I have a sundown sa-12 in a 2ft 35hz ported custom built box powered by a 1200w hifonics Zeus amp. Inside a 2000 Grand am. Lately I have been hearing the rear deck of the car, and platsics, Rattle more than I can hear the bass. The bass just doesn't fill the car like it used too. Usually it's like that in the cold weather so I always warm the car up so the rubber surround is less stiff, but nothing seems to be working. The sub moves fine doesn't seem blown, there's always been kind of a paper rattle sound when I turn up the volume, but Its not something you hear unless your right next to the sub. Could there be something wrong with the box? Or Sub? Maybe amp? There's no sound dampining material in the trunk or doors. Any help would be apreatiated. Thanks!