AKG K612 PRO Reference Studio Headphones


Pros: Neutral sound signature, Auto-adjusting headband, Large Soundstage, Minimal leakage, Good value
Cons: Very large, Loose fitting, Proprietary earpads, Non-detachable cable
These headphones were my daily drivers for a little over two years. They were also my first pair of open headphones. I retired them when the earpads became yucky, flat, and uncomfortable.


100+ Head-Fier
Pros: HUGE Soundstage, neutrality, crispness, comfort, design (subjectively)
Cons: A bit much clamping force when out of box, needs good amount of power, a bit much brightness if you are really sensitive on high frequencies

First of all, I want to introduce my gear while writing this review.

I'm using my AKG K612 PRO headphone with my Fiio X3 2nd Gen dedicated DAP. Currently I don't own any headphone amp but planning to buy an A5. I'm gonna update this review when I do. 

I use my lossless archive while writing this review. All files are 16/44, 24/96 and 24/192. All of them are checked with spectrometer software. 


Out of box, this headphone is great when it comes to packaging as well. It's simple but more than enough. It comes with an 3,5 to 6,5 adapter, warranty card, some serious boxing. Unfortunately, there is not a carrying box, this should be my only problem with packaging. 

After getting the headphone, it feels expensive because of the alloy speakers on two sides. Cable isn't detachable, that might be a problem for some but for me, no problem since you can't use that headphone outdoor because it's open-back. It will leak the sound like your stereo speakers lol


When you first wear the headphone on your head, after 5 minutes, force on your ears might be a problem especially if you have glasses. In this case, you have to be careful while wearing the headphone. It will fit your head if you pull down and stick the headband to your head consistently. After that, your ears won't even touch the pads, which feels awesome. In fact, after first days, comfort gets even better. 9,5/10 for comfort, -0,5 for first days.


For the sound section, I will give one certain example per genre which will make my opinions more revealing. 

>Progressive Metal

-Dream Theater - Dance of Eternity [16/44 FLAC]:  
Wide, huge sounstage shines here. This song sounds like there are instruments in your room that located on different places. So, instrument seperation is above excellent. You can hear even time signature changes clearly. Last and important, headphone doesn't give any color to the track. Neutral side.
10/10 for progressive segment.

>Thrash Metal

-Megadeth - Tornado of Souls [24/192 FLAC]: 
Well, it sounds phenomenal for the price but marginally, it sound a little too much bright. If you are a loud listener like me, it might be a little ear piercing on some certain parts. But headphone is really accurate when it comes to speed. Bass lacks a little bit on some certain parts again. Neutral side.
9/10 for thrash segment. -0,5 for some piercing effect on high volume and -0,5 for a little bit lacking bass on certain parts.

>Melodic Death Metal

-Children of Bodom - Downfall [24/192 FLAC]: 
Vocals sounded joyful, not ear piercing. Detailing is good and there is enough ''dark'' sounding for the genre while guitars sounded bright like the vocal. Keyboard is detailed, you can hear instruments clearly on vocal parts. But vocals are not significant enough, felt a little bit ''behind''. Bass is better than thrash here. Neutral side.
9/10 for melodic death segment. -0,5 for disappearing vocals and -0,5 for a little bit lacking bass on certain parts, again.

>Doom Metal 

-Draconian - Bloodflower [24/96 FLAC]: 
Yeah, feels dark. I was afraid because of the thrash segment. After that I realized that was about signature brightness of Megadeth. It's not that bright here. Well, it's not a direct hit for the genre though. Beyers should be better for that. Female vocals are whole another story, sounds excellent.
9/10 for doom segment. -1 for more than enough brightness. Doom should be really ''doom'' that's why I'm unforgiving here with giving -1 instead of -0,5.

Note that those are not the only artists that I've listened. Those are only my favourite ones for the genres I specified.


Well, I don't have enough time to do critical listening for my all tastes but those are main points. I have this headphone for only a few days atm. I have to say that this headphone is a GOD for the price. So cheap on amazon.de, don't miss the price. You should consider if you have enough power though. My X3ii drives it brilliantly but it still lacks ''something''. Phenomenal headphone for a metal music listener but you will really enjoy if you listen to hard rock pieces too because of significant similarities between genres. I don't have any experience with jazz or classical tracks but people say good things. 

