AKG K712 Pro

This is my first review on this site, so if I make any errors please let me know

Physical
Build: Eh... it's cheap feeling, with plastics everywhere, making it feel flimsy. The leather headband is nice, and the plush earpads feel great, but I can't get over the creaking noises they make when I adjust them. I suspect this is to make them lighter but I do not know.

Comfort: Excellent. The earpads are plush and deep, while the leather headband feels luxurious and comfortable, and doesn't snag my hair. The self-adjusting headband works great and I have no problems with it. The 712s are very light feeling as well, and I catch myself forgetting that I'm wearing them.

Price: I got mine for 80 dollars so lucky me, I guess...

Looks: dimensionally these guys are the same as the 702s and the 701s, but with a different color palette. I love the orange, it is absolutely striking to me and makes the 712s stand out, in a good way. The leather headband is super great looking as well, with orange stitching. Overall I love the looks of these cans.

Auditory
Lets start out with some EQ graphs

Frequency response

Bass

Some rolloff towards the low end, to be expected

Mids


Treble

Build: Solid.
Comfort: Excellent. Very light. Leather strap can pull hair, though.
Isolation: Open.

Bass: Roll off under 50Hz. Bloated midbass. 1.25/3
Midrange: Lower mids emphasis with upper mids fall decreases clarity of the mids. 1.5/3
Treble: 6k peak gives sharpness to the sound. 1.25/3
Tonality: Above average. 2.50/5
EQ: Needed. For my preferences, mandatory. Try Serious SBAF or Optimum HiFi +4dB.

Detail: Good. 2/3
Imaging: Fantastic soundstage, probably second only to HD800. 2.5/3
Dynamics: Below average. 1/3
Tech: MidFi soundstage king. 3.25/5

Bias: 3/3
Interestingly, this is probably my most used headphone. Why? 1) Comfort. Light, open and breathable. 2) Soundstage. Loving the openness of the sound, it is high on my enjoyment list. 3) It is clear and detailed headphone when EQd. With EQ fixing tonality issues, it really shines.

Score: 2.5/5

Value: Worth the price. In Europe you can now get it for about 200 EUR, which is great price for what it offers. In my local shops, price is more like 350 EUR, which is a different proposition. Of course, you have to value soundstage and comfort and be prepared to use EQ.

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Introduction:
AKG, formed in 1947 has its strong dominance in the professional audio industry since decades. From a vast catalog of studio microphones and studio monitoring headphones, we are going to take a look at the revered K712 Pro which is second in line only to their flagship K- Series headphones, the K812.

The K712 Pro retails for 499$ and is frequently available for 350$.


Specification:

• DRIVER TYPE- DYNAMIC.
• DESIGN- OVER EAR.
• EARCUP STYLE- OPEN BACK.
• FREQUENCY RESPONSE- 10 HZ TO 39.8 KHZ.
• SENSITIVITY- 105 DB.
• IMPEDANCE- 62 OHMS.
• MAXIMUM POWER HANDLING- 200 MW.
• CONNECTOR- 3 PIN XLR (UNBALANCED) TO 3.5 MM WITH 1/4'' ADAPTER.

Gear Used & Tracklist:
Denon DCM500AE as CD Transport | Schiit Modi 3 | Schiit Loki | Schiit Magni 3 | Aune X1S | iBasso DX160.




Unboxing:
The headphones come in a black carboard box with a velcro lid. Inside which we find the headphones, a high quality black velvet carry pouch, two cables - a black coiled cable and an orange 3 m straight cables, both having the screw on capability for the included 1/4'' adapter.

The unit which we are reviewing today is the one made in Slovakia.


Scalability:
Scalability for this headphone is very high. . On Magni 3 high gain, the knob needs to be kept at around 11-12 o' clock almost all the time. In quiet recordings, the knob needs to be turned all the way to 2 o' clock. The headphones have been tested on the Aune X1S Headphone Amplifier (on high gain) and iBasso DX160 DAP and neither of the two have enough power to drive it properly. When under powered, the K712 Pro sounds thin and harsh with almost non existent low end.

A considerably powerful desktop amp is absolutely necessary for the K712 Pro to drive it properly even though the sensitivity and impedance are not indicative of such power demands.




Fit:
The suspension headband has no issues and helps in distributing the weight evenly. The pads are massive in size and no part of the ear touches the sides of the pads. I suspect the same for everyone's ears. The pads are plush velour filled with memory foam, they do not cause hot spots or get sweaty for me and conform as expected. The gripe being that the pads are not as deep as I'd like. I have small ears and they always touch the insides. It does not touch the driver directly as it is damped. Thankfully AKG has the pads netted inside to make the experience just a bit more comfortable.









The intro of Flight To LAPD sounds very satisfying on the K712 Pro with enough presence, in stock form. Most open back headphones sound thin and downright skip frequencies that low.

The deep rumble is brought out better when subbass is EQ'd. The stuffy and stabbing electronica in the background of Pulk/Pull Revolving Doors throughout are enveloping and have clean and strong attack. The bass notes in Another One Bites The Dust are absolutely clean and tight, tastefully done. Separation from the vocals is stupendous and yet it manages to be omnipresent.





Listening to this song on this headphone is not a pleasant experience due to its shouty upper midrange. The guitars have a ear ringing glare which is deeply unpleasant after a minute.





Money For Nothing having a "clinical" sounding master is not an ideal pair with this headphone. The experience sounds too digital, lacking life. I would describe the experience of listening to the Lindsey Stirling tracks as a system shock. The violin sounds lush, soulful and full of energy. Detail retrieval and texture in this region is very good. Its intimacy almost tricks the listener into being on the stage. The thumping bass cutting in from the background makes for a complete and beautiful experience.




The writing on the board in Letter is accurate throughout but the fuzziness diagonally front is easily noticeable. The intro of Across The River depicts the depth in stage when the instruments are introduced in the mix at different distances from the listener. The Magni 3, although doing a good job, a higher quality amp will bring about the layering as more three dimensional.





All the instruments in the mix of Once Upon A Time In The West are laid bare left-right across the soundstage with crisp and well defined edges. The separation along the center image is reproduced clearly giving a vivid sense of space. The separation along the center image in Three O'Clock Blues is also made clear in this song at around the 2:50 mark. The cymbals crashing (very) slightly to the left and right alternately are heard clear with admirable well defined edges.





The song Right Action comes out a bit too eager and "in your face" because of it's mastering. When heard through the K712, the experience can get a bit overwhelming sometimes. Snare hits sometimes sound aggressive and electric guitars too crunchy. The experience of hearing Marry You through the K712 is nothing short of majestic. It is lively, dynamic and feels like being in the front row seats. The snare hits and cymbal crashes never sound sibilant or sharp in any way. Eric Clapton and BB King are outlined clearly in the mix. The stage is wide and the "oomph" factor seems to be amplified.




Both great songs to test vocal performance, texture in the vocals are brought about immaculately, including the breath of the vocalists on the mic. The hoarseness, strain and breathlessness in the voices are lifelike and intimate. Absolutely no complaints.



Sax, Pianos, Violins, Hammond Organs have a soulful rendition full of life and body, sounding lush. They never appear to be distant with respect to vocals or the sax. Decay of snares and tom drums are not cut off in the track Take Five and are replicated accurately, giving a sense of realism and recording space.



Conclusion:
The K712 Pro is a technically sound headphone. Its drivers are very capable, fast and clean.

The review has been conducted in stock form but all the sonic gripes can be fixed and even enhanced by EQ. The subbass can be cranked up and the upper midrange can be toned down and the headphone responds remarkably well, making the headphone near about perfect from an enjoyment standpoint.

People looking for a headphone that is fun and exciting to listen to should really shortlist the K712 Pro, provided they have a beefy and capable amp to drive these cans to their full potential.




*All ratings are accurate as of date of publication. Changes in price, newer models may affect Project A3's views on the performance and value of the reviewed product.

AKG K7XX vs AKG K712 Pro

I’ve been listening to music on speakers and headphones since I was in the 1st grade. I always loved music and always had pretty good ears! I remember I could always hear the bus streets away when others couldn’t and I could always tell when and who was in the driveway based on the car sound and we didn’t have loud cars and I'm not a car person.

I’m a person who likes to have a pretty natural sound where nothing is over emphasized. I’ve been enjoying AKG headphones since my first pair as a kid that i saved for months and it was just the K44’s that i got to listen to in the store which were night and day compared to the cheapo headphones that i heard from the dollar store and Walmart.

Now i’m 28 and had quite a few pairs of cans nothing like others here but more than anyone i know of. AKG K44, DT 770’s 80ohm, AKG K553, AKG K7XX, Polk Audio UltraFocus 8000’s(Not bad BTW). When it comes to the type of music that i listen to well, I pretty much listen to everything besides metal and what some would call “Hard Rock”. I do however love oldies and music like Elvis and the Beatles and pretty much everything from the 60’s and 70’s. I also love Pop and Rap and Country. I game as well and love having a 3D style sound stage as i have to wear headphones now instead of having 5.1 speakers(Due to life) which is my preferred way of listening to everything. The speakers i used to own are the Polk Monitor 70’s as my fronts and Polk Monitor 40’s for rears and a CS2 center with a BIC 12 inch sub but again can’t do that anymore lol.

Brings me back to these headphones which i will only be comparing to the K7XX’s as i found almost no one who really did this at least very few. These now cost $330 on Amazon compared to $200 on massdrop for the K7XX. I’ll compare the things that i noticed first and to me it was pretty apparent as soon as i put them on my head and listened to them, i owned the K7XX for 2 years BTW and the K712 Pro’s for only a few hours.

