I don't trust them after what they did with HD58X - they announced one thing and released a completely different one. The original was based on HD660S/HD700 driver
I know for a fact that this is not the case. I own both the prototype and commercial version and it is NOT the same driver as the HD660S nor the HD700.
The driver response of the original version was found too 'sharp' in the 5kHz range and lacking low bass. Drop coupled this info back to Sennheiser.
The same happened with HE350 (it has my mods in the production version).
Also with this headphone I have been involved a tiny bit. What you see measured is a proto and they are still working on it. There will be feedback from the proto and Drop as well as Sennheiser actually do something with this.
Yes, 2dB more subbass (30Hz) is not going to turn this into a Harman type headphone nor is this the goal.
Distortion in the lows is improved so expect better damping.
One can only do so much without changing the entire headphone (goal is to use HD800S tooling).
The HD800S by itself is an excellent headphone (with some EQ) and given the lower distortion and need for 2dB less subbass boost at 30Hz may make this driver even better than the already excellent HD800S.
And this at a lower price for US residents.
I wouldn't burn down the HD8XX without actually hearing it.