always try to go for double the power handling, ie 200W speakers with a 100W amp. It is absolutely safe to use big speakers with a small amp though: 200W speakers are fine with a 10W practice amp.

Series And Parallel

Ok this is the ever so slightly technical bit. Speakers have a positive and a negative terminal. This is so that we know which way they go when we apply an electrical current to them from the amplifier. If we connect the positives together and the negatives together then they are connected in parallel. The positives are always connected to the tips of jack plugs and are usually marked with a + or a red dot on the speaker itself.

Parallel Connection

Connecting speakers in this way has a number of effects:
  • You increase the volume of sound.
  • The impedance is reduced below that of the lowest speaker.
  • The amplifier will have to supply more current.
  • The power handling (the watts) are doubled To calculate the new impedance you need to use a bit of algebra and know the impedance of all the speakers, R1 ,R2, R3 etc. to calculate the new overall or total impedance Rtot the formula is
                   1   =  1  +  1  + 1
                  Rtot    R1    R2   R3
    If you had two speakers and they are both 8ohms the calculation is:
                  1    =  1  +  1  = 1
                  Rtot    8     8    4
    So Rtot =4ohms Fortunately we usually only connect up speakers with the same ohms in parallel so that if you divide the ohms of a single speaker by the number of speakers in parallel then this gives you the overall impedance. So three 8ohm speakers in parallel would be 8/3 or 2.6667 ohms. Anything more complicated and you have to do the sums.

    Series connection

    The positive on one speaker is connected to the negative on the next one. They make a daisy chain. The plug is connected to the positive on one speaker and the negative of the other, pin to positive still. Series connection also makes changes:
  • The ohms increase
  • The sound level decreases
  • The current from the amp decreases
  • The power handling is doubled. Calculating the ohms is easy, just add them together. For example two 4ohm speakers give you 8ohms. The final method of connecting speakers that you will come across with musical instruments is used as a useful way of connecting four speakers without reducing the ohms too much. Effectively you are just combining the two ways we have already looked at and it is called series/parallel. This is the classic 4x12 connection. First connect pairs of speakers in parallel. Then connect the two pairs of speakers in series as if they were single speakers. (sorry about this but I lost the diagrams that made everything clearer try the Celestion website and look in Dr Decibels Secrets). If you have a couple of 2x12 cabs and you want to connect them together then this would be a good way to go about it. If the internal wiring is in series then no problem, if they are internally wired in parallel, and they probably are, then you need your repair shop to make a lead up to connect them in series. If you want to calculate the impedance you need to do it in two parts, first caculate the impedance of each parallel pair then add them together. In practice if all the speakers are the same then the ohms will be the same as for a single speaker. This is a really useful way of doing things because you get double the sound of a single speaker without using any extra power from the amplifier or having to drive a really low impedance speaker. The power handling is four times that of a single unit. The disadvantage? You have to pay for and carry four speakers at a time. There it is then, I hope this is fairly clear and if you are one of life's experimenters you have a reasonable chance of getting the sound you want without too many costly mistakes with your gear. I'd really like any comments or questions. Good luck.
  • 49 comments sorted by best / new / date

      I think a simple diagram on the connections,and types of wires would probably help the most..
      Hi Phil, Im building a guitar cab consisting of two 16 Ohm, 100W speakers wired in parallel. Now, I know that their combined impedance would be 8 Ohms but I'm slightly confused as to what their RMS power would be (Is this the same as power handling?) and, more importantly, how I would go about calculating this. I would be very grateful if you could help me out here! Thanks, Mark
      PLEASE HELP!!!!! hi guys i built a exact replica of a mesa rectifier 2x12 i put 2 old fender speakers in it from a fender m 80 it sounded pretty good not as deep of a sound though. i then put 2 brand new eminence swamp things in it and i sounded like complete dog shit the most hollow and thin sound ever??? they are 4 ohm i have them run independent im new with this kind of stuff any help would be greatly appreciated thanks Louie
      CALL ME STUPID!! I'm searching the web and after I posted here I find that this KB has a "Master Equalizer"! Not what I expected an equalizer to look like (what do I know??) it has 5 settings - 2 for built-in speakers, 1 for headphones and 2 for external speakers!. Setting #5 seems to get rid of most of the distortion on my old computer speakers - hard to tell on a synthesizer, some notes are still a bit fuzzy on some voices. But that might be normal. So it seems that an external amp/speaker will work - then my question is, "how can I incorporate my expression pedal?" and can I use it on the headphone output? Currently it's in the old case and I just put the keyboard in where the old keys used to be. I simply picked out the fattest wires (gray) and fed my KB output into them. That seems to work (except for the distortion) the volume controlled sound comes out of the organ speakers which are not bad. Not very portable though! I have tried to buy an expression pedal as an after market accessory with no success. Am I barking up the wrong tree here?
