Alright, so plenty of you guys know guitar rigs better than I. My guitarist's rig is making a weird, distort-y sound when he plays. It's not the head, as we've tested another one on the same cab. We thought it was something loose in the cab, so we opened it up and tightened all the speakers down. Still happening. I can hear it rattling when I'm playing bass alone in the room. What do you think? Loose grill? I'm thinking maybe, but haven't tried to tighten it up yet. Don't want to dig in unless he's around, you know? Anyway, any thoughts would be helpful, and thanks!