AKG K 550


1000+ Head-Fier
Pros: Effortless big and natural sound. Beautiful built and looks
Cons: Thin pleather ear pad, just a slight lack of low-mid body and warmth
The AKG K550 revisited.
At the time, shortly after I bought my Audio Technica A900Xs I had auditioned the AKG's and I felt my choice for the A900Xs was the right one. I felt the K550s had this weird grating low treble peak that showed up just too often, unlike the low-treble/high mid peak of the Denon D5000s that only got aggressive ocassionally.
The price at the time for the K550s was 300 euro, the A900Xs I got for just 150 euro.
Fast forward in time: the K550 (MKII) now sell for 150 US dollar and encouraged by some reviewers who mention that the MKII version solved the problems of the MKI, no longer a grating treble peak, better clamping and fit and slightly increased bass I took the shot and bought them.
Maybe my ears have changed or the K550 MKII really is an improvement over the MKI version, I dunno, but the low treble peak just isn't there anymore. I tried the most difficult recordings with soaring highs and big contrasts in dynamics. Baroque violin concertos, where the lead violins are recorded so up close that it is impossible to get away with some aching or grating. And some choral works, where most crescendos will make the headphones loose control and start to ring a bit.
To name a few:
Geminiani Concerti Grossi (After Corelli) - Chiara Banchini
Bach Violin concertos - Elizabeth Wallfisch
Haydn Die Schopfung - John Eliot Gardiner
Haydn Die Schopfung - Rene Jacobs
With the violin concertos mainly the slower adagio parts are the difficult parts, because it are HIP (historically informed performance) recordings in where the violins play without vibrato, so the long legato lines, close-miked can grate very easily.
The difficult choral parts are the ones in where the choir all of the sudden sing much louder. 
None of my headphones, including the Sony MDR-Z7 (which is universally qualified as extremely inoffensive sounding) handle these recordings without problems.
The AKG K550s don't sweat, they sound so even over every frequency.
Therefore they surely must lack something? Maybe a soul?
Nope. They just don't loose control, that's it. 
They sound big, have a great soundstage with good width and depth, excellent for classical music. But they don't sound thin and too bright with smaller scaled music, something I do feel ocassionally with the BeoPLay H6s.
The bass is big enough to give music body...talking about body...if I must find something the K550s lack a bit is some low-mid warmth or coloring, something the A900Xs have and what make their sound one of a kind. But the A900Xs can sound grainy, something the K550s never do.
All those years I have dismissed a pair of headphones that are easily one of the best pair of closed headphones under 600 US dollar...and they can be had for a mere 150 US dollar.


Member of the Trade: Audio Excellence
Pros: great sound stage. reasonable tasteful bass. Great MIDDD range
Cons: Pads wear out and they do not sell replacements. it can be too big and fall off.
few months back my friend tried these headphones. Few days ago she wanted to buy it from me. And I quote her to start this review off "I've never heard music like I did with this headphone"
Hello ladies and gentlemen. I am a hobbyist that creates reviews and post beautiful Instagram photos of various audio equipment. That being said, my passion for audio quality started with my Sennheiser HD598s. However over time I felt the HD598s lacked bass. But I loved my HD598s and wanted something that contains the sound stage + bass. I came across the AKG 550  and immediately fell in love with it. If anyone asks me "what should my first audiophile headphone be?" I would without hesitation recommend you the AKG 550. You might think I am crazy comparing open headphones to closed ones but you will see my reasoning in this review.
The company operates in Austria, and was founded in Vienna in 1947 by physicist Dr. Rudolf Görike and engineer Ernst Pless. Originally, its main business was to provide technical equipment for cinemas: loudspeakers, film projectors and light meters. The business slowly expanded and AKG started selling car horns, door intercoms, carbon capsules for telephones, headsets and cushion speakers. The first AKG microphone was used by radio stations, theaters, jazz clubs and cabarets. About this time, the company developed its first patents, the moving coil technology and the principle of mass load membranes, allowing its products to have extended frequency ranges. With the creation of the D12 microphone in 1953, AKG achieved international fame, setting the standard for voice transmissions. Being the world's first dynamic cardioid microphone, it possessed excellent sonic qualities for that time, making its way into radio stations and recording studios from across the world.The product was improved through subsequent upgrades, spanning the famous C414 and C12 microphones.In 1984, AKG became a public company, listed on the Vienna stock exchange. As a blue chip company, it was one of the most traded stocks.The company was acquired by the American company Harman International Industries in 1994. By this time, AKG's United States subsidiary had been established (in Los Angeles in 1985). AKG Acoustics USA, still headquartered in the San Fernando Valley, also houses regional offices for Crown Audio, another Harman Industries subsidiary.

In 2010, the company received the prestigious Technical Grammy award.




The build quality on these headphone is phenomenal. Its practically metal on metal on metal. It is extremely sturdy. With that being said, it is bulky enough to consider it a full sized headphone. The headphone is adjustable through some real nice mechanism. The fit is very comfortable and the stocks pads are one of the softest I've ever felt. However the downsize is that you cannot buy the stock pads anywhere, not even from AKG. I have a pretty standard head and it is pretty big on me. I bought these because it is a closed headphone, but they do not isolate sound very well due to the fit being too loose. Also the wire is nondetachable terminating in a straight 3.5mm jack. 




AKG advertised these as "sound stage of an open back in a closed set of headphones" and they have every right to. These do have a sound stage the surpasses many closed set of headphones. However like I have mentioned before, these do not have the qualities we would be seeking from a closed set of headphone, I would categorized these somewhere in the semi-open headphone zone. The sound stage is give or take at the HD598 level.



This is a MIDDD ranged headphone. However there is some bass like will satisfy you. This was something lacking in the HD598s. the treble is clear but can get sibilant in certain songs. Overall, the sound is something of preference and this was a good experience for me. 


Overall Thoughts


This headphone does have negatives here and there but in the end... for the price point, it is one of the best entry level headphones you can purchase. 


also follow me on Instagram for pictures of audio gear I review. https://www.instagram.com/jayzlee95




review provided by soulsikreviews.com


video for reference only



Hmm...... a tube amp? Interesting. I'm a portable guy myself, so I'd prob never buy a tube amp. But having said that, they look so cool! lol 
Nice. Yeah if you do like the Oppo's DAC, then the 10 won't disappoint! If you do get it, PM me and I'll give you some suggestions on how to use it, like about the Personal Audio Profile and stuff. 
@RockStar2005 Sounds Pretty Good ! Yup, I do enjoy tubes at home, on the go I usually use IEMS, hey I'll follow you, why don't know follow me back so we can keep in touch. thanks!
That's cool! 
Alright sounds good brotha! 


New Head-Fier
Pros: Very balanced monitor style. Great with classical music. Great construction
Cons: Bass could use more body. Bulky and sometimes sweaty.
Bought these bad boys on sale from Harman Audio. Very clear and balanced sound for the price range, I have also had some good Grado SR80i headphones that I gave to my brother but the AKG K550 has very good sound with little leakage compared to open backs (good for office use). I love how Beethoven and Bonobo sound, these headphones have a very 'true to life' reproduction. So far I have found that I notice many details in tracks that I have not heard before! 
Perhaps not the absolute best audio in the world, but definitely one of the best values in the crowded sub 300$ space. If you can get them on sale, I would highly recommend them to any budget conscious audiophiles. 
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The last time I used the K551's in office, someone asked me where did I got that helmet from! But, the 551's if they sound same like the 550's were having a good body on midbass, compared to my current Beoplay H6's. What source do you use with it? 
Hi Dexter thanks for your comment. Yeah they are definitely big headphones. Currently I just use the Macbook pro sound output, but I have been interested in getting a DAC/AMP combo. Maybe when I get a bonus I can get a good one. Wishing you well.


