I was getting this annoying vibrating rattle from the driver side door between 2500-3500 RPM. So I took the panel off and was amazed by what I found. There were wire connectors hanging right next to sheetmetal. The speaker wiring was all over. The speaker itself was screwed into the mounting ring poorly (thank you Bryn Mawr Stereo/Tweeter for the quality workmanship!
) and those window tensioner clamp thingies were misadjusted.
I adjusted the windows, wrapped the hanging wire connectors in foam and taped them to the panel, and removed and properly screwed in the speaker. No more rattles and the door closes much more solidly. This must be how Mercedes does it.