One speaker output - 2 cabs

kelpbeds

I have a Marshall Plexi with one speaker output (other output space is now a master volume) I want to connect 2 Marshall 1922 2x12 cabs to the one head.
On the back of the cabs are two inputs (one for mono at 8 ohms and the two for stereo at 16 ohms)
I was led to believe that I could come out the speaker out on the amp to one of the cabs and then use the other connection on the same cab to connect to the other cab. And that they would then be running in parallel, so I should set the amp at 4 ohms (whereas to my way of thinking they would be now in series and therefore the amp should be set at 16 ohms)
Anyway. It doesn't work. When I connect the cabs only the first cab works. Tried them both ways round.
Any ideas?

Thanks

ICBM

The jacks on the cabs are for stereo and can’t be used like that. It would be easy to modify them so they can be - you need to bridge the jack switches.

The cabs will be in parallel regardless of looking like they’re in series, so the amp should be set to 4 ohms.

kelpbeds

Thanks - could  I take the output from the back of the amp and use a splitter to then send two cables one to each cab?

kelpbeds

Or to bridge them do I just connect the inside ring of the one input to the inside ring of the other input and connect the outside ring of the one input to the outside ring of the other input? (so connect them in parallel basically)
Thanks

ICBM

kelpbeds said:

Thanks - could  I take the output from the back of the amp and use a splitter to then send two cables one to each cab?

Yes.

kelpbeds said:

Or to bridge them do I just connect the inside ring of the one input to the inside ring of the other input and connect the outside ring of the one input to the outside ring of the other input? (so connect them in parallel basically)

Yes, they need to be in parallel.

The plate should look like this on the inside -



On the right-hand jack, you need to bridge the two gaps, or for ease you can cut the two plain wires and rotate the jack so you can then solder them to the same pins the wires are on.

It would probably be best to put some tape over the panel print on the back just so no-one tries to connect stereo inputs to it, which wouldn't be a good idea with the jacks paralleled.

kelpbeds

That's brilliant, many thanks for your help

rico

kelpbeds said:

That's brilliant, many thanks for your help

Give the man a wisdom!