I have a 4x12 and a 2x12 both rated 8 ohms stereo, to use both at the same time, I set the head to 4ohms (its a Peavey Triple XXX... and i lost the instruction manual, and i want to be careful since i am dirt poor right now and couldn't afford replacing it)

__________________

Shouldn't it be 8 ohms mono? ???

Anyway if the impedance on both cabinets is eight ohms and you connect them both to the back of your XXX, set the impedance selector to 4 ohms.

I would advise rewiring the cabs to at least 16 ohms though, makes the presence control a little more responsive and the sound a little tighter (this can be proven).

__________________

There is no presence control but ok, I see your point.

Ummm then if I play them in the stereo input... Is that bad Without having 2?

__________________

Oh there is no presence! NVM then! The amp will still be tighter though.

Is there stereo and mono inputs on the cab?

You should run both cabs in the mono jack, then halve the impedance (i.e. the cabs are 16 ohms mono, run 8 ohms on the head)

__________________

Whats the difference between the mono and stereo? I thought if you used the mono it only used half the available speakers or something... Pretty retarded question I realize hahaha

__________________

Mono uses all the available speakers.. If you run it in stereo you'd need 2 speaker cables to use both sides. The stereo jacks are divided in one side each of the cab, and the mono jack uses both.

__________________