Those are hard terms to use for a ranking. I gave my rankings toward the end of my still incomplete review. Clarity and details could just mean + / - treble, stuffed tissue in the cups, too much bass clouding the highs. It means different things to people, so I can't comment on it. I tried to write my review in a way that was easily testable and verifiable for anyone reading it and leave the "fancy" adjectives out because it doesn't help anyone except sales for headphone companies.
For separation, if you mean whether it sounds like the instruments are placed in different areas, the HD-650 is not as good as the other two. The HD-650 sounds like you're watching / hearing the concert from the middle of the concert hall. That gives the impression that the soundstage is huge. It isn't. Because the cups are deeper than the other two, the sonic frequencies all kind of mash together before they reach you. How shall I put this... it's like crossfeed is happening on each channel by itself. While crossfeed is great for 1960s sources, like the Beatles, when stereo was first invented, most of the time crossfeed is not only unnecessary, but detract from music enjoyment. In the 1960s, you had entire instruments or voices be either all on the left or all on the right. That is super fatiguing. Nobody does that anymore, so crossfeed is less useful as time progresses. So in essence, crossfeed is a "mono" making effect, away from stereo imaging.
If you have house speakers, you can tell right away. If you sit close to your loudspeakers, you can hear instrument separation, but when you move away from the speaker, they all sound like they come from the same area. That's how I feel about the Sennheiser HD-650. You would think that would increase the soundstage though right? It doesn't. I think because the drivers are still ultimately only 1/4 inch away from your ears, it's not enough distance to create a larger soundstage. I think the only illusion of big soundstage comes from being open air and when you listen to a live performance. It really feels like you're there, but I believe it's just a physical illusion translating into a sonic one. Don't get me wrong though, illusion or not, it's still a cool effect and I much prefer the feel of open phones.
So anyway, separation. I like the DT-880 over the rest by a little bit for rock music. It's still my favorite rock headphone to date, but just barely over the others. Always remember, these differences are really small to me, but commenting on them makes it seem like it's huge. Umm. The Denon makes the soundstage seem big because the bass is so deep, that it reminds me of being in a living room with hardwood floors, or a movie theater. The Denon and DT-880 have little soundstage differences that are cool.
HD-650 has a better resale value though, so I kept that.
Panda Bear - Take Pills on the Denon AH-D2000 sounds like Brian Wilson singing on an elephant riding through India while there's a war going on in the background with bombs being dropped. The HD-650, not as much.
. Music and music hearing have to be fun with or without EQ no matter which headphone is used and not at all a mental torture..
