The JBL subwoofer causes noticable vibrations w/i the spare tire or toneau cover. The cover is tight. The spare is tight. Noraml listening volume about 15-21 on the radio face. Bass is at a resonable level. A little distortion can be heard from inside, but really noticable when your outside next to the spare. It is definately comming from the spare tire/toneau cover. Not the speaker. Anyone have this problem? Maybe a normal sound too because the subwoofer is in the tailgate. Thanks.