See you all ! 




100+ Head-Fier
Pros: Good value, balanced, accurate. Audiophile grade sound for a bargain.
Cons: Larger heads might have fit and/or comfort issues. Lacks bass impact compared to higher end competitors.
I got my pair on sale for $150 USD. I have had a few lower end AKG headphones and have never been disappointed with the value and sound signature they offered. It's been a long time coming but I was finally able to get a higher end AKG in the K612 Pro. In this review I will be comparing it head to head with the venerable Sennheiser HD 600. Here in Canada the HD 600 is about double the price but offers a good benchmark to compare with.
My source in testing is the 1/4inch headphone output of my TEAC UD-H01 DAC/Amp connected via USB to my Windows 8.1 desktop. I use the foobar2000 player with EQ off playing various files from FLAC to m4a to mp3 (VBR/CBR 320). In terms of sound signature preferences I like more mid centric headphones with tight, accurate bass (quality over quantity). I frequently have long listening sessions and I do get irritated by sibilance on certain bright headphones like the DT 990. I enjoy all genres of music spanning across many different era's. Enough about me, I've had this headphone for a few weeks now and after 50+ hours of burn in and constant use I am happy to share my experience.
Design/Build (7/10)
Packaging is average nothing too fancy. Upon opening the Velcro lid on the box the headphone is sitting in a plastic bag with warranty card in the box. The 3 meter cable comes with the 1/4 inch screw on adapter attached. The cable is not replaceable but is of reasonable thickness and should hold up to abuse. The first thing I was drawn to was the real leather headband with quality stitching and AKG engraving. A really nice touch at this price point. The headband is also flat on the inside vs the bumpy one on the Q701. To keep cost down this unit is made in China though.
Ear cups are plastic with black and silver metal grills. The ear cups do tilt up and down but do not rotate flat. The replaceable ear pads are a thick and plush padding with velour covering. Simply twist to unlock and they pull right off. Over the inside of the drivers is a thin padding with a 1/2 inch circular cutout in the center to expose the driver to the ear. The padding is then covered with a soft breathable nylon material which is attached to the replaceable ear pad. The nylon feels great on the skin if the ear should ever touch the inside. The nylon covering is a nice touch. Most headphones, including the more expensive HD 600, leave the inner foam exposed.
Right and left are large and clearly marked. It's a small detail but I like to be able to tell which side is which in the dark. The top right side of the leather headband has a small engraved graphic, not sure if it was AKG's intention, but it serves the purpose well. The outer headband portion is made of two steel bars with plastic coating. The auto adjusting headband design used on the K612 is a unique feature to AKG taken from the K701/Q701. The inner leather headband is suspended with elastic nylon strings and moves along the tracks of the outer steel portion held together with plastic guides. It seems to work well, it slides up and down quietly and effortlessly.
Style wise I really like the simple black and silver color scheme. It looks nearly identical to the K702/Q701 (black). On the head they do appear huge though because of the dual headband design. Overall the materials, look and feel reflects the price. You know you're holding a professional grade piece of equipment. The main difference between this and the Q701/K702 in terms of design is the cable. Honestly though, as an owner of headphones with removable cables, it's an overrated feature. Connectors are bulky and wear out. If you take care the cable will last a lifetime. I have yet to actually "need" to replace the cable on any headphone of this quality. I can't personally comment on long term durability of the design yet, however, it's been in use by AKG for decades now.
Comfort (7/10)
After several weeks clamping force is light to moderate. But this can be formed by bending the outer metal headband to your liking. There is plenty of flex in the headband. At only 238 grams comfort on the ears was never a problem. I did not have any issues with sweat either. However, I did have a bit of a hotspot on the top of my head after 2 or more hours. As nice as the leather headband is, it's not padded at all. The nylon elastic part forming the auto adjust feature pulls the headband down even more. The larger your head, the farther the elastics will be stretched, and the harder they will push down. I have an average size head and I felt it. So people with large noggins might have a more serious issue.
