I experienced distortion from the rear low frequency component between the seats of my 1999 M-Roadster. To my suprise what I found when I removed the "speaker" grill was an oval curved duct that started high and ended facing forward toward the bottom of the grill. This was the exit port for a dual low frequency band pass bass box located high between the roll bars. It was this port that was rattling at certain low frequencies that sounded like a blown woofer. The fix is to remove grill by puling out evenly on both sides at the bottom, then down to clear the tabs at the top. Then remove the duct by pulling forward and down. Locate the two rings (one smaller, one taller) near the top of the duct that snap into the bass cabinet when the duct is re-inserted. Place two beads of silicone based adhesive all the way around the duct (I used white so I could see it on the black duct), one between the two rings and one in the back of the rings toward the end that inserts into the cabinet. These two beads should be enough to secure the duct in place when re-inserted and yet should dry soft to prevent furhter rattles. As you re-insert duct there should be a slight "snap" when correctly seated. The flat back side of the duct that extends the duct downward should not touch the car as this will allow further distortion. Let the adhesive dry before using the stereo or drive the car. I let it dry overnight but it is fairly warm now in Southern Cal, note the temperature in your area and the adhesive manufacturer's instructions. Reinstall the grill top first then snap the bottom left and right into place and you should be ready to rock. Hope this helps all.