I removed the fabric mesh that's attached to the (outer) metal grill of my HE-500, then reinstalled the 'naked' grill.. to very favorable results. Note that the micro fabric is (very lightly) glued to the metal grill.. so you will have to peel it off. I'm sure it would be quite easy to get some light glue to paste it back onto the grill for those worried about voiding the warranty. Since the fabric is cut out to the same size as the grill/driver housing.. re-gluing is not even a necessity. Bottom line: it's a safe (easily) reversible mod.
While I loved the HE-500 stock sound.. I wouldn't have minded taming its slightly forward bass & midrange, while increasing treble presence a smidgen. Essentially. I would have liked a slightly more neutral, laid back twist (and more treble air and presence) on the stock tuning. The treble has always had an alluring quality on the HE-500 to me.. but it appeared dark or buried, at times, behind the slightly aggressive, forward midrange & bass. Removing the mesh fabric & reinstalling the 'naked' grills did precisely what I hoped for in coaxing some brightness and neutrality out of the HE-500.
Post mod.. the midbass quantity reduces to a near perfect amount for my taste.. the bass still maintains a nice soft, punch that simply perfect. Bass still extends deep.. and it's better textured and faster with the tamed midbass. While it doesn't have the presence and quantity of the stock config, I much prefer this softer more balanced bass presentation.
Moving onto the midrange.. it's every bit as liquid, clear, balanced, dynamic and detailed as it was in the stock config. But taming the bass back added some serious magic to the midrange. It's clearer, less aggressive (more space between the listener & the stage) and airy. I can sense spatial queues easier and it's less fatiguing, overall. Vocals, in particular, seem better articulated as they simply seem to have more room to 'breathe.'
The treble benefits in much the same way the midrange does.. but it's got noticeably more presence. Some might experience some very slight sibilance with poorly recorded material.. but on the whole.. the treble has a much more enjoyable quantity and presence vs the stock config. Treble presence is slightly north of neutral.. but not emphasized in such a manner that would feel derogatory to even the most ardent neutral-minded listeners. Again, it's quite perfect for me, actually.. and it's very well suited to the overall tuning. I can hear the lovely ortho clarity and timbre of the treble with more enjoyment now than the feeling I got with the stock config.. where it felt a half step behind the midrange, which tended to steal the show.
In relation to how I'd describe the stock tuning : forward, aggressive, and upfront.. I'd describe this modded tuning as sultry, inviting, romantic, and delicate. I was pretty set on moving onto the HE-5LE (which, by most accounts, is more neutral than the HE-500).. but this little mod has squashed that desire. The HE-500 has officially become my favorite headphone. While the Paradox remains the most reference grade, neutral phone I've heard.. the HE-500 is its sexy "girl next door."
I'll be doing further listening to see if I hear any nasty, adverse peaks or resonance.. but so far.. I'm really impressed with this (extremely simple) tweak. I hear a lot of what plin reported with his dampening mod.. Will report back with more impression in the coming days.
BTW.. it also looks pretty damn cool without the fabric mesh!