I tried to remedy this by forming the leather headband in an arc to conform to the top of my head better. Then I stretched the elastics out by hand being careful not to stretch them to breaking point. This helped but I still find myself pushing it up periodically to relieve pressure. I anticipate this should be less of an issue as the elastics stretch over time.
Another note for those with large noggins. I only have one fingers width of clearance left on the top of my head for adjustment. That really isn't very big at all since I have an average size head. On my HD 600 I am only half way up the available adjustment. Comfort wise I give a clear edge to the HD 600 because of the larger oval ear cups and superior headband support, despite being 20 grams heavier. In terms of durability I would say they are about the same. Style wise the HD 600 probably looks fancier with the granite counter top like finish and larger see through metal grills.
Sound (8/10)
Boy do the K612's like power! At only 120Ohms they require more power than the 300Ohm HD 600 to achieve the same volume. On my TEAC UD-H01 it needs about 15-20% more power. That being said I could drive it from moderate to ear bleeding levels from 11 to 12'oclock on the volume knob. My TEAC is not considered very powerful (40mw RMS at 32Ohm) so I would say anyone with a modern desktop or even portable amp should be fine. I did not test the K612 without the amp, but from what I have read mobiles and onboard audio devices usually don't cut it. Unless they have built in amplifiers. They are totally open and offer no isolation. Sound leakage is significant, on par with the HD 600. The sound did not seem to change at all before or after 50+ hours of burn in.
If I was to use a single word to describe the sound signature of the K612 it would be "accurate". It really is very accurate across the entire spectrum. It's very neutral, even more so than the HD 600. I consider the HD 600 a bit more forward in the mids and slightly more rolled off on the highs. More laid back I guess you could say. So I was worried that the highs could get irritating, as they did on my testing of the DT 990. So I threw some Kenny G at them on high volume. After more than an hour I experienced no irritation at all. No sibilance whatsoever.
A track I love to test imaging and soundstage with is Letter by Yosi Horikawa. The K612 was impressive, on par with the HD600 for sure. Truly great at this price point. The only real weak point for some will be in bass response. Although very tight and accurate, it lacks a bit of oomph compared to the HD 600. You just don't get as much impact. This really doesn't take away from anything else though, and you still hear the low tones right down to 12hz. It's just not going to please those bass heads among us. Heck, even the HD 600 is considered light on bass by many.
The HD 600 still has the incredible ability to resolve details and present them in a more natural way. It's hard to explain but all the little nuances in vocals and stringed instruments are brought out a bit more. You hear them on the K612 too though, just not quite as clearly. It's something you wouldn't miss that you could only tell by a direct side by side comparison. This slight improvement will be enough to justify the upgrade for some. All things considered the K612 is still among the best sounding headphones in its class.
Verdict (8/10)
I consider the K612 an improvement over the Q701 at a lower price point. Not only is the headband more comfortable, the highs are less irritating, and the bass is fuller. AKG has never had a better sounding headphone at a lower price point. Audiophiles will be pleased with the reproduction on this headphone. The only real competitor in its price range is the Audio Technica AD900X. But I think more people will prefer the sound signature of the K612, it works better across more genres. A lot of people have fit/comfort issues with the headband on the Audio Technica's too.
Although I do think the HD 600 is more comfortable, natural, and revealing with improved bass. I am keeping the K612. It's rare to find a headphone in this price range that has such a versatile sound signature. I would not hesitate to buy it again. It's a great bargain under $200.
OK.  I bought the K612 in part because of this recommendation and discussion.  Thank you for the time you put into your review.  I'll let you know if I concur.  :wink:
Really, the reviews on these headphones with proper amplification were universally flattering, and I don't think there's anything else in the $150 price range that competes, especially as I specifically wanted accurate, open headphones.
Thanks.  Enjoying my K612 Pro's...
Great to hear you like them.