First thing that I immediately noticed was the sound stage! Which was way more 3D sounding. With the K7XX it seriously sounded like i had a left and right speaker on my ear and a center up front with NOTHING in the back and not a lot of space in the front. All the sound was left-right-center and nothing else. Still miles better than most headphones under the $300 range from what I heard from my friend’s place who collects over 20 pairs of headphones(I will one day slowly getting there). However with these K712’s i barely even hear sound coming from the driver itself its instead just in a separate environment all together. Absolutely amazing with no complaints at all it's basically like I got my surround sound back!

Second thing that I noticed was just how much more comfortable they were. The K7XX just always moved around on my head with any movement at all. Oh and lets not forget the plastic creaking sound that always came out of my right ear cup every time you barely make the slightest movement. Had these on now for 4 hours and they don’t even feel like anything and I wear glasses too.

Third thing that I noticed was a superior treble response. The K7XX’s always sounded too warm to me like the tweeter in the speaker was paper with very little precision. I feel this is why the sound stage was so weak in comparison to these. Adele’s voice sounds way more authentic with these compared to the K7XX’s for example and the violin in Lindsey Stirling’s music actually sounds like a violin who would have guessed? I even thought Pandora was the worst audio I ever heard with the K7XX as everything sounded to mufflied turned out it was the K7XX the whole time, sure we all know Pandora isn’t the best or anything but it seriously sounded bad to me. Now i’m listening to “Stand by me” by Ben E. King and it just sounds so beautiful as I type this.



I guess the one other thing that I noticed was smoother and tighter bass. I find it to be extremely fast and quite accurate and it doesn’t distract you from the other pieces in the music like the DT 770’s that I have. The K7XX’s were pretty decent too but the mid bass kind of sounded too thick and not realistic at all.

Leaving me to volume, with these i have to turn up the volume on my Objective 2+Odac combo more than I did with the K7XX’s still have plenty of power left and i still only use the low gain on the unit but i might be upgrading to the ATOM AMP+ATOM Dac which is coming out very soon.

I want to say something about this industry and why I respect JDS labs and NwAvGuy who to me was basically a hero in the industry, google his name and read his blog he is the reason why we even have such great AMP’s and DAC’s in this price range.

I got out of audio for quite some time as i got sick of all the snakeoil. I’m a very logical person and to me a AMP or DAC shouldn’t alter the sound in any way and you should be hearing the sound the way the engineers made it. There’s a lot of snakeoil in this industry from people who think a 2000$ dac sounds better than a great engineered 100$ dac when measurements say otherwise. Audiophiles in general I feel seriously hurt this industry and that is why many never get attached to it. I feel that many audiophiles have no clue what diminishing returns means and fall for crazy things like $2000 cables and 1000$ power strips(not even making this up google it they exist and yes people on this site buy them).

Things like “synergy” are nothing but BS. If you buy a bright pair of headphones and pair it with a tube amp to warm the sound you will not only be trying to change the very pair of headphones that you bought but you will be introducing distorition into your music which is very measureable over the tubes. How does that make any sense if you don’t like bright headphones then don’t buy them? We have like 100’s of pairs to choose from for under $500 pick one that you enjoy. Bright-Bassay-Neutral, big and small sound stages everything why pick a pair to just use a tube amp to change the sound or a EQ(unless you need a EQ for the flattest response).

To others here I will give a decent guideline in terms of pricing before diminishing returns heavily kicks into action and I will list the components that make the biggest difference to sound in order.

Source yes this is the most important part to any quality music or sound if you are only listening to free online services with low bit rates like Pandora and Youtube or worse you are never going to improve that sound much go find high quality sources like MP3 320kb’s or FLAC files.

Headphones - After the $350 range diminishing returns kicks in super fast and you have to start spending 5X that amount to get a big difference in sound. Even then my friends HD800’s aren’t even a complete upgrade from these somethings aren’t even that noitcable and that is on his crazy DAC/AMP combo which cost over a grand alone(I know shaking my head too).

AMP- $100 right now the ATOM amp from JDS labs and the magi 3 Hersey from Schiit is more than enough power for even 600ohm low sensitive headphones. Both these amps have a flat frequency response with extremely low distortion levels(can never get rid of distortion 100%) that you can find online with measurements at AudioScienceReview.

DAC- $100 is really it you can find the MAGI 3 not the multibit(measures terribly) but the standard one for just $100 it doesn’t alter the sound but it does recreate the 1’s and 0’s into what the sound engineers created, and does so with crazy good measurable performance too, Atom DAC might be worth looking at too once it comes out. Other good options are the Topping E30-D30-D10.


Don’t let anyone talk you into spending more on a dac or AMP if anything the above equipment is overkill and thankfully you can get this quality of sound for much cheaper than anything you can on speakers. External DAC/AMP isn’t even necessary in all cases if you have sound from a PC then yes i do recommend both as a computer is a terrible place for audio to be in and NO sound cards are not any good and terrible for performance per dollar(check out AudioScience reviews for this) and if your a PC guy you know what performance per dollar means! If you need a AMP you will probably notice it quite quickly due to not having enough volume even in sources where the media is quiet it should still get loud enough for you due to the AMP if not you should think about getting one and I highly recommend getting that first before buying a DAC.

Also avoid buying too cheap as some dac’s and amps aren’t even worth it like anything there is a happy medium and what i listed above are great choices.

Lastly, do i recommend these headphones? They are superior to the AKG K7XX’s in every way but price. Don’t let my comparisons scare you, the K7XX’s or even the sennheiser 6xx are amazing products for the $200 range but i feel the K712’s Pro’s are worth the extra cost to me, superior comfort, soundstage, sound frequency. In fact for a while they will be my last pair of headphones for probably anouther 5 years or so and I'll probably stay out of this industry once again after I get my new DAC/AMP from JDS labs. I’m thankful for sites that are starting to pop up and finally put an end to this snakeoil in this industry but still too many here fall for it and have no idea what ABX comparisons are. Best thing about PC hardware is it's not really subjective and it's all measurable down to every component. Truth is i can’t tell you what sounds good to you only you can answer that!

Good places to go for research include AudioScieinceReviews+NwAvGuy you will think me later after you save $$$.

Build and Aesthetics:
The entire body is made up of plastic except a few small parts that use metal.
Although people can scoff at an almost entirely plastic build, it results in a very lightweight headphone. Since this is mainly intended to be used in studio/home, the plastic build isn’t that big of a deal. But at 350$ (INR 25000) it would have been better to see more metal incorporated.

Fit:
Uses the classic suspension strap mechanism of AKG, the strap here being made of leather; no complaints regarding the headband, works all the time and works great.
The earpads are velour filled with dense memory foam. The pad size is massive so your ears will not touch the circumference of the pad. But the pads are not that deep and rather shallow, and big sized ears will touch the mesh inside. Overall, the pads are super comfortable, although they get dirty really quick.

Amping:

It is deceivingly power hungry at 105dB/mW and 62 ohms. With portable devices you will be able to power them but forget about driving them. A desktop amp/dac is absolutely necessary. The cans seem to keep on sipping power like it’s nothing. It requires a lot of power from a quality amp to show their true potential. When underpowered it will sound thin in the upper mid-range with very less bass impact (verified with the Aune X7S). The Magni 3 can drive these well at its price range but the depth in the soundstage is not as well pronounced. A Schiit Asgard 3, Lyr 3 is recommended. With proper driving power, the lows are more impactful with more depth in soundstage.
You must have a quality amp/dac if you’re looking to buy these.

Soundstage and Imaging:

The soundstage is the star attraction of these cans. The K701/K701/K712 Pro are some of the widest staging headphones ever. Since the soundstage is so wide, the music is always airy. It reaches extreme left and right but the sound never quite comes close to your ears. As a result, the sound is always very relaxing. The complete opposite of the likes of the 600/650 where the sound is always in between your ears and intense.
You might expect that the imaging is going to take a hit given the super wide soundstage, but it’s not. The imaging is accurate even in the extreme left and right; the center image is a bit wide and very accurate. But when it comes to diagonally ahead of you in the left and right direction, the imaging is a little bit fuzzy.
But overall, it is excellent to see the imaging not being compromised as much given its soundstage capabilities.

Sound:
Starting with the bass, these cans have an astonishing bass extension, which is quite rare in open backed headphones. The bass is very fast and clean throughout. It is never bloated, doesn’t bleed into the mids and is very coherent with the rest of the frequencies. When underpowered the bass quantity is quite less and not punchy at all.
But thankfully, these headphones can be EQ’d marvelously. Boosting the subbass in the EQ results in some clean, controlled and fast thumps. The subbass rumble is also astonishing with EQ (Track- Flight to LAPD from Blade Runner 2049 OST, Mountain from Interstellar OST).
The mids are natural, they are full bodied and not tinny and their presentation is not in your face. It’s when you hear vocal based songs that you notice that the vocals have a layer of warmth over them, which does make them sound a bit unnatural but quite pleasing (Track- It’s A Kind of Magic by Queen, I Feel the Earth Move by Carole King).
The problem arises in the upper mids, where there is an awkward hump at 2kHz. The peak although not ear shattering, is evident in some rock and roll songs where the electric guitars sound overly crunchy and in some cases, it can get a bit too intense (Track- Between a Rock and a Hard Place by Rolling Stones, Grand Designs by Rush, Diamonds and Rust by Judas Priest).
The treble response is absolutely master crafted. I would like to make it absolutely clear that these headphones are never sibilant (unless the recording is, obviously). Violins, saxophone, trumpets and any instrument with high frequency extension just sounds phenomenal with such a beautiful timbre. The entire treble range is full of energy and vibrancy. I almost had an out of body experience in some of the string based songs I tested (Track- Artemis by Lindsey Stirling, Marry You by BB King and Eric Clapton ).
The treble range is the most forward among all the frequencies. If your music has a lot of strings or instruments that have a lot of treble extension, they will be presented first to you. Then comes the vocalist who’s a step back in comparison, along with the rest of the band.
The over response in the upper mids and the energy in the treble range results in what I would call a slightly bright sound compared to neutral. This combination also results in a very euphonic and euphoric sound that always keeps you tapping your feet. I am personally allergic to bright headphones but to be honest I never felt the need to tone down anything in the k712 pro: because of its dynamism. The K712 is very dynamic when driven properly. Its speed is also very commendable given it’s a dynamic driver. Feel this portion of this song is a bit harsh? Bam, its over.

