I just received my damping mod kit from markl (Lawton Audio), and installed it on my D2000 along with angle pads.
Headphone and earcup before mod:
Headphone and earcup after mod:
I must say, I love this mod. All the pieces included were fit nearly perfectly (just had to trim a couple pieces). It was easy to install. The instructions mentioned I may want to add some superglue to hold some of the damping material in place. I had the glue at the ready, but didn't need it, the self-adhesive stuck everywhere it needed to. I think the finished product looks very good, all the little driver parts symmetrically covered and all.
First impressions of the sound...I love it! The stock D2000 was a love/hate for me. I liked the overall signature, but I couldn't really listen for very long because it was too fatiguing (not sure if it was the boomy bass or bright treble...or both). After the mod, I noticed immediately that the bass is brought under control. With stock D2000 it didn't matter what I was listening to, I was constantly aware of the boomy bass. After the mod, I'm not always thinking about bass. I think this may be due to both the damping mod and the angle pads, which put the drivers further away from the ear (and angle them more). Post mod, the sound is cleaner - I can hear deeper into the mix and find more microdetails. You can see just by the pictures there are going to be many fewer reflections going on in the chamber. So overall the sound is more even across the spectrum (by reducing bass boom), and it's cleaner and less fatiguing. Time will tell more on the fatigue factor, but I've done 2-3 hours of high volume (for me) listening tonight, and I'm not fatigued, whereas earlier today at work before the mod, I was fatigued after only a half hour and had to quit.
I should note about the bass, it is still there. I did my Flight of the Cosmic Hippo test and confirmed it is very much still there. It's still a bassy headphone compared to most other headphones. It just doesn't boom and echo through every song like before. For me it's not a tradeoff, it's improved across the board.
Terrific mod, I highly recommend it to anyone considering it. Congrats and thanks to Mark for figuring out how to make this headphone sound so good!
Edit 6/21 - Oops, the vintage Pioneer amp I was listening through had it's 6k filter switch engaged. Once the filter was set to off, the highs fatigued my ears again. All other impressions above remain, just note the mod did not fully tame the highs for me. I've now also done the damping mod to my D7000s, same benefits as to the D2000s, but the D7000s don't have the fatiguing highs to me (they've always been better in this regard to me, after I burned them in).