Previously known as ahnvx
Pros: Sound, Fit, Style
Cons: Ears Can Get Sore
I've constantly said I wanted to try these.
I've seen the price tag stay at $200, and it's appropriate.
It's big, but has elements.
It's sound is stand out, Class A, $200 Sound.
The AKG K550
I've been wanting to try these since I seen the price tag, after searching for an upgrade, looking at the MDR-7506, and seeing these side by side, the MDR-7506 is OK, but has a purpose. It's a Studio Monitor, that's it's justice.
The AKG K550 is an important piece in it's price range, and it reminds us as the why the M50 lost it's reputation.
I finally got a chance to borrow these.
Let's discuss.
Build Quality:
- To one who can appreciate, is to one who's more likely to fall more in love.
Those are definitely words to live by when looking at this as a beginner headphone. 
It's a big headphone.
- She's built like a brick house.
Not to be confused with the song, but the headphone is heavily proportioned, and has a beautiful slick look, also durable... more durable than most.
Easily put, it's a headphone that for it's price, though not a Studio Monitor, it's built to take a beating like one.
We aren't going to get into Highs, Mids, & Lows, but we'll discuss this sound signature widely.
My impression of the sound at first was that it had an artificial sound to it.
Be It This Is A Sub-Open Back Design by sound.
The Soundstage is a bit awkward though. I'd compare if to being in a square shaped room, and telling everyone to face their corner and begin to play.
This created a mere echo in the vocal signature, quite disturbing, but after some burn in the sound smoothed out, but remained to sound in that pitch.
The Bass is VERY FULL, TIGHT, & COLORFUL, it's full of character. I can't say that there's even a true sound for the Bass. 
That said, this headphone will kindly fit any genre, and is polite to Hip Hop, & Rap for a change.
I think after seeing that this didn't budge much with Rap based genres I found my disappointment.
Techno, House, & other Electric genres lacked clear detailing, they weren't as vibrant, and you didn't feel like you were getting to experience the vibrations and clicking that some people find in these genres.
On my last bit of information, I think with the things this can has to offer, it's the best in it's range if you aren't looking for a Studio Monitor.
It's unique, and I would also argue, if you're not used to Warm, or Cold Sounding signatures, and don't wanna jump into a random experience, this is perfect for the job.
I didn't find a genuine sound fit to this, it never had a too Bright sound, it wasn't ever truthfully relaxed, and the Bass notes, undertones, and playbacks weren't Warm sounding.
It's mixed, almost giving you a hollow type of sound.
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Headphoneus Supremus
Pros: Comfort, Isolation, Balance, Detail
Cons: Nothing at this price.
Been a while since I bought some new headphones. The HD800's put an end to that for the last couple of years... But I wanted some closed back for certain times and so snapped these up. 
The balance of these is very good indeed, as is the tone. The AKG sound in a closed back pretty much. More midcentric than the KXXX with a closer image - slightly warmer but still with plenty of bite at the top. I'm impressed with the isolation as well- wasn't expecting too much - I wear glasses and I still get a very good seal. The comfort of the pads is another plus- very soft. 
The mid frequencies are much better on these than the KXXX and this is most welcome. (no nasty peak at 4k)
I wouldn't normally recommend any closed back hp for classical music but these sound great. Obviously not as airy as their older open back brothers, but the imaging is very focused and certainly open enough for large scale orchestral works. The detail retrieval is on par with the KXXX imo, only a little more more smeared at the lower end. 
I would describe the sound sig as typically AKG - 'dry' apart from the warm bottom end. I've read a few reviews that describe these as sounding more like an open headphone. They do have an ample soundstage for closed but they still sound like a closed headphone.  
Yup, an absolute bargain for what they are going for these days!   

Mark K

Pros: Clear high band, acceptable mid tone
Cons: Absolute lack of bass
Well, the infamous K550 was there. Big, comfort at an incredible price. I had to wait for one week before I got mine so I put it on.
Absolutely better than K701 I had a while ago. However, the overall quality is killed by zero presence of the bass. Where have they gone?
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I assume you didn't wait for them to burn in, did you?


New Head-Fier
Pros: Spacious - for closed back. Non-fatiguing, easy going sound. Work surprisingly well with iPhone.
Cons: No better than a reasonable £30 pair of open back 'phones.
I tried these with a Benchmark DAC1, a Fiio X3, a Fiio X1+E17 and various lesser devices including an iPhone. They seem pretty easy to drive. [size=13.3333330154419px]Music was a mixture of classical and Jazz - both CD quality and HiRes.[/size][size=13.3333330154419px] [/size]
My value rating is based on the £107 I actually paid from Amazon. I am having to keep reminding myself how cheap they now are in order to give them much praise though. [size=13.3333330154419px]I guess the heavy discounting of these should have told me that they were not that special.[/size]I would certainly have been pretty pis**d if I had paid full price.
Their best attribute is a surprisingly spacious presentation - about as good as a cheapish pair of open 'phones. To me they didn't sound any better than my £30 Jays-vJAYS except, for some reason with an iPhone. There seems to be some sort of synergy going on with the iPhone and they made it sound better than I have ever heard it. IF the iPhone was my sound source I would have been very pleased with the K550's but it isn't, so I'm not. They have a pretty laid-back relaxed presentation without any intrusive exaggeration but also without clearly presenting the fine nuances that you can always hear in real life (musicians breathing, fingers sliding on strings, valves clacking, scores being tuned, chairs squeaking etc). IF you can get them comfortable, they would probably be OK for long-term, relaxing listening but if you are trying to listen carefully, they just don't deliver.
Although huge, they don't actually look too silly when on your head. It is difficult not to think of Dr Who and the Cyber-men though.  They feel fairly robust and appear well made but I don't find them comfortable. I have no problem with head-squeezing or seal - that's all works just fine for my head. My problem is that the padding on the top of my head just doesn't protect me. After a few minutes I am uncomfortably aware of the weight pressing  down on the top of my skull. Easily cured with a bit of foam padding but do you really want to do that..........
For £107 they are pretty good value for CLOSED 'phones but in no way exceptional - unless you use an iPhone.
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100+ Head-Fier
Pros: Open Stage, No Congestion at High Volumes, Quality Built, Reference Response Curve, Comfort
Cons: Artificial Treble (can be improved with burn in & DAC/amplifier), Earcups Maybe Too Large For Some

I got these headphones around the national holiday. These came out about 2 years after I had got my K701. I was first attracted by its classy design and colour. I thought I would never get another pair of AKG headphones since K701 has been my favorite all the time. I finally decided to purchase a pair due to the discounted price of $180 USD including shipping in my country; and most importantly, I needed a closed can(s) to enjoy music at night without disturbing others. In this review, I will skip all the con(s) about these headphones and straightly elaborate on the sound quality and cozy build structure of these headphones. The reason is that at this price point, there are really no con(s).


Design & Build Quality

The build quality and design is simple but sturdy, is black/grey but classy, is far from top notch but flawless. I believe the design is better than my K701 because K550 has more grainy metals to withstand any abuse. The headphones are consisting of 3 major parts – the ear-cups, the joint, and the headband padded with synthetic leather. The ear-cups are able to rotate from the joint (by a little), and the joint can also rotate from the headband for approximately 90 degrees. This clean and versatile design allows me to store the headphones in my hobo handbags. Nothing feels flimsy or sticking out which will cause a problem. The headband adjustment is locked by a click. The numbering system on the headband will allow you to adjust the headband length to your most desirable positions. This helps a lot because getting a good seal on this K550 may be tricky because of its size.


The leather on the ear-cups and the headband are so comfortable that I actually enjoy wearing them once in a while. Although I would prefer the alcantara material (like on the K701) for the hot summer, the seal and comfort is better with the leather or leather-like material.