      I have Yamaha portable keyboard (YPT410) and really miss the expression pedal that I used to have on my old Technics organ. Also, as I start playing for friends and family, I realize that they don't hear the same thing as I do! (because the speakers face straight up at me). I tried wiring the keyboard thru the Technics speakers (and pedal). I needed a small amp to do that so I bought an "AudioBuddy" to amp the KB output (headphones) before inputting to the Technics pedal circuit. But this seems too powerful and I have to crank every other control down. This works (better when it's warmed up!) but I have distortion. Also I tried running directly into some old computer speakers (c1994) - they're big but I have no idea what RMS etc. They do include an amp so this works but still I get distortion - most noticeable when I play more than one note. I usually have these speakers on my TV and they work fine. The YPT410 is a $300 KB so $300 for a speaker is a push. I suppose I would spend it if I was sure it would work and if I could include an expression pedal. Phil, I seem to specialize in weird questions but any help would be appreciated. Thanks
      Phil Starr
      Hi Ken, I can help a little with your distortion problem but not with your expression pedal. I would expect that to be designed to work with specific instruments and certainly with lower level signals than your headphone output but I am really just making a poorly educated guess here. With any keys you need an amp and speakers that are essentially flat across the frequency range and capable of handling a terrific dynamic range. Recorded music has the dynamic range compressed (loud bits are reduced and the quiet bits enhanced) so the average level can be louder without the loud bits overwhelming the speakers and amps. Your computer speakers won't be able to handle the loud bits of live music unless the volume is turned right down. The equalizer boosts certain frequencies which adds to the overload problems if your amp is underpowered, setting #5 is probably the flat setting so stick with that. The rest of your distortion is coming because each stage has a limit of how many volts it can swing. Guitar amps usually have two volume controls, one at the guitar end usually called the gain and one at the speaker end called volume. Turning the first control up causes the early stages of the amp to overload causing distortion and the volume controls the sound level. If they want a clean sound then they turn the gain down and the volume up so the sound level is the same but undistorted. The headphone output is overdriving the later stages of your set up. Turn right down on the keyboard and your amp up and you should be able to get the maximum undistorted output. I play my 1000 bass through a 1000 amplification system. In the end you have to spend similar amounts on both, in the meantime look for a second hand practice amp designed for instruments. If you can't afford a keyboard amp then try a bass amp which are usually designed to have a clean flat response, avoid guitar amps. You can pick up cheap bass practice amps for 20-30 over here.
      Maybe this has been asked already, but I have a Fender bassman tube amp rated at 100w and have one Seismic audio 15" speaker cab rated at 200w and 8 ohms.. I understand that a second cab exactly the same would bring the ohms down to 4ohm at the amp, and thats fine since the Fender can go as low as 2ohms setting.. I was curious to know If I am able to connect more than two cabs(same as above:200w at 8ohms) to the amp somehow without the ohms going any lower than 2ohms?? I have two jacks on the back of each cab..
      Phil Starr
      Four cabs of 8ohms in parallel would be 2 ohms, if you just connect them up with all the existing sockets. The other way of doing it and in my opinion better would be to connect them in series parallel. This will give 8ohms overall. You'll need two series jack leads to do this or get someone to make up a box with the required connections. I'm playing tonight and just off to set up so google series parallel and pm me if you don't find what you are looking for
      Ok.. I sort of understand the series parallel circuit, but to hook up the cabs that way, I'm still confused on what I need..
