Wow. The
modded TH900 continues to amaze me, especially with its sub-bass impact and sound stage. I preferred it to the Audeze LCD-3F and X both for bass and sound stage, and the modded TH900 mids actually come close to the orthos. IMHO the XC is outclassed as narrow and dull sounding in comparison. The X comes close in signature, but overall I prefer the TH900 even though it's more colored. Maybe the taller and larger sound stage plays a strong subconscious string of preference, but as far as musical enjoyment goes, I prefer the TH900. The Stax L700 is also in the same class (a notch under the Omegas), but it is faster and more neutral with better mids and similar or better sound stage. In the sub-bass though, the TH900 trumps everything. For the price range one cannot go wrong with either the [modded] TH900, or the Audeze X, or Stax L700. For stock headphones I'd rate the L700 first, the X second, and the TH900 third. With the mods, and not considering the 20-25 Hz range, I'd put the L700 first, modded TH900 second, and Audeze X the third. Since I have a Stax 007 and I need a closed heaphone, so far there is no competition for the TH900 and even less for the modded ones.
Note that I haven't heard the Ether C, which may be even better, with its carbon fiber cups and planar driver. Nor the LCD-4, nor the Abyss, but these are 3 times the price. Nevertheless one thing I am skeptical about is whether any headphone is better than the modded TH900 in the sub-bass impact and sounding so physical. It certainly betters the HE1000 as well in that area, and also the HE6+EF6 (although the latter is less colored and overall better). It's not even the driver, but the ingenious loading that makes it this good, competing with transmission line speakers. In my eyes (coming from speaker design) that makes the TH900 one of the most technologically advanced headphones out there, together with the distant ancestor hero Sony R10.
Again I wonder what the Fostex bio-dyna drivers could do in a Sony R10 or similar style enclosure with wooden driver plate, or a carbon fiber version. Certainly such a TH900 version that would be more welcome than the minor changes in the TH900 mk2. Fostex does seem to have the technical know-how for this, perhaps the question is time, or economics.