I heard all the cans mentioned so far in this thread at Capital Audiofest this past July so I will try subject to the usual FWIW/IMHO/YMMV disclaimers.
The 560's and 400i's are well designed and generally fairly neutral but the 560 is a little fuller and more "refined" sounding. Both are lightweight as planars go because the drivers are single ended (meaning there is a magnetic grid on only one side of the driver). In practice, this means that the force exerted on the driver varies as the driver moves which would allow harmonic distortion to creep in (a little) and dynamics to flatten out (a little). These effects weren't obvious to me in listening. The Audeze's are "darker" (Guy13, I really think you'd prefer either of the Hifiman sets) ans substantially heavier. The Oppo's are beautifully made but quite heavy like the Audeze's and tended pretty significantly towards a "warm" signature. The clamping force also felt pretty high.
The other planars I heard there were all electrostatics: the Kingsound KS-H3 (not my cup of tea; rather 'thin' sounding); the Stax SR-507, a strong contender for Ugliest Headphone Ever but good sound at a modest price for 'stats; Stax Sr-009 (easily the best planars I have ever heard and a strong contender for best cans I've heard period). Too bad the 009's plus the required amp cost twice what I paid for my first car.
I concluded from this show that I am not convinced that the low mass advantages of planars are (perhaps) not as significant (to my ears anyway) are not as big as they might be in roomspeakers. Headphone drivers are pretty small, lo-mass buggers to begin with. Also, all the planars I heard suffered (even if slightly) from looseness in the deep bass due perhaps to the stretched membrane tends to ring' at its low end. Most obvious in bass drum. I didn't notice this with the Stax though. So maybe I'm just not a 'planar' guy although who knows if Sennheiser jumps in as rumors have it. I would expect anything from them to be (at least) in the price range of the HD800 though.
Hi dB Cooper.
I did try the HiFiMan HE400 and they did sound good, however,
they felt very heavy and did not have enough over the head clamping force.
I also found them a little too big,
maybe because the were not clamping hard enough.
The other thing is that my Bottlehead Crack
is not the ideal amplifier for the HE400.
Too bad that my HD650 are veiled and dark because they
are super comfortable and light.
I would like to listen to the Audeze, OPPO and the Stax
to hear how better they are than everything I've listen to up to now,
but I am almost sure that I would like the Stax because I use to own a pair
30+ year ago.
I would like to buy the SR407/507, which are more or less affordable,
but again, you need a special amplifier that cost an arm and a leg.
Next week I have a meeting at my Vietnamese audio friend
Mr. Khiem to listen to his Bottlehead Crack with the Speedball upgrade
which I don't have in my Crack and I will bring my HD-650
and see/hear if the veil will be lifted and the darkness will disappear
even if it's only partially.
That will be a very interesting test/audition.
It will confirm if I still want to buy/exchange
my HD650 for a pair of HD-600 ???
This afternoon I will choose some CDs that I know well to bring with me
for the Tuesday morning audition.
I might also bring with my on my motorcycle my Rega Apollo CD Player to try with his 1,000 USD DAC which I forgot the brand.
All that is more for entertainment that for serious upgrade,
since I don't have the $$$.
Guy 13