Amp makes wierd droning noise

OK- so I have a JBL BP.600 hooked up to a Audiobahn 12 in DVC sub rated at 700 watts rms.  It wired to 2ohms.  Anyways its been making this very low (in tone) droning noise when i drive over uneven or bumpy pavement.  I've checked all my wiring, adjusted the various input levels to no avail.  I contacted JBL and they said it could be a crack or loose connection in the amp.  However, I was also reading online about some sort or crossover protection.  Does anyone have an answer to this, or know what crossover protection is? 

thanks- MIKE

thanks-

I tried what you suggested and bounced the car and shook the box and again it made the noise.  However i am still bafled by the cause.  The JBL tech guy suggested it may be the lifted trace or a crack on the PCB.  I have no idea what that means but he said it would have to be sent in to be fixed.  Does anyone know what that is and or have they ever had that problem with an amp?

ok i disconnected the sub...no sound.  The sub runs normally until i bounce the car or shake the box.  Then the sub makes this monotone reverb kinda tone over the music.  After i stop it continues to play as normal.  My amp is mounted to the enclosure.  I could try taking the amp off the enclosure and ina sense isolate the sub to the vibrations.

thanks-Mike

Yes, try moving your amp off of the box as far away as you can and see if the noise returns. You might want to check your ground also.

I noted this post in the recent thread about your deck.

"Those kameleon decks where riddled with problems. We get so many back for service calls that it's disturbing. My suggestion would be to get rid of it and get something else, cuz once you get it working again, it's gonna break again."