They have developed a rumble/distortion in the bass. I assume I need to redo the foam on the woofer. But I can not figure out how to get the grill off. On the back there are six screws. I would rather not remove the screws unless I have to. I got the pair off craiglist a year ago. They say "Reference Series" on the front. I believe they are the Atom model since they are very small, maybe 8" tall.