To begin, I was feeling a little disappointed coming from K701 when I was listening to these cans for first few hours. After 60-100 hours of burning in, the bass opened up and the artificial treble (which seemed like plastic spark) smoothed out. As several master reviewers had mentioned, there seemed to be a very slight disjointness between the bass and sub-bass area (of course, they have heard headphones around $1K mark). However, in term of the fullness and tightness of the bass is on par with my K701. Master reviewers would obviously magnified the disadvantages of these headphones, but they should consider there are very few competitions at this price point with this kind of sound quality in a closed full-size headphones. The T5p is triple the price, the build quality on the SRH840 or 940 may not be as good, the M50X may have a smaller soundstage. Nothing is perfect in this world especially with closed headphones. It is easy to make an open headphone sounds good, but it is harder to tune closed headphones. The K550 produced a full and tight bass with good and not-too-forward mid(s), and a nice sparkle treble without any harshness. The vocals are accurate and shine on these headphones.



The overall sound quality is impressive on these closed headphones considering they were at $180 USD when I purchased them. For people who prefer a reference sound signature with price-to-value ratio in mind and an amazing soundstage in closed nicely built comfortable headphones, you will not be mistaken by this K550. Just remember to give it a little time to burn-in and find a good warm source (like my Audioquest Dragonfly) to match the lean signature of this headphone.


100+ Head-Fier
Pros: Non-overwhelming bass, detailed vocals, great soundstage
Cons: Can't find yet
Excelllent headphones, coming after ss 9h headset, senn's 429 558 598 and i love these most, i differentiate details better in vocals now, i can say if vocalist is blowing into microphone while singing, there are more details in vocals which i cannot explain in english,  coz i'm not good at this section in english. Bass is not overwhelming, it is what i like most, not muffled, also if you EQ the bass it will sound much better as it did on my nokia with eq presets. Priority is for home use, but it's perfect using outside with phone, cable thickness is not the problem, as you can roll it around the phone, and put everything in the pocket without all stuff sticking out too ugly.
So much better in games with hearing steps detailed, soundstage is right as i wanted, with 9H i wanted to hear games world better/wider than i heard, akg550 fills this hunger, love it. Orientation in fps games maps is very good right now for me.


500+ Head-Fier
Pros: imaging, clean sound
Cons: no carrying case included
I have been using AKG K550 for past few weeks and enjoying them pretty well. This is my first foray into mid fi and I think its a solid contender for getting into mid fi sound especially as it has very low barrier for entry (whole setup). I am driving it with Audinst hud mini, entry level dac/amp and it drives it with authority and good clarity.
I have been using Sennheiser HD518 extensively, and have auditioned HD595 as well as HD650 before this. So thats my reference point here as HD5XX series is rather popular and what you can expect to get if you go for K550.
First some sound signature differences between sennheiser and akg. k550 requires you to be engaged to music instead of being half asleep to enjoy. k550 has this comparatively thin sound that changes very fast according to notes being played, thus conveys note level information with much more clarity. this clarity improves dramatically in hd650 but still k550 is clearer. For me, I need to actively listen to music and be engaged to enjoy k550.
So is one inherently better than other? I don't think so. both sounds are usable according to mood. (its not that I am feeling sleepy all the time, so why Sennheiser only collection?)
So now about K550. First some observations about K550 that are striking:
Great isolation without any clamping pressure whatsoever. No seal issue for me. I would attribute this to ear pad material. Its most certainly is something special that blocks sound very well. It must be in contact with your skin to achieve seal.
Very forgiving for low bit rate material. my much lower hd518 is almost un listenable out of phone with lower bit rate tracks as I could see some holes in music. k550 polishes it and makes it listenable, I think. It might have something to do k550 being easy to drive, not sure why it does that.
Very clean sound. no grain whatsoever. hud mini is inherently grainy and with grainy old recordings of the old like led zeppelin, it was almost un listenable on hd518. (all three recording, dac/amp, headphone are grainy making too much of it). on k550 its pristine.
Now I would describe frequency response a bit:
Bass: awesome. Goes very deep, is tight and reasonably textured. Exactly what I wanted.
Mids: Rich, detailed, not upfront. very enjoyable.
Treble: Now I am terrified of sibilance or bright sound. But k550 sounds exactly like I wanted it to. I don't think its dark sounding, but its got this peculiar way of doing treble. Treble extension is good but detail is very less thus to my ears sounds perfect. (better safe than sorry. won't cut any points here cause of my preference. I am looking for enjoyable headphones than perfect ones).
A word on soundstage:
Good sized. Its a closed headphone and has good width and depth with that limitation. Most impressive part has to be imaging. Pin point imaging if its present in recording, even if two same instruments are playing, it places them very well in sound stage.
Comfort is very good as it exerts very little pressure on head, but as its a sealed design, it gets sweaty. Ear pads don't allow a lot of breathing.
Build quality is good mixture of metal and plastic. not built like tanks and I intend to take good care of them. especially i don't want to change alignment of cups and thus affecting seal.
All these things make them a worth can but what makes them 5/5 special is, well they are very enjoyable. Even with their relatively thin sound, they have this deep and satisfying bass thus make for a very convincing presentation. Their sound stage is wide but they don't have diffused presentation like my HD518 that renders each component of music completely separate. Instead it presents a good mix of music, instruments often inter lapping but still sounding separate with note level detail, harmonious with each other. If you think about it, that is how you hear music when in a hall with musicians. Not completely separate from each other.
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I own them (Actually K551) they are very good. They are true Hi-Fi Headphone, so the quality of the sound restitution entirely depends
of the source file itself, the way it was recorded in studio and the device used to reproduce the sound. My iPhone for example is too weak
to drive them well but on my laptop and my desktop computer with Audigy 2ZS, the result it's quite nice.
I Also heard quite a lot negative reviews regarding the bass. Once again it's an audiophile headphone and is it neutral, it will not "create"
bass like many others, but will reproduce as it has been recorded. For example, I listen these day the album "Speck of Gold and The Afterlife Lounge" from "Afterlife" the bass are sublime and deep, the sound is very good.
I totally recommend the K550/551.
Nah, I disagree with both of you, respectfully. To use the word "full" in regards to the bass is totally exaggerated. It also does not "reproduce (bass) as it has been recorded". It is just not there, regardless of how you place them on your ears and play with the seal to make them tighter. It may be audiophile for detail but they got the bass levels way wrong. I reckon people try to justify the bass by saying things like it's "as produced".
It's also wrong to say others "create" bass. These "create" absolutely none whatsoever.
Again, these are just my opinions. On the whole i found these very thin sounding, too bright... and very boring (and I'm no basshead, i like a neutral flat headphone, but even then you need at least a little bass presence). It put me of AKG which I used to like.
They would be a great headphone if they had bass at a decent listening level, didn't have to be excessive.


