I'm one of those people that like my music loud with a descent amount of bass but I knew not to have a lot of bass of the stock speakers on my 2010 focus so I put the treble a little higher then the bass which made them sound a lot better and still vibrate the doors at a high level of volume. Well I think I may have blown one of the speaker but not really for sure because the rattling only starts on high volume with a good amount of bass. If you leave the volume at a moderate level you get no rattle at all. I thought it was loose speakers so I went to You Tube on how to remove the door panels and check to make sure the speakers hadn't come lose which they hadn't so I then proceeded to put the door panels back on a take everything out of the glove box to see if it was rattling something in the glove box which it wasn't so now I have learned to deal with it for the most part. So does this sound like a bad speaker or something else causing the rattle in the passenger side door. Thanks.