First, a disclaimer: I am running these off my laptop through a FiiO Q1 as a DAC and a Schiit Magni 3. These are not high-end amps, but if you don't already own really expensive equipment and your budget is less than exorbitant maybe you will be running them through similar equipment. There's been much ado about how these headphones need high-quality amplification to sound their best, so some of the problems I'm about to describe may be ameliorated somewhat with different equipment, and from some of these reviews, it sounds like this is true.

Comfort, looks, etc.: I don't typically have issues with comfort, but I will say that out of all the headphones I've tried these are by far the most comfortable. The clamping is enough to prevent them from shifting (on my head), but light enough that they never press too hard. The headband is comfortable enough that I hardly feel it most of the time. As a bonus, I like the way they look, but this is of course a personal preference and you can look up images yourself if you want. I wouldn't say the earpads are terribly soft, but they are again very comfy. Build is mostly plastic, as others have said, but I don't care about this at all; if you really need headphones with a lot of metal to feel good about yourself, perhaps you should look elsewhere.

Bass: No issues for me with quantity or quality. It's tight enough that I've never really had any issues at all with poor resolution or distortion. Others have said that the bass is pretty much perfect on these; they may be a bit on the bassy side but I've never had any issues with this either. There is a bump towards the upper end of the bass that extends into the lower mids; while this doesn't translate into muddiness it may bother some people who want a leaner or airier bass presentation.

Mids: As with the upper bass, the lower mids are forward, resulting in a tone that's overall warm (but not dark). I prefer a warmer tone, so this area is perfect for me. They sound full, never thin or empty. The upper mids are where the problems start to creep in - as has always been the case for the K7s, there is an interesting bump at around 2kHz. I listen to a lot of vaporwave, and with the way a lot of these tracks are mastered, this area already emphasized, making the listening experience for these tracks quite painful at times. Without EQ, anytime this area of the frequency spectrum is busy or congested at all, you will notice it, and the K712 will exacerbate the issue. I have EQ'd this area down slightly (2-3 dB from about 1850 to 2300) and it makes the headphones sound less energetic but more natural. Luckily this spot doesn't seem terribly slow, because they respond pretty well to the EQ. At times this bump can be welcome in that it gives certain instruments (guitar, some percussion) more energy / presence. But it is there and that isn't going to change.

Treble: This is the area that really gave me a lot of trouble when I first got these. I have heard that higher-quality equipment can smooth out the treble consistently, but with what I'm using, I got quite a bit of sibilance from especially modern pop recordings: any time vocals were mastered with the intent of making them more "present" / "intimate" (which seems to be done often by boosting a certain area of the treble to reveal the "grain" of the voice) the listening experience would get quite overbearing and piercing. The same goes for some recordings with a lot of cymbals or percussion in general. For me, cutting around 9.5-10.3kHz more or less controlled these issues, but I've heard reports of different peaks for different pairs; 11kHz for some, 9 for others. If you buy these I would recommend sweeping this area to see where the glare seems to be located. Other than this, the treble is pretty resolving and clean, though you may notice some grain if you don't fix the spike(s). Obviously a high-quality source is basically required for these; unlike some more forgiving headphones, any deficiencies in quality are going to be noticeable here.

Soundstage: This is why I bought these, and they certainly delivered; the soundstage is wide, with pretty excellent imaging, but never feels too diffuse or forced. If you really want an "intimate" soundstage, these are not for you and you should look elsewhere; what you're paying for when you buy these is an experience of space, and that's what you get. For me, however, the wideness of the soundstage and perceived distance of certain sounds results in me listening to music louder, so that's something to be aware of. However, for me, the was pretty much perfect and exactly what I wanted. Great for classical music; really great for field recordings and ambient, which are my genres of choice; really good for jazz, and other live recordings.

Overall: After (not really drastic at all) EQ, the K712 is pretty much exactly what I wanted, but before EQ, it could be shrill and harsh especially with some genres that I listened to frequently. Even after EQ, it is pretty unforgiving of bad recordings or sound quality, but when something is well-recorded and especially suited for the K712's strengths - width, dynamic range, a sense of naturalness - the result is breathtaking.

But the K712 does sort of seem to be suffering a kind of identity crisis of sorts. The earlier members of the K7 series were criticized for their clinical, thin sound; the K712, along with some of the other later members of the family, have made up for this by boosting the upper bass and lower mids to make the headphones sound warmer and fuller-bodied. Despite these alterations, the K712's have retained the upper-mid bump and sometimes peaky, bright treble of the earlier headphones (though apparently to a slightly lesser degree) as a sort of signature component of the more recent AKG sound. At first, I was pretty confused by this, as I noticed that despite the overall warm sound of the headphones they were quite fatiguing to listen to for longer periods of time. While the combination of bright treble and present upper mids with warm lower mids and bass may be a bit odd-sounding, it does mean that these are great all-rounders and usable for a lot of different kinds of music.

Conclusion: Despite some issues with the treble and upper mids, I'd recommend these to anyone who's looking for a pair with a wide soundstage and who's either unafraid of brightness (these are still going to be less harsh than anything by Beyerdynamic, for example) or who's unafraid to EQ when necessary. They're really, really great, the best I've used, but I'm still on the road looking for that magic "perfect pair."

Once the treble weirdness is fixed, these really are fantastic, resolving, spacious headphones that do everything I can think of really well. Again, they are not for everybody, but I find myself liking them more and more. Yet for all my love of these headphones, they lack the kind of spark that makes me truly fall in love with them. For reference, I find myself slightly preferring the K553's - despite the fact that they're technically inferior (except for their FR, which is more neutral), they seem to have slightly more character in some way. I would recommend the K712 for anyone, but for me it's not truly inspirational.

Also, a note: if you are buying these used for $300 or more, you're wasting money, as they are available from Europe for under $200. I bought mine for about $190 (with shipping it came to about $220 as I needed them shipped fast in advance of a move).

Allow me to preface this review with some background information.
 
I have experience listening to different present-day AKGs, including the Q701 Quincy Jones Signature, the K702 65th Anniversary Edition (Austrian-made), the K7XX Massdrop First Edition, the K240 Studio, and the K612 Pro. The K7-Series, while highly detailed and comfortable, proved to be a mixed bag for me sonically, with the models being either too intimate sounding, too mid-forward, or too dark. I did believe that these flaws belied a truly great-sounding headphone lurking beneath, but it was simply a matter of sorting out the right acoustic balance. And now I can say for sure that the K712 Pro hits the mark dead on for me, and has become my new favorite neutral open-back headphone. Now onto the review.
 
Build and Finish:
 
The K712 Pro resembles the K702 65th Anniversary (Annie) in many ways, from the charcoal-colored matte plastic body, to the colored stitching on the smooth (no bumps) headband, and the colored center ring on the driver housing. But this time it is in a deep orange color accent theme, with the twin headband rails, headstrap stitching, inner driver ring, and cable being orange, rather than the electric blue of the K702 Annie. Some people might not like this color scheme, but I think it stands out nicely, if looking somewhat like it was themed after a KTM motorcycle (coincidentally another Austria-based company). The K712 is well made, but it does feel a little more plasticy than something like a Sennheiser HD600 or HD650, and certainly more than a Beyerdynamic DT880 and DT990. 
 
The K712 is made in two different places: formerly Vienna, Austria; and presently, Bratislava, Slovakia. AKG users have bemoaned this now complete abandonment of Austrian manufacturing of AKGs, but with the Slovak-made models, you still have a headphone assembled in the European Union. The Austrian-made models like mine have "Made in Austria" silk screened on the center driver cover, while the Slovak models do not have any country-of-origin markings. While I cannot comment about sound or build quality differences between K712s made east and west of the River Danube, those who may want a potential collector's item should opt for an Austrian-made model. 
 
What it comes with:
 
The K712 Pro comes with two cables: a 3-metre straight cable, and a 3-meter black corded cable for plugging into mixing consoles. Also included is a satin-lined black velour carrying bag, which other K7s do not feature, so you get a little more for your money with the K712. 
 
Comfort: 
 
The K712 Pro features AKG's tried-and-true self-adjusting headband, which features a leather strap suspended by elastic bands. It makes the K712 a highly comfortable headphone, in addition to its moderate weight, but the bad part of this is that the elastic bands will begin to weaken over time and lose their tension. This will cause the headphone and the ear pads to slide down your head over time, and it also means the headphone will not sit firmly on the head. So far as I can tell, the solution to this is either to send the headphone into AKG for an elastic replacement, or perform a DIY fix. 
 
The ear pads on the K712 are thicker than the older K702 Annie pads, but are not as thick as the K701, K702 and Q701 pads, and are not angled. Despite this, the K712 retains its spacious ear cups, with the padding made from dense memory foam that conforms nicely to the shape of your head to form a comfortable seal. If you wear thin-armed glasses, then you should have no problem wearing the K712. My ears are notorious for have a problem with rubbing up against driver covers, or getting irritated from having the backs of pads rub against them. With the K712, neither of these comfort issues are present, especially considering the moderate clamping force, and the pads that do not collapse like Sennheiser HD650 and Beyerdynamic DT880 and 990 pads often do. The earpads also run fairly cool for my ears.
 
