Review to come

 
[size=small]What is there to say about the new flagship Sennheiser that hasn't already been said over the past year.  With that in mind, I will give my impressions about this headphone and why I believe that most people that don't like it haven't listened to it properly amped and for long enough time.  This is a headphone that easily wows for the first few minutes you try it on....often blowing away any other headphones you've heard before.  However after that initial honeymoon is over, many are very bothered by the highs, lack of bass, large soundstage on certain kinds of music, and being overly analytical.  To me, the HD800 is very much of a Chameleon, like the Stax SR-007 Omega, meaning that even though they are easily amped, they are extremely revealing of the power, source, cables, amp, etc. and will drastically change in sound signature depending on what equipment you have them hooked up to.[/size]
 
[size=small]As other have said, these are probably the biggest and most comfortable headphones you'll try on.  They are so airy that you don't feel that your ears are enclosed inside the cup of a headphone.  The construction is impeccable with perfect weight distribution and styling to match.  The cable / connectors are very well designed for a stock cable and reeks of quality.  I upgraded mine eventually and found there to be positive benefits.  Otherwise, the paint can get slightly dinged up over time, but that is nitpicking.[/size]
 
[size=small]These headphones are ruthless (much like the Stax O2) and have caused me to upgrade my source to a Perfectwave DAC and my amp to a Woo Audio 5.  Even then I wasn't content and had to roll in a bunch of tubes until I found the ones that had the best definition, bass, and impact.  Because of the difficult nature of these, I've had a love hate relationship with them but believe that I've recently built my system such that I'm extremely happy with them with almost all music I listen to.   I have tried the HD650, Denon D7000, Beyerdynamic T1, Hifiman HE-5, and Stax Omega 2 hoping that they will displace my HD800s, but at the end none of those were good enough in my eyes to keep.[/size]
 
[size=small]For people that own HD650s, you will be in for quite a change of sound.  Gone is the Sennheiser veil and the enclosed soundstage, but the mids in my eyes are pretty close to the signature Sennheiser sound.  When not amped properly, these will sound thin, sibilant, with too much instrument separation.  When properly amped with an amp that has enough power and has a sound signature that will complement the HD800s, they will have the deepest bass you will hear (if the song is meant to have bass), wonderful instrument separation and soundstage, and beautiful highs without being sibilant or shrill.  Because they have such an amazing dynamic range, songs are rendered beautifully, with good timbre, and with a ton of impact.  Songs that have acoustic passages like jazz or guitars are the best I've ever experienced by far.  Granted they are not bassy like the D7000s, but in my eyes those are overly bassy even on songs / passages that aren't meant to be.  On a good system play "Hyper-Ballad" by Bjork and you will be amazed by how deep these headphone can go, its astonishing![/size]
 
[size=small]With all of this said, I highly recommend these headphones only if you are willing to invest in the rest of your system to make these shine.  There are easier headphones out there such as the T1, but in my book the HD800 rewards extremely well as your system progresses up.  I also suggest that you don't look into too many people's impressions of these based of a few hours of listening because they require a whole lot more time to adjust to and fully appreciate.  As for price, based on the recent trend of headphone flagship pricing (Audeze LCD-2, Stax O2, AKG K1000, Beyer T1, W5000) I think they are very appropriately priced for their amazing technical proficiency that I find unrivaled, especially in the dynamic headphone arena.  Good job Sennheiser!! Its pretty obvious that you have spend countless years of R&D to make these headphones just right!![/size]

 
 
Equipment Used: PS Audio Power Plant Premier > Macbook Pro > USB > PS Audio Perfectwave DAC > Woo Audio 5 (Shuguang 300B-Z Output, Shuguang CV-181-Z Driver, EML 5U4G Rectifier)
 
Aesthetic / Build Quality:
This headphone is quite a handsome headphone with very clean lines.  The magnesium frame is very sturdily built and the 3D wings have been tweaked over the years by Audio Technica, and you can tell that this is a great frame that will last with lots of abuse.  The Wooden cups are of American Cherry wood and have a nice reddish / orange color with nice lacquer.  In terms of wood it looks a lot better than many Denon headphones and JVC and once again you can tell that ATH has spent a long time perfecting the art of making wooden full-size headphones.  The pads are made of a pleather-like material and are a little thin for my tastes and not large enough inside for my ears.  I wish they were real leather as it would feel more quality.  As for the cable, it has a rubbery coating sheathing to it, but feels nice since it is lightweight and doesn’t tangle at all.  Wooden plug is a nice touch.  Overall, the headphone is extremely well put together, feels very well engineered, and fits on the well extremely well.
 
Lows:
I consistently found this headphone to produce very deep bass in almost all the songs I played.  It was well controlled and nowhere near as loose as a Denon D5000 was in my book.  The bass extends very deep and can be a joy on neutral sounding songs, but sometimes overwhelming in bassy recording.  For example, the bassist on Diana Krall’s S’Wonderful would be overemphasized and at time compete with Diana Krall’s voice.  On most songs though, the bass is a joy to listen to and makes songs feel very musical and with good attack.

Mids:
The W1000X have very good mids in most songs, but I feel that they tend to get drowned out by the bass and treble, especially once that the volume levels are raised.  There is a slight emphasis on the treble and bass, leaving the mids ever so slightly behind.  This compounded with the large soundstage but things like vocals a little bit too far back for my likings.  This may be fine for many listeners, but I have a tendency to prefer a slightly more upfront presentation with more forward mids.