New Head-Fier
Pros: Great detail especially in the treble, Well defined bass, Outstanding soundstage, Extremely comfortable, Built like a tank
Cons: Treble can be harsh at louder listening, Not enough bass for bassheads (Not a con for many)
I got these headphones around Christmas time in 2012. I loved the design at first sight, I find it understated and classy where others find it hulking and ugly, it's all a matter of opinion. After the excitement of unboxing them and plugging them straight into my phone I was horrified by how quiet, lifeless and lacking of detail they were. But rest assured this first impression didn't last long.
Design & Build Quality
As you can probably tell from the introduction, I'm a fan of these headphones looks. For me they fit my head perfectly but for others the size of this headphone is just too big to get a good seal, so it may be wise to try them out to see where you stand in this regard. Build quality is excellent, the headphones are largely made from metal which feels very solid and has some sort of powder coating which feels very nice to the touch. The plastic on these headphones is similar to the soft touch you find on many phones these days, it's certainly not as solid feeling as the metal but it is seemingly high quality plastic. I have had these headphones well over a year now and I am glad to say that the build quality hasn't degraded and they feel as solid as the day I bought them.
The earcups can be rotated 90 degrees which is useful if you're taking them travelling to save space, but the absence of an included carry case makes this a useless feature for me.
The inclusion of a removable cable would've been a welcome one but it's certainly not a deal breaker for me. Another note about the cable is that it is very long, so I have resorted to tying part of my cable up to shorten it. Obviously this is a pro for some people but it definitely makes the headphones cumbersome for portable use. The cable itself is very high quality though and the jack feels solid with plenty of stress relief on both ends.
If you're used to a plethora of accessories coming with your headphones prepare to be disappointed. The AKG K550 box comes with the headphones themselves, a 1/4" to 1/8" screw on adapter, some paperwork and that's pretty much it. Not a whole lot. However for me the only disappointment was that AKG didn't include a carry case, even if it was soft case it'd be better than nothing.
These headphones have a generous amount of cushioning on the earcups making for a extremely comfortable fit around the ears themselves. However I would have opted for adding more padding on the headband as after a few hours or more there is a certain point on the headband that gives me a slight ache, nothing too uncomfortable but something could have so easily been fixed by adding more padding. Overall, the headphones feel light on the head, soft around the ears and I can wear for a few hours at a time with no discomfort. 
First off, I love the sound of these cans. They are relatively neutral, while still sounding a little exciting and not too analytical. They have a flair for the high end, producing magnificently detailed trebles which I find brilliant at this price point. Bass, although possibly lacking the presence of other headphones around this price I find the bass to be extremely well defined, this is accentuated in songs where you have short, punchy stabs of bass more so than when you are listening to a thicker, more full-on bass centric track. The mids aren't as well defined as the rest of the spectrum with some warmer sounding guitar tracks not providing quite as much presence in the mids as the bass and treble. With that said I still think the over signature of these headphones is very good. 
I have been using these headphones with my PC, using an Asus DGX sound card. Quite basic as sound cards go but I think they provide just the right amount of amplification to get the most out of these headphones. I use the 32Ohm amplification setting in the Asus control panel. When using the headphones with either a mobile phone or my PCs integrated sound card I found volume to be lacking which in turn affected how well define the headphones were but by using the equipment and settings stated above the sound is extremely well defined and the volume of the headphones is boosted a lot with no distortion. The soundstage also opens up a lot with amplification. For a pair of closed back headphones I find this pair extremely open sounding and seperation between instruments and the width of the soundstage is all very good.
Overall I am even more impressed with these headphones now than when I first bought them. A recent price drop to £109 in the UK means that these headphones represent amazing value. I don't feel like they can be beaten as far as sound quality and build quality goes, as long as you like the fairly neutral sound signature.


