These cans aren't all that well thought of but I read an old thread on Head-Fi where a guy ("ziplock") had modified a pair and, afterward, thought they compared very favorably to his Beyerdynamic 770s.
The mods, as he performed them, are dead simple. It takes maybe 5 minutes and the transformation is remarkable. Here's what he did.
1. Remove the backs (one screw each).
2.
Carefully remove the small foam plug in the pole piece. (I used tweezers instead of a toothpick. Recommended.)
3. Done. Leave the backs off.
When I read this I had to give it a try since I'd been pretty unimpressed with my Sonys.
Removing the foam is the biggest improvement. (WTF is it there for anyway???) The bass, weak and flabby before, was as tight and as strong as it could be but well in balance with the overall tonal character. The mids are strong and the highs are sweet and clear. It's as if the cans had been playing through a pillow before..... and they kinda were.
I wasn't comfortable leaving the backs off because of all the exposed wires. The difference with and without backs is more subtle than with and without foam but there is a difference. Without the backs there's much more air and a broader, deeper soundstage. Because of this I decided to do something to open the backs up but, at the same time, protect the wiring and drivers from inadvertent damage.
At first, I just "Swiss cheesed" the covers. It worked but not quite as well as without backs at all. Plus it looked sorta low rent. That's when I decided on the wire screen.
I took a 2-1/8" hole saw, located the center of the circular area of the covers and then removed a big section of each back. Before cutting, the backs look like this.
The source for the screening was one of those ubiquitous desk accessories made out of lightweight expanded metal, in this case, a letter organizer. I cut out circles of the material about 1/4" larger in diameter than the holes, placed them in position with the covers face down on a towel and then "domed" the screen by pushing on it with my thumb all around the perimeter of the holes. Then I ran a bead of JB Kwik around the edges of the screens.
All the air and the big soundstage returned.
I'm sure there are better cans out there, lots better, but these are really pretty damn good now, especially when compared to the stock MDR-V600.
Here's the thread from Head-Fi that got me going.
http://www.head-fi.org/t/247925/interesting-mod-for-the-sony-mdr-v600-56k
John