      Phil Starr
      OK, you need two series leads, they are unusual because they have three plugs. I've not found anyone who sells them, they need to be plugged in the right way or they won't work properly so I guess they are troublesome for the makers. One plug goes to the amp and the other two to the speakers. This puts two speaker cabs in series. Connect the other two in series the same way and then connect the two pairs in parallel the usual way, by using the other socket on your amp if you have one or a splitter if you haven't. Another way of doing this is to have a box made with one input and four output jacks wired in series parallel. Sorry I make up my own but it is a simple job and any repair shop should be prepared to make up some leads or a box fairly cheaply. You could try an email to
      hi there not sure if this thread is still running though would appreciate any response . that said ! i have a vox a30 ! can i plug in a 100w extension cabinet that has 2x100watt speakers? then flick the switch to 8 ohm and not destry my amp its all valve ?? also do the size of the cones need to match as the speakers in the cab are bigger than the vox..? thanks
      Ok so I have a 15 watt tube amp rated at 8 ohms I want to use a 212 cab so Id need a cab with 2 16 ohms speakers wired in parrallel correct? And what wattage could the speakers be without damaging my amp?
      Phil Starr
      The wattage won't matter, you are not going to blow the speakers with 15W and using 100W of 300W speakers will make no difference to the amp. Just match up the ohms. Yes, you are right about this. Choose what sounds best to you.
      Ok this is killing me, I have a Peavey 6505+ Head (4/8/16 selectable OHM switch), its 120 Watts. And I just purchased a 2*12 PPC orange cab, which is 120 Watts and 16 ohms parallel inputs. Two questions: 1- you mentioned that the speaker should handle more watts than it is given, otherwise it might get damaged, (did I purchase a wrong cab) ??? 2- Do I configure my amp to give out 8 OR 16 Ohms?? Cause each V30 speaker has a 16 Ohm impedance. and if theyre in parallel Im assuming I should give each 16 Ohms? Please clarify, Im kind of a noob in this.. Regards
      Thank you so much for posting this, it helped a lot. My question is concerning the part about combo amps specifically peaveys. So are you saying ohm output and wattage isn't a factor if you're using for example a peavey combo amp as a head via extension speaker outlet socket but only if your combo amp has the socket internal disconnect switch? basically im curious if i can use a combo amp as a head for a full 4x12 cabnet thank you
      Hi Phil Good article - thanks I have an old Carvin Combo 100 watts output @ 8ohms There is a jack for adding additional speaker which the manual states would be in series with the in built speaker and should be 4-8ohms I have two 8 ohm speakers (150watt) Can I add both these in series - ie daisy chain ( the necessary sockets are there in the speakers) I want one additional speaker to expand the sound in a marqui venue and the other as a feed back speaker for me Hope you can help Thanks Ged
      Hi Phil, I have two degrees in Electrical Engineering, from the top rated school in the country. I love your article. You do not try to show how smart you are by throwing out a bunch of buzz words. You structured your article like it was written for all of us, not a select group. Very well done. Thank you for taking the time to compose it. When people ask me these questions in the future, I will refer them to this article. Thank you, DR
      Hi Phil. I'm looking for replacement speakers for a 1964 Fender Bandmaster. The spec for the amp states 40 Watts but inside the head it says 175 Watts. I should size speakers based on the 40 watts right? Also, the cab has 2 12" speakers. Is that 20 watts each - so the speaker watt rating should be 30 watts minimum, yes?
      Hi everyone. Quick question. I have a Traynor YBA-1 Tribute head that runs 40W at either 4 or 8 ohms. I've purchased a single 12" cab that has a Celestion Greenback (16ohm, 25w) in it. 1) Can I run this? 2) Should I replace the Greenback, and with what? Thanks, fretboy1969
      Hi Phil I have an AC30 2x12 with 25w 8ohm greenbacks in it, i like the 'vintage 30' 60w 8ohm speaker sound mixed with one greenback and i realise that replacing one greenback inside the combo cab is a straightforward swap however, i also wish to build an extension cab to use with my combo with the same configuration so as the internal speakers operate at 16 ohms and any external cab is to be the same rating does this mean i wire up my extension cab with 2x8 ohm speakers in series? what configuration will the connecting cable have? and does it make a difference to the overall sound if i have the 'like' speakers in the two cabs diagonally opposed when viewed from the front please? Regards Carl.
