Just got mine in from the 11.11 sale. A week later than my bud despite in the same city, cursed bundling different orders I spose.
I have the he-x4, which is what these are supposedly, and it seems to be the case. Primary difference beside the headband is the pads. The he-x4 used a microfelt/velour hybrid whereas the 400se v1 uses a mesh hybrid, and that's where the primary audio differences come from. I measured both on my crude measurement rig.
https://imgur.com/a/UjZmDx6
I had picked up a couple of openheart 8 core cables 1.5-2 years ago, and they were nice and didn't tangle or kink, though it was hard to tell the left and right plugs apart. But the ones I bought were no longer available, so I tried a different version, and they were just so stiff, despite being slightly more expensive. They actually felt far worse and tangled/kinked more easily than the $4 cables I use when loaning to friends.
FWIW, there was no difference to my ears or on a frequency response graph (crude testing rig) between all the cables, including the old stock hifiman cables and even some regular electrical wire, lol.
It's a 3d printed mount and 3d printed ear with a calibrated linear mic attached with approximately the same ear volume. It does the job for me, and I'm not keen on spending hundreds to thousands more for a iec711 clone or whatever b&k everybody using these days. I may change out the ear one day for a silicon cast of my own ear, since that can be done pretty cheap.