Revisiting HD700
I love this headphone's bass, but the cups are resonant to death to my ears without the literal Sennheiser veil that keeps dust out and partly covers up the devs' mistake(s) at the cost of overall fidelity and clarity.
I previously used fiberfill to try and remedy the situation, but this time I decided to try some 3M Transpore medical tape, going from others' T50RP modifications experiences, and I am extremely happy with the result, though there is room for improvement:
Tape only on the upper half of the cups, and only on most of the flat surfaces. Now the sound is much more open, less colored and more transparent and resolving, soundstaging much improved, I really should have done this last time. There is room for improvement as it is still not quite as open-sounding as my modified Beyerdynamic T90, but at least the lower mids do sound more open than even my K701. I tried cutting some holes in the earpads before trying the tape to see if they improve the sound a bit, and they did, but not as much as I hoped. Open-back headphones usually have earpads with perforated inner sides. Fiberfill tends to leave debris behind, it is more often used inside of studio speaker cabinets. I use it inside of closed-back headphones as they often lack acoustic treatment on the inside, which is why they often sound "closed" or like they are playing back music inside of a hall of some kind compared to open headphones (and music already comes with its own reverb).
edit: I forgot to mention, I didn't put tape on the lower half as that is sure to hurt bass, in my experience, the upper half is the critical portion to overall midrange, treble, and soundstaging quality, the upper half of the outer ear is what picks up higher frequencies, the lower half is mostly for bass