2 x 12" 8 ohm speakers. Series or Parallel

surfguy13

Just about to install two 12" 8 ohm alnico speakers into a 2x12 cab.  I currently have two 16ohm drivers wired in parallel in the cab for 8ohms.  I am using a Marshall clone head based on a bluesbraker circuit and the amp has 4, 8 and 16ohm options.

Not sure whether series and running them at 16ohms will give me the best sound or whether parallel at 4ohms may be better?  I have always had my bass cabs wired for 4ohms but have never run a 2x12 guitar cab at 4ohms before.

Just wanted to get the best out of the speakers so any advice would be welcome!  

ICBM

Series at 16 ohms.

Parallel is better for bass because it increases the damping factor of the speakers, but that's the opposite of what you want for classic rock guitar sounds.

16 ohms also uses the full winding of the transformer, which increases its inductance and also makes the sound brighter and more dynamic.

surfguy13

ICBM said:

Series at 16 ohms.

Parallel is better for bass because it increases the damping factor of the speakers, but that's the opposite of what you want for classic rock guitar sounds.

16 ohms also uses the full winding of the transformer, which increases its inductance and also makes the sound brighter and more dynamic.

What can I say, absolutely brilliant, thank you @ICBM, that really does sum it up perfectly.  Series it is!  

RiftAmps

ICBM said:

16 ohms also uses the full winding of the transformer

I've often questioned this @ICBM - the entire secondary winding is always energized, even when using the 4ohm tap on a 4/8/16 setup. We know this to be true because NFB is often tapped from the 16ohm regardless of which tap is used for speaker connection - see many Marshall amplifiers.

The transformer/OP valves don't care which tap you use, as long as the reflected impedance is correct.

ICBM said:

which increases its inductance and also makes the sound brighter and more dynamic.

Yes, inductance increases but that's not the only variable in that scenario, so not entirely sure how you've reached that conclusion?

ICBM said:

Parallel is better for bass because it increases the damping factor of the speakers, but that's the opposite of what you want for classic rock guitar sounds.

Agree with this

ICBM

RiftAmps said:

I've often questioned this @ICBM - the entire secondary winding is always energized, even when using the 4ohm tap on a 4/8/16 setup. We know this to be true because NFB is often tapped from the 16ohm regardless of which tap is used for speaker connection - see many Marshall amplifiers.

The transformer/OP valves don't care which tap you use, as long as the reflected impedance is correct.

Yes, inductance increases but that's not the only variable in that scenario, so not entirely sure how you've reached that conclusion?

I know, I always questioned whether it matters too! You could have a 100V Line winding on top - many transformers on old amps did - and it wouldn't be better to use that just because it's there... but for whatever reason, I have found it to be *usually* true that you seem to get a brighter and more dynamic sound when you use the highest impedance available, assuming that's possible.

surfguy13

Great advice on the wiring @ICBM. ; Installed a pair of alnico speakers at 16 ohms as you suggested and the performance of the cab is definitely improved.  Its almost as if the amp has had a power boost; both high end and low end seem so much crisper and more dynamic.  OK, I am replacing old ceramic speakers with alnicos so that may have something to do with it but the cab feels tighter and I seem to be getting far more sustain.  

ICBM

surfguy13 said:

Great advice on the wiring @ICBM. ; Installed a pair of alnico speakers at 16 ohms as you suggested and the performance of the cab is definitely improved.  Its almost as if the amp has had a power boost; both high end and low end seem so much crisper and more dynamic.  OK, I am replacing old ceramic speakers with alnicos so that may have something to do with it but the cab feels tighter and I seem to be getting far more sustain.  

That's far more likely to be the difference in the speakers - parallel vs series wiring matters, but is much less important. You could try those same speakers in parallel if you can be bothered to find out though!

surfguy13

I can definitely be bothered.....it would be 4ohms though, is that OK?  

ICBM

surfguy13 said:

I can definitely be bothered.....it would be 4ohms though, is that OK?  

Yes, if the amp has a setting for it.

surfguy13

ICBM said:

surfguy13 said:

I can definitely be bothered.....it would be 4ohms though, is that OK?  

Yes, if the amp has a setting for it.

Brilliant, thanks for that.  yes, it has 4,8 and 16 so no problems.  I'll give it a go!!