[Taowolf51]

 
Here is the original Kees Mod post:
http://www.head-fi.org/t/396267/how-bright-is-an-ultrasone-pro-900/
Post 70.
 
For the sound quality, it brings the bass back a notch, brings out the mids, makes the highs a little rounder (not as metallic), makes it feel a tad more organic, tightens the bass, and overall makes it a little more balanced. The thing that changes it the most is the cotton wool (basically adisposable makeup pad). I would pull it in half (so it is half as thick) so that it doesn't do *too* much to the bass. You should listen to them for awhile, mod it, and listen again. If it is too much, remove some thickness from the makeup pad. Originally I only used the chair gliders (those little felt pucks), but in time, I added the makeup pad as well (making it a bit less than half as thick). Also, be careful with the screws, they can easily be stripped if you unscrew them enough times. Be sure to screw them back in with a decent amount of tightness, you don't want anything to be loose (changes the sound).

 

[dch27]

Thanks for the advice.  I am goin to go ahead and listen to them for a few more days before I do anything.  After letting them run for about 10 hours they already sound a bit better.  
 
Its too bad there is nothing that can be done about the sound leakage.  Not that it should matter much for me. 

 

[Taowolf51]

They don't really leak sound that much (at least in my experience). They do a bit because they have velour earpads instead of pleather or leather. The velour actually makes them easier to wear for longer (velour can breathe, so it doesn't get hot in the earpads).
 
Also, be sure to keep the case and extra earpads. The extra earpads are great for listening for a long time. The earpads over a few hours can flatten a bit. If you switch them out with the new ones, they're more comfortable and cool (like the other side of the pillow). And by the time the spares compress, the originals have uncompressed.