I got the Yamaha orthos from Steve this afternoon. I'm very impressed by these headphones, even in stock form
comfort- better than Grados. Not as much clamping and the pads feel better on the ears. Still fatiguing after several hours with glasses on.
sound- nothing to complain about. The bass has great impact. Extends down to about 30-40 Hz which is respectable. Exceptional midrange, that is approaching electrostat quality, but doesn't quite get there.
I was expecting the treble to be a bit muted from what I've read, especially the upper treble. This hasn't been the case and there is a sense of "air" in the upper registers in live recordings.
Two things that really impressed me- the way it handled the tone of piano. So far only the SR-007 Mk1 has been able to do it completely right. Even the K1000 on the various setups I've heard sounds slightly off. Secondly the speed- attack and decay is impressive. On thrash metal with the double bass beats the orthos are able to keep up (and they are able to differentiate the two beats), whereas my Senn HD580 and MS2i have a harder time. Better microdetail than both dynamics as well.
Slightly disappointing- the drivers sit so close to the ear (I'm guessing even closer than Grados with flat pads) the sound stage is about on par with a mid/upper end Grado. Lacks the spacial imaging and depth and width of soundstage of the SR-007 mk1.
And in their unmodded form they sound closer to dynamic headphones than electrostats. I can accept that modding will improve that, but I don't want to give up the bass quantity I'm getting from them right now dampening the drivers more.