I've just bought a second 2x12 and wanted to make a temporary 4x12.
One cab is loaded with 2x16ohm G12-75 and the other 2x15ohm G12-65. And hence 8 ohms per cab.
How would I go about wiring them so that I can use the 2x12 for general use on the 8ohm setting of my amp but then when I need the extra speakers I can daisy chain them and put them in the 16 ohm jack without needing to rewire every time.
With a single pole two position switch. Wire the cabs in series. Terminate the actual series tap connection between the two cabs to one switch select position (8 ohms) and terminate one end of the two cabs in series to the other switch select position (16 ohm). Take the switch common back to the amp cab out -. The other end of the two cabs connects to the amp cab out +

This can be done neatly with an output jack. Make sure the switch is solid duty variety since its going to carry some power.

Id draw a pic but im using my phone

Make sure the cabs are in phase and always make sure if you use the series switch that your amp output is set to the same ohms before firing up.

EDIT: Drew a pic when I got home.
Series Cab Switch.jpg
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Last edited by Phoenix V at Sep 6, 2013,
Thanks man, this is perfect!
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One comment -- to avoid beaming ice-pick treble (unless you *want* to beam ice-pick treble), consider putting the speakers vertically, in a 4x1 column rather than in a horizontal configuration that ends up with four 12" speakers in a square. You'll get wider horizontal dispersion and you'll be better able to hear what you really sound like.