Sound:
 
Now this is where we get into the most important distinguishing feature of the K712...
 
As I mentioned earlier, I have not found all of the K7-series headphones to be the most satisfying to listen to. The Q701 was extremely spacious sounding to my ears, but I found its overly left-right-panned soundstage to be unnatural at times with older stereo recordings, causing all of the music to go in either direction, and making the center image go dead. In addition, I hated the upper midrange hump, which caused horns and saxophones to trigger an immediate cringe from me. So I thought the soundstage and glare needed addressing. Next I owned the K702 Annie. The Annie was a significant departure from the Q701, with what sounded like a large amount of dampening added to it. Instead of the overly-panned soundstage, the Annie now sounded closed in and highly intimate, the treble was significantly darkened, and there was a slight boost in the midbass (the Q701 had good bass extension though). But there was still that funky upper midrange bump that still stood out relative to other frequencies, especially since the treble was decreased and the bass was increased. The pads also did not have quite enough depth, causing my ears to touch the drivers. So next I tried the K7XX, which was a Chinese-made 200-dollar K702 Annie, but with deeper earpads, and a more toned-down upper midrange. Unfortunately for some reason, this combination managed to end up soundnig dull and lifeless, which spoiled that AKG magic. So finally I tried the K712. 
 
To my ears, the K712 combines a mix between the K702 Annie and the regular K702 or Q701. The headphone overall has an unstressed, fairly musical sound with an overall even tone, and a slight emphasis on the upper midrange and treble. There still is that upper midrange peak at around 1-2,000 Hz, but this time it meshes better with other frequencies since the bass and treble are more even with one another, so the balance ends up sounding less harsh and more neutral, while allowing that presence region boost to contribute to a more musical and engaging sound. The K712 still has that upper midrange increase but just a better tuning of it. Soundstage is great for a headphone of its type, and is the most evenly balanced of any K7 model. It does not pan excessively to the left and right like a K701, K702 or Q701, and it does not sound compressed like a K702 Annie can sound. It has plenty of depth, while imaging and placing instruments accurately. It will not sound out of your head like a Sennheiser HD800, AKG K812, or Sony MDR-MA900 will, but it has better imaging than a Sennheiser HD650, which while being deep sounding can sound blobby with the placement of instruments, and often sounds like a HD600 with simply more depth added. 
 
Treble:
 
The treble on the K712 rarely gets harsh, but could possibly sound sibilant with excessively treble-heavy music (even an HD650 can sound sibilant in the right scenario). There is air in the treble, but overall it sounds mostly neutral. In comparison, the K712 is brighter than an HD650 but much less bright than a Beyer DT990. The K712 sounds great with jazz, acoustic and classical, since the treble has smooth presentation, and contributes to good instrument placement. 
 
Midrange:
 
The Midrange is where the K712 gets into its stride. The midrange has plenty of detail, and rarely sounds stressed. The K712 sounds more musical than you would imagine, and it does not have a bright or overly warm tone that distracts the listener from enjoying a realistic-sounding song. The midrange to my ears is about as realistic and even as you are going to get in an open back headphone for 500 dollars or less. It makes the K712 much more enjoyable than the Q701, which can be irritating, and the K7XX, which can be overly dull. 
 
The bass on the K712 Pro is as neutral as it is going to get on a K7. There is plenty of extension down low, with excellent tightness and a clean tone that makes it easy to distinguish notes. In comparison to the HD650 the bass on the K712 is much less warm, and has a tighter sound, with often better extension. The HD650, especially when underamplified, can overly warm in the bass, and that bass tends to contribute to a pleasing and euphonic sound, but at times can get in the way of hearing finer details. While the K712 has a neutral to somewhat leaner physical bass impact at times, with a good amplifier and a good DAC, it can take an EQ boost, and you can get some good performance with bassy music. That said, the K712 only becomes bassy if the sound it is playing is highly bassy; it does not introduce a bass boost if it does not need to. 
 
K712 Pro vs. K702 Annie
 
Now just to clarify this, the K712 is NOT a rebranded K702 Annie. The two headphones sound noticeably different, though I have heard some newer Annies have been retuned to more closely resemble the K712 sound. Compared to the original Annie, the K712 sounds more spacious in the soundstage, a tiny bit lighter in the bass, and more lively with a more present treble and a more proportionally-balanced upper midrange. To my ears the K712 is better balanced than the K702 Annie, and less dark. 
 
Amplification:
 
First off, do not expect the K712 to sound great plugged directly into an iPhone, iPad or iPod Touch, because it will not. You are going to need to budget in a good amplifier and DAC if you want to enjoy the most this headphone has to offer.
 
The K712 tends to exhibit the same characteristics that are present on other K7s when it comes to amplification: harsh and thin sounding when underpowered or driven on a bright amplifier, dull when not driven on the right source, and revealing of cheap quality DACs. The K712 has a tendency to be less forgiving with poor amp/DAC matches, and often sounds like what you plug it into-to an extent. 
 
I have driven the K712 on the Schiit Audio Lyr 2 hybrid tube/solid state headphone amplifier, and the pairing produces good results, with a tight and unstressed sound, though the stock tubes are a little dull. The Schiit Modi tends to not be a very good source DAC with the K712, as it often sucks a ton of bass impact out of most headphones, and sounds compressed, so I would look at a better quality DAC, or one with a better sound, like an HRT Music Streamer, or Meridian Audio Director. A good sounding and detailed DAC is crucial to the K712, so make sure not to overlook that requirement. 
 
I have heard of people running the K712 off of OTL tube amps like a Darkvoice 336SE, and achieving pleasing results, but do keep in mind that an OTL amp like the Darkvoice or Bottlehead Crack is not going to be the best for impedance matching, as the K712 has a fairly low impedance of 62 ohms, and that impedance tends to stay dead even throughout the frequency spectrum, unlike the Sennheiser HD650. So either a hybrid amp like the Schiit Vali 2, Lyr 2 or Mjolnir 2, or an OTC amp like the Woo Audio WA6 or WA7 would likely be the better option if you choose to run the K712 on a tube-based system. Solid state amps are an excellent choice with their lower distortion figures, lower noice floor and lower output impedance than most tube amps. 
 
As for being driven on a 2-in-1 portable DAC and amp unit, I have been experimenting with both the new Oppo Digital HA-2SE, and the famed Chord Electronics Mojo, costing USD $300 and $600, respectively.
 
The HA2-SE uses the newer ESS Sabre ES9028Q2M DAC chip, which Oppo claims provides a quieter noise floor than the previous Sabre chip in the HA-2. While I do not have the two to compare, I can say that the HA2-SE makes for a very good pairing with the K712 Pro, extracting a good amount of detail, while driving the K712 loud and maintaining a tight and spacious sound. Some people do not like Sabre-based DACs because of their harshness in the upper midrange and lower treble, known as the "Sabre Glare". I do notice some Sabre Glare on the HA2-SE but it does not prove to be a deal breaker, though this glare does not always bode well with the upper midrange emphasis on the K712, and can make the K712 occasionally shouty or blare sometimes. This does not dissuade me from recommending the K712 with the HA-2SE. They make for a pairing that is a great deal enjoyable, and the bass boost switch on the Oppo can add a nice rumble to the K712 when your music calls for it. 
 
But the winner so far is the Chord Mojo. The Chord Mojo is twice the price of the HA2-SE, but handles the K712 excellently, and it should. There is no lack of power and performance, and while the Mojo does not necessarily sound quite as spacious as the HA2-SE on the K712, it makes the headphone sound less stressed and more effortless, with more detailed bass and better imaging, and a less bright tone. That said, the Mojo is considerably more expensive than a K712, so if you cannot justify purchasing it, I can absolutely recommend the K712 with the HA2-SE. 
 
That concludes my review of the K712. Thank you for reading this lengthy writeup, and if you are in the 300-500 dollar market for a neutral open back headphone, and are willing to give an AKG a try, I can safely recommend the K712 Pro. If you like transparent and neutral-sounding headphones, and want a lighter-feeling headphone with more soundstage than an HD600, and a less metallic sound than a DT880 or DT990, then I do not think you will go wrong with the AKG K712 Pro.

I have these headphones for about 3 weeks and I think they are great for overall listening to music, even for a long time, however, I don't think you can drive them without an amplifier because the audio quality from a phone or just a poor build-in dac isn't good, the bass sounds muddy and the highs lack detail.

So I've got the Magni 2 and Little Dot 1+(Mullard M8100 tubes,OPA2107 op amp) and I must say that the Magni feels like the inferior amp for this headphone the bass has less impact, the soundstage is smaller, has less detail although it has more bass and the presentation feels faster. It looks like the tubes add a little impact and smoothness.

Overall, these might be good as a second pair if you already have like a Sennheiser 600 series headphone (I have HD 580s) or if you want something different, but I don't recommend them as a first pair for people that don't know what they're going into (try out an akg open-back headphone before deciding to buy)

Anyway I got these for cheap (they are made where I live) and I keep them for sure.

8/10

Before buying you should know that sometimes(maybe a first revision or something) the K712 has a loose wire on the left ear. My first pair had this problem (sound from the left ear was gone after the first day of use) but thank god the second pair I got is fine(for now).

overall great headphone at its price.

This review will compare between the two semi-flagship headphones from two companies; The K712 headphones from AKG, and the HD700 from Sennheiser.
 