Pros: Balanced response, Versatile, Closed-back with an open sound, Build quality
Cons: Lack-luster with classical, ears touch drivers, take a while to break in, lose some personality with time
            When I purchased my AKG K550, I was in the market for a closed-back headphone that gave me the best open-back sound while containing the noise so I could use them in a dorm room. The AKG K550 does that and much more.
            After a few days of pink noise break in and heavy music listening, they really showed their true high-performance colors. The highs were balanced and resolving, the mids forward as in any AKG headphone, and the lows are rich and placed perfectly within the frequency spectrum. I was initially blown away by the response of these headphones for being closed back, as they offered a very distinct open-back like sound, while being a convenient closed back headphone. The isolation on these headphones is beyond excellent if you can find the right seal and headband adjustment. Many people have had issues with fit, but with a little tweaking they are easy to seal and will accommodate any head size.  I’ve had these headphones for a few months now, and sadly they have become a bit more dull and less dynamic with time, but not to the point where they aren’t fun to listen to anymore.
            The build quality of the K550s is fantastic. The top headband is made of brushed aluminum with the AKG logo laser-etched into the top. You can bend and shape the headband in anyway if you do it sensibly (don’t fold it or snap it…). The hinge where the band is connected to the ear-cups is a high-quality soft-touch plastic. I sometimes find it difficult to gauge what some people mean by high-quality plastic, so for comparison purposes, the plastic used is like what you would come across in the interior of a car’s dashboard; solid and sturdy, but lightweight and soft to the touch (if that helps at all). The lower part of the hinge is a textured aluminum that is also soft to the touch and feels like it will last for ages. The hinge and ear-cups are held on by a solid aluminum bolt, which looks mighty-fancy, and screams quality and durability. The back of the driver encasings are aluminum with the AKG logo again laser-etched into the metal, and the outer ear-cups are the same soft touch plastic used for the hinges. The leather for the ear-cups is very-high quality, although I think it is a pleather material as opposed to a genuine leather material. I like to compare it to that of the Bowers&Wilkins P7. The cable could be considered a bit long for portable use. I’m not sure why they made it so lengthy as these were marketed as a portable headphone. There are easy remedies for this though, I used a suggestion from the K550 appreciation thread and tied a Chain Sinnet (monkey braid) knot with the cable (I’ll post the link to how to tie this at the end of the review). Although these headphones are designed in Austria and made in China, AKG did not skimp out on anything on the quality side of things. I can tell they will be in good condition for a good amount of time. Also, I’m not really sure what brands are trying to go for when they state, “Designed in ________.” It doesn’t mean anything different to me. It seems to me as if they are trying to say something designed in Austria is better than something designed in China, and without stating this, a consumer would be turned away by the “Made in China” decal. Don’t let this influence your purchase when dealing with any headphone.
            I’ve seen some occasions where people have had issues with the comfort of these headphones, but for me that was not the case. Once you break the leather in, it becomes soft and cool. At first, the ear cups made my ears a bit sweaty after a few hours of listening, but with time, the leather has worn in and become a bit cooler for long listening sessions. My one complaint would be that my ears do touch the drivers and become a bit sore after a while. If I shuffle them around on my head a bit it takes care of the problem and I can go on until I need to repeat the readjustment. If that’s something that bothers you, these may not be for you, although there are some mods that can take care of the issue. Many people also complain about the lack of padding on the headband, but I find it to be adequate and haven’t noticed any issues with comfort on the top of my head. If you find the right fit and seal, these headphones are very comfortable, just note that the drivers aren’t to deep inside the ear-pads, which is not ideal for most people.
            I listen to a wide variety of music, and I believe that it is important to include a descriptive listening evaluation in these reviews so I can convey to you how they sound throughout the spectrum of music because everyone has a different taste and wants something different when they are trying to decide which headphones to purchase (the broader the review, the better). Before I go into a listening analysis, as stated, I’ll just again say that these headphones are my favorite closed back cans that have the capability to be portable, are extremely durable, and still sound incredible. Remember that they wont be as detailed and honest as an open backed counterpart, but they’ll come close to performing as an open backed headphone with the benefit of not having sound leakage and having good isolation. As compared to many of the closed-back headphones around this price range, they are some of the best, and I HIGHLY recommend giving them a listen and if you’re in the market, considering to purchasing this product. You will not be disappointed.
Test Songs (all FLAC files)
1. Pop (female vocal): ZZ Ward – Put the Gun Down
            ZZ’s vocals sound a bit recessed but resolving. A bit of distortion when the snare is on top of her voice. The drums sound harsh, a bit trebly, but nothing unbearable. The kick drum is supposed to be “decayish” on this song, so I’m disregarding the thickness of the low end drum response. Guitars sound detailed but a bit laid back. Bass is full and round, not too forward, there’s enough there to be honest to the mix. Overall a great sounding track on the K550s. There just seems like there’s something missing dynamically.
2. Pop (male vocal): John Mayer – Paper Doll
            John’s vocals sound exquisite. When the harmonies come in they sound separated and lush. The guitar is panned but doesn’t lose ANY tone. It’s a full and dynamic guitar sound. This is my favorite part of listening to this song on the K550s. The bass is full, maybe a little light. Sean Hurley, John Mayer’s bassist uses a fender jazz bass on this recording though, so it is very true to the sound of his instrument. The synth effect at the end has a “middy” push. It is very clear and harmonic. The K550 handles male vocals exquisitely. This is a great example of what this headphone can pull off.
3. R&B (female vocal): Beyonce – Listen
            Again I find that Beyonce’s voice is a bit recessed, but resolving. This seems to be how the K550 handles female vocals. Nothing too noticeable, but if you are listening for it, you will definitely notice. The strings sound fantastic. The balance between the instruments is breathtaking. The background vocals are very deep and full, maybe a bit back in the mix. The peak of the song sounds great. Everything is separated. It sounds very theatrical (this was in the musical and movie Dreamgirls, so that might be where the theatrics come from). Bass sounds a little light for my taste; it sits right in the frequency range where this headphone has a bit of a struggle. The piano is very clean and precise, this headphone loves acoustic instruments.
4. R&B (male vocal): Luther Vandross – Never Too Much
            This song sounds spectacular. The bass is so detailed and fun to listen to. The midi instruments sound so true and artificial, but that’s what the track is going for here. The strings again sound fantastic. I cant get over the sound of the strings, it’s bright and lush, but so easy and pleasing to listen to. Guitar sounds a little treble heavy, but that could be what they were going for in the production. Luther’s vocals are simply incredible. I feel like he is singing to me. They are so dynamic and intimate. These headphones pair so very well with his vocal timbre, it impresses me every time I listen to this song. The whole harmonic range is so smooth and it feels as if the K550 just dances around the frequency spectrum with ease.
5. Jazz (instrumental): Bob Acri – I Remember Clifford
            Wow. That trumpet. The warmth and resonance is so defined and resolving. The bass is deep and detailed; I love how the producer placed it in the mix and how this headphone responds to it. The drums sound so full. This song paired with the K550s is just right. It sounds most like a home theater in the sense that everything sounds so open and responsive.
6. Jazz (instrumental… again): John Coltrane – Giant Steps
            I chose to do another instrumental jazz tune because the previous one is slower. This contrasts that with a fast saxophone melody and an analog recording style as opposed to the newer Bob Acri recording. Everything just sounds so easy. The saxophone is all in the left channel, which is where its supposed to be because of the old stereo recording style. You can really hear John Coltrane’s real sound on this track. These headphones respond so well to instrumental jazz. It’s a joy to listen to. The piano, bass, drums, and saxophone sound perfectly separated. The honesty of the sound is remarkable for these open-backed headphones. All of John’s notes come out sounding full and dynamic. A lot of other headphones struggle with doing that on this song.
7. Jazz (female vocal): Dinah Shore – Then I’ll Be Tired of You
            As opposed to the pop and R&B female vocals, female jazz vocals sound very forward and proper in the K550. I was going to listen to a Norah Jones tune, but that is more of a pop production style, older female jazz vocal production is different. This is a true jazz performance and standard. This headphone also loves Dinah Shore’s voice. It’s rich and detailed. Close your eyes and you will feel as if you are there sitting next to her. The band sounds very mid-heavy, which I like, but the bass is thin while the vocals are present. The drums sound great out to me, which is odd because drum production back then wasn’t spectacular by any means. This headphone isn’t at it’s best for female jazz vocals, but it can still handle it remarkably well.
8. Jazz (male vocal): Frank Sinatra – Theme from: New York, New York
            The horn intro sounds fantastic. Frank’s voice is full and intimate. The horns are spectacular, lush and vivid. There is little distortion and listening on the K550 makes you feel as if you are there in the concert hall this was recorded in. The realism of this track is fantastic. Everything sound “right.”
9. Ambient: Grouper – Vital
            The accuracy in this song is great, although it sounds a little thin overall. Open-backed headphones do this song justice. This song just sounds normal on the K550s. Ambient music can be very dull if it is not in full detail, and unfortunately that is the case here. The only thing that sounds up-to-par is the acoustic guitar, but with the thinness of the vocals, there is really nothing special here.
10. Hip-Hop: Blu – SLNGBNGrs
            If you mainly listen to hip-hop and aren’t a bass head (uncommon), these are the headphones for you. This is just magical. The bass and vocals are perfectly mixed in with the synth and the beat. Everything is so rich. When the instruments hit the lower frequencies, it is so rich and punchy as it’s supposed to be with this style of music. I could listen to hip-hop all day with these because its so fun and pleasing.
11. Electronic: Squarepusher – The Exploding Psychology
            Boy, if you want an accurate headphone for electronic instruments, you can’t go wrong with the K550, simply incredible. Everything is so dynamic and rich; it’s presented in a way in which every nuance can be picked out. The bass is thick and I find these better for listening to electronic than an open backed pair because of the accurate and punchy bass response electronic artists go for. The sound field is fantastic and all the different textures sound perfectly separated. If you purchase these, you will automatically appreciate dynamic electronic music.
12. Classical (orchestral): Bela Bartok – Musik fur Saiteninstrumente und Celeste
            Hm. Not much here. The soft strings are very unrefined. The louder part of the piece is thicker, but the strings nonetheless sound thin and undetailed. The cello and bass sound ok, there is not to much to say about the lower strings. Although smooth, this is where the K550 struggles a bit. The dynamics sound brittle, maybe a bit loose. It struggles to handle the whole orchestra without distortion. The bass is nice at the louder sections, but the highs are just so bland and relaxed.
13. Classical (film score): Hans Zimmer – Time (Incetpion OST)
            A bit better than the Bartok symphony, but there is still something missing. The better production quality makes up for the K550’s lack of harmonic response in the strings. Not much distortion as opposed to the previous piece. The electronic instruments in this song sound accurate, and have a nice dynamic effect when paired with the K550s sound stage. Again, the strings sound like they’re just… there.
14: Classical (solo piano): Yundi Li – Chopin: Scherzo no. 2 in B Flat minor op. 31
            The piano sounds a bit thin. When Yundi hits the lower range of the piano it fills up a bit, nothing to write home about though. The reverb is nice, maybe a bit thin as well. The K550s do not do the piano justice here.
15. Folk: Wesley Jensen – Of Life of Love of Tears
            This song sounds great. The reverb and accuracy of the instruments is well presented. The acoustic guitar sounds full, rich, and balanced. Vocals sound nice and detailed. You can hear all of the tones coming from the guitar and by this I mean fingers sliding across strings, fret buzz, etc. The main focus of this tune is the vocals, and boy do they sound great.
16. Rock: Tom Petty: You Don’t Know How it Feels
            Sounds very familiar to the folk example. The vocals are well presented, the drums sound great, acoustic guitar shines as it’s supposed to. Maybe a bit too laid back though, everything could be a bit more forward although just boosting the master makes up for that but can make the K550s get a little messy distortion wise.
17. Hard Rock: Iron Maiden – The Number of The Beast
            The intro to this song sounds great. The guitars are well presented with good detail. The bass is accurate, maybe a little light when in unison with the guitar. The only complaint here is that it sounds a little treble heavy, a little more low end would do this genre good.
18. Metal: Meshuggah – Lethargica
            The distortion on the guitars sounds great. The bass and kick drum don’t interfere with the other instruments. Vocals are very detailed; the mids are very apparent and blend well with the rest of the songs dynamic level. The lower register of the eight-string guitar really stands out to me here, great tone, not too “floppy” as lots of other headphones make this song sound.
After listening to these pieces and evaluating how they sound with the K550, I’ve come to appreciate this headphone even more than I had before. It’s got such a great sound that is so unique to its closed-back design. Although it does lack a bit of precision and detail for classical music, it is well rounded for the other genres, which have a more forward-sophisticated production style. The bass is deep and refined, the mids forward, and the highs sparkly and detailed. The build quality is phenomenal, the sound is unique and balanced, and if you find the right fit, these headphones will keep you well isolated from outside noise. They used just the right amount of tuning in these cans and it really shows how great the engineers at AKG are. What they’ve created here is a masterpiece. If you get the chance, give them a listen; you will be glad that you tried them out.
If you are considering buying these and would like me to listen to anything to tell you how its sounds, I would be more than happy to do so, just message me and I’ll respond shortly after.
Here’s the link to the Chain Sinnet (monkey braid) knot for cable management: http://www.animatedknots.com/chainsinnet/index.php?Categ=decorative&LogoImage=LogoGrog.jpg&Website=www.animatedknots.com

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Jeff Y
Jeff Y
soundstage of pretty much all akg headphones except for the k450 seems very strange to me. love the build and the comfort though


New Head-Fier
Pros: Sound, Overall quality, Comfort, Closed-back but they don't sound like it, Bang for the buck
Cons: Non-removable cable, Cable is very long (3m), Can be hard to drive from small devices, not recommended for small heads because of sealing issues
This a review, as well as bit of a comparison to the Focal Spirit One, as those are the last headphones I owned and I absolutely loved them. 

