two 3x12 cab wiring? possible?

[giam23]

ok technically the title is misleading as its two 3x12 cabs but anyway.

i recently picked up two old 3x12 PA columns unloaded for filthy cheap. they match nice under my 66 JTM50 PA head. Now i didnt think about this until now but you cant wire these normally as they are in 3s

Heres my thinking (assuming all speakers are 16ohm and they measure at 13ohm):
Each cab has a pair in parallel, which is then in series with the 3rd speaker. this means each cab is 19.5ohm so if you plug both cabs into the amp in parallel then you would see 9.75ohm. this should work on the 8 ohm setting right?

or do i give up and just put 4 speakers in and either cover the other holes or leave them open like a ported cab. keep in mind i havent bought any speakers yet but i will be buying some vintage 16ohm celestions as they might end up in a marshall cab later on

 

[fitz]

Higher speaker load is better than lower on a tube amp OT tap, but still adds more stress than a matched impedance.
Have you considered 2x16 parallel and then series with an 8 for a 16 ohm cab load?

 

[TassieViking]

If you have 2 in parallel and then in series with the last one the speakers will not get even load, speakers in parallel get 1/4 of the power while the speaker in series gets 1/2 of the power.

I think 3 x 16 ohm speakers in parallel will be just over 5 ohm so you should be able to run them on a 4 ohm setting

If you wanted to try some different speakers in one cab then 2 16 ohms in parallel with one 8 ohm in series will give you 16 ohms, the 8 ohm speaker needs to be double the power rating of the 16 ohm speakers.

Weber has some 24 ohm speakers available, that would make it 8 ohm with 3 in parallel.
Weber silver wolf, grey wolf etc.

 

[RLW59]

You mention that the speakers you buy may end up in "a Marshall cab" someday. If that's a 412, might not be much point in buying 6 speakers now.

If you start with 4 speakers now, you can do a lot of experimenting. Start with just one 312 cab -- 2 speakers with the third hole open, 2 speakers with the third hole covered, all three speakers. See which configuration sounds best. If it turns out that 3 speakers sound best, then shop for another pair of speakers.

 

[PelliX]

Heres my thinking (assuming all speakers are 16ohm and they measure at 13ohm):

DC resistance is just a ballpark indicator. Don't base your calculations on it, but rather use it as a ballpark confirmation of what you've deducted by crunching the numbers, so to speak.

Each cab has a pair in parallel, which is then in series with the 3rd speaker. this means each cab is 19.5ohm

Hm? Two 16 Ohm speakers in parallel = 8 Ohms. Add the third speaker in series and you're at 24 Ohms (8+16). If you run two cabs in parallel with that setup you've got a 12 Ohm load (24/2). Yes, ballpark figures as impedence is measured at a given freqency (or average across a spectrum) and most people tend to play all kinds of notes.

That would be alright on an 8 Ohm tap. The idea of the 24 Ohm speakers is actually interesting. Also, if you have some kind of attenuator which abstracts the load presented to the amp, you have a lot more flexibility.

 

[RLW59]

Do you have pics, or a brand and model number so we can Google exactly what you've got?

Fender did a 610 open back combo. Univox did 612 closed back extension cabs for a while. Fender went with a mild impedance mismatch, not sure how the Univox's were wired. It could certainly be fun to try them as a pair of 312's.

 

[RLW59]

The Super Six Reverb was a Twin Reverb chassis driving 6 10" speakers.

 

[giam23]

Do you have pics, or a brand and model number so we can Google exactly what you've got?

Fender did a 610 open back combo. Univox did 612 closed back extension cabs for a while. Fender went with a mild impedance mismatch, not sure how the Univox's were wired. It could certainly be fun to try them as a pair of 312's.
View attachment 156477

They are a pair of Aussie made eminar columns pictured here, yes I am aware the baffle on the left one is upside down that’s how I got it

You mention that the speakers you buy may end up in "a Marshall cab" someday. If that's a 412, might not be much point in buying 6 speakers now.

If you start with 4 speakers now, you can do a lot of experimenting. Start with just one 312 cab -- 2 speakers with the third hole open, 2 speakers with the third hole covered, all three speakers. See which configuration sounds best. If it turns out that 3 speakers sound best, then shop for another pair of speakers.