Mr Vicarious

New Head-Fier
Pros: Well-balanced, natural sound, analytical yet musical, bass deep enough to satisfy and tight. Comfortable.
Cons: Slightly dry sound, needs a strong headphone amplifier.
I came to this headphone after 10 months with a Philips X1. Although the X1 is a good headphone, towards the end of my time with it, I become increasingly dissatisfied with its sound signature.
I stopped listening to music regularly and for a long time I didn't realize that the X1 was to blame! Although every time I used it I would be impressed by its abilities, the sound was ultimately just too bass orientated for me; and also the treble tended towards a glassy tone in some music. So after some research, in steps the K612 Pro. Now this headphone is quite different. Less bass but better proportioned, the sound is more natural with a pleasing delicacy to the sound, particularly the treble, that although a little dry, is open, articulate, never harsh or sibilant and only very slightly rolled off at the top. The mid-band is detailed, expressive and free of any nasty colourations, however the upper mid-band does have a tendency towards the already mentioned dryness of tone, but that's really a minor quibble.
The headphone images very well and keeps various musical strands from merging into each other even in busy,complex mixes. Sound-staging is good but not a particularly strong point of this headphone, it keeps everything at a medium distance; not very deep or wide. However that suits me fine as I find headphones that are very adept at sound-staging somewhat artificial in their representation of the music, not really true to life at all.
The bass on these headphones is just right for me; tight, fairly punchy and ample amounts when called for - okay, perhaps a smidgen more and it would be perfect, but considering this is a £100 ($160) audiophile (or audio enthusiasts, if you prefer) headphone, I'm generally happy with it. Anyway, bass quality is more important to me than bass quantity and the K612 Pro delivers on that front.
In respect of amplification; you'll need a fairly powerful, preferably dedicated, headphone amp. With low power portable devices and laptop headphone outputs you will not get sufficient sound quality or volume. So if you don't have a suitable amp, you should factor in the cost of one if you decide to purchase the K612 Pro.
In respect of comfort; there are no issues at all, not for me anyway. The headphone is very light and the clamping force of the earpieces is fairly gentle, the leather headband sits gently on the head too, and the cushions which are soft and pliant don't cause (me) any irritation.
So summing up, I heartily recommend this headphone. It performs well in all areas and shines in some, such as neutrality and resolution. I doubt you'll find a better headphone in its price range.
I recently return my Fidelio x1 because weren't enough prominent the vocals, I wanted a sound more neutral, natural, detail and acurate
These headphones are better than the Fidelio X1 on those points?
I was looking for the HD600 but it's to expensive


New Head-Fier
Pros: Bass texture, incredibly smooth across all frequencies
Cons: Treble can be harsh at first; takes time to mellow out
First impressions
When I first tried these headphones out of the box, I was a little disappointed at how the higher frequencies seemed to be more forward than the mids and bass. It wouldn't have been a huge deal, except that the treble was also completely unforgiving on sibilant tracks, which really put me off. The saving grace at the time was that the bass, while not having a huge presence, had a buttery smooth texture that made my mouth water. The clarity and precision of the low end also extended well into the upper midrange, making the k612's perfect for acoustic, classical, and jazz. The overall impression I was left with was somewhat reminiscent of  a more neutral k240 signature with vastly improved separation and detail. 
After three months
Wow. These cans have absolutely blown me away. The treble has settled down completely and now sits perfectly with the bass and mids. The entire spectrum is wonderfully blended without sounding messy or lost, and the imaging seems to have improved as well; the sense of space is more natural and the separation remains consistent without isolating instruments completely from one another. 
Took about a week to break the headband and pads in, though for me nothing about the way these headphones sat was noticeably irritating. Structurally sound, with both metal and plastic parts. The cable is not detachable, which could be a deal-breaker for chronic cable destroyers. 


