if you push it down and you feel a grinding crunchy feeling most likely the sub crapped out, and the coils may have just gave out , smell inside the sub for a burnt smell if that the case then its gone, it happened to me when i plugged a cheap 500 watt sub to my sony 2200gtx to test how it would sound when i bridged it kicked but for like 30 minutes untill i smelled something burning in trunk made me cough pretty good , just a test sub it was like only $30 R.I.P