Installing an impedance switch in a 4x12 cabinet

[bentoast]

Hello! Been browsing the forum for a bit and have a question!

I have a speaker cabinet with 4 16Ω speakers. I want to re-wire it to a switch so I can toggle between 8Ω and 16Ω to use with different amps. I have an idea, but I thought I might ask for advice from people who probably know more about this than I would. How would I go about this?

[MikeO]

You can't get an 8 ohm total load with four 16 ohm speakers.
-Four 16 ohm speakers wired in parallel will give you a 4 ohm total load.
-Four 16 ohm speakers wired in series will give you a 32 ohm total load.
-Four 16 ohms speakers wired series-parallel will give you a 16 ohm total load.

[MikeO]

Two 16 ohms speakers wired in parallel will give you an 8 ohm total load, so if you wanted to wire the cab stereo, you could get 8 ohms per side.

[MikeO]

The Marshall 1960 cab has four 16 ohm speakers, and is switchable between 4 and 16 ohms when run in mono, or 8 ohms per side when run in stereo. You could replicate that setup if you want more flexibility. I'm sure there are wiring diagrams all over the net, but you would probably need a new jackplate with the appropriate switches.

[Tortuga]

MikeO has it right. If you're not comfortable wiring up your own, you can get one of these:

https://www.amazon.com/Jack-plate-Mono- ... B00E1P4LGE

[Tortuga]

Just make sure 2 of the speakers can handle whatever power you're putting onto them. If it's a 100 watt head and they're 25 watt greenbacks, you might be asking for trouble.

[bentoast]

You can't get an 8 ohm total load with four 16 ohm speakers.
-Four 16 ohm speakers wired in parallel will give you a 4 ohm total load.
-Four 16 ohm speakers wired in series will give you a 32 ohm total load.
-Four 16 ohms speakers wired series-parallel will give you a 16 ohm total load.

See that's what I was wondering. I kept thinking about how impedance either multiplies or divides, and I couldn't figure out how it would be possible to do 8 ohms in that setup. Thank you for clarifying that it cannot be done.

MikeO has it right. If you're not comfortable wiring up your own, you can get one of these:

https://www.amazon.com/Jack-plate-Mono- ... B00E1P4LGE

This is brilliant! This would look nice and clean as well.
I'm assuming additional wiring would be needed then to pull this off? Where might I find a wiring diagram to hook this up and make the magic happen?

[Tortuga]

Two 16 ohms speakers wired in parallel will give you an 8 ohm total load, so if you wanted to wire the cab stereo, you could get 8 ohms per side.

You missed Mike's other comment, OP - yes, it can be done, but not with 4 - 16 ohm speakers - you can only use 2 of them, in parallel, which halves the impedance to 8 (putting them in series would double them for 32, which you don't want)

Here's a link to the wiring diagram. All you gotta do is run the left +/- pair to one of the speakers, and then run leads from it to the other. Same for the other pair of speakers.

The hard part is already done