2X12 Cab - Series or Parallel?

[odourboy]

It's been asked before and it will probably be asked again, but there's conflicting opinions on this, so I'd be curious what you all think (being more informed than your average bears!!)

In my latest build (a D-clone in parts acquisition stage), I'll have 4, 8 and 16 ohm taps on the OT. I'm going to put together 2X12 cab to go with it. I'll most likely go with 8 ohm speakers, so the question is, should I wire the cab in series and use the 16 ohm tap or in parallel and use the 4 ohm tap?

So some people think you should use the maximum windings on your OT (which I believe would be the 16 ohm tap). Some think you should use the minimum windings to reduce distortion. I've read that series wiring will cut the damping factor in half (makes sense) but is that a good thing or a bad thing (an audible thing?) on a guitar amp?

Opinions sought!!

(Side question, or am I making a mistake with the 8 ohm speakers and should I instead get 16 ohm speakers and wire in parallel and use the 8 ohm tap?)

[mooreamps]

Well, the way I do it ; I get the two 16 ohm speakers, wire them in parallel, and plug into the 8 ohm output jack.

Now, that being said. I'm debating pulling the output transformer "out" of the chassis, and installing it inside my 2x12 and 4x15 cabs. I'll wire it up correctly inside the box, less guess work outside the box.

-g

[Darkbluemurder]

Wiring speakers in parallel has the advantage that if one driver fails the other keeps going (the question is only how long if it has to handle all the amp juice). If a speaker in series wiring fails, then the cab is silent.

As for tone - if you go for 8 ohm speakers try both ways and see what you like better. But there is no reason to use series wiring in order to use the highest impedance tap on the amp - the taps are there for convenience.

Of course if you go with the 16 ohm speakers you can only wire them in parallel - there is no amp I know of that has a 32 ohm output transformer which would match the series impedance.

[drhulsey]

Opinions sought!!

This is the most versatile way to wire a 2x12 cab, especially if you have to different sounding 8 ohm speakers. It gives you not only parallel and series, but each speaker individually. This is not original with me.

[odourboy]

Opinions sought!!

This is the most versatile way to wire a 2x12 cab, especially if you have to different sounding 8 ohm speakers. It gives you not only parallel and series, but each speaker individually. This is not original with me.

That is slick!

[odourboy]

Wiring speakers in parallel has the advantage that if one driver fails the other keeps going (the question is only how long if it has to handle all the amp juice). If a speaker in series wiring fails, then the cab is silent.

I'm not convinced this is a strong arguement. How often does a speaker fry so badly that is goes open circuit? OTOH, if it did happen, maintaining connectivity to the other speaker would save your OT from cooking.

As for tone - if you go for 8 ohm speakers try both ways and see what you like better. But there is no reason to use series wiring in order to use the highest impedance tap on the amp - the taps are there for convenience.

Well this is really the heart of the question. Transformers are far from 'ideal' components. I'd like to believe there's no reason not to select whichever tap is the most convenient, but my gut tells me one might be better than the other.

Of course if you go with the 16 ohm speakers you can only wire them in parallel - there is no amp I know of that has a 32 ohm output transformer which would match the series impedance.

My thougts as well. Plus, I can more easily break up the pair to use individually or sell if they're 8 ohm.

Any opinions on the damping factor impact?

[skyboltone]

Now, that being said. I'm debating pulling the output transformer "out" of the chassis, and installing it inside my 2x12 and 4x15 cabs. I'll wire it up correctly inside the box, less guess work outside the box.-g

Let me see if I got this right. You're going to run your high voltage from B+A in some sort of cord, then run the two outer taps back up the cord, into the amp and to the ouput tube sockets. And what exactly are the advantages to that? What sort of connectors will you use? Wire type? Shielded of course. Hmmmmmm.

[benoit]

Now, that being said. I'm debating pulling the output transformer "out" of the chassis, and installing it inside my 2x12 and 4x15 cabs. I'll wire it up correctly inside the box, less guess work outside the box.
-g

What benefit would you gain by doing this? I assume you're talking about somehow mounting the OT in the speaker cab (i.e. not bolted to the chassis).