"Expect and discover. The perfection."
-box art from AKG K712's packaging
 
"The HD700 Truly excite your ears."
-quote from cover page of Sennheiser's HD700 manual
 
Along with the first impression, I noticed that the K712 needed more power (the hungry hungry hippo). I had to crank up the volume  about 1.5~2 times for my listening level with Senn's HD700 on my Schiit's Magni 2. I will update the review once I get the Valhalla 2 or Asgard 2.
These I-don't-look-cheap, you know? looking K712 costed me $280, which, honestly, it's a bargain for me. my HD700 costed me $400 though, so keep that in mind. (both are used by someone else for 1-2days without even a scratch on headphones; however, HD700's are more burned in than my K712, my K712 was only used for like ~15 hours, while I used HD700 for at least 8 hours per day since It was next to my bed; that would equal about 200+ hours of use on my HD700.
 
 
Build Quality:
it doesn't look cheaply made unlike the HD700 when compared. HD700 has more of plastic-y feeling, while the K712 has more metalic feeling.
K712 is made in Slovakia, though raw materials are assembled by machines. there is a video of showing how K702's are made in YouTube. If you really need to know how AKG's make headphones, go to YouTube, search video for "How It's Made Headphones"; the video is published by TRR56.
The headbands are elastic, so there is no need for spending 30 seconds of your precious audiophile life trying to perfect the K712 for your head.
 
 
Comfort:
For me, the HD700 won the comfort war. while wearing HD700, my ears doesn't even touch the driver, while the comfy cushions on headband/earpad virtually makes me feel i'm wearing nothing on long term listening. looks I need some proper adjustments with wearing K712s, for the drivers (or the earpad) to not touch my ears. headband itself is elastic, so for the most users, headband will automatically stretched for size of your head.
HD700 wins by a little.
 
Design:
I mean, who would care since you normally wear these at home? It's not like a pigeon would get impressions on your headphones and run into your windows for the beauty.
(I've only seen one idiot pigeon running into windows for plants inside my apartment in South Korea)
 
It would make a difference if you wear headphones outside, though. Personally, for me, I would like to get some decent look since I use my open-backs outside, because my neighbor is quiet.
for design, which is really, a subjective matter; even more subjective than our picky ears. In my opinion, both of the headphones have very aesthetic look; the HD700s have the look that represents like "I listen to reference-class headphones and it even has better look than your Beats by dre", while the K712s give more of.... calmer, not flashy, but not ugly design.
For me, HD700 wins the Project Runway war.
 
Sound Quality
Here's where the distinctiveness that we can see where Sennheiser's sound and AKG's sound.
I can't really decide which would "Win" the Sound war; K712 has balanced sound while the sennheiser have emphasizing treble with bass, giving different "purposes" each other.
The treble on K712 is much relaxed and soft than the HD700's treble everywhere. (the HD700 is infamous of treble spikes noticed by some HD700 users, including myself)
 
Sennheiser's HD700 has forward  bass with even-more emphasized treble that still shows some degree that mids do exist in HD700, though, not dominant.
It gives perfect sense that the HD700 is in middle of HD650 and HD800; HD650's darker, forward mids with lovely bass mixed in with HD800's bright sound with precise imaging with wide soundstage, giving a "who art thou?!" sense of half-blooded child from sennheiser (oh yeah, with more of HD800's silver mesh look).
 
unfortunately, some users found HD700's treble fatiguing due to spikes; many users (such as myself) had to do a modification, known as the anax mod  to the HD700 (originated from HD800), whereby the installed foams around drivers dampen and reduce the emphasis on treble, adding little bit of emphasis on mids and bass instead. 
 
HD700's mids are less present than the K712 because of the dominant bass and treble; but it gives somewhat "immersive" feeling with wide soundstage on my symphonies.
 
K712, however, emphasizes on the clarity with separations of instrument unlike HD700;, while it has emphasized treble and bass, with immersive feeling.
well, it says on the box of K712; "for precision listening, mixing and mastering".
K712 has narrower soundstage than HD700; but it has the sense of realism because of balanced soundstage.
 
On beethoven's 9th symphony (ode to joy, which is also known as the the finale) , both headphones have clear separation of instrument while it really shows distinctiveness of the both companies sound that pursue on.
 
the HD700 gives very immersive sound with bass and treble; with mids that are present, but not really as present as treble and bass. it gives some kind of "live" feeling with the immersive soundstage, further defining the HD700's characteristics, while having full vocals.
 
K712s have different approach; while it has the balanced sound with much softer treble than the HD700, it has much narrower soundstage than HD700. it gave me more of HD650/600 feeling in soundstage; not narrower as HD650/600, but not wider than the HD700. The K712 tries to show the details in the symphony,  while HD700 tries to show the "live" sounding with the wider soundstage. K712s also have the balanced, precise and three-dimensional soundstage, that made me "wow" with the separations of instrument, while having full vocals, but not full as the HD700's vocal (but I wouldn't say K712s have thin vocal).
 
Overall/extras:
The HD700 is more of genre specific (I mentioned this on my HD700 review), it would only show it's true strength on classical music because of the emphasis on treble, unless it is toned down using EQ/mods. K712 is more of balanced, used for many other genres; especially for hearing into details of the music.
I would use both of them for home use, but use HD700 more often for outside use since K712 is just hungry with my Fiio E18 amp+dac; HD700 becomes more balanced if used with E18; losing few emphasis on treble but adding it to mids.

AKG K712 Pro Review
 
This is a review I have put off for a long time, I've owned the AKG K712 Pro for about a year now and have tried it on numerous systems. The source is a variety of uncompressed music files on the computer playing through Foobar2000. I'll try to keep this review short and simple, may try to update it later. To put it simply, the K712 is my favorite headphone I currently own, edging out the HD 650, HD 600, and DT 150.
 
The system consists of:
 
Schiit Lyr 2(high gain) w/ '89 Amperex Fat Bottle(Voskhod Rocket) silver shield tubes
HRT Music Streamer HD set at highest bitrate and lowest latency
Schiit Wyrd
Furman M-8X2 Power Conditioner
Ela Audio solid silver RCA to RCA Interconnects
Venus Audio Canare AKG cable
Ice Age Audio 10 AWG Cyro treated Power Cable(for amplifier)
Pangea Audio Silver-plated Copper USB cables
 
 
Build Quality and Comfort:
The build quality of the K712 is very good despite it's light weight. It's made of high quality plastics, feels solid in the hands, and seems to be a headphone that will age well, only concern is the elastic bands losing their elasticity over time. The K712 has a matte finish and feels quite nice to the touch. Comfort is excellent. The pads are plenty deep and the memory foam is very comfortable. I never had comfort issues with these headphones. The clamping is just right and doesn't seem to change much with use like it does with the HD 600/650 which I found to lose their clamp by a fair margin. 
 
Amping: 
This headphone is a pain to amp properly, it's just so picky due to it's revealing nature and the interesting presentation of dynamics that is typical of modern AKG headphones. This headphone has caused me a lot of frustration to amp properly but I finally got it right. These headphones need a lot of power to truly shine, we're talking orhto levels of current and a good deal of voltage swing, they become a completely different animal with a lot of power behind them.
 
Sound Quality:
 
This headphone can be a mixed bag sonically until you get them happy, they aren't as hard to get to sound right as some of the previous incarnations of the K7 family, but like all headphones in the K7 family they are very picky and honestly benefit from a good system. In my experience every little thing matters for the end result. This review is based on the system I currently use, results will vary depending on the system.
 
Bass: The bass on the K712 is nothing short of amazing to me, it's deep, well extended, has excellent slam, and has excellent excursion factor competing with the DT 150 in this regard. It's a very tight and quite fast bass, never ever seems to sound slow or confused in anyway. The bass has a lot of weight to it.
 
Midrange: You would think this headphone would be slightly recessed in the midrange based on the graphs but that is not the case at all, it's just as present as the mids on the HD 600/650 and very comparable, there are shocking similarities in the tuning and timbre of the mids between the K712 and the Senns leading to an absolutely gorgeous and beautiful sounding midrange that portrays vocals in a beautiful and pleasant manner. The mids are very clean and clear and full, they never ever sound hollow or recessed in anyway. 
 
Treble: The treble on these headphones is very revealing, it has more energy than those of the Senns but this creates a pleasant contrast to the Senns as the treble has wonderful dynamics and honestly sounds more natural in this region. Treble can be harsh and sibilant on certain systems, but on the right system they are very smooth and clean and not harsh in anyway, even smoother than that of the HD 650 surprisingly. The headphone has a small bit of air to it's sound, which is nice coming from the HD 600/650 and DT 150. 
 
Imaging/Soundstage: The imaging on these headphones is simply fantastic, very precise and gives an excellent sense of 3D realism. The soundstage is large and quite wide but also its circular and has plenty of depth and is quite tall. It isn't like the ovalish shaped soundstage found on the Q701. All imaging and soundstage complaints I had with previous K7 series have been fixed with the K712. This is the soundstage and imaging champ of all my headphones.
 
Transparency: This is a very transparent headphones, it's incredibly revealing of the system. And the headphones simply disappear from the head when listening to them.
 
Clarity/Detail: The clarity and detail of this headphone is simply exceptional. It's somewhat more detailed and resolving than the HD 600/650. The DT 150 is closer in terms of detail retrieval to the K712, haven't been able to figure out with is more detailed of the two. Though I would say the clarity of the DT 150 is a little better than the K712.
 
