Okay so I have never had any experience with blown speakers. I've never really pushed it hard enough. I have a GK stack so I get the usually overdrive growl known to GK but that's it. Until, the other day I notice that when I would play about 12 frets up on the E or the A string a horrible farting/distorting sound was coming from my bottom right 10" speaker. I took the grill off and examined the speaker but there is no visible sign of tearing or damage. What's up? Is it a voice coil? HELP