Series Parallel or Parallel Series Cab which is it?

908SSP

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5,801
Remember a few weeks ago we discussed the difference between series/parallel and parallel/series in a 4x12 cab? I was not completely clear on the wiring and I certainly don't understand why it would sound different but this picture was posted in the emporium and I was wondering which wiring scheme would it be wired to and at what ohm? Honestly it isn't the easiest thing to follow what with all white wire. But I have wired a few cabs and never done one like this.

 

John Phillips

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13,040
That is two parallel pairs in series.

Look at the right-hand two speakers - they're paralleled, and obviously the left-hand two are as well even though you can't see the bottom one. The 'horizontal' wire at the top is the series link. The two wires at the bottom go to the jack.

That's different from the standard Marshall wiring of two series pairs in parallel. It will sound very slightly fuller and deeper.

It's the same impedance though - the same as each individual speaker, which is 15 ohms (visible on the top left speaker).


FWIW, 'series-parallel' and 'parallel-series' tend to be used at random with no consistent meaning, so it's unwise to rely on the description. I just think of them as a way of describing a combination of the two, which does at least always produce the same impedance...
 

908SSP

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5,801
Thanks Dis and John it does look like that pdf file. Not an obvious way to wire it my opinion. I tried the 4 ohm jack on my 4x12 Scumbag speaker 1960 Marshall cab and I think there is slightly more bass. I think I will rewire it for a single jack in 4 ohms eliminating the circuit board.
 

amper

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664
Originally posted by John Phillips
That's different from the standard Marshall wiring of two series pairs in parallel. It will sound very slightly fuller and deeper.
Is there an easy explanation for that, John?
 

John Phillips

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13,040
Hmmm... Randall Aiken can really explain this one!

Basically, in the parallel-pairs-in-series wiring, each speaker is more heavily damped, because it's in parallel with another speaker (low impedance) and in series with another two in parallel (also low impedance). Low impedances in parallel damp a speaker.

In the series-pairs-in-parallel wiring, each speaker is less damped because it's in series with other speaker, before that is then in parallel with two more in series (higher impedance). The speakers being in series lowers the damping quite a lot.

Something like that, anyway ;).
 

GregR

Member
Messages
18
really, the only difference would be whether the two center connections are joined or not.

you either have a wiring scheme that looks like this: II

or one that looks like this: H

you could just put a switch on the cab to either connect or disconnect the two center wires and flip between the two "damping" modes. the rest of the wiring is identical otherwise.
 




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