Dynamics: This is one of the standout features of the K712 and honestly a trait I have found with most AKGs, it's honestly why I became a fan of the AKG sound and it's also what makes AKGs so frustrating for me. The dynamics on the K712 are simply incredible, the headphone has an interesting ability to portray the dynamic information of the source in a way and magnitude that the HD 600/650 and DT 150 simply don't. This leads to quite drastic differences from different recordings. Some recordings sound extremely dynamic and others sound flat and lifeless. This can be heard on other mid-tier dynamics, but not to the same degree as the K712. It's as if the dynamic range is a bit compressed on the HD 600/650 and a lesser degree the DT 150 in comparison. 
 
Conclusion:
 
The AKG K712 is an excellent headphone and easily competes with other mid-tier dynamics in its price range. It's comfortable and lightweight. I haven't compared it much to planars as I don't own any other than an unmodded T50RP. If your willing to spend time with the headphone and come to appreciate it's sound and live with it's pickiness then the headphone is well worth the time and investment. But it may not be for everyone. The headphone is on the warm and lush side and may not please everyone. It's basically an evolution of previous K7 series and has many sonic traits of the HD 600/650 with an AKG flare to it and is an excellent competitor to the HD 600/650. I personally think it's a bit better than the classic Senns, but that ultimately comes down to preference and the system. 

One headphone for all people? I think the K712 tries very hard to please everyone and in doing this misses the boat in focusing on being the best at any one thing. Great headphones but it's not that simple! Well built but delicate. Much better pricing through Amazon than the $699 MSRP but unless you already own a suitable amplifier you are probably going to end up budgeting for one of those too. With tons of competition between $150 and the $700 MSRP it's actual value comes into question, especially when some of their biggest competition bears the name of the same manufacturer. They have a big sound stage, but not the biggest. They have extended bass, but aren't really for bassheads. They are detailed and analytical, great for critical listening, but not as good at this as even some of their older models. They are fairly neutral but are they actually a serious solution for the sound professional? Who are these really made for?

K712 vs memories of K701:

These are the first AKG K7 series I've heard in something like four years, after I sold my K701, mostly because the *bumped* headband caused me discomfort. The K712 is FAR more comfortable, on my decidedly large head. From memory (on the same amp, source and music) it seems like the K701 was brighter, perhaps more "neutral", whatever that means. The K712 certainly do NOT want for bass! By contrast my memory of the K701 was a lighter on the bottom end, more forward in the mids and perhaps more "bright" on top which in particular made them a very revealing listening experience. I remember a good portion of music sounded so bad on them (compared to the stuff that sounded SUPERB) that I didn't even want to hear certain songs on the K701. Every recording and mastering error was revealed. The K712 seems more "forgiving" of bad quality recordings for some reason. I also remember the K701 having a more spacious sound stage but perhaps that's just because I've been listening to M50s in their absence...

K712 vs ATH-M50:

To my ears the biggest difference between the K712 I just got and the M50 I've been listening to for quite some time is the obvious trait of whether or not one is closed or open backed. Historically its often that fans of the competition like to say the AKG open backed cans lack bass. AKG paid attention and first released the Q701 (which I have not heard) that was said to have improved the bottom end and now the K712, which have bass in spades! The M50 by comparison is often noted as having a LOT of bass, often trading blows with cans like the Beats... and winning. I found the K712 was VERY close to the M50 in the bottom region. The K712 also definitely sounds bigger, more spacious, more "speaker like", than the M50.

The K712 is more resolving, more detailed than the M50. At first, when I was really listening close for any obvious sonic flaws I kept catching things that made me think one or possibly both drivers were somehow messed up. I'd throw the M50s on and listen to the segment in question again and sure enough, there it was. The M50s showed it too but seemed like it just wasn't as obvious. This happened on songs I thought I knew pretty well, too! At one point I heard a sound in the rear of the left stage that made me think my 18 year old son was trying to get my attention (sounded like his quiet baritone.) I took the left cup off and turned around in my chair to see what he wanted... an no one was there! With good recordings the K712 can make things you've never noticed before jump out of the music at you... Almost "hairs standing up on the back of your neck" spooky how this happens. Putting the M50s back on my head and listening very closely, sure enough, there was that sound was again. The M50s produced the same sound but it was so awash in the rest of the audio that I had just never noticed it before. The M50 is a great, capable, pair of headphones. They don't resolve details quite as well as the K712, nor do they have the same sort of spacious sound stage (no closed back can I've ever heard are any different in this regard) but... they are less than half the price of the K712! This shouldn't be interpreted as a deficiency in the K712 but rather a testament of just how good the M50 IS. It's what I consider "the point of diminishing returns". The K712 DOES sound better, to my ears, but you pay twice as much and do not, arguably, receive twice the value.

COMFORT:

Comfort, since my masochistic love/hate relationship with the bumpy K701 a few years ago, is now the top of my list to check off when buying headphones.  A pair of cans you seldom use, no matter how good the SQ, are the worst ones of all!  The K712 is very comfortable from the smooth headband to the velour covered memory foam ear pads.  The clamping force, if anything, might actually be on the "too light" end of things.  They haven't fallen off my head yet but lots of head movement as a test will reveal these slide around a bit more than most will find ideal.  

BUILD QUALITY:

Bitter sweet trade offs. Far more comfortable than the K701 I used to have. No more bumps on the headband! The "memory foam", velour covered ear pads are super comfy too... BUT take very good care of them! AKG wants almost $50... EACH... to sell you replacements! The K712 is one of the largest earphones I've ever tried. HUGE ear cups help produce it's outstanding sound stage and fidelity. And yet these are extremely light as well. But that also means there isn't a whole lot of metal in them. All in all these feel exquisitely "delicate", like a beautiful hummingbird or dragonfly. I wouldn't want to sit on them. The velour bag that is included is a nice thought but really, for these cans I'd much rather have a solid hard case to put them in when I'm traveling. Not exactly flimsy but "built like a tank" (or a pair of M50) does not come to mind.

SOUND QUALITY:

Like it's relatives the K712 thrives on current and voltage stability. Yes, you can plug them into an iphone or the headphone jack on your computer or something but to really hear them at their best will require a good quality amplifier, the more powerful the better. The K712 is a highly dynamic headphone, sound reproduction wise, and can go from revealing the softest, quietest subtleties to thunderous drum crashes instantly, without sounding strained, but it takes a well built amplifier that will provide plenty of headroom to really make it happen. But given what it thirsts for these are a real treat with just about any music. They are full of bass, nice mids and detailed highs... But do none of these things extraordinarily well! I think I would trade some of this "improved bass" for a slightly more analytical presentation in the mids and treble, like I remember the K701 as having. That said I perceive no weakness in their sound either. Nothing too bright, too boomy, too "fatiguing".

Some critics of the older models liked to claim that these are only good for classical or possibly acoustic jazz. I never felt that way about my K701 and with the K712 it becomes a meaningless point for debate. Vivaldi, Eminem, Rammstein, Kroke, Benny Bailey, Shpongle, Pink Floyd, Dianna Krall and Three Dog Night all sound excellent on these 'phones. I listen to a wide range of musical genres and I have yet to sample any of them that made me think these weren't excellent headphones for that particular flavor of music.

VALUE:

Replaceable ear pads, even at a bit of a premium price, nice. Replaceable cables are a nice feature that any headphone over $200 should have. The K712 includes two cables, one straight and one coiled, and both are just the right lengths for practical use. Well machined, gold plated screw-on adapter from going to the gold plated 1/8" plug to the larger 1/4" size. Velour travel bag? Does anyone really put a $700 pair of headphones in a fancy pillow case? AKG could have kept that and lowered the price another $20 or something.

With an MSRP of $699 I think AKG was very brazen in the market it wanted to challenge. Not that I've heard any $700 headphones but for THAT kind of money I think they had better leave zero room for complaints. The K712 aren't that. At Amazon's price around $350 I think they become a much more solid contender although some of their stiffest competition also wears the AKG badge. Priced much lower than the K712 perhaps a K702 or Q701 would have fallen a bit more in the middle between the K712 and the K701, sound quality wise, perhaps not quite as much bass and lower mids but slightly more detail and neutrality? Off the cuff I think that if I would have paid anything close to the MSRP for these cans I'd probably be sending them back and buying BOTH the K702 and Q701 just to find out for myself! But at anything close to $350...

Called me crazy after I have had so much "not so good" experiences with AKG headphones, from K701 to recently K554, K501. My ears were badly hurt by recent ear infection but I still put my bet on this pair of headphones
They do not disappoint at all. All these bass, though restrained and subtle, all show up.

This is going to be a short review, just letting you know in advance.
I listen to mostly contemporary pop, classic rock, as well as a little classical. In my search for a good headphone to use for all around listening, I stumbled across these, and I must say I'm quite impressed!
For me, the bass is absolutely perfect. Of all the headphone I've heard, these have the best quality bass I've heard. It's not just the quantity, but the control that really sets these apart. It even extends down below 20 khz, barely audible but you can feel it!
Aside from the improved bass performance, it's overall very balanced, but I like to nitpick so I must comment on just one flaw these phones have. In the lower treble, the 2kz has a peak that sounds somewhat unnatural in some recordings. It doesn't bother me that much, but sometimes it makes poorly mastered recordings sound strident and compressed, therefore less "airy" sound. I just EQ it down by 2 decibels, and it sounds almost perfect. 
The treble not sibilant at all, and it's very detailed yet not fatiguing to listen to. I've read that some people think there's not enough mids, but that's only an illusion created by that 2 khz peak, it has very good mids. 
Overall, very solid headphones for the price, other competing headphone such as the Beyerdynamic DT 880 and Sennheiser HD 600 will have a tough time beating it.

Not quite a review but thought I'd quote my recent observations.
 
