It seems to me that loss of brightness is somewhat confused with loss of resolution - there is a certain correlation (like details drowning into the noise floor with DACs), but it's also subjective, bound to personal perception.
I tested the D7200 against the best e-stats and IMHO they are not masking anything, it's just lower level and differently placed in the sound stage and perhaps sounding slightly differently with some equipment. Depending on ancillary equipment that lower level may mean loss of resolution as well, since now some of the details got drowned into the limits of the system as a whole. When that happens, there will be a change in how we hear a certain aspect of the music in space, time and harmonic content (like a background noise, a reverb, a decay, the body and colors of the instrument sound etc). When the change is big enough, we may perceive it as
losing that aspect, even though it's still there, one can hear it, but it's not quite the same. I am not sure I could explain well what I mean. When you put ice into water, it disappears, even though you may make its form out under water when it's moving.
IMHO it is the pads that make the D7200 sound more dull or more constrained (even constricted) than it
could. It's not bad pads at all, it's just too thick, too hard and has too much damping mass in that small acoustic space.
Those bloody pads matter as much as crossovers, internal damping and room interactions matter (all together) with speakers.
The D7200 drivers are as resolving to my ears as any other Fostex or better headphone. Not as resolving as e-stats, but not far either.
The D9200 drivers are brighter but also resolve better, still with nice harmonic structure.
The D7200 drivers are far more neutral and linear than the D7000, D9200, Fostex TH900, TH600 and many other drivers. It's state of the art that it's not as bright as the TH900 and D9200 drivers. Therefore IMHO has the best possibility to sound with realistic tonality without artificial enhancements.
Many aftermarket pads can make the D7200 sound more direct, but IMHO most of them will sound even worse than the stock pads. I tried more than a dozen pads with the D7200, not counting mods.
So far I found 3 ways out of this:
1. Sell the D7200 and get the D9200. A bit on the brighter side now, but reference level, especially in closed headphones. Don't touch it, pair with warm equipment, enjoy.
2. Get replacement pads for the D7200 and modify them (remove about 30% of the internal foam thickness). More open, better kick, better treble, bigger sound stage. Your ears have to be compatible with this change (thinner pads).
3. Get Stax SR-009 pads and
modify them by removing the white ring from the internal foam (reversible and much easier to do than #2, but much more expensive). More resolution, much bigger sound stage, very natural. More open and bigger sounding than #2. Comparable to #1 but with no treble issues. Today this is my preference but I keep #2. around.
[4. It is possible that changing the cups would help as well, but there is no aftermarket for this. Unless one can obtain D9200 replacement cups and mount them on the D7200 (they seem to be the same size and design, same CNC process). Why would someone do that? Because it's IMHO easier to correct the D7200 lack of treble level than the D9200's enhanced treble.]
In all cases the apparent resolving power is increased together with openness and treble level. Interestingly also the bass extension, transparency, definition and sound stage improve. All by changing pads. (Of course you can change cables as well
.
To fix honkiness in some D7200 samples, you need to use extra padding in the cups (e.g. a thin layer of Creatology foam pad that covers the internal back of the cups).
Interestingly enough, this problem disappeared for me in about 2 years time (verified by measurements). Similar effect happened with my Fostex headphones. The wood seems to get better with time.
So I have removed all cups damping from all these, that made the sound much more defined.
If one is not into mods, again I recommend getting the stock D9200.
Of course the D9200 will benefit from mods as well
, but IMHO it's not worth the hassle, since its treble will become a hard-to-fix issue, unlike with the D7200, which is near-perfect after the mods. Cymbals, timpani, saxophone, wind instruments have so nice definition, natural clarity and body resonance, without any glare or treble haze. All other closed headphones seem to be colored or thin or thick in comparison. It's a joy to listen to them. The modded TH900 are even better in some respects, but much more colored, suiting more to jazz and electronica than to classical and chamber music - side by side I prefer the natural neutrality of the D7200, since it's closer to the e-stat tonality.