Okay, so I'm buying a mesa 400+ and powerhouse 1000 cab together for $1200 from a guy i know who's band plays shows with us. I should be getting the amp next Friday and am pretty excited about it, except for one thing. The amp sounds great and for our bigger gigs I barely barely have to turn it, master on 5, volume on 2, not much. But if I turn the volume up more it starts getting a really nasty dirstorted sound, not overdriven or grindy, but distorted. The level that this comes out is a lot louder than practical playing volumes so it has never affected a performance and I didn't get to really experiment long. I've never heard blown speakers before and I'm wondering if this is a possibility or if maybe it's just the grill vibrating harshly. I'm not sure how to go about this and the speakers look fine from the outside but I was wondering if there's a way to tell if it is blown and if not how to fix my problem. Thanks.