my 94 ls

every time i turn the key on, change the station, or the song on a cd a loud thump noise comes from my sub.

i have a new pioneer radio(cant remember model) a rockford 250x2 amp, and a mtx thunder 6000. i have also had a 7000 in it to same problem.

 

did it thump the very first time you turned the new radio on, or only after you used it a while. its possible the radio or the amp has a burnt ground run going to the shielding on the rca jacks.