      Phil Starr
      For some reason this didn't come up on my profile so I've only just got it. If the speaker is 8 ohms and the amp is set to 8ohms and the internal speakers are disconnected then you'll be fine. The amp won't worry about the power rating or the size of the speakers. The only thing you need to worry about is the impedance
      I've been looking for a guide like this for ages... thanks
      Phil Starr
      I'm abit time limited at the moment so I haven't time to chase up the brand specific information. I am working on theory only. I strongly recommend that you don't operate the Mesa without a load connected, even with the power right down valve amps need a load unless the designer has included a dummy resistor in the design when a speaker is not connected or a standby switch for each channel which is what I would do. You could of course use any little speaker or an 8ohm resistor as a load if the volume is right down. You might be ok but I wouldn't risk it without an ok from Mesa first. Why not email them. Most transistor amps are ok open circuit (no speakers) but I wouldn't recommend it as a long term practice as a few amps will oscillate without a speaker and part of their protection is that you can hear what they are doing. I would prefer to use the crate in mono mode even if you use a 4ohm speaker unless the manufacturer specifically advises against this. The amp will try to put at least 300W peaks into the speakers in this configuration but will be limited by the power supply to 150W and less if you turn it down you should benefit by having much cleaner peaks. From what you say about the Crate it looks like a 2x75W power section which can be operated in a bridge mode but with a 150W power supply. It is safe to use a 100W speaker with the volume down. There are two ways you will blow the speaker; you might drive it beyond the excursion limit and this you will hear, as you have been advised. The other way is through overheating which you won't hear but this takes a long time, if you genuinely have the volume low and aren't playing for hours at high volume then you would have to be very unlucky to have any problem. Fine for practice but not so good live in a loud band. If you want to pursue this further I would be happy if you pm me and I will try to find out a bit more about the specifics. I have so far always found that manufacturers are pretty good at responding to emails
      Very interesting. I'd love to see this get more in-depth. I've never been sure how to devirginize myself when it comes to these scary things, this is a good introduction. Greatly appreciated.
      Phil Starr
      Thanks for the comments. It is hard to know how technical to get. I'll watch how the comments are going and try to respond with another article or two. Any specific comments or questions would steer me in the right direction.
      so if i want 4 cabs i can connect 2 in parralel then put the other two cabs coming out of the previous 2
      Phil Starr
      depends upon the cabs impedance. If they are all the same then treat the cabs as single drive units and connect them in series/parallel.
      dark templar
      Thanks for the article. Is there a way to measure RMS from a speaker with just some info on it's PMPO? I have a practice amp that delivers 15watts RMS to a 4ohm load. I want to replace the speaker with a subwoofer unit with 60watts PMPO 4ohms. Would that be ok for the amp? Thanks.
      Phil Starr
      Just in case anyone else wants this information PMPO is about advertising not helping you to make sensible decisions. There is no definition so manufacturers can claim almost anything and they don't always claim the same things so you can't compare PMPO powers from two different manufacturers. Always look for RMS or AES figures
      Phil, first of all, thanks for taking the time to explain this! It's a great article with just the kind of info that's really needed. And thanks for slipping in a few digs at sweaty drummers too : My questions are as follows: 1) I have an old Mesa Boogie amp that was manufactured with the usual 3 outputs: 8ohm + 4ohm + 4ohm. I was told that all 3 were short-circuited to create a 5.3 ohm output. Does that sound about right to you? 2) I've heard from several technicians who've repaired my amp that using a lower ohm output -- in my case 5.3 ohms against an 8 ohm speaker -- creates a fat, bassy sound. Does that sound correct to you? (From what I understand form your article, this is supposed to cause the amp to reduce or need less output?) 3) Is there any harm in slightly mismatching ohms this way?
      Phil Starr
      sorry but I'm not really familiar with Mesa Boogie amps so I'm reluctant to give specific advice on these. With valve amps and their matching transformer there are many more possibilities for designers to play with which is why most of my article sticks with the simpler physics of transistor amps. The output of your amp has both capacitors and the transformer in it and these will combine with the speaker to make a tuned circuit. This might well give you a little more bass with this mismatch though I am surprised it is so marked. There is little to worry about in this level of mismatch, the only thing that really threatens valve amps is leaving them open cicuit.
