System pops during start up.

I just got my system installed. When I turn the key to "on" the head unit turns on as it should. Just as soon as it does I hear a very loud "Pop" or "Thump" coming from my speakers. I've had the head unit for a month prior to getting my amp and other equipment installed and I never heard this sound before. What can cause the loud thump and how can if fix it? Is it damaging my speakers? Help!! Here are my specs: Alpine CDA-9831 Head Unit Polk Carbon C400.4 Amp Polk Momo MM2104 10" sub Polk Momo C570 Door Speakers (Front) Alpine Type S Door Speakers (Rear Fill on head unit power) Mike

I found the problem. The installer had used the "Ignition" wire on the back of my head unit instead of the "Remote" wire. Oddly, the remote wire was labeled "REMOTE" which made it quite obvious as to which one to use. HMMMM. Anyway - all is well now and the only "thump" I here now is coming from my sub! Thanks for all the input! You all were a great help. In Christ! Mike