Headphoneus Supremus
Pros: Detailed, transparent, smooth and linear sound, revealing, very natural sound, precise imaging, good sounstage, non-fatiguing, and comfortable.
Cons: A bit finicky to amp, needs a good amount of power, and pads take a few weeks to break in.
This is a brief review of the K612 Pro, to my ears it's my favorite and the best headphone under $200. I'm using a Hifiman EF2A as an amp and an ASUS Xonar DX as a DAC.
Build Quality: The K612 is a well-made headphone and feels solid in my hands. Only gripe is the cable isn't detachable but it's not really something I'm worried about as the cable quality is good and I take good care of my headphones.
Comfort: This headphone was comfortable from the beginning to me but the stiff pads did bother me after a bit. A few weeks of use and the pads soften up and become much more comfortable. I have no complaints about the leather headband, there are no bumps and is plenty big enough to distribute weight well.
Amplification: This headphone must be amped and have good synergy for it to reach it's full potential. If it's underamped it may clip a bit in the sound and sounds lifeless, dull, and flat sounding. People buying this headphone need to go in knowing it needs to be amped. It seems to respond the best to warmer sounding systems.
Soundstage: I personally find the soundstage on the large side on this headphone, while it's not huge, it's not really what I call medium sized either, just simply large. The soundstage has good width and the depth and height aren't bad either.
Imaging: The imaging of this headphone is very accurate and precise, this headphone excels imaging. You have a very good idea where the instruments are located and there is good separation.
Bass: Bass when the headphone has good synergy is very textured and detailed, extends unusually deep for an open headphone and has a large and powerful presence with plenty of impact.
Midrange: The midrange on this headphone is what some may consider forward, it's delicate, precise, has good dynamics, and just sounds very natural and organic. It's just beautiful sounding.
Treble: This headphone is rather sensitive in terms of it's treble response from system to system. It is detailed and revealing, so flaws of the recording aren't hidden. It's quite accurate but can have sibilance issues with some recordings and systems and some systems the 2-4khz region may be a bit too present which can lead the headphone to sound a bit hard and dry on some systems. It has a good and accurate treble, it is slightly rolled off at the very upper registers and doesn't have a lot of air like some other open-backs but it's not lacking air by any means, it's just not an airy headphone.
Conclusion: The AKG K612 Pro is an excellent value for what you pay and is an excellent headphone for people seeking a neutral and linear response. It's among one of the most neutral I have heard and is a real treat if you are willing to work with it to bring out it's potential. The headphone is rather sensitive and is very transparent for it's price. It's a headphone that needs a good system behind it that synergies well with it.
i have a soundblaster z , its amps up to 600ohm is that enough ? , manily used for gaming and some music


500+ Head-Fier
Pros: excellent bass extention, exceptional neutral midrange
Cons: 2khz spike, non-detachable cable, not cumfortable with glasses on (in early weeks)
Updated review:  5/28/15
Build Quality: Great build quality. Overall solid professional looking open back headphone. Cable is strong and thick, non detachable cable isn’t/wasn't a big deal breaker for me, still compared to 7xx series, 612 uses lesser quality materials (plastic, leather headband) and can gradually loose the elasticity of the auto adjusting headband mechanism over time. Btw I have first batch of Austrian made 612pros, so I can't speak much for the build quality of Chinese built variants.
Comfort: I’d say pretty comfortable after few weeks. 612pro doesn't have much clamping force. Velour pads can be little hard at first, but after few weeks it will become soft, so have little patience in first few weeks.
Sound Quality:
612pro is one of the most neutral headphones in this price range imo. With right synergy 612pro can be a great all-rounder. Bass presentation is one of the star features in this impressive can, it can render deepest bass notes with exceptional texture, very rare for an open back headphone. Despite the ability to render the lowest notes still bass extension is very linear, so some might find bass is lacking little body. Impressive non-resessed neutral midrange is the other star feature of the 612pro. Neutrality of the midrange one of the main reasons why I prefer this to 7xx series, and many other cans.  612pro has a very good non-fatiguing treble presentation, I never found 612pro's treble bright, metallic or sibilant,  but with some systems I found the treble can be dry, edgy due to the spike in frequency response at around 2khz which is very common with AKGs, so specially some female vocals can be fatiguing, dry due to this, so I believe that's the reason people recommending warmer amps to fix the synergy with AKGs.
612pro is not a basshead can by any means, but this is one of my top recommendations for EDM and many modern bass heavy genres, because this can render deepest low notes with exceptional texture. If you are used to heavy boomy, untextured bass presentations, 612pro will surely show you what you have been missing all these years, finally you can reinvent yourself as a real basshead who admires deep textured bass presentations. 612pro is surely is a fantastic option for vocals too. Vocals sounds very natural due to excellent neutrality of the mids, instrument timbre is very lifelike, very transparent, vocals can be upfront and can be very intimate sometimes. To me, this is a true all-rounder which can perform well in almost all the genres. 
612pros soundstage is just perfect for my preference, it's not too huge or too airy, and imaging is exceptional for a medium sized soundstage, and can be a great gaming headphone too, if you are into competitive gaming. 
But be warned, this is not an easy headphone you can drive without an amp, you must use a decent amp/dac to get he most out of this, I found 612pro is harder to drive than DT150, dt770.880.990 (250ohm variants) and many others, so be prepare to spend some money if you already don't have a decent amp, it can be a worthwhile investment in long run.
So, who might find 612pro interesting ?
If you used to brighter, leaner sound signatures like in q701, k702, still you might be looking for a bit more low end response, then you might find 612 more balanced and interesting. or if you are in to V shaped cans like dt990 you might find the non-recessed midrange of 612pro more intimate, or if you are in to boomy bass presentations, you might learn to appreciate the detailed bass presentation of the 612pro, or if you are just looking for a neutral open back option, AKG's 612pro is an excellent open back all-rounder.
I wear glasses and find them very comfy