Man, where to start with these; right off the bat let me tell you that I absolutely love them. They are totally different from the Spirit One, and in a very positive way. When I first got the 550's, I was surprised at how heavy the box is. Now to anyone who thinks you get a lot of accessories with the K550's, I have to disappoint you. All you get are the headphones and a quarter inch adapter, the latter of which is gold plated and screws on top of your cable. Everything about the headphones exudes quality, which couldn't be said about my Spirit Ones, as their headband and joints are made only of plastic, and thus cracked under my big head. The 550's cable is not removable and it is 3 meters long. That's definetly something to keep in mind. Alternatively, you could go with K551, which have a detachable cable. Me, I just couldn't justify the hefty price difference between the two.
When you put the K550's on your head, there are two things you immediately notice (coming from Spirit Ones): Man, there things are huge! And; Man these things are comfortable! Seriously, comfort is insanely good, which once again can't be said for the S1.
I don't know if I would take these out in the public though, as they are quite big and the cable is looooooong for mobile use. 
Enough of the chatter now, and let's get to the sound :)

I listen to music through the following setup: 
-HP Envy 17 Laptop with FLAC's or Spotify- FiiO E07-K Andes USB DAC/amp (To bypass the HORRID beats audio on the laptop, that RUINS anything connected to it)- AKG K550
When I first started listening, I noticed that you absolutely need a good seal with these headphones, in order to enjoy them. For me, that's easy. But for anyone with small heads, and/or women, this might be a real issue. Try not to buy them blind like I did, and try them in a store to see if they fit. Once I found the perfect seal, I was amazed at how much bass there was. Compared to the Focal, which are said to have a lot of bass, I was really surprised because the AKG have more of it. The bass is deep and very well extended into the sub-bass range. It also never sounds boomy or muffled, nor is there too much of it. 
Next, I wanna mention the soundstage: WOW, do they sound different than anything I've owned before, even though they are closed as well. They sound very similar to the K701, which I had the pleasure of testing. Instrument separation is excellent, and there is no "overlapping" of treble sounds, like I've noticed in the Focal. Mids are not as warm as the Focals' and overall, the K550 sound more detailed and technical, while the Spirit One are very warm and love vocals. Not to say that the AKG's don't, it's just a different kind of love :) . (The upper mids can sound a little (too) prominent at times)
Now for the highs, as they were the most notable change for me in comparison to the Focal; they are a lot more prominent and not rolled off, especially in the lower to mid-highs. They provide a nice amount of sparkle and excitement in my opinion, but sometimes at a cost: The 550's are kind of "unforgiving" when it comes to older recordings and lower bitrates. They will bring out every imperfection in the sound and can thus produce hissing and siblances. This was notable on older rock/metal recordings or such that weren't perfectly mastered, which is most of them. (Dream Theaters older albums are an example here).

Overall, I'd call the sound open, pleasent and enjoyable. 
Should you buy these headphones? -Absolutely. That is, if you can find a good seal, and you don't plan taking these on your commute every morning. The great sound, quality and comfort, as well as the the awesome bang-for-buck ratio are reason enough to buy them. But for small heads, and a closed portable, I'd still favor the Spirit One.
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Pros: Looks sturdy, bass is tight and midrange is lovely
Cons: Hard to get a good seal. A bit-lean sounding. Treble is a bit odd but still good
This headphone has a great neutral sound but I can see many people finding the bass a bit too lean yet not light. This can be due to poor seal which as mentioned earlier is a bit tough to get for some. I personally did find the bass very good however there are times where I feel it’s a bit lacking. But even with the perfect seal, people who are used to big bass and stuff may find this headphone a bit light in the bass.
With a good seal, I think the bass is very good. It’s flat, impactful but not overbearing at all. There’s not much emphasis on the upper bass and lower mids area so it’s not as warm as what I would call as a warm-sounding headphone. Overall midrange sounds natural
The treble part is a bit raised but I didn’t find it bright at all as some would call it. It can be somewhat grainy depending on the audio track that you’re listening to but the mid to upper treble region has good clarity for this type of headphone. Some people also find the treble a bit artificial or indistinct and while I did find it to be true, it isn’t really that much. I think some of the AKG's cans have this same treble signature.
Soundstage is pretty good for a closed back headphone but perhaps this might simply be due to the cups being too big that it creates that perception. Imaging is average and it gets confusing when I listened to some treble-heavy Dream Theater tracks. But the overall dynamics is good.
I only tried Fiio e11 and it did make the bass a tiny bit more prominent but other than there's really not much change.
For full review and some pictures, feel free to read the original review post here: http://www.headphone.ph/akg-k550-review/


Pros: Good mids, and decent treble
Cons: Subpar build quality for a 300$ pair of headphones
Well, the K550s don't sound bad by any means, however, the sound signature isn't really for me. I like a little less mid focus and a bit more bass. Less neutral and more fun, really. 
Now the build quality of the K550s are not superb by any means. Firstly, the headband cushion was peeling off in the corner right out of the box. Which was really disappointing. The construction of these headphones felt flimsy, even though it is built of aluminum. The M50s have much better build quality than the K550s. 
It's really love or hate for me. The comfort isn't great either. My ears touch the drivers which causes them to hurt my ears after only an hour of use. 

