when i turn my car on my subs make a thump noise. then i cant turn them up too loud or one starts making a pop noise and its not bottoming out. subs are new and brokin in. i think it may be a ground problem but it seems like its grounded right. first ground i had was all amps grounded to one of my extra batts in the back of the car and a 2 guage running from the batt to the body of the car. i diddnt get a thump but it made a high pitch noise thru the subs constantly. then i grounded amps to the body of the car but now it thumps and i cant turn my subs up without them making a sound like somethings loose or its hitting something.