Some more impressions on the TH900 and R10:
For classical music, the R10 is definitely preferable to me compared to the TH900. It just has a more satisfying and convincing tonality with strings. For acoustic folk however it's more of a toss up, depending on the track. With other genres (rock, pop, metal, jazz, hip hop, electronica) I'm giving the nod to the TH900. Here's a summary of my thoughts thus far:
- Vocals on the R10 sound slightly less synthetic, which isn't to say that the TH900 sounds artificial, but that the R10 is just absolutely stunning when it comes to rendering the human voice. For instance a female voice will sound exceptionally clear and detailed, to the point where I hear the subtle hesitation in her singing--- ie the movement of air in a somewhat hesitant exhalation--- and the slickness of salivation as her lips smack, yet it's never artificial and retains a smooth quality I'd say the R10 is the only dynamic that can best the TH900 in this regard, excluding the W3000ANV (which is more a matter of taste given its colored nature). With the TH900, vocals are relatively more closed-in compared to the R10 which sounds slightly more open in the midrange.
-Both have an amazingly organic and clear midrange, however the mids on the R10 sound more forward and slightly warmer / smoother compared to the TH900. The transition to the highs is also smoother on the R10, but they seem a tad brighter than the TH900's. I'm not sure if the R10 is actually brighter, or if its just accentuated more by the lack of bottom-end presence relative to the TH900. There's a certain "glassy" quality to the mids and highs of the R10, and part of that is what I've taken to call the combination of smoothness and [non-harsh] brightness. It's most apparent on Appalachian guitar work and vocals.
-The lows are superior on the TH900 as far as I'm concerned. Again, I have one of the "bass light" R10s, and we're talking about a 20+ year old headphone, so there could be a bit of degradation of materials inside the cups that is accentuating this. Going by memory of the "bass heavy" R10 however I'm still compelled to give the nod to the TH900, but I'm not going to say for sure as I don't trust auditory memory much. Suffice to say the R10 sounds thinner overall compared to the TH900 which has a fuller sound. This plays a big role in the above-mentioned genre preferences.
-Imaging on both headphones is very impressive, but I'm getting the sense that the TH900 has an edge here. In terms of spatial simulation, curiously the R10 portrays the sounds of a room amazingly well, and so it's probably more dependent on the recording in question. For example the R10 can make a piano sound like it's in the room more convincingly compared to the TH900, but the actual location of that piano will be a bit more vague on the R10, whereas I can spatially identify it more easily on the TH900. Similarly the R10 can sound absolutely grand with the right material, but on other material can sound very constrained and mostly "within" the cups. In comparison the TH900 gives a more consistent out-of-head experience but isn't quite as enjoyable with large-scale symphonic pieces compared to the R10.