Mark IV Combo built-in speaker + external 8-ohm speakers?

[SeasonOfPain]

Hi all! Just joined the board; been a long-time Triaxis owner, but last week I picked up a new Mark IV WB Combo and a Mesa Std 4x12. In addition to the 4x12 I have two Mesa Recto 2x12 cabs (one vertical, one horizontal).

I've gotten great sound from all these cabs running from the 8-ohm output (unplugging the built-in speaker). What I'd like to do is run both the built-in and the external cabinet. However, I'm unsure about how the parallel hookup will affect the impedence. The Mark IV has 1x8 ohm out and 2x4 ohm outs.

The cabs:
4x12 - 8 ohm or 2x4 ohm inputs
2x12 - 8 ohm inputs only
1x12 combo - 8 ohm (I assume?)

Which Mark outs should be used with which speaker ins when running in parallel?

I'm sure this is a very basic impedence question, but I'm used to running 2 cabs out of a stereo 50/50, so forgive my ignorance.

 

[chedgeco]

SeasonOfPain,

It looks like all of your extension cabs have 8 ohm inputs, yes.

What you would do is use the 4 ohm outputs on your amp. Plug the 1x12 combo speaker into one of the 4 ohm outputs and attach the other 4 ohm output to "one" of the extension cab's 8 ohm inputs. The amp will see a total impedence load of 4 ohms.

chedgeco... 8)