      Phil, thanks for your speedy reply. Perhaps a transistor amp question then? (I realize it may not be expedient to answer brand-specific questions but I am asking in the chance you may know and are able to answer. The product manual and "support" center has been unhelpful and unsupportve with my questions.) I recently acquired a Crate Powerblock, and it outputs as either: a) mono, 150W, 1 x 8ohms speaker, or b) stereo, 75W per channel, 2 x 4ohm speakers I'm wondering how much room there is for mismatching speakers: 1) In mono mode, is it safe to connect a 100W 8ohm speaker to the mono 150W outlet, if I don't push it hard? I am told I have to be incredibly loud and it'll be obvious I'm pushing the speaker too hard, way before it breaks. 2) Is it safe to connect a 4ohm speaker to only one (say the left) side of the stereo output, while leaving the other unconnected? With my Mesa Boogie 2-90 (stereo amp), there were 2 separate volume controls for left and right, so I could opt for using it as a mono amp, by connecting a speaker to one only one channel and being careful to leave th volume on the other channel completely turned down. With the Crate Powerblock, it seems you can also use it as an amp modulator, and connect only to a PA through its XLR out (no speakers connected), so I reckon it should at least be intelligent enough a unit so that it can detect that one speaker is not being connected when in stereo mode, and not dump a bunch of power that goes nowhere but stays to fry the circuits.
      Thanks so much for your reply. You are a wealth of information. I am currently on tour in switzerland until early April, and will follow this up when I get home. Yes, the Crate does operate exactly as you described: when in bridge-mode it's 150W to a single 8-ohm speaker. I did finally get a reply from Crate about the same questions I posed to you: "We are presently up to 2 weeks behind on e-mails and voice mails. We apologize for the wait, and hope to recover soon. "Since the amp is Solid State, you shouldnt have any issues. I normally switch things around every now and then, just so the amp sections do roughly the same amount of work."
      ok so my quetion is if i run a 65w rms 4Ohm speaker and a 30w rms 4Ohm speaker in parallel at 100w @2Ohms will the power flow 50/50 to each speaker or will the 65w rms one draw more power and leave the 30w rms one with less?
      Phil Starr
      Impedance isn't good or bad. It is just about matching speaker to amp to get the best out of both.
      Hi Phil I have a Genz Benz head which runs @ 8 or 4 Ohms, I want to use two cabs both of which are rated @ 4 Ohms and both have two jack inputs, Can I use one output from the amp to the first cab and then from that cab connect to the second, would connecting this way still give me the 4 Ohms I need
      Phil Starr
      If you connect two 4ohm cabs in parallel then the amp will be running into 2ohms. Without knowing the head I can't predict what would happen. PM me if you want any help with this.
      Hi. I have a Roland Jazz Chorus JC-50 amp(a mono version of famous JC-112) and can't seem to find specifications about the amp anywhere on the net. So I don't know exactly what the power is, impedance etc, but I guess since the JC-112 is 2x60W, and according to one review where a guy said JC-50 was 10W less in power than JC-112 it's probably 50W. The original speaker was buzzing like broken or something so I bought a Celestion Greenback G12M 25W/8Ohm speaker which is phrased all over the internet. My question is, since the amp is supposed to be 50W (I guess RMS), and the new speaker is 25W, should I have purchased a 16Ohm version instead? Would then the risk of burning the speaker be lowered? And would the only effect be the halving of the amps power? Would there be any serious audible side effects in terms of sound coloration except being quieter obviously? Thanx in advance, David.
      Phil Starr
      Ok the amp is 50W solid state according to wikipedia. but it doesn't say into which impedance. I suggest you email Roland to find out. What was the impedance of the original speaker? it may be marked. Without reliable figures I would guess the amp will give more than 25W into your speaker especially if you use a lot of distortion and would probably develop less than 25 into a 16ohm speaker. You would lose 3dB in volume into 18ohm but the Greenback is a high efficiency loudspeaker so it might be less than you think. Changing the speaker will change the tone as speakers are more coloured than amps. Your speaker may not match the cabinet very well which will also change the tone at the bass end. If you want more detailed answers pm me and I'll try to help.
      First let me tell you that I have been looking for an article like this on the internet for days...thank you for putting this one together it is very helpful. I have a quation about hooking up Yamaha's S112V in parallel. The Yamaha EXM312 mixer amp is rated at 300 watts per channel at 4 ohms. Does that mean that if I attach two S112v's rated at 8ohms in parallel I will be able to take advantage of the 300 watts the amp supplies? My second question is: How do I attach the physical speakers in parallel? Do I need to know their internal wiring? Thanks for all your help Tommy
      Phil Starr
      Yes, you've got it. I'm pretty sure that the S112's have two sockets on the back which will be wired in parallel. just connect them with an extra speaker lead. As a general principle you will find that most extra speaker connections are parallel and if you want to make a series connection you need special leads made up.
      hi phil just like to say thanks for the article realy helped been looking for something like this for days
      Good stuff. Pity about the lost diagrams.. (for noobs seeing is understanding).