Okay, last night I took the subs out and played them free air for a little bit on a couple of songs to see what happened, but no mechanical noise came from them. My thinking now is that it's the amp since the speakers seem fine and it's happened in two different boxes. I'm thinking there's still a chance it's the subs because it only happens at higher volumes (ie more power going to the subs), but higher volume also only put out about 350W to each sub and it was making the pop. I wanna just say screw it and throw another amp in there, but that's extra money I'd rather not have to spend. I do have an immediate replacement plan on the subs if they are bad, but it's a one time use and I don't want to use it prematurely. Guess I'll go with another amp and see what happens. //content.invisioncic.com/y282845/emoticons/crap.gif.7f4dd41e3e9b23fbd170a1ee6f65cecc.gif