Please, tell me which output to use to run my MC212 out of my DSL40. I want to run all three speakers at the same time.
Not experienced with your hardware, but looking at the specs online I dont think this is directly possible.
I beleive your amp has a 16 ohm speaker, and the cabinet is 4 ohms in mono mode or 2 x 8 ohms in stereo mode.
The outputs on the back of the amp suggests there can be total loads of either 4, 8 or 16 ohms.
It looks like there is no way to combine the speakers to provide 4,8 or 16 ohms.
You could in theory rewire the speaker cabinet in series to make the 2 x 8 ohms 16 ohm (as I assume in mono mode they are wired in parallel to give 4 ohms)
This would in effect give you 2 x 16 ohm speakers (16 ohms from internal speaker and 16 ohms from rewired cabinet).
Looking at your amp model online it looks like it has 2 x 16 ohm outputs so the internal speaker would plug into one and the cabinet would plug into the other.
Maybe someone else has actually tried this and can comment?