I have a Marshall Valvestate combo with one Celestion Gold 100Watt speaker at 8 ohms, I am also getting a Mesa Boogie 2x12 Extension cab with 2 Vintage 30 speakers, whole cab is 8 ohms. The combo has an extra plug for speakers. Could i plug in both the speaker in the combo, and the extension cab, totalling 3 speakers? Would it work? Good idea or not?
as long as the ohmage ends up being ok, you can use any number of speakers you want.
Yes, you can. Basically, the amp is going to see the Mesa cab as one 8 ohm speaker, and the Celestion as another 8 ohm speaker. If it has parallel speaker outs, it'll run at a total of 4 ohms, which should be ok. The wattage of the amp is going to be divided pretty much 50/50 between the Mesa cab and the internal speaker, though.