sounds to me like you have an aftermarket stereo, or one was installed previously.

If you want to reduce the door speakers bass, you need some bass cutoff capacitors.

I'm not sure what rating for the cutoffs, but they make many different kinds.

The door speakers should be what are called door subs. so all they put out is bass.

I think if you went with a low mid capacitor, you would cut out some bass and add midrange to those speakers.

My 300ce does have door subs like your 500e, but they are all factory speakers, and sound just fine.

of course the 300ce has a longer door, and the door subs sit next to me, not the seat.

I'm sure others will have opinions on this, you might want to post in car audio forum, scott from la jolla audio should be able to provide a real good answer for you.

Alon

__________________
'92 300CE - Sold
2004 C240 - 744 - C7 Wheels - Android Radio
2002 C320 - 816 - Sport Wagon - Sold
2006 E350 Wagon - 368 - Dead
2015 GL350 Bluetec - 197U