last october i bought two Kicker CVR10's.. for the past few months i have been very pleased with the set up and how it sounds. last week the left sub developed a rattle when i crank up the sub. it still gave sound but sounded like something on the inside of the sub. i took it out to see what the other sub sounded like alone and a few days later that one started to rattle. is this a problem with the subwoofer or is it an amp problem. i was told i could have something to do with the amp.. anybody have a clue?