Quote:

rob80b said:

  Well the K712s showed up, just doing some preliminary comparison with my K701s with the bass port mod. Won’t see what they’re really up to as I’m currently in my shop with an Imac running uncompressed iTunes into a 25-year-old Technics receiver.
Except for the color, black vs white, physically they look more or less the same, different leather head band and pads of coarse.
So what’s up, well I felt my HD700s took a step toward the AKGs (a good thing) and so far these 712s have taken on somewhat of a Sennheiser flavor, being warmer, less airy, less tinny (nasal) than the K701s.
The higher shriller notes that Feist reaches on  “The Reminder” were almost painful on the 701s but passed almost unnoticed on the 712s coming across smooth and very well controlled, nice. But with less air the 712s lose some of the almost holographic sounds from the track “The Water”, but overall the 712s come out the winner on this album.
Using the opening bass notes from Massive Attack’s “Angel” (appears to be the litmus test for bass) showed that the bass port mod on the K701s may have added some reinforcement in the upper bass but the K712s win hands downs with regards to fullness and extension, no contest.
Went on to listening to Kraftwerks “The Mix” and never returned to the 701’s, IMHO the K712s for all intents and purposes, disregarding appearances, are a completely different phone…….smoother, warmer, bassier...  obvious as black & white!

 
 
Should be interesting this evening when comparing them to my current favorites, the HD700s on the Bryston gear
Anyway, that's all for now, gotta get some work done.

 

Click to expand...

 

rob80b said:

  Did not get a chance to do some heavy listening comparing the HD700s but immediate observations were quite enlightening.

"Way back when".. on these forums AKG and Sennheiser were more or less diametrically opposed, the K501s and HD580/600s were two flavors of the day, Grado being a third..... the advent of the K701s and HD650s made this opposition even more so.
Not to go into the attributes of each as there’s more than a decade of that on the forums, but here I am today with the Sennheiser HD700s and AKG K712s and damned if these two offerings do not share more similarities than differences, but in a nut shell the AKG now has bass-deep bass and has become much warmer while the 700s have shed the Senn veil and are crisper and clearer.
Appears that both manufactures in their strides to appease the masses have come head to head with similar offerings, at least when it comes to overall sound.
Without critical listening both phones could by many sound the same, but Sennheiser have put a lot of R&D into the HD700s, especially with regards to the head cup/baffle design and the driver integration and IMHO the results are rewarding with regards to staging and image placement, this of course coming from a speaker guy. 

 
AKG pioneered angled placement with the K701s pads (not to mention the K1000s, another kettle of fish), but never could really hear the difference and the cup/baffle design has been used forever with minor modifications and then there are now the new memory foam pads.
The 700s for me also have slightly better attack and decay, snares having a wonderful snap and bass notes are a little tighter and central images are less recessed. But the K712s as I noted earlier are no slouch either, running off the Bryston BHA-1 they are a lot less warm sounding than when I first heard them paired with the 25-30 year old receiver mentioned above, bass was also better controlled as was focus and detail but not quite the linearity of the HD700s.
Without direct comparisons and depending on associated equipment IMHO it would be a coin toss as to which is the better phone.
There are differences but they’re close so I’m sort of torn if I’ll keep both, the biggest deterrent for the K712s is the 3 pin XLR as I much prefer the added 6dB gain using balanced as single ended, depending on source, the volume control can get maxed out on the Bryston BHA-1.
The K712s need major surgery for the conversion, unlike my K701s, K501s and DF240s, although I’ve spent a special request to AKG service to if one can get the left cover “without” the mini xlr socket installed and either install a 4 pin mini XLR or even better…hard wired.

Click to expand...

rob80b said:

  Bit more observations while in the thick of things.
 
How much bass do they guys have, well I did mention previously that I’m a speaker guy, right, (not solely though

) so I do compare my phones output periodically to them. Doing just that while listening to Underworld’s dubnobasswithmyheadman the K712s had more apparent bass than my Dynaudio Special 25s  which are augmented with a 15” Velodyne, and it’s dialed in rather flat using Velodyne's SMS-1.
I’d really have to say that the K712s may have too much of a good thing, the Senns HD700s are much flatter and match the speakers/sub output to a T, but without taking an actual reading I would venture to say the AKGs may have a bit of a mid bass bloat.
The HD700s also match my Dynaudio 25s tonally, again the 712s coming across warmer and less defined, the HD700s having better image focus and staging, which I attribute to the Sennheiser’s attention given to designing and integrating the new ear cups, baffle and driver.
Still the K712s are an enjoyable listen and a far cry from my original K501s and K701s and if I hold onto them, probably my go to for movies.

Click to expand...

 
This AKG may win over stuck in the mud Senn hd600/650 stalwarts but alienate previous AKG K7xx lovers, my previous K701s are up for sale.

Overall great headphone. Love lightness+comfort. Very clear sound with great highs, lows and slightly less pronounced mids. Sweet open sound stage. 

Final verdict from me (intro):
 
Originally I had listened to the K712s on a Yulong U100 and they were the most expensive headphones I'd ever used. I was dissatisfied but I didn't feel it was fair. I don't want to be the guy running in frantically, waving his arms, talking complete nonsense. 
 
I have spent plenty of time with these headphones now. I have A/B'd them with a the Avid Omni HD, Yulong U100, Yulong DA8 (through the headphone out and via the Denon PMA-750) as well as straight out of my Galaxy S Note II. I've pitted them against the Sennheiser HD280, Sennheiser HD25-II, and the Hifiman HE-6.
 
Look and Feel:
 
I think these headphones look great. They would be comfortable but my head is too small for them, they droop down the sides of my head. The pads are easy to replace and the cables are easy to swap.
 
No physical issues IMO.
 
Sound:
 
 
I spent an hour writing garbage and then re-listened. The bottom line is I don't like the K712s' boosted bass, I also think the 2k peak (creating a sort of aggressive immediacy is a choice that needs to be considered). Properly amped I liked the K712s but they still sound like headphones against the HE-6's. They sound notably lower quality when it comes to better recordings, but they're decent headphones (even if they feel like they're struggling to reproduce music sometimes instead of just being a window). They aren't sibilant in the treble at all, despite what I previously felt.
 
I give them a 7 because I don't love them but they're not bad. 

The AKG 712 Pro engineers decided to  create a  newly designed headphone rebut to all the critics of the AKG sound which they say tends towards  treble extension at the expense of the rest of the sound.
The problem is, the engineers forgot to put the treble back into the new design after they warmed up the overall tone with more low mids and bass extension..
The AKG 712 Pro box says......'"Now with 3db more bass", and after listening to these for a few days, ive concluded that perhaps 2 db would have been the answer, as these headphone are just too soft/dull/relaxed sounding.
Im not certain if the treble and mids are just too dialed back by design,  or if they are just being covered up by that "3 db" of "added bass".
Whichever, or whatever, these phones have no zing or sparkle in the treble and the mids need an air pump.

published on January 19, 2014

 
- download a printable 3-page PDF version of this review (link goes to a location on my Dropbox)
 

(click for larger photo)
 
Intro
 
This is basically a short mini-review of the AKG K712 from while I owned it for a few weeks in December 2013 through January 2014.
 
Equipment Setup
 
- Source components: NAD T533 (DVD player)
- Headphone amplifiers: HeadAmp Gilmore Lite w/ DPS, Garage1217 Project Ember
- Comparison headphones: Audio-Technica ATH-AD2000 & ATH-AD2000X, Sennheiser HD598, Shure SRH1540
 
Evaluation Music
 
- Boards of Canada - Tomorrow's Harvest
- Carlos Kleiber & VPO - Beethoven 5 & 7
- Erin Boheme - What Love Is
- Half Moon Run - Dark Eyes
- In Flames - The Jester Race
- Julia Fischer - Bach Concertos, Paganini: 24 Caprices
- Katy Perry - Prism
- Massive Attack - Mezzanine
- OSI - Fire Make Thunder
- Phantogram - Eyelid Movies
- Sarah Jarosz - Build Me Up From Bones
- The Civil Wars - The Civil Wars
- The Devin Townsend Project - Deconstruction
- Yggdrasil - Prose Edda
 
Amplification
 
Most headphones tend to sound good enough on just about any amp, and although I wasn't able to test the K712 on any "budget"-level amps, I'd imagine that to be case with them as well. I'd say that anyone planning on buying the K712 should definitely factor in a dedicated amp for them, even if it's just a cheap one, as it's one of those headphones that really comes alive the better it's amped and requires high current & voltage in order to start sounding especially good. Case in point from my own system: the Gilmore Lite amped the K712 moderately well and didn’t reveal any audible sonic issues at low to moderate volumes, but at anything close to high volumes it started disproportionately subtracting the bass & mid-bass, leaving mostly only the mid-range and treble intact which resulted in a distinctly unbalanced sound. The Project Ember with the right tube (a 12AX7VKA), on the other hand, was able to push the K712 to high volume without any sonic subtractions and proportionately preserved bass quantity.
 
And the K712 sounded downright amazing on the Project Ember w/ 12AX7VKA, much better than it did on the Gilmore Lite. In fact, it was so good that I could've easily considered the K712 & Project Ember combo to be a "final" end-game setup, and in a lot of ways I vastly preferred its sound over other dynamic and planar magnetic headphones that I've previously heard, including the Sennheiser HD800 and Audeze LCD-2/LCD-3. Of course there are some aspects that I consider the Sennheiser and Audeze flagships to do better in, but overall the K712 was surprisingly awesome-sounding and held its own against the vastly more expensive flagships. The Project Ember (using a proper high-gain tube) is definitely an amp pairing that I’d recommend too.
 