Makiah S

Formerly known as Mshenay
Sponsor: HeadAmp
Pros: Neutral Sound, Tight Bass, Full Bodied Mids, Isolation, Comfort
Cons: Lacking Mid Weight, Poor Treble Attack, Too Little Bass for Some
View attachment
[size=14pt]AKG K550 [Price $160 Used][/size]
[size=14pt]Test Process[/size]
[size=14pt]Source Win 7[Foobar2000 WASAPI] -> oDac -> MonoPrice Premium Coaxial Cables -> Matrix M Stage [0  [w1000x Akg K550/+18 db Gain Lme 49990 OpAmp][/size]
[size=14pt]Will be compared again'st my w1000x and my Beyer Dt 990, since I intend to use this headphone as a portable, with all genres. I want to see how it does against my two "specialists" Specifically, the Dt 990 will be compared only with Classical and EDM [I got lazy and only did classical and Dub Step] genres. Songs 2 and 7.[/size]
[size=14pt]As always gain and volume are adjusted for each headphone. [To ensure each has equal volume levels, despite gain.][/size]
[size=14pt]7/9 Songs are without EQ, Benga-Invasion and Kidnap Kid-Animaux  do feature an EQ added by me. This should demonstrate the ability of a headphone to handle EQ.[/size]
[size=14pt]          In addition, from this review and out, italic text will contain comparisons against my reference headphones. In addition, comparative points of interest will be included in Head Fi review posts, with all Blog Posts reaming more simple and to the point![/size]
[size=14pt]Personal Back-story  [/size]
[size=14pt]I recently sold my old Beyerdynamic Dt 880 Pro 250 ohms, and since then I've been in search of something that captured it's sound! I think I may have found just such a can.[/size]
[size=14pt]Build [5/5][/size]
[size=14pt]I am impressed, the headband is metal with a nice extension feature. Nice physical feel in the hands, not as tough as the Dt 990, but not nearly as fragile as the w1000x. A solid build! Still these are composed of more plastic than metal. Yet the plastic has a nice look and finish to it![/size]
[size=14pt]Very Sturdy[/size]
[size=14pt]Closed Back Dynamic Operating Principle[/size]
[size=14pt]32 Ohm Impedance[/size]
[size=14pt]114 db Sensitivity[/size]
[size=14pt]32 Ohms[/size]
[size=14pt]12-28.000k response[/size]
[size=14pt]Ease of Use [Comfort/Fit/Isolation] [4/5][/size]
[size=14pt]People complain about the fit, and the lack of clamp force and sadly I did not experience any of this, I put them to 4 on each side slapped em on, pressed them in ever so slightly and enjoyed. I will mention that they sound DRASTICALLY changes depending on how far from the front of the pads the front of your ears are. Essentially for me, the closer the back of my ears are to the back of the pad the Thicker the lower mids are, the closer the front of my ears are to the front of the pads, the thinner the entire can sounds![/size]
[size=14pt]In addition, these cans actually isolate very well! Much more so than the w1000.[/size]
[size=14pt]But still these are STILL easier to put on my head and adjust than the w1000x, yet a little more fickle than the Beyer Dt 990![/size]
[size=14pt]Sound Signature and Character[/size]
[size=14pt]          Sound Stage:  A very wide sound stage, good instrument seperation.[/size]
[size=14pt]The Akg K550 is fickle with it's sound stage, with vocals it really shines and widens. Not as initimate with vocals as the w1000x, yet with pianos and wood instruments it's not quiet as wide as the w1000x or the Beyer Dt 990, how ever my w1000x is Modded so it's... well much tighter than stock.[/size]
[size=14pt]          Sound         Signature-  Easily the most neutral balanced headphone I have heard to date. The bass is tastefully tight and deep, the mids are warm and delicate, with good punch. The treble as well is smooth and very refined! Although it still retains some of the Closed Back sound.[/size]
1 - Lisa Ekdahl _ Of My Conceit
A vocal jazz piece, Lisa's voice is the main focus. Yet behind her is a lovely piano and a delicate guitar strumming! The piano provides a nice upper Mid and Treble balance, while the guitar provides lower mids and some bass. Both of these elements compliment Lisa's voice. A song best on a warm neutral can, a larger sound stage is excellent with this song as well!
          Treble- It's nice. Great detail, yet lacking sparkle and quick decay. Air and extension are nice. Again very neutral, as I know that I honestly prefer bright cans.
The w1000x, is brighter, faster and has better decay in the treble. Treble on the w1000x is not quiet as smooth, but again I'm not a huge fan of overly smooth treble. I enjoy the extra dynamics of a slightly  sharper treble.
          Mids- The details in the vocals is excellent! There is a good balance of smooth lush sound and detailed quality!
Actually, the k550 have more details than the w1000x, which is slightly smoother and more enjoyable. While the w1000x retains and projects just as much detail, it's not as tight with vocals as the k550 is. Still the w1000x's more smoother intimate vocals are just as punchy and more enjoyable imo, although ever so slightly less detailed. In addition, the K550 places Lisa's voice a little farther away from me. Showing it's transparency and neutrality! Still I'm a sucker for the more intimate vocals of the w1000x. It's also important to note the Angled drivers of the w1000x really give it a slight edge.
          Bass- Very tight, good warmth in the bass with a nice little bit of impact.
Both cans handle this bass well! The Akg K550 however does it a little nicer.
                   Dynamics- Very nice, the left and right channels feature different instruments, and they flawlessly shift from louder to softer notes.
These two cans handle dynamics very similarly! Both do a great job!
2-  Anne Gastinel & Francois-Frederic Guy Sonata for Cello & Piano No. 2 in G minor, Op. 5
Classical track features heavy focus on mids with sparkles of lower treble and the balance between the Cello and Piano!. Another song benefitting from a larger sound stage and a well balanced head phone. The bass of the cello accentuates nicely against the Piano.  Both having deep beautifully lush tones. Air and extension make this piece come alive and lack of it, can kill the mood entirely! Then entire audible spectrum is equally beautiful through the entire song!
          T- The treble is very smooth, well defined and good clarity and details Truly the treble is very neutral! Yet it's still retains beauty and flawless detail.   
Not as smooth airy and well extended as the Dt 990,  in addition the is not as airy  and bright as the w1000x
          M- Nice tone, this is an extremely mid heavy piece... the piano and upper mids are flawless. Decay is good, yet could be a little quicker.
Again, the w1000x... has the better mids... a little more lush  yet also punchier than the K550. Slightly, more sound stage and clarity on the w1000x as well..  Still the Dt 990, remains the Classical King, with more delicate, detailed and well extended mids. Not to mention more sound stage! Non the less, honestly even with the slight, lack of refinement. The k550 does a wonderful job with classical!
          B- Very tight and well placed, the bass never impedes on the delicate mids!
All three do the bass equally well, each with a delicate touch of the cellos bass every time it's needed, stll the w1000x and Dt 990 are just ever so slightly tighter, with that lower mids bass combo punch!
Dyna-Really wonderful. Very quick, no sluggish change in dynamics at all.  
3. Yoshida Brothers -Love
The two brothers are performers of the traditional Japanese music style of Tsugaru-jamisen which originated in northern Japan. They debuted in 1999 in Japan as a duo playing the shamisen, and it remains a main instrument. In addition to traditional Japanese percussion, this track features a very gusto male shout. What sounds like a verbal battle cry, is over top the delicate shamisen. The punchy yet warm mids of the male vocals pair well with the light upper mids and treble of the Shamisen.
          T- Shamisen has a great tight snap to it, good smooth extension to those higher notes!  
          M- The mids of the Shamisens are, just as lovely and gentle as they should be. Quick on their feet, and with a deadly accurate attack. The mood of the song is capture nicely in the mids. The male vocals are actually wonderful! Not too deep, but warm enough with power. A good balance of warmth and power.
The w1000x has more Gusto, more body in the mae vocals, making them a little less punchy but more powerful,  Honestly, both do These male vocals really well, both have a good balance of power, punch and warmth. With a little more warmth and power on the w1000x, with the K550 maintaining  the same power and a little more punch over warmth. Also the Shamisen, has a better attack on the w1000x. Due to a little more weight in the mids, where as the K550 has a nice snap to it, a little lighter but just as quick as the w1000x. Still the K550, lacks that... mystic woody tone in the Shamisen.
          B- The bass is very... super tight. More percussion than an actual bass line, non the less what's there is well represented by the K550.
w1000x, does equally as well considering how little bass there is in the track.
                   Dyna- Amazing as always. This can is proving just as light on it's feet as my others!
4 Kidnap Kid- Animaux
A nice Vocal DnB Tune. A really demanding tune, as the mids and bass over overly overtop another. The sound is very... wonderful! The beauty of the mids right atop deep tight bass, followed by drops of nice punchy vocals. Best of all, the pesky 150hrz makes a return in this tune for a lovely meaty support for those mids. The layering and texture of the bass is, something I'm still not used to! I feel a little spoiled each time I hear it!
          T- Good energy and balance on the mids. Smooth and pleasant, in no way drowned out or invasive of the rest of the frequency.
The highs are equally enjoyable on both cans. Not much to say about them really. Both maintain good energy and relative placement of the highs.
          M- The mids have nice body, but still lack a little in weight. Yet they remain playful and smooth. Over top the bass line, the warm mids work well with the deeper more impactful tight bass.
