Audio Systems: Car stereo/radio works & stops then works & stops, car stereo speakers, magnet moves

Question
Dear Mr Ruesta,
I have a Nissan Altima 2003 2.5S automatic car. It has a factory installed stereo. The other day I was hit from behind by another car. (There was no external damage to my car as such I forgave the driver who hit my car)
But later the next day i noticed that while playing radio or cds my car stereo speakers work intermittently (start and stop and start suddenly.) This is prominently seen when you change speeds or brake or go over bumps on the road.
This looks like a loose connection somewhere (otherwise why should it start).
Please advise me what and how to do about it.

Answer
the speakers work with a magnet  outside and a magnet inside in the middle of the speaker,  there is enough space for a coil but if you hit this hard the magnet moves and the speaker coil sees ground when is moving ,

check both of the rear speakers or unplug and see if the radio works better with front speakers only
that way you know where the problem is

good luck