My issue with bluetooth/self-powered headphones is always the maximum volume when listening to orchestral music.
According to Sennheiser support the HDB630 can reach 105 dB/1 kHz.
I have a hearing imbalance of 6 dB which I compensate for, so -6 dB max volume. Based on the frequency response measurements I might also want to increase the lower treble a couple of dB, since for me that helps with placing instruments in the orchestra.
So that would be ~97 dB max. Absolutely loud enough for pop, rock, techno and other genres with relatively low dynamic range. Not really enough volume for large-orchestra symphonies recorded with realistic dynamic range.
Pity, having an all-in-one that includes ANC sounds appealing.