Well all this talk of the sheepskin leather pads made me pull the trigger on them. Here are some better shots of the ring and the pads on the HD650.
Here are the pleather pads with the rings in them. You can see that the material gets pinched in the ring a little bit. After 7 months they have a pretty good imprint of the headphones in them.
Here's a picture of the ring next to the pleather pad after removing it.
Here are the headphones with the sheepskin leather pads installed.
First impressions:
The sound.
Sounds about the same as the pleather pads, same amount of bass but the highs seem even cleaner than before. Not louder, just cleaner.
The comfort.
Much more comfortable than the pleather pads, very soft and supple. Much more comfortable than the stock velour pads. Best part is they don't squeak/creak on the arms of my glasses. These are the first real leather headphone pads I've ever felt, and I must say I thought they were going to be stiff. Boy was I wrong. These are now by far the most comfortable headphones I've ever worn.
The look:
Wow they look much better than the pleather pads. Very nice.