One channel of my old Sennheiser headphones was intermittently cutting out whenever I moved the cable at all, and replacing the cable didn't fix the problem -- it seemed that there was a loose connection somewhere between the cable and the driver. It was an easy fix: 1. Pop the grille off. My headphones have HD-650 grilles, but the 580 and 600 grilles attach the same way. If you don't have a nylon tool like this one (part of a set of automotive trim-removal tools I purchased from Amazon for like $10), use an old spoon -- or anything that isn't as sharp as a screwdriver: 2. Note the orientation of the grille and of the cable. The cutouts you see here on the edge of the grille go toward the bottom of the cup (the grille is solid at the top of the cup), and the cable is inserted with the "R" or "L" facing outward: 3. Unplug the cable. 4. The driver is held tightly in place by four strong clips around its perimeter. Work your way around the driver and pop it loose from each clip individually: 5. Once released from the clips, the driver just lifts out: 6. The internal wiring is very fragile. As you can see, the upper wire in this photo is properly fastened to the round terminal next to the spring connector, but I broke the other wire earlier and had to solder it to the extended end of its spring instead. Works fine, sounds identical, etc., but it wasn't fun to do with the tools I had available at the time. So be careful. 7. Look closely at the picture above. See the gap in the middle of the lower spring connector, where the coils have been pushed apart? That was my problem. The pins at the end of the cable are meant to make solid contact with the springs, but over time the springs apparently stretched enough for the connection to become intermittent. One of the two pins is minutely thicker than the other, so maybe I did it by forcing the cable in backward once. Here's how the pins fit into the springs when the cable's plugged in: 8. So this is disappointing, but I don't have photos that show the actual fix. Sigh. It's easy to describe, though: With the cable unplugged, use fine-tip needle-nose pliers -- or a tiny screwdriver, or maybe tweezers -- to squeeze or push the spring coils together so they're evenly spaced and will make better contact with the cable pins. I also used a tiny screwdriver to push some conductive foam into the space next to the connectors, just to be sure. You can test the repair by plugging the cable into the loose driver before you reassemble everything. 9. To reassemble: With the cable unplugged, snap the driver back into its four clips. Orient the grille so the cutouts are at the bottom of the cup and press it back on. Orient the cable so the "R" or "L" is facing outward (because, again, one pin is a tiny bit thicker than the other) and plug it back in.