[k21000]

It looks like one of the tiny connector contacts (female) have pushed through inside on the right speaker. It's where the 2 gold plated pins from the headphone cable fit into. I don't know how to get into the unit to see if it can be fixed. It has been giving me some trouble for a while now, but usually I can wiggle the plug on the end of the cable and the speaker comes back to life. Now it has either pushed inside or come out some how, so the speaker does not work at all. You can still see the gold contact on one of the connectors though. I will post a pic later. I used to have trouble with the cable on my old 580's and had to replace it a couple of times, but never a problem with the connector contacts on the actual headphones.

 

[Feanor]

use a small spoon or the tip of a knife to remove the back grille (no cable inserted obv.), it should come off fairly easily (be gentle). I've had the drivers coming loose a few times, at those times the sound from that side tends to cut off. Once you remove the back grille, you can gently take out the drivers and check where the problem is.

 

[Ham Sandwich]

Here's a set of pictures that show how to remove the grill and the driver pod so you can look to see what may be the problem.  The set of pictures is how to fix the "intermittency" problem that the old pre-2000ish 580s had.  The 650s have a new design and don't/shouldn't have that problem, but the pictures of how to get in and remove the driver pod will be useful.
 
580 intermittency repairs pictures

 

[k21000]

Thanks for the tips. The 580 pics do show where the connector meets the cable and the spring system. That is the exact area which I need to get to on my 650's. It looks a little scary though, I am really worried about damaging them! I would love to see some pics like the ones Ham Sandwich posted but specifically for the 650's.