First impressions are very positive. Whopping soundstage for a start! Staging/imaging is excellent. A little more intimate than the HD800 with a little less air. But the soundstage size is not far off, and I'm surprised at this - not as wide though. Different trebles, the HEX rolls off at the top but is more neutral lower down - more like the HD600 here. The efficiency is as described and these are very sensitive, I'm happy just to plug them into either of my dacs that have built in solid state amps (Q DAC sounds particularly good, this has a very neutral quality hp stage built in).

I mostly listen to Classical music and so I've thrown some of my tester tracks at them including 'Birtwistle - Earth Dances' conducted by Boulez. This is a massive complex orchestral beast that covers the whole range of acoustic frequencies. The hex is handling it very well, the rumbling of the timpani is clear and powerful. There is a nice bite to mid treble that is similar to the HE400i, this is picking up loads of little details. Strings are so hard to get right with headphones IME, these sound natural but without the extra air of the HD800. The HEX are more mid centric making you focus more on the mids rather than a large "whole" as the Senns do.

Biggest difference between these and the HD800 is the smoothness. But you knew that already

Bass is slightly above neutral in my opinion. This adds to the overall warm sound. Very good bass, integrates into the mids - I hear no hump. The HD800 has tighter bass but less quantity. These have less bass than the HE400i (which has a midbass hump similar to the HD650) but it extends lower and has much greater definition. I've played some familiar modern jazz tracks from the Act label (very well produced) and the double bass has authority and definition without much bloom. In fact these sound absolutely amazing with jazz it has to be said. The space in between instruments sounds spot on, compared to the HD800 where small ensembles can sound too stretched apart. The soundstage remains huge - but intimate at the same time.

Voices sound better than the HD800. This was night and day for me here. The texture and realism is quite astounding. But the upper mids in general are taking me a little time to adjust to coming from the Senns. I like how the Senns dip slightly in the lower treble this makes strings for example sound more pleasing, especially with the extra air at the top. But this is a purely subjective preference and strictly regarding orchestral music.

*second day*
Had a long and more thorough listening session tonight. Again early important impressions before I get too accustomed, as i believe your brain can tell you anything sounds good - especially if you've paid the price of a second hand car for it

In all seriousness these headphones should be flying off the shelves. Why? Because they for me bridge the contrast between dynamic and planar drivers for me. They sound open and revealing yet smooth and controlled. fast, natural without the "grain" associated with dynamic drivers. Soundstage is up there with Sennheiser but without the lifted treble up top.

I think some may be put off by the efficiency; they may have very expensive powerful amps. The HEX only need a wire with small gain. These are advertised for portable use and yes they work great even plugged into your phone. But seriously, these are high end headphones that deserve a good source/DAC. Neither Apple or Samsung are this

I'd describe them in a nutshell as a HD600 with a much larger stage, no sign of bass hump - much deeper/lower clearer bass. Smoother and super clear but with a similar engaging sound that makes you forget you're listening to headphones. (is that not what a lot of us head-fiers have been after, like forever!!!)

A few words on the physicalities.. I'm all about the sound and will wear something created from barbed wire if it sounds good. But thus to say, these are very comfortable -not as light or head friendly as the hd800. They look to me tougher and should handle plenty of knocks etc. the cable is the most ergonomic creation I've seen in hifi.

But its all about the music. For those who have eclectic tastes I'd recommend these over the HD800 instantly. All music sounds good out of these that I've tried - Electronic, ambient, classical, pop, Jazz, rock.

I won't be losing my HD800 however. These are still the kings for classical music in regards to absolute resolution imaging etc when amped right.

Your call

Few early impressions from my first night and following day with these fellas (I think early impressions are important before they have time to brainwash you ). I was pleasantly surprised by the treble straight away. It's hard not to have preconceptions when a headphone has been labelled this or that.. So I try as hard as possible to listen with my ears and no-one else's when judging SQ. My music preference is Classical and Jazz.
 
So... Starting with the overall balance and image: These seem balanced to me in regards to treble and bass. I hear both a hump in the mid bass and also a peak in the upper registers. This creates an exciting/fun sound. Its fun, but also refined at the same time. There is a missing part in the upper mids (just like the HD800) that helps create a smoothness. This gives this headphone a more U shape compared to the HD800 because of the extra bass lift. Sometimes I'm getting the feeling that the bass is sometimes segregated a little too much from the treble. Bass extents low but is more concentrated further up. The imaging can change from recording to recording... One minute I'm really impressed then the next I'm thinking it doesn't sound right compared to the HD6xx. This is obviously to do with the angled drivers and overall different presentation. Something I'll no doubt get used to.
 
