So, I received the D5000's in today... I thought I'd add some quick first impressions before I spend some time doing a more in-depth eval this weekend....
First off, I must say that they are very fine cans indeed. The overall sound quality is excellent. Also, for being closed cans, they provide very little isolation from the environment. I can easily hear everything that's going on in the office... it doesn't even reduce the very low hum of the fridge in the kitchen while I'm sitting in the living room... honestly, they might as well be open. Ambient attenuation is very poor, or rather, close to non-existent.
The imaging is more precise that my 580's. The detail presented is superb, if not a bit unreal. It's as if there's a high-shelf EQ around 10kHz. In fact, I tried adding up to a +10dB high-shelf @ 10kHz as a rough experiment. That's how much boost at that range it took to get the highs of the 580's to sound roughly similar in tonality. (note this was a 2 minute exercise, I didn't spend time to dial that in precisely)
The bass range is very full and extends deeper than my 580's, and isn't as dramatic as the Beyerdynamics DT770's. However, acoustic bass lines bloom disproportionately as they go lower in register (seemingly at ~80-100Hz). Rising bass lines recede disproportionately to the lower notes when the line crossing into the upper bass region.
Those two combined observations, make the presentation sound a bit "scooped" to me—accentuated airy highs and bloom in lower bass.
The overall subjective presentation is very relaxed and non-fatiguing, but detailed and precise. There's a certain midrange character/detail that seems attenuated around 3.5-4.0kHz... that contributes a bit to the "relaxed" character.
Definitely the best sound quality out of closed headphones I've had the pleasure to listen to—Senn HD25-1, Beyer DT250-80, Senn HD280, Senn EH250, AKG K271S, Beyer DT770. By far the closest in character to the Senn 580/600/650 line compared to those above that I've experienced, which is quite impressive.
SO... bearing that in mind, these are FANTASTIC headphones. Very enjoyable and pleasant to listen to. Those niggles I'm commenting on above are just that, details in the sound quality and presentation that I'm picking on. If you're reading this, and are wondering if they sound great....they sound great. You will enjoy them if you don't have anything else of this caliber to compare them to. You might even enjoy them if you haven't found satisfaction in what you have.
FOR ME, for five bills and in light of those details delineated above (especially the lack of ambient attenuation), I am currently inclined to send them back and wait patiently for the right closed cans to come along, however.... I haven't decided. Again, for me, the ambient attenuation is a BIG reason for having closed headphones, otherwise, my 580's do just fine leaking in the environment left and right.
I'll decide on it this weekend and post more.