When I bought them, it took me nearly two months to get them because of the shortage of supplies.
The voice is very amazing, a little dark, and you won't be tired after listening for a long time. I have NDH20 and NDH30 at the same time. Their bass is almost as good in their respective fields (open/closed). NDH20 puts more emphasis on sound insulation and has a depression at the intermediate frequency to prevent ear canal resonance. The NDH30 sounds more like the HD650, but has more accurate bass lines and more details.
I also have KH310 speakers and switch them back and forth on RME ADI-2 pro. It can be considered that Neumann's two earphones are very successful, and they are quite close to the sound of KH310 from a specific point of view.
Compared with NDH20, NDH30 has improved weight - it is lighter, and the neck is less prone to fatigue when wearing. And the wire is softer, and it is less likely to have unnecessary winding. However, it also inherits a disadvantage of NDH20. When the wire is rubbed, noise can be heard in the earphone.