New Head-Fier
Pros: neutral but good impact in the bass, tights bass, price,great for gaming, design.
Cons: it needs a good synergy
this is my first "serious" pair of headphones So the review cant be very full, but I try to give the possible useful information. I was looking for a pair of headphones with a neutral sound but with a good bass impact and suitable for gaming, and i am very satisfied with them.  they do very well with all my music: particularly they are fantastic with black eyed peas and alicia keys ( quality of bass and voices is fantastic !) . i think they do very well with hip hop too, but maybe some song ( for example Eminem marshall mather lp2 ) would benefit from a little more bass (but really very little).. k612 has a very good imaging !! when i play FPS games , the position of enemy are very precise!
however they need a good sinergy .. i tried them on a fiio e10 and on another soundcard of my friend, and k612 was lean in the bass and lack of detail...
but with my EF2A they are special!! more punch in the bass, more details, more clean, bigger stage.
i dont know if it depends by quality or power of amp but they are special with EF2A and they sound more better with a good dac ( dac of matherboard are not suitable) .
very raccomanded !!also for the price : i paied them 135€(shipped) and in the forums they are compared with headphones much more expensive ( sennheiser hd600 for example).
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100+ Head-Fier
Pros: Roomy ear cups, smooth, linear, natural sound, non-fatiguing highs, well behaved bass, AKG mids, not hard to amplify
Cons: initial ear pad comfort, picky with DACs, hard wired cable (good quality though), not for bassheads, synergy with systems
I have owned several other AKGs, including the K240s, the K702 65th Anniversaries, the and Q701 Quincy Jones Signatures (basically the same thing as an updated K701/702). The K612s sound-wise lie somewhere between the K240s and the K7-series, while having a unique sound signature of their own. 
Build: Made in Austria, and very close to the K7-series, but not exactly. They feel high quality, but not quite as exquisite. The plastic on the ear cups is of a slightly lesser quality compared to the K7s, but is still good quality nonetheless. The headband is a stitched genuine leather band just like the K7s. The cable is 10 feet and hard wired, so not detachable via a mini XLR jack like on the K240s and K702/Q701/K712, but is good quality. It terminates to a 3.5 mm jack with an included 6.3 mm screw on adapter. 
Comfort: Keep in mind that these are not fully broken in. The K612 is right up there with the the K7s, but WITHOUT the angled ear pads and headband bumps of the K701/K702/Q701, and a harder padding than the memory foam on the K702 Annies and K712. The pads are fairly hard against the head due to the firm padding and the clamping, so will be a bit less comfortable at first. However, when they start to conform to the shape of your head, they become much more comfortable. The pads are deep enough for most people's ears, however I have a point on my left ear, and recently I found that point touches the driver covering, causing irritation. To remedy this, I took off the left pad and removed the foam ring insert. This supposedly changes the sound ever so slightly but I don't really notice. Since removing that foam insert I find the left ear pad much better. As far as I know, the K612 pads are interchangeable with the K7-series ear pads. 
Sound impressions:
Lows: The K612s lie somewhere between the K702s and the K240s, with having more bass than the K7s, but less than the K240s. Both the K240s and K702s have a sub bass roll off, with the K702s having a lean bass overall, and the K240s with a strong upper bass and mid bass. The K612 have a thickish sound to them, but with the bass being surprisingly linear across the board and without any particular hyping of the sub bass, mid bass or upper bass. As a result I find the K612 has a very clean and accurate sound to the bass. Now bassheads might not like this, because for tracks that are mastered to require a boosted bass, the K612s will sound untextured and the bass will end up sounding artificial. However, if the track is mastered to not