Thanks for the info. I installed SoundSource (Mac) and the Oratory and Sample 2 EQ. I don't hear much difference between no EQ and Sample 2; the Oratory seems to take care of the bass boominess and that was my biggest issue. So I'll play around for a bit and see. It does seem like there's a bit of unit to unit variation, per this thread, so there's that, too.Hint on connecting the Hirose connectors to the headphone fast, every time ... grab the silver connector between thumb and forefinger, insert it gently into the collar on headphone and rotate it until the cable connector hits the headphone slot. Then pinch back your forefinger and thumb so as to roll your grip back to the collar behind the silver collar and push the cable connector in until it clicks. Practice this in one, careful motion two or three times, and you should find that you can connect fast each time from then on, pretty soon without even thinking about it.
On EQ, you may already know this, but try the Oratory/Harman EQ or the ASR/Robbo9999 "Sample 2" EQ as a starting point. I found that with the Closed X, I dialed back the low bass a couple of dB below Harman just because I thought it integrated the smooth FR from bottom to top a little better for acoustic sources, and the Harman curve is a little bit north of neutral on bass anyway. But of course that's a preference item, and with the low distortion bass, these headphones are easy to EQ to taste. (I had the opposite experience with my Senn HD6XX headphones, where EQing the weakish bass just increased the audible bass distortion. After hearing the clean bass from these headphones, I can never listen to the HD6XX phones -- that I once liked a lot -- just because of it.)
I haven't tried taking the white filters out yet but from reading (some of) this thread that also looks to be worth trying.
ETA: One subjective comment is that these headphones play studio reverb (i.e., on vocals) with remarkable clarity. That detail repeatedly stands out to me.