I had a bazooka EL8 (tube) put on today...how come when I turn on the car there is a thump that comes from the sub and also when I push the shift button on the headunit to move to another song on the CD the thump goes on again..it kinda bugs me..IS THIS NORMAL ?OR do I have to go back to the installer to have this addressed. Thanks. If your shop wasn't too far I would nhave gone there myself. Anyway thanks and MERRY CHRISTMAS!