require a colored bassline, or is natural bass from recorded instruments, the K612 does exceptionally well. Like most other AKGs it likes recorded bass a lot, but unlike the K7s, it still does well with synthetic bass if it is mastered right. The K612s are good headphones for quicker, more transient bass like with progressive trance and liquid funk. The bass right out of the box will not sound right, and will have a dip in the mid bass, so burn in is a must to bring out the bass potential. The timbre of the bass has a sort of acoustic, instrumental or almost "wooden drum" sound to it, which gives it superb transparency for recorded music. if you listen to powerful piano playing like Alicia Keys, the K612 does an excellent portraying a sense of sound of low notes she plays. If you listen to Arabic pop or Bollywood, the K612 does a superb job representing tambourines and tables. Coming from a Sennheiser HD598 or in some cases an HD600, you will find that the K612 doesn't have that speaker-like, slightly synthetic sound to it like they have. Its bass has a very "instrumental" sound to it.
Mids: In one word: linear. They are linear across the board, without being glarey in the upper mid range like the Q701s and K702s are. Because of this, they are very easy to listen to. There is a smooth mid range without being dipped to sound tolerable, like on Beyerdynamic DT990s. I have absolutely no complaints with the K612 mids. They are pretty much perfect for me in this regard. They have that characteristic AKG house sound for musicality, so you aren't missing anything there. The mids really don't make any compromises to be easy to listen to. They aren't rolled off, they aren't dipped, and they aren't veiled like with some Sennheisers. 
Treble: These headphones have no particular spike in the treble. It's quite linear across the board, with roll off happening towards the 8-10,000 Hz range. You have to play REALLY badly mastered music for these headphones to sound sibilant. The treble is there, but it isn't forward, harsh or glarey. The K612s are't as dark as the K702 Annies, but are definitely are more forgiving than the K240s, which I find are rolled off in the lower treble but abruptly have a HUGE spike at the sibilance range that makes them piercingly painful with badly mastered music lest I EQ the treble down.
Soundstage: The K612 has improvements to the bass, but there will be inevitable trade offs made. One of these to a minor aspect is the soundstage. The K612s just cannot compete with the soundstage on the K701, K702 and Q701. They do however have a more open soundstage than the K240s. Despite not having as wide as soundstage as the leaner K7s, I do find the K612 soundstage more natural due to not having the tendency to pan extremely left and right with mono recordings, causing the center stage to go dead like the K701/K702/Q701s do. 
Amping: I run the K612s off my Maverick Audio A1 hybrid tube and solid state amplifier and Schiit Audio Modi DAC. I am more than happy with the system, with the K612s taking a liking to the Modi. The K612s also like the FiiO E07K DAC and battery powered amplifier. They don't need as much current as the K7s, and due to being 120 ohms, they can be run off an OTL amp like the Schiit Valhalla. The K612s like the K7s are picky with DACs more than amplifiers; if your DAC is distorting from not being able to handle the equalizer on your computer, the headphones will make this horrendously obvious. So make sure your DAC is up to snuff. The internal DAC on Macs just won't cut it. 
Hi, Can you please explain in more detail how do these cans perform with FiiO E07K? Is FiiO powerful enough for good listening of rock and soul? Thanks
Now built in China-and it shows, with ill fitting frame and noisy metallic frame rods clanging on the plastic cups causing intrusive noises when moving your head. Even raising an eyebrow creates noise. The ear pads are comfortable but the head band caused me to have scalp pain for several hours after use.
They still sound very good though-as you describe.
No way I can see to edit my last post-so just to add that with more use it's now much more comfortable to wear, though I still have to make sure I keep my head and face still. Sound very good, as before.