Soundstage: This took me a while to understand fully. It doesn't seem that much bigger than the HD6xx series when you first put them on, but when the music calls for it they are capable of going very wide indeed. (something the 6xx can't do) So depending on the music, they don't over-stretch a cozy quartet, but they will expand to let an orchestra breath. The depth is good but not much different to the 6xx. What is better, is the space around instruments and overall control of different timbres. No smearing.
 
Tone: The overall tone is warm. Very warm at the bottom but also reasonably bright at the top. The treble extends all the way up and is on par with the hd800 for allowing the top to breath. Every nuance in the recording is there. There is also no hardness in the treble as with the 6xx series and I'm putting this down to the dip in the upper mids. The bass seems to change with amplification. On my trusty NAD vintage amps (the best amps I've tried with HD800) the bass is big, warm and thunderous at times! There is a slight bloat in the lower mids but not as much as the 650. Changing to a solid state hp amp and the bass drops significantly. It is tight and better controlled. But this loses too much drama for me. It turns a fun hp into a more delicate and easy listen. 
I'm still sussing the mids out. I was expecting these to suffer with the freq response graphs I'd seen posted. But just like the HD800 they are actually very pleasing. Strings sound silky smooth, violins don't have the hardness (grain) that the HD600 especially can show. Now, I know a lot of folk like the response to be flatter in the upper mids as this gives electric guitar grit and texture for example. But from an acoustic perspective the mids here are pleasing. Maybe a little polite, but pleasing. Vocals sound natural to me, again for the same reasons quoted above.
 
Compared to the other top Senns. (HD800, 600, 650)
These come across as being more different than better. Yes they are technically impressive but I believe it comes down to music enjoyment - as that is the their job right? Last night I was getting shivers up my spine with some of my favourite classical tracks and so this is a good sign. Other times my attention was drawn to the "sound" of the headphone itself. So only time will tell if I can switch off completely from the technical merits/effects of this hp to immerse myself fully into the music (like I can with the HD650, but couldn't with the HD800 sometimes).
Putting my HD650's on this morning after another hour with the HD700 and I welcomed the airy, relaxing sound.. But I could soon hear the 650's shortcomings in regards to the treble and separation. I went back to the HD700 and welcomed the refinement and smoothness. They do inherit a few traits of the HD800 but are very different to my ears. The HD800 are still the kings of dynamic headphone hifi in respect to accurately reproducing music.    
 
Love the design and size of these. Small, light and fit over my ears comfortably. Might change the cable though.  
 
Early days, but I think I'll be welcoming these to live alongside my trusty 650's. For my preference the HD700 are better than the HE500 or LCD2 for example, so in that respect they are an absolute bargain now.   
 
*Edit 4 months later*
 
Delighted with this purchase now. So much so I sold my HD650 and now use these as my main headphone. All headphones have a burn in time (whether brain or or whatever) and these when amped right can sound outstanding. Seriously, there's not much to miss having owned the HD800 for two years. These are more fun. So.. Unless you have a high end set up, I'm sure you could live very happily with these rather than paying for the HD800. Especially if you want a bit more oomph down below   

Bought one of these to keep me going while I save for a replacement dac for my bedside rig. My previous Dac's have all been in the lower to mid end so this review is based on that level- Arcam, Cambridge Audio, Beresford etc. 
 
What would you expect for approx $80 (I paid £60 so look around rather than just Amazon) for any audio product? Well these days it seems that you can expect more and more... Technology and price wars is giving us audiophiles with shallow wallets lots more options. This little Dac made in Austria comes very well packaged and is about the size of two cigarette packs stuck together. A standard cheap wall wart is supplied and no other cables included. No USB, which is fine for me as I prefer to use spdif converters for PC use. So what you get inside the dac is nothing that doesn't need to be in - just the D/A conversion. Inside there is the Texas Instruments TLV320DAC23 and Cirrus Logic CS4344. Although you can use 24/192 khz with the coaxial input, I personally don't see any need. It is indeed impressive for such a cheap component but in my experience with pc audio 16 bit is all you need, unless you have a collection of HD tracks. Otherwise all you are doing is putting extra strain on your pc and slowing it down. 
 
Streaming music from Spotify premium and the sound is nice, I'm struggling to find negatives... The low end goes deep and is nicely pronounced. The top end sparkles. The mid range is smooth and voices sound natural. The smoothness goes right to the top and the sound is not grainy at all. (which I have heard before in cheap dacs and older machines) The soundstage is neither wowing me nor making me want more. 
 
Now to the nitty gritty and fickle side of me The bass could be tighter, there is very slight blurring when the music gets complicated and there could be more space between the instruments. But!, this is compared to much more expensive machines. 
 
