The rear decks of the 79-85 W126's suxx. The speaker is fixed directly on it and is not stable. I used to have an 85 500SEL (EUR). I found some Pioneer 80W 3way speakers with an oval shape. They were all right but I had to do something else to get a better sound. When you take off the speaker, you'll see that there is a sort of moss covered with a thin plastic, this part is usually completely rotten by the time and that make some silly noise when listening to music. If you cut it out and replace it with some wool, it should perform well. Also, the crappy thing that covers the speaker messes up everything. Usually when listening to some rythmic music, the woofer touches the cover so try to give more space between them.
Hope this helps

------------------
-------------------------------------
WEB Site : http://www.adamou.dpn.ch
A.S.C. 1999
-------------------------------------