Fancy wiring for a speaker cab -- is this possible?

[bduersch]

Okay, this could be a relatively easy electrical question, but I'm not about to blow an amp or a speaker based upon my complete lack of electrical knowledge.

I've got a 2x12 cabinet with two 16 ohm speakers wired in parallel, making an 8 ohm cab. There are 2 speaker jacks on the back, connected in parallel as well, so if I chained a second 8 ohm cab I would end up with a 4 ohm total load.

What I would like to do is install a switch on the jack plate that does the following...

In one position, the cab works exactly like it does now... the speakers are connected in parallel, resistance is 8 ohms, and the second jack is connected in parallel as well.

In the second position, the cab turns into a stereo cab, where each 16 ohm speaker is connected to its own jack.

Anyone have the electrical skills to pull this off?

Thanks,
--Brent

(Optional extra credit question... if I had a 3-way switch, could I wire the two positions above plus a third, where the speakers are connected in parallel, resistance is 8 ohms, and the second jack is connected in series, allowing me to run both cabs on a 16 ohm load?)

[steve]

There's a better way - replace one of the jacks with an interruptor one. It would allow you to have the speakers remain in parallel when you're plugged into the one jack you designate as 'Mono' or what-have-you. Internally, that plug is chained over to the other speaker via the 'second' or 'Stereo' jack... so, as soon as you plug in the second speaker cord, the 1/4" jack breaks the connection to the original speaker, thereby connecting the second jack JUST to the second speaker... and allowing the 'Main/Mono' speaker to continue working with the original cabling.
8 Ohm in parallel - mono, or 16 Ohm x 2 - stereo.
Viola!

(I have a Marshall 2 x 12" that I've done this very thing to, except that this one never had a second speaker jack, so I had to add that from scratch, too.

Hope this helps - ask away if you have other questions about this.

[bduersch]

Steve--

Come to think of it, I think I used to have a Johnson 2x12 cab that worked like you described. It was pretty cool, but not exactly what I'm looking for in this case. Let me try this again, but a little simpler this time...

I want a 2-position switch on my cab that gives me the following 2 options:
1) stereo operation: jack A -> speaker A, jack B -> speaker B
2) mono operation: jack A -> speakers A & B in parallel, jack B = parallel out to another cab

If this isn't possible, then I probably will go the route with the interrupter jack like you described.

Thanks,
--B

[steve]

Damn - I just found out that, if you take too long to submit a reply, the message window is cleared... SO I just lost my original message to you.

Okay, I have figured it out, and I'm going semi-lo-tech on my method of getting this info to you.

Okay, here's a link - go into the Pictures folder, and there's a .jpg for you.
It's a shot of the quick wiring diagram I jotted onto a Post-It pad...
=]

Go to the Pictures folder, and the (currently) only pic in there is for you...

It's hi-res, so should be quite legible (if rather large).

Uses a DPDT switch, and the existing jacks.
Remember - adding a third speaker or cab lowers the ohms accordingly... be sure your power amp/power section can handle it.

Hope this helps.
... the more I think of it, the more I'd suggest something else - instead of tying the grounds together, you could get a 4PDT switch, and do the same relative wiring scheme for the ground wires, as well. This will keep things isolated in case you run an entirely different signal path to the other speaker when in Stereo mode, helping to eliminate the speaker lines as a contribution to ground loops and such.

Other questions, fire away. I'll do what I can to help.
Sorry for the crudeness of the diagram - didn't want to take the time to do a full-blown schematic in a CAD program or anything.
=]

[steve]

PS - once you've gotten the diagram, let me know, as I guess I'll delete that pic from my space. It's an almost embarassingly quick and 'dirty' way of documenting the idea, but hopefully it gets the point across.
Let me know.

[bduersch]

Steve--

Cool... that's exactly what I was looking for!! Thanks for your help!

--B

PS--I did download the picture in case you need to free up space

[darren wilson]

My Genz Benz G-Flex 212 is wired kinda how you'd want. It's got four jacks. Mono 4-ohm, left and right stereo 8-ohm and a mono "thru" jack. No switching required.