The rehersal space my band uses has a beat up Marshall 4x12 cabinet that I need to use with my Bumbox head. The head has taps for 4, 8, and 16 ohms. The cabinet has no markings telling me its resistance. I figure it's either 8ohms or 16ohms, but I have no idea which one. Last week I just used the 8ohm out figuring I was still safe if it was 16ohms. My sound was a little muffled last week, so I'm figuring it's a 16ohm cab, but I don't want to take chances with my transformer. Is there a way I can use a DMM or something to test the reistance of the cab without opening it up?