Pros: big soundstage, precise imaging, immersive sound, clear lines from individual instruments in, e.g. chamber music or jazz quartets
Cons: rare sibilance
my experience with headphones is very limited, as is this review, but i thought someone might benefit from these observations, someone who wants to listen to classical and jazz.
i started with the hd700 by listening to the melos quartet playing schubert's "death and the maiden," and then checked my impressions by playing segments on my fidelio x1.
wow! the hd700 had what felt like a 220-240o soundstage- i was sitting in the center of the quartet. the tone was wonderful and i was surrounded by the music- the first violin to my left, the cello on the right and a bit behind me, the viola front left and the 2nd violin front right. the last 2 were a little hard to separate, especially because they were often playing in unison, but then i could hear snatches of their playing that i had never noticed before, and which placed each of them clearly.
the x1 in comparison had about a 120o soundstage, with the instruments much less clearly demarcated. the x1 placed the instruments at a bit of a distance, in front of me, perhaps 10 feet in front of me, not around me. also i had thought the x1 was incredibly comfortable; the hd700 is significantly more comfortable.
i tried some orchestral music with mendelssohn's midsummer night's dream [previn and the lso] and the contrast between the 2 headphones was the same. i did think i caught a little bit of sibilance in the hd700 on some very high, bright, moments in the overture- cymbals? i'm not sure, but it was just a moment or two, and worth the price for the rest of what i heard. then some chopin, some bach. with solo instruments the contrast was less soundstage than air- the spaciousness of the hd700 and the richer tone it produced.
the x1 is a bit warmer, and i'd expected it would provide the better bass, but i was wrong. it was warmer, but the bass on the hd700 was richer and clearer.
time for jazz: i started with antonio carlos jobim and elis regina- i suddenly got confused about what set i was wearing- the fidelios felt a LOT more open than they had with the classical pieces. i think that the recording had a lot more channel separation, which the x1 used to good effect. nonetheless, the hd700 were in another class- richer, more immersive sound.
of course they SHOULD be in another class: they cost 3 times as much.
i stopped bothering to switch back and forth. i didn't need any more convincing. art farmer; bud powell; branford marsalis; charlie hayden and pat metheny; chet baker and paul bley.; the clayton brothers [and that only got me to "c"]... my head was bobbing and my feet tapping in a way they haven't for a long time.
my "normal" sound system uses flac files streamed from a vortexbox to a squeezebox touch, then optical to a gungnir dac, then cable to a nad c375bee amp, then to kef iq9 floorstanding speakers. i think i've got a pretty good system, not ultra-audiophile, but good. i was listening to the headphones from the phones outlet of the nad amp.
the hd700 is better than my "normal" sound system. it was a bit of a shock to realize that, but my "normal"system can't hold a candle to listening with the hd700. i can't imagine what i'd have to spend to get a speaker system that sounded as good, as rich, as immersive, as these headphones. [not counting putting an addition on my house for the listening room.]
so i'm impressed and enormously pleased by the hd700. for what i listen to - classical music and acoustic jazz- they are wonderful.
edit: the hd700 is also relatively easy to drive. it was louder than the x1 with volume set the same on my amp. i just got a fiio x5 that i'm hoping will be able to drive the hd700. i'll post the results here when i get around to actually checking.