As a warning: For anyone who feels the need to pop out the HD6xx driver be extra careful. I believe I just ruined one side my HD600 for the worse a la Tyll:

http://www.youtube.com/watch?v=mBpic9jbjzs&t=8m20s

The dome itself is in tact but there are some crinkles in the surround plastic that I can't get out. I am going to order the HD650 drivers and see what kind of results I get. As I've mentioned before, I've always felt that the HD650 was a more refined sound despite the darker tuning, so it'd be interesting to see how much of that is from the driver vs the construction. Will post comparative measurements.

Back up to MAP again on Amazon. Glad I got in when I did.

Sorry for another post, but this is very interesting to me.

For the past month, I was privileged enough to finally be able to get a loaner pair of HD800's to check out. Those were the only headphones I have listened to for the past month until I shipped them back out yesterday. So I got out my HD650's after not listening to them for a month. Immediately I noticed how much darker they are (Marv told me a while back that the HD650's were a darker headphone, I kinda understood what he meant, but now I really understand what he meant). This is not a bad thing, in fact it is a good thing for me personally. I learned that perhaps I do not actually prefer a darker headphone - but this is where I learned a lot about the HD650 and how much more I appreciate them. I lowered the bass frequencies on my EQ (I use iZotope OZone 5 and 6 plug-in for EQ, one or the other) and with the mod Marv posted for the HD650's a while back that I did to mine, I realized I can get pretty darn close to the HD800 sound signature when EQ'd properly. Of course, the HD650's do not possess the clarity of the HD800's IMO, but for the price of the HD650's, they are just so much more amazing to me now and I have gained a deeper appreciation of what a great headphone they are for their price-point.

For me, I still prefer the HD800's, but the HD650's are a very close second, and if they were ever damaged, I would get another pair if I could not get a pair of HD800's.

I think some people would prefer the HD650 over the HD800, depends on the listener, but that just goes to show how great a pair of headphones the HD650's are. I definitely have a new appreciation for how great these really are.

I covered the HD650's back side with small cut bits of microfiber cloth (costco, blue) adhered by elmer all purpose washable school gluestick, putting cloth on gluestick then on headphone. I covered the bare plastic, except the circular part of the driver itself, and I put bits of free nonglued cloth into the slots to cover the steel damping mesh. The glue is washable, easily removable, and adheres weakly.

It's more listenable. The treble is smoother, mids are more textured and clear, and the bass isn't so bloated (less bass bump, less roll off, less distortion) and hits a little harder, faster. A little less claustrophobic. I have some other mods in place, though. Can anyone corroborate?

Inspired by this thread, I moseyed on down to the Headphone Bar to get myself a pair of HD650s. I ended up trying out a bunch of headphones, and falling madly in love with the HD800s. They had one pair in stock, and there was no way I was going home without them, budget be damned! I'm never going to let these go - this is the smartest foolish purchase I've ever made. 

What rig did you hear the 800's from before you bought them?