The part marked in red is what I removed, along with all of the white mesh, including the mesh in the driver itself. You have to be very careful as you can easily damage the driver. This is not for the faint of heart.
First you need to remove the driver, and it is glued in place.
Next remove the white mesh, and cut out all of the red from the first picture. Try to leave a clean finish on the plastic.
Then remove the white mesh from the rear of the driver with a small flat head or sharp knife.
Proceed to remove the 6 supporting structures from the rear of the driver.
Take your time here. I just used pliers and gradually started to move them up and down breaking the plastic.
Last remove the metal grill and plastic hex opening from the cover. (Pic two left side.)
This completely opens up headset and the sound as well. It prevents the sound from bouncing around everywhere inside making you hear higher pitches twice. Although it looks ugly from the outside, it sounds fantastic. Still not as good as the HD700, but better than an HD600/HD650.
Only proceed if your willing to throw a pair away due to messing up the driver.
Thanks for the info, I don't think i'm ready to tear away that much out of my precious pair just yet. These things are really expensive for me, maybe i can get a used HD518 from amazon (for the same price i had to pay for a HD202 locally) to try the mod.