Also, I recently snatched up a prototype HE-6 and am quite liking it with the stock pleather(?) pads and the MrSpeakers Ether Flow Angled pads (both, after a bit of EQ). Mine has 4 screws.
Also, are prototype HE-6's supposedly warmer/smoother than production HE-6's? A buddy of mine told me that early units were met with suggestions of more treble which was then applied in the production models.
That said, I don't find them sharp or bright. I'm using them with a Gustard H10 on max gain (+12 gain). I don't hear clipping or distortion, and I get a bit of headroom.
Matched at 300 Hz. Measured with MiniDSP EARS with default headphone compensation. No EQ applied with the measurements above.
Normally, I show 20 Hz to 20 kHz, but I think I got a somewhat bad seal with the stock pads which I hadn't realized until now. The bad seal can be seen with a gentle lift towards 20 Hz with a fast decay towards <20 Hz.
Comparison to the HD600 and HD800:
Matched at 300 Hz. Measured with MiniDSP EARS with default headphone compensation. No EQ applied with the measurements above.
Used some wire mesh to make the grills as suggested by a buddy. I may look into some acoustically transparent fabric to stop dust from getting in. Should I just reuse the ones on the stock Hifiman grills?