So... I have spent quite a bit of time with the Black and I must say it keeps surprising me.
I expected a laid back signature but the more I listen to the Black the more I think it's more smooth than laid back per se as it features more energy than I would have given it credit for. Treble is smooth but I wouldn't call it recessed either, I don't see the Black as a descending signature but rather bump in the mid bass giving it rhythm, linear in the mid range with a gentle but well thought out upper mids bump providing articulation (never congested despite the presence of the lower mids), and just the right amount of lower treble to provide more excitement than you would think. Upper treble is where things are more subdued but still nuances and air is present enough to provide good contrast.
Ah and the black background and low distorsion are both a component of the signature as well, not to mention the softer attack and smooth decay.
Those help provide a fatigue free listening experience, even pushing the volume you'll never get any ear fatigue so long late sessions are a treat!
Last but not least I went through my Jazz playlists and I was so surprised at how pleasing and rich instrument timbre was, it's north of neutral but very very pleasing and satisfying.
Overall I am pretty impressed with the layering and soundstage as well.
Those babies need time to grasp all they have to offer