i have a 93 SL 500 and my stereo sounds very low volume and no bass .
what is wrong with it?
and very distorted.

It could be there are some loose connections somewhere inside the car, possibly where the speakers connect to the back of the stereo. Im not sure if your car has an external fader, but sometimes the external fader control can also be a cause for bad audio. Also if this only occurs when listening to the radio it could be a bad radio antenna connection. I would pull the stereo out though and look behind to check for loose connections first though.

Becker Autosound Website they can help you