OK, got a 'new' X2HR for modding, knew this headphone since the first generation X2, but never liked it. To me the SHP8900 or 9500 were always better to start with, they only lacked build quality.
These days I did some mods. If you are in a love/hate relationship with your X2, you might give this mod a try
1. Dampen the rear chamber with damping wool,
slightly compressed damping is ideal. I used two layers soft synthetic fibre, 15 mm each to fill the inner volume. A smaller and a bigger cookie fitting the shape of the cup. Just leave the screw wholes free for a tight fit.
This helps to linearize the frequency response up to 1.5k, gains efficiency (!) and reduces slightly peaking in the highs.
2. Close all the membranes on the plate where the driver is mounted, gaffer tape will do the job. I guess I use silicon later on instead.
The two small ones above and below the driver and the long one on the recessed edge. I took different measurements of 30/60/100 % variations, but all closed was simply best.
This reduces the peaks further, interference problems in the highs get also banned pretty good.
If you take a look at the measurements don't be fooled, the way I measure misses the pinna gain, so the recessed region around 3k sounds right to the ear.
The 8k notch is not really evident and a measurement artefact, when sweeping the frequencies 8 kHz is clearly on level. This said, you have always some individual interference with over ear headphones, whereas a IEM got one peak only most of the time.
Overall the harshness of the original is reduced to a level where it's not this disturbing anymore, the highs ... are much more accurate than before and way more pleasant to listen.
And yes, bass gets much tighter too and looses the wobbely feel. I think the softened bass is a result from unlucky vent design of the X2 that disturbes mids and therefor precision including subjective bass response. Interpreting the red graph of the regular X2, we can asume, that there's a big amount out of phase energy around 1.2k and vice versa @ 1.8k. Adventureous!
Blue and green graphs of the modded X2 shows a more defined function in this region and way less interference in the upper octave.
EQing is easy and most important: useful now, you won't be dissapointed. This is how the X2 should have been from the start.
Red graph is raw X2HR in all it's 'glory'
Blue is the measurement with physical mods
Green is physical mods + simple 3 band EQ
