I guess my 2001 M Roadster (70,000 miles) has gotten to the age where the speakers are likely all getting brittle in spots. I got a bad rattle on the passenger foot-well speaker. It was a 3 inch long break on the paper/fabric right parallel to the edge of the outer perimeter where the cone material meets the metal rim of the speaker body.
Reading past posts on fixes, I first looked for a replacement pair-and found by buying and installing two up front that the available high quality 4 ohm speakers lost a lot of low end-not made up by the woofers-probably due to the fact that all stock M Roadster speakers are 2 ohms.
Not wanting to replace the entire 10 speakers plus maybe a new amp to cope with the higher inductance, I repaired mine. Used GE Silicon Glue. It spreads easily, remains flexible (important in a speaker) and should last pretty much forever. It was about $5.50 for a tube that could repair 50 speakers plus a lot of other broken stuff too.
The result is a sound equal to when the car was new. Wish I had done this first.
By the way, my factory battery just died after nine years and 70,000 miles. I have never had any BMW battery or any other last longer than six years.Mike H