It depends on what year your M5 is?? I have a 2000 car and this was before BMW offered the enhanced M audio package with the 2 subwoofers. Before this, it was a wimpy sub enclosure with some 5" speakers and did a very poor job with low frequencies. The newer option on the 2001+ cars is much better, but is still not as good as some good aftermarket subs. I have 2 10" Kicker free-air subs firing upward through the rear deck powered by a Precision Power amp and it absolutely rocks!