Forgiving highs.. hmm, if by that you mean something that's a bit smoothed out, warmish, definitely not having that brightness that will make your ears bleed, yes.
But it's not without its temperament. They can sound sibilant sometimes. Which is amazing, since I am a fan of really bright signatures... maybe it's just a preference or maybe I have old ears, but I do like a bright sound, grainy. The Z1R have that, but smoothed out, curvy, liquid. The HD800S have it too, quite similar, but with less punch on the mids and bass, less fun. Sub-bass totally absent (yes, regardless of amping).
Oopss, got carried away, thought I was on the Z1R thread, but - you did ask about bass.
Alright, now back to the thread subject, I do love the HD800/800S. But bass-wise, hmm, it's not a signature that matches every track. Actually, I think HD800/HD800S + Z1R are a brutal perfect combo (I have a two-headphone holder on my desk and like to think in sets of 2) because one is a really brilliant open set and the other is an outstanding closed set. The Z1R is just better overall (for the price) - BUT - the HD800/800S have qualities that the Z1R cannot match (air/soundstage, that holographic feeling, a brighter, apparently more detailed sound even if that's not extra detail).
They're both bloody good. But if you want a solid midrange/lows and can go closed... well...