Question about Impedance

[Sweet T]

Okay, so I have a Super Reverb clone at 2ohms. I also have an extension cabinet at 4 ohms with 2 12's. The maker assures me that the PT can handle the 4 ohm cabinet, and I think he's assuming I'm unplugging the 2 ohm cabinet. So, what happens when I plug that thing into the external speaker jack? Does that run the impedance to 0 or something?

[cameron]

Adding the 4 Ohm cab to the extension speaker jack will bring the total impedance to 1.3333...

The Super should be able to handle that (not many amps would be too happy with that load).

The formula for impedances in parallel, for given impedances p and q is:
1/x = 1/p + 1/qwhere x represents the resulting total impedance. Thus in your case, you're adding 1/4 and 1/2, which gives 3/4, and the reciprocal of that is 4/3, or 1.3333....

[Sweet T]

Cool, thanks man.