But lets get serious folks, for $80 - $100 you are going to be very happy. If this is your first Dac to upgrade your pc soundcard then you are going to be blown away! Second more, it looks and feels well made. Sits very neatly on your desktop or placed on top of your hifi. Its also small enough to be hidden away
 
Perfect for noobs wanting to spend more of their budget on the amp and headphones, or anyone wanting a little dac for a bedside rig or such-like.
 
Edit. A month later and this little Dac has kept me from upgrading... If you have a nice spdif converter this dac is as good as it gets before you are willing to fork out loadsa wonga. And even then make sure you've got enough resolving transducer at the ready

Been a while since I bought some new headphones. The HD800's put an end to that for the last couple of years... But I wanted some closed back for certain times and so snapped these up. 
 
The balance of these is very good indeed, as is the tone. The AKG sound in a closed back pretty much. More midcentric than the KXXX with a closer image - slightly warmer but still with plenty of bite at the top. I'm impressed with the isolation as well- wasn't expecting too much - I wear glasses and I still get a very good seal. The comfort of the pads is another plus- very soft. 
 
The mid frequencies are much better on these than the KXXX and this is most welcome. (no nasty peak at 4k)
 
I wouldn't normally recommend any closed back hp for classical music but these sound great. Obviously not as airy as their older open back brothers, but the imaging is very focused and certainly open enough for large scale orchestral works. The detail retrieval is on par with the KXXX imo, only a little more more smeared at the lower end. 
 
I would describe the sound sig as typically AKG - 'dry' apart from the warm bottom end. I've read a few reviews that describe these as sounding more like an open headphone. They do have an ample soundstage for closed but they still sound like a closed headphone.  
 
Yup, an absolute bargain for what they are going for these days!   

Ok, this is a headphone that I've been meaning to try out for a while. So after spending most of the day with them I'm going to give a few quick impressions. (I don't believe in burn-in mechanically with dynamic drivers)
 
I've listened to all my usual recordings for testing equipment, from ECM Jazz, recent top notch classical recordings, Ambient from the likes of Tim Hecker, BT, Jon Hopkins. and some favorite rock Zepplin, Black Crowes. REM.
 
This is just my opinion... 
 
First impression was very good, smaller soundstage than what I was expecting but nice and airy. They are soo light! You can forget that you are wearing them. 
 
Going through some quality classical recordings mainly symphonic and the sound is very light and weightless. Floating there. Not much bottom end though. I put some Beethoven quartets on and the bass is much better suited here. The cello sounds very detailed and punchy. Played some Jaavi Sibelius and I noticed some added texture to the strings. Nice, but not sure if its pronounced a bit too much. 
 
With jazz I'm enjoying all the air and placement of instruments, but I'm immediately struck by a slight lack of oomph at the bottom end. By that I mean the kick of the drums with the double bass. Its very distant. There is bass plenty in quantity, only its kind of stuck at the lower mids and refuses to budge! I'm also now detecting some sizzle in the upper mids. Snare drum is pronounced or emphasized a little. I'm admittedly a bit of a tonehead so I appreciate realism more than any other attribute from headphones. So as the hours go by I'm getting more annoyed by the this. In fact this is the first headphone that has actually caused me some fatigue in a long while... (and I own HD800 and K701) Its the forward upper mids that are ringing. 
 
Ambient music works very well with these. Because of the forward mids all of the fine details and layering come across very well. The air of these is great for creating a big floating wall of noise. Really great with this genre of music. Electronica with deep bass is great from the top to mids but they fall short at giving you any bass satisfaction. E/Qing them doesn't help at all. They just can't give you sub bass.  
 
Rock music, I'm again a little disappointed. Electric guitar sounds great (Grado great) 'Whats the Frequency Kenneth' guitar sounds gritty and raw. Perfect tone. But as soon as the other instruments take part all focus gets lost for me. There is instant burring. This recording is commendable for its simplicity. A headphone such as the HD600 will clearly define the four instruments in use and create the space, even though they don't have that big a soundstage. What we have here is an airy sound, but the instruments are squashed too much together. Very forward and a little intrusive for my liking. I'm constantly thinking Grado. Maybe a Grado with a rolled off very top end and big airy pads. 
 
I used a Necosoundlab dual mono SS amp for my impressions with Arcam and Cambridge audio dacs, tried them on my other amps but there was clearly a massive impedance mismatch. I would not use these with anything of high impedance.
 
Remember these are just my honest opinions, and I can see why peeps like them, especially if you appreciate forward mids. But I wouldn't put them up against a DT880, HD600/650, K701. All these headphone are a clear league above these. You could ask what do you expect for the price of these?? Well for the same price you could buy a lot of good used headphones that will be better or a brand new K701.