Highs:
The highs on this headphone are really wonderful and well balanced with the rest of the spectrum.  Cymbals and high pitched guitar strings really sparkle and add a lot of dynamics to songs.  Even with these great and extended highs, it never feels fatiguing to my ears.

Soundstage:
The soundstage is truly wonderful and expansive, which is something I would never have thought a closed headphone could do so well!  It isn’t as big of a soundstage as the HD800, but still allows for a lot of room / air between instruments, especially in Jazz and acoustic genres.  One is able to very easily pinpoint where the instrument in placed in the field of space.  This does have downsides though because the vocals also seem to be pushed back and at times get a little lost between all the other instruments.  This means that this headphone isn’t ideal for more classic rock songs where an upfront presentation is preferable.

Conclusion:
I think it is a wonderful headphone with a very good and balanced amount of bass, akin to the Denon D7000 headphone.  As Skylab mentioned, they don't have much coloration to the sound and should be considered relatively neutral and thus very easy for most listeners to enjoy with a wide variety of music genres. 
 
The soundstage is expansive, as is the bass and treble in the songs, but the mids feel not as forward as the the other ends of the sonic spectrum.  I feel that this headphone is a lot more linear or with a little bit of a V-shaped sonic signature.  At lower volumes, all respects of the sound spectrum work on the same level, however as you start bringing up the volume, Bass and Treble increase but mids get slightly drowned out.  This makes it not work too well with classic rock songs and ones that aren’t as well recorded, resulting in a thin and slightly more distant presentation of the song.  With most of the music I listen to, which is Jazz, Indie, Acoustic, 80s though it truly excels with.   Overall, I think you would be sacrificing the mids a little for much better soundstage, better controlled and deeper bass, and great sparkling highs that aren’t fatiguing.  For the price, i think these are an exceptional value for the money and easily competes and beats the Denon DX000 series in many aspects.

 
Equipment Used: PS Audio Power Plant Premier > Macbook Pro > USB > PS Audio Perfectwave DAC > Woo Audio 5 (Shuguang 300B-Z Output, Shuguang CV-181-Z Driver, EML 5U4G Rectifier)
 
Aesthetic / Build Quality:
This headphone has been criticized as having a slightly flimsy frame that presses on the ears too much.  But after having these 1.5 years and using them daily, I can tell you that these are great headphones in terms of comfort and durability.  They look the same as the day I bought them and have gotten more comfortable with time.  The frame needs bent a little to accommodate larger heads and to relieve pressure on the ears.  As of right now I can wear these almost all day without discomfort due to the leather pads.  The leather pads are very nice but not the nicest of sticking jobs, but are still great to have.  As for the wooden cups, they are really beautiful and have a deep coloring due to the many many layers of lacquer that are on it.  I would call the style of this headphone’s styling functional and understated for casual people passing by, but once you hold them in your hand, you can tell the detail and craft of them.  Overall, a great design for a portable headphone!

Lows:
The bass feels well controlled and defined, but never really extends too deep in a song.  While it is quite satisfying, it can feel slightly recessed due to the mids being more upfront.  However, on songs that have prominent bass in them, this headphone manages to balance itself out and sound just right.


Mids:
This is really where this headphone truly excels!  I think that a combination of small, upfront soundstage and prominent mids make this headphone a joy to listen to.  I would characterize the mids as being very lush and liquid, extremely easy to listen to.  Singers and instruments all are very involving and intimate to listen, with great timber and tonality.  The mids are the reason why I cannot get rid of these headphones....they just always sound so right and I can never get tired of them.
 

Highs:
Treble is quite good, but sometimes feels a little rolled off and not as extended as on the W1000X most of the time.  Despite this, I wouldn’t call these headphones dark by any means and the lack of extended treble doesn’t quite bother me.  It can get a little fatiguing when a song has a lot of highs since the ESW10 can get a little congested at times.
 

Soundstage:
Right away, one can tell that these are portable headphones by the relatively restricted soundstage.  To me the soundstage felt quite linear (2D) and not very expansive, meaning that instruments could be identified left, center, and right, but not in depth.  Vocals and instruments were very upfront, where the singer always felt he was 5ft away from me vs. 30-50ft on the W1000x, making songs feel more intimate at times.  This seemed to work a lot better on Rock songs and reminded me of a closed version of the Grado RS-1 in tonality.  However, when a musical passage gets overly complex and layered, the ESW10 has a harder time keeping up and sounds start to blend into one another.


Conclusion:
To me, one would get the ESW10 if they like a pretty forward set of headphones with upfront mids that are amazing to listen to.  They remind me a little of a more closed Grado RS-1 in terms of soundstage and upfront nature, but not as fatiguing to my ears.  For this great presentation that works wonderfully on electronica, rock, indie, jazz, you are sacrificing a little on the soundstage and on the bass and treble, but the headphone never really feels lacking in any of those departments.  I would characterize the sonic signature as being an inverse - V shaped, meaning that the mids are more forward than the treble and bass.  However, since the mids are so wonderful to listen to, this created a wonderful and intimate listening experience for most music genres.  

The beauty of this headphone is that is sounds almost as good out of an ipod as it does out of a very expensive home rig, meaning that it is very forgiving of the upstream you feed into it.  Factor with with the great portability and ergonomics and you have a winner for an on the go lightweight headphone.