[mhuss]

Damping just means how long it takes the speaker to stop moving after the signal stops.

A lower impedance source will provide better damping, if all other things are equal.

How does this translate into sound? Well, for lack of a better explanation, low DF sounds "looser" and high DF sounds "tighter."

This is really academic with a tube/valve amp, because any of the taps have a higher output impedance then even a mediocre solid state amp, and IMO you'd be hard pressed to hear much if any damping-based difference between the 4 and 16 ohm taps.

--mark

[odourboy]

This is really academic with a tube/valve amp, because any of the taps have a higher output impedance then even a mediocre solid state amp, and IMO you'd be hard pressed to hear much if any damping-based difference between the 4 and 16 ohm taps.

--mark

That's the sort of info I'm looking for! Thanks Mark. Any thoughts on the sonic merits of using the 4 ohm tap versus the 16 ohm from the 'use the least transformer, minimize distortion perspective' versus the 'use the whole transfomer' school.?

[mhuss]

Unless you're building a jazz amp , you're going to be "bending" the transformer anyway when you're cranking it up, so I wouldn't worry about the relative amount of distortion.

I can't see how it would make a difference anyway, since AFAIK it's more how it is wound, how the lams are stacked, what they're made of, etc. that wound affect the THD of a moderate signal passing through the OT.

--mark

[jaysg]

In my latest build (a D-clone in parts acquisition stage), I'll have 4, 8 and 16 ohm taps on the OT. I'm going to put together 2X12 cab to go with it. I'll most likely go with 8 ohm speakers, so the question is, should I wire the cab in series and use the 16 ohm tap or in parallel and use the 4 ohm tap?

Some Rivera 2-12"s are done with series 8 ohm speakers. They're always identical speakers -- not risking any mismatched response. Some of their amps have an NFB control called Focus. (I suppose the common term is Soul control.) When mated, you have the ability to dial it back in, if it seems too loose. If you did that on your D-clone, you might want Nominal to be mid-sweep, not at one end.

[odourboy]

In my latest build (a D-clone in parts acquisition stage), I'll have 4, 8 and 16 ohm taps on the OT. I'm going to put together 2X12 cab to go with it. I'll most likely go with 8 ohm speakers, so the question is, should I wire the cab in series and use the 16 ohm tap or in parallel and use the 4 ohm tap?

Some Rivera 2-12"s are done with series 8 ohm speakers. They're always identical speakers -- not risking any mismatched response. Some of their amps have an NFB control called Focus. (I suppose the common term is Soul control.) When mated, you have the ability to dial it back in, if it seems too loose. If you did that on your D-clone, you might want Nominal to be mid-sweep, not at one end.

Curious you should mention the focus. I have a Rivera. And I also built a 'Focus' control pot into the NFB loop of my lfirst D-Clone build to tweak because I thought the Rivera NFB control was a cool idea.

[mooreamps]

Now, that being said. I'm debating pulling the output transformer "out" of the chassis, and installing it inside my 2x12 and 4x15 cabs. I'll wire it up correctly inside the box, less guess work outside the box.-g

Let me see if I got this right. You're going to run your high voltage from B+A in some sort of cord, then run the two outer taps back up the cord, into the amp and to the ouput tube sockets. And what exactly are the advantages to that? What sort of connectors will you use? Wire type? Shielded of course. Hmmmmmm.

Just one cable to connnect between the amp and the cab. No guess work.

-g

[novosibir]

This is the most versatile way to wire a 2x12 cab, especially if you have to different sounding 8 ohm speakers. It gives you not only parallel and series, but each speaker individually.

That's from one view point genious, but becomes horrible, when the 'corrosion's devil' will be creeping into this total of 8 switching contacts.

I've learned it the hard way over many years, that it's almost always better, to keep things as simple as possible.

Larry