I have a bunch of random loose old celestions, all are 16 ohm, but im planning on buying a quad fo speakers for these columns, ive got other random mepty cabs so ill eventually swap them.

 

[Frodebro]

DC resistance is just a ballpark indicator. Don't base your calculations on it, but rather use it as a ballpark confirmation of what you've deducted by crunching the numbers, so to speak.



Hm? Two 16 Ohm speakers in parallel = 8 Ohms. Add the third speaker in series and you're at 24 Ohms (8+16). If you run two cabs in parallel with that setup you've got a 12 Ohm load (24/2). Yes, ballpark figures as impedence is measured at a given freqency (or average across a spectrum) and most people tend to play all kinds of notes.

That would be alright on an 8 Ohm tap. The idea of the 24 Ohm speakers is actually interesting. Also, if you have some kind of attenuator which abstracts the load presented to the amp, you have a lot more flexibility.

If I had to run those cabinets, I would probably do three eight ohm in series per cab for 24 ohms, then run both cabs in parallel to bring it down to 12. That way all six speakers would be running equal current.

 

[JohnH]

Awesome cab! I'd suggest to wire it so each speaker is treated equally. If you do things like two in parallel then one in series the series one will take a much bigger share. Same if you do that twice and combine.

It might depend on your amp taps but one recipe is three in parallel to make 16/3 ohms = 5.3 Ohm. Then all the same as a group, wired with the two groups n series. That'd be 5.3+5.3 = 10.6 ohm, fine to run off an 8 Ohm tap and every speaker gets the same share of power.

 

[Matthews Guitars]

If you put two in series and one in parallel, OR two in parallel and one in series, the power distribution between the speakers will NOT be equal and the results will be unsatisfactory. One (or two) speakers will be louder than the other(s).

Three 16 ohm speakers in parallel makes a 5.333 ohm load, perfectly safe and acceptable on the 4 ohm tap.

 

[giam23]

If you put two in series and one in parallel, OR two in parallel and one in series, the power distribution between the speakers will NOT be equal and the results will be unsatisfactory. One (or two) speakers will be louder than the other(s).

Three 16 ohm speakers in parallel makes a 5.333 ohm load, perfectly safe and acceptable on the 4 ohm tap.

three 16 ohm in parallel sounds like the best option. im going to want to run both cabs so i could modify one of the cabs to have another output jack. one cab piggy back onto the other with a speaker cable, and from the second cab to the head. this way you can easily wire the two in series to get 10.666 ohms and use that on the 8 ohm tap. this way you would have to use both cabs and cannto use them seperately. that may be possible with switching jacks but i cannot be bothered figuring that out for the moment

Also worth noting most od the amps i will be using this with do not have a 4ohm tap, only 8/18

 

[mark 11:11]

this is a left field suggestion well more idea than suggestion
if you have 4 8 ohm drivers and a pair of 16ohm drivers
put a pair of 8 ohm drivers in series and now treat that seris pair as if it was a single 16ohm speaker [as far as wiring is concerned] you them put a 16ohm driver in parallel
you now have an 8ohm cab.............
obviously this means the pair in series get half of that cabs power and the other single 16 gets the other half but its just a thought
you would end up with an 8ohm cab so put both in para off the 4ohm tap on the amp or put the two cabs in series and use the 16ohm tap
this is just an idea which would work best if the different power to each coil isnt an issue like a pair of 25w greenies and a v30 as the 16ohm speaker just an example
edited because i wrote 4 of a pair instead of 4 of and a pair of

 

[GIBSON67]

Awesome cab! I'd suggest to wire it so each speaker is treated equally. If you do things like two in parallel then one in series the series one will take a much bigger share. Same if you do that twice and combine.

It might depend on your amp taps but one recipe is three in parallel to make 16/3 ohms = 5.3 Ohm. Then all the same as a group, wired with the two groups n series. That'd be 5.3+5.3 = 10.6 ohm, fine to run off an 8 Ohm tap and every speaker gets the same share of power.

This is the best answer I've seen.