Comparison to: Sennheiser HD598
 
Compared to the HD598, the K712's soundstaging felt more concentrated and continuous, but also more closed-in. The HD598 had a great "out & away" type of soundstage to really provide an illusion that music was occurring a good virtual distance away, but the K712 took sort of an opposite approach and brought everything forward more, closing the distance gap so to speak, but still sounding very open, separated, spread-out, & wide. In a very loose sense, I'd say that the HD598's soundstaging was quite similar to the HD800's in sounding "out & away", which I thought was overdone on the HD800 and made it sound unnaturally large & diffuse. The smaller-scale soundstaging of the K712 came across as more realistic to me and not as over-the-top as the HD800.
 
The K712 also had a better tonal balance to me, fleshing out the mid-range a bit more (specifically the vocal range) though it was somewhat at the expense of treble quantity. The HD598 had more treble quantity in comparison. Neither headphone had much bass, though the K712 did seem to have slightly more quantity throughout the 30-200Hz range. And despite having more bass quantity, the K712 was very "controlled-sounding" and was never boomy, flabby, or too thick. Its bass was always clear, distinct, & taut and was more rhythmic than deep. But probably the biggest difference between the K712 and HD598 was the way in which the K712 presented a cohesive sonic image that included left, center, & right (the HD598 sounded as if it had a hole in the center) and presented the music as if it were right in front of you (not away from you, as the HD598 did), with more physical tactility as well. Sort of unexplainable but the K712 simply made vocals, female in particular, sound physically present and very much in-front-of-you while the HD598 lacked that presence factor.
 
I'd describe the K712 as a moderately-detailed headphone with a good level of clarity (not as good as the HD800 in that aspect, which I consider to be one of the clearest-sounding dynamic headphones), a wide & open soundstage (smaller than the HD800's but probably larger than most other headphones), and some marginal lack of lower mid-range, mid-bass, & low bass. That is, it wasn't what I consider heavy- or thick-sounding, and I wouldn't call it very appropriate for music that relies on bass and/or overdriven guitars like metal or hard/heavy/prog rock, or low-pitched male vocals. The K712 seemed to be at its best with classical and generally acoustic music, and less good with music that involved a lot of electric or synthesized instruments, though I could definitely see others liking it for rock, metal, & electronica too, depending on sonic preferences.
 
Indirect Comparisons: K7xx, HD800
 
I can't say with certainty how the K712 compares to AKG's previous K7xx headphones, but as a previous owner of the original K701, original K702, and K702 65th Anniversary, it did seem to have the most balanced sound that I've heard out of AKG's K7xx line with the most amount of bass as well. I always considered the K701, K702, and K702 65th Anniversary to lack a convincing physical sound, and the K712 seemed to retain a trace of that characteristic as well, but it did seem to have the most physical presence, particularly when playing female vocals. But most importantly, and the reason why I went with the K712 instead of the Q701, was because of the headband. I've always disliked AKG's bumped headbands on their K7xx headphones and was glad to finally see the bumps removed on the K712.
 
I was never very impressed by the HD800 despite the fair shake I tried to give it on various amps that included the HeadAmp GS-X (MK1), Luxman P-1u, SPL Auditor, Schiit Lyr, Avenson Audio Headphone Amp, and a Rockhopper-built M3. Regardless of the amp I used, the HD800 always lacked mid-range to me and had too much treble quantity as well, and the only music that I could remotely tolerate it for was ambient electronica, bluegrass/folk, and generally acoustic, female vocal-based music. Although many others have said that the HD800 works well with classical music, I personally could never get past its torturous treatment of violins specifically, as it just made them too fake- & wispy-sounding, and I'm saying that as a violinist.
 
The K712, on the other hand, made violins sound much more realistic to me with a lot less of the glossy & wispy signature of the HD800, and its smaller-scale soundstaging came across as more convincing as well, with large studio-type acoustics instead of the extra-large auditorium acoustics of the HD800. It was also way more musically dynamic to me and conveyed the subtle transitions between piano (p) and forte (f) properly, including sforzandos, which the HD800 never did on any amp that I tried.
 
To the HD800's credit, I do view it as the vastly clearer-sounding headphone with a nicely refined treble and distinct & deep bass, but for me it was just never able to convey proper tonal depth & musical dynamism. The K712's higher mid-range quantity and greater dynamic range provided that for me, and because of that I'd call the K712 more musically versatile than the HD800, and in a few important ways, distinctly superior. Yes, I am indeed saying that a $500 headphone can subjectively sound better than a $1500 headphone in certain ways!
 
Summary
 
The K712 wasn't perfect to me—no headphone ever is—but it sure was a surprise, even after all the headphones I've gotten since 2006, when I got the original K701. I would've liked it more if it had a bit more upper treble quantity, along with more quantity in the lower mid-range, mid-bass, & low bass (particularly in the 30-50Hz range), but I still really enjoyed it overall and got more musical satisfaction out of it than I ever did with the HD800 and LCD-2/LCD-3.
 
Although I do think AKG has been over-milking the K7xx line for far too long, the K712 was easily the best-sounding K7xx to me and I think a lot of other people would be surprised by it as well. Certainly not for everyone but it's probably worth a try, especially for those who haven't yet heard an AKG K7xx.

This will be a somewhat compact review and comparison to the HiFiMAN HE-400, they're roughly the same price around here. Starting with some pictures.
 

 

 

 

 

 
Accessories
While I don't consider accessories that important I guess I should mention them. K712 comes with a straight and a coiled cable, 6,3mm adapter, and a carrying pouch.
HE-400 comes with the stock cable, 6,3mm adapter and a carrying pouch.
 
Comfort
The comfort of the K712 is good. The headphones weight is 235g which is very light considering their size. The self adjusting headband works well and the earpads feel nice on the skin. I don't think the fit is too loose despite having a small head. During the first hours of use there is some pressure building up on the head from the headband, but that disappears after a while when it adapts to your skull.
Compared to the HE-400 they're obviously much lighter, HE-400 weights 440 grams which is almost double up. The headband on the HE-400 is very well designed though, and I don't have any comfort problems with them. So apart from bulkiness HE-400 is just as comfortable. Both stock earpads are fine too although I know some people don't like the HE-400 pleather pads, if that's the case then you probably like the K712 pads more which is soft memory foam.
 
Build quality
While the build quality in general is good, the K712 does feel a bit plastic considering the price. Especially the bows that connect the cups feel very fragile. The headband and cups themselves are good though, and the mini XLR connector for the cable works well. The stock cables that come with it are good.
In comparison the HE-400 is built like a tank, but the coaxial RF connectors are bad and the stock cable is extremely bulky.
 
Sound
 
Sources: CA Dacmagic Plus DAC, Lake People G109-S headphone amp
Files: My own FLAC library and some Spotify Premium streaming
 
First I'll focus on the K712 and after that a comparison.
 
As a whole, the sound provided by the K712 is impressive. I never really find it to offend or do something bad. It does expose bad recordings though, no way around that.
The bass is very well controlled. With music where slam in the bass is not intended you get none, zero. However, try turning up some Infected Mushroom or Ludacris and you will be treated with some serious rumbling or impact, depending on the song (for an open headphone). The presentation is very convincing on "Ludacris - How Low", I can dig out all the low frequency details in the background and the rapping is in perfect balance with the beat. With "Koan's - Selena's Song" it's very easy close your eyes and be carried away by the firm bassline backed up by the deeper rumbling and the ambient sounds, I imagine this is very close to how the artist wanted it to be.
Varieties of rock is probably their strongest point for me though. The balanced yet slightly warm presentation together with the rather wide soundstage is a real winner. In "Dayshell - Avatar" I can separate instruments very well and get a sense of how the song was recorded, but it doesn't get too analytical, it's very easy to still simply "enjoy the ride". 
With metal you do run into this problem where a large portion of the music is rather badly recorded and mastered, and the K712 does expose it quite effectively. When it's good it's really good though, as an example my In Flames Clayman and Reroute To Remain rips sound brilliant. I do occasionally wish the drums had a bit more "kick" in them though, something the HE-400 has spoiled me in.
The K712 does vocals so well that I can really appreciate music like Celine Dion's despite I don't normally have any interest in it. Material like the old Nightwish with Tarja Turunen sounds fantastic.
Regarding the treble there isn't much to point out. It's smooth, it's good. No fatigue, no emphasized sibilance, amount is just right.
 
Not much to add. But yeah the sound is great. To counter all this praise, I do find the sound gets a bit "too secure" sometimes. It's like, you listen, and you know it sounds great, yet it's a bit boring at the same time. But that's probably inevitable with something that performs so even. I think a 4/5 star rating is fair, could maybe be 4½, but it loses a bit on the build quality, and on price. I haven't actually compared it to the older models, but if there really are changes made that qualify a ~250€ rise in price I think AKG should make that more clear. On the other hand, they clearly compete with the HE-400 that are priced similarly, so...
 
Comparison to the HE-400
When you compare these two headphones, the weird V-shaped frequency response of the HE-400 is very noticeable. The HE-400 has a great bass presentation in my opinion, and the texture on drums is brilliant. On the same time, this combined with the rather small soundstage gives you this very intimate and warm sound that can be a bit too much. Vocals also sound a bit strange on the HE-400 when compared to the K712, this is probably related to the dip between 5-6 KHz. HE-400 also has slightly more emphasis on treble, especially sparkling sounds like cymbals, sometimes this works out great, sometimes less so. HE-400 definitely has a higher fun factor, so this does boil down to taste. I would still say though that the rock solid performance of the K712 makes it better overall. There is slightly more sibilance on the HE-400.
 
AKG K712: Is more neutral, has a larger soundstage, is an more even performer.
HE-400: More bass impact, slightly more treble, does some material very well while falling short on other, more forgiving with bad recordings