I found the D7000 to have noticeably more of a warm sound and overall tone. It didn't have the same low end extension, of which I think the 900 can best just about any headphone out there. It also didn't have the same treble emphasis/sparkle and articulation or as vast a soundstage as the 900. It had more body to the mid range and a more forward midrange overall, though. I think, for someone looking for a more neutral to u shape with a warm sound might go D7000, but for those who like more brightness up top and a v shape frequency response would appreciate the TH900. More treble extension/air going on for the 900, more midrange body going on for the 7000, in a nutshell.
I just never really feel in love with the D7000 like the TH900. In the end, it's all your preferences though.
I'm with him except on the part of not "feeling in love with the D7000." I owned my D7000 for years and loved them for the life of my ownership. I jam a lot of EDM music and a friend of mine bought them way back in the day and I listened to them and my jaw hit the floor. It caused me to go buy them at the time and enjoy them for many years.
I find the TH900 has a rather open sound for being a closed headphone. Going back and forth to my HD600 (total open can) it's impressive how open the TH900 can be. Granted, as I've said earlier, these were zolkis modded (a partial custom Lawton type of tweaking) so it's hard to say if that's the difference maker or if that's how a stock TH900 can sound. I linked below the forum member who owned my TH900 stock and then had them modded. He gave me the modded pads but currently just use the Dekoni pads he hooked me up with. After owning Grados in the past I'll take the cushions of the Dekoni lol. Anyways, he compares how the difference is between a stock TH900 to the modded ones on my head as we speak.
EDIT: Zolkis thoughts on the modifications
Edited by N0sferatu - 3/16/17 at 11:36am