Forgive my editorializing. The only thing I don't like about short and totally negative comments about a particular headphone is that it tends to kill further discussions. Yes, I own the P9's and actually like them quite a bit. I think people posting their thoughts certainly have the right to air their opinions. But, we all should leave room for alternate opinions. As ever, I should take my own advice, even in the non-headphone world.
Are they neutral sounding? No, they are a bit bass heavy for this non-bass head

. Another plus they drive pretty well through my AudioQuest DragonFly Red, and scale up with better DAC/AMPs.
IMHO they are kind of like a rich dessert, you don't want too, too much of its sound for long term session listening.On the plus side they are very well built, though I find the leather ear cups a bit sticky on my ears
Are they anything like my HD-650's or my Audeze LCD-2? No. But I like a variety of headphones, and I plug in different ones depending upon my mood, sources available, and type of music. FYI I'm currently listening to Hubble Pie's (via Tidal HiFi level) "30 Days In the Hole", now that is rich bass
Probably the most negative thing I can say about them is that the original price was/is mind boggling, but I went for them anyway. But this is all now water over the dam, as they have been discontinued. I probably should seek out replacement ear cups as back up, before replacements disappear (if they already have not).
So happy holidays! In these Pandemic times I very much value the social aspect of these forums, as well as the good advice and opinionated, opinions (as long as they inform).