That's what I have on my J$ pads. A very thin nylon. I like the increased micro detail but sibilance can get annoying on tracks. For electronic it's great. I kind of want something that's inbetween without choppig up the pads. More than stock Jergpads V2 but less than transparent J$ pads. I feel like these need a little bit of nudge in the high end without It becoming a problem, at least for my tastes. I'm wondering if opening the grill will achieve this.
I believe jerg has both his HE400/500 with more open grills and I'm assuming he came up with these pads using those earphones that way. Unless he can clarify.