I am hearing a rattle when I play bass heavy songs in my mini. It specifically happens at low notes which makes me think there is something in the speaker. Has anyone had this problem or know how to fix it?

 

Dynamat. Odds are screws or clips have rattled loose too. Also could have a blown woofer (they tend to rattle too)

 

I would say the speaker is blown IMO. I'd replace them if it were mine.

 

If the speaker was blown, he would probably have distortion at other levels too.

OP, see if you can use the head unit to figure out which speaker it is (adjust fade and balance to each speaker). You may find out it's not the speaker, but the surrounding materials.

 

Almost every single rattle complaint Ive seen so far has been a seatbelt vibrating against the trim

 

Lightly push on the lower speaker grill and/or door trim to see if the noise disappears. You can then try felt shims in the door panel trim to see if it will resolve the issue.