Help! My mesa studio 22 has a 4 ohm jack and an 8 ohm Jack. The internal speaker is 8 ohms, and I have an external cab with one 8 ohm speaker. How should I do this? Plug main into 8 ohm, external into 4? vice versa? Or find a way to plug into the 4 ohm with some kind of y speaker cable, if such a thing exists?