Again the w1000x maintains more mid warmth body and weight, the track as a whole is more intimate, yet the increased sound stage of the w1000x [again mine is modded] keeps the separation of mids and bass clean. It should be noted though, that with EQ the w1000x get's a little smudged in it's mids,. where as the K550 does not. The K550 also lacks some of the imaging of the w1000x. The sound is a touch more forward, yet not as intimate. .
          B- Bass is wonderful, this being a more laid back tune the bass line stays nice and tight, while still having impeccable weight and body.
Being that this is a DnB song, I do prefer to eq my DnB. Using FooBar a +4 @110hrz and -4 @156hrz gives the bass a little more body while not removing any weight and still remaining tight!
Immediately the w1000x displays a bass with slightly less control and more body. Using the same Eq setting drowns  up the mids ever so slightly on the w1000x.  The k550 displays a little more clarity when eq'd over the w1000x, yet the w1000x has full bodied weighty mids along with a punchy yet laid back bass [it matches the mood of the song very well]. Ultimately, it seems the K550 needs to be eq'd to have the more laid back and intimate sound that pairs so well with this Drum n Bass tune!  Yet Some may prefer the Tighter less intimate presentation of the K550 over the equally clear but more intimate presentation of the w1000x in this DnB tune.
                   Dyna- Dynamics are smooth, the neutral sound aids in a clean shift in the dynamics of the tune!
The w1000x is has a touch faster dynamics, or rather the increased attack in the mids leads to a better dynamic shift, as both cans have equal mid decay. Both cans handle the bass and highs exceptional well!
5- Dai Qing Tana & HAYA Band- Missing You
Beautiful Mongolian vocals, and a world music sound that breaches more than just Asian styles. This track features a lovely guitar to your left, a cello to your right with Dai Qings delicate yet warm deep lyrics right in the middle. A perfect tonal balance is ideal for this track, as it's simplicity does not allow for any distraction from the overall mood of the song as a whole!
          T- This song has a VERY thick and warm bottom end sound, that being said the bright energy of the guitar is never lost in the mid warmth. The highs prove to be well defined without being bright! 
Actually, the highs in this song some times get a little lost in the upper mids, seeing as the guitar is only peaking at about 2.3 2.4k hrz these are the lower most highs, and for these lower treble, the K550 keep a slightly better serration between them and the upper mids. Yet the w1000x is brighter by a touch though. Both are very pleasant with these low treble notes, in addition the w1000x has a little more attack on the notes as well.
          M- The powerful lower mids from the guitar have nice body to them, and sufficient weight,  a real master of balance, the Akg K550 clearly defines it's upper and lower mids. Each having nice body and a little bit of weight.  The upper most mids [also lower treble] maintain good presence despite the powerful lower mids and beautiful airy weight and body of Dai Quing Tana's voice. The deatils in the vocals are wonderful  Her voice remains the focal point, with a lush body and just a touch of weight. Which suits her airy voice very well! The Cello in the right channel as well has a lovely tone to it, good body but it could use a little more weight.
The w1000x also adds an intimacy to the vocals that the K550 does not, yet both do a good job with this mid heavy track. Still the w1000x has a little more sound stage, thus the weighty sounds remain intimate and yet well spaced. Not to mention there is the beautiful tone of the woody mids on the w1000x. Where in which the Cello really shines.
          B- The bass is as always, well controlled on the K550, yet the more controlled less full bodied bass does take away from the Cello's beautiful weight. Non the less the Cellos retains it's lovely body on the tighter bass notes!
It should be noted these Bass Notes, are in conjunction with the lower mids very much in this track. As the Guitar and cello each have a sense of Mid and Bass in their lower notes due to nature of the instrument.
Here both cans do really well, where the K550 lacks weight it does a little better job of retaining a clear sense of body. Where the w1000x adds weight, the body get's a little too much decay. Again these are for the very lowest notes on the bass and cello respectively. The we1000x still has a touch to much bass decay, especially when compared to the more neutral K550.
                   Dyna- The K550 as always does a great job with it's dynamic shifts, the Cello especially fades in and out of the track often!   Always coming into focus nicely, and exiting cleanly.
 Still though, the extra decay in the bass of this track especially take away slightly from the dynamic quickness of the w1000x. So for a track like this, with multiple heavy mid presence, the K550 remains a little more dynamic than the slightly mid focused w1000x.
6- 3nd_ Algorythm       
Great tune from a Japanese Rock band, wonderful energy and great layering. A nice high energy rock tune. The kick of the drums and the clash of the cymbals, combined with sweet guitar mids and a mellow bass line. The bass in particular shifts a lot, the skilled bassists really shows off from time to time, combined with dual guitar tracks. Balance is a great benefit, as is a good sound stage to this song.
          T- The symbols and upper range of the guitar are nicely presented by the k550.  The drums especially have great energy on them!  
The slightly brighter w1000x however is a little more pleasant. The additional sound stage really brings adds  enjoyment to the brighter and airier treble.  In addition to an slightly bigger sound stage and a little better 3D imaging. [But again my w1000x is modded]
          M- The K550 does rock very well, everything is well placed and the decay is excellent throughout. The mids retain great body.
Tough battle here, the w1000x is magic for rock. The big sound stage and excellent separation pair excellently with the forward mids. There is an warm high energy to the w1000x in rock that the k550 doesn't quiet have  Yet the K550 has a touch more detail due to it's less forward mids! There are in fact 3 guitars in this track, one to your left right and center! The K550 and w1000x both do a great job to balance these out! Still in the end, the combinations of forward punchy mids and bigger sound stage leave the w1000x more engaging! Still both are equal in clarity and detail, with the k550 being not quite as fun  seeing as it lacks some of the aggressive attack [and sound stage] of the w1000x.
          B- Bass, the k550s best feature. The bass line in this rock track has such great texture placement!
Ahh bass, the w1000x one shortcoming, this is not an aggressive bass line. It's very clean and punchy but still a strong bass line. The w1000x adds a little to much attack and decay to the bass. which is nice yet it losses a little bit of the texture because of this. Granted I've modded A LOT of the decay out of the w1000x bass, but it's still no match for the k550 very neutral bass!    
                   Dyna- The k550 does a great job as always, it's slightly less aggressive attack and always quick decay make it nice with the rock dynamics.
Again both do a good job, but I give dynamics to the K550 for it's tighter bass line. The bass on the w1000x still has a touch to much decay to be as quick with dynamics in rock as the k550. Yet where the w1000x lacks in it's bass decay, it makes up for with quick dynamics in it's punchy forward mids. [Having both excellent attack and decay on those mids] Where as the k550 does not have the attack of the w1000x, which for rock is a little missed.
7-  Benga- Evolution  
A lovely mid intro, builds to a very aggressive and tight drop. While the mids are an excellent addition to this song, the cymbals and bass are the focus here! Aggression is key in this track, the tighter and deeper the better. The faster and punchier the more enjoyable!
I will admit, I do enjoy my Dub Step eq'd ever so slightly. That being said, I do use the same modest eq for both cans. A +1 boost at 55hrz leading to a +4 boost to 110hz, followed by a -6 decrease at 156hz following a slight incline to +2 at 1.2k hz then back to +_0 I prefer the mids boosted a pinch, and that pesky 156hrz when removed or eq'd out bring a VERY tight bass line to any track, As this frequency is a VERY meaty upper Bass... that said I remove it as it lacks deep impact or TIGHT punch imo.
          T- Treble is accurate and neutral with the K550, although the often lush mids of this tune drown out the treble a touch. Some brightness is nice for DubStep.
About the same, both have great treble detail, the Dt 990 has a little more air and extends nicer. Quicker on the decay as well. With EdM the brigher treble of the W1000x and Dt 990 are preferred.
          M- Mids are a strong point in this Dub Step tube for the K550. The slight touch of weight and nice full body are great again'st that DEEP bass line!
Mids are lusher on the w1000x, but a little too weighty and lush. On the Dt 990 the punchier nature of the mids cut's against that deep bass a little more pleasantly! Like the Dt 990, the K550's nicely bodied [but neutral] mids are a better contrast to the bass!
          B- Great tight bass. A perfect balance of attack and decay.
The Dt 990 and k550 both have a nice tight bass. Although the Dt 990 just has more bass to it! The open back design allows all of that BASS to stay nice tight and super aggressive. Where as the k550 while equally as tight, lacks sheer bass quantity when compared to the Dt 990. The w1000x doesn't even need to be mentioned,  as this track is best with a TIGHT bass line. While having more bass than the k550 it's not tight enough and has to much decay. Still enjoyable though.
                   Dyna-  Excellent, good fast shifts!
What... Dub Step song with Dynamics... you mean other than... BASS no BASS... just kidding. Seriously though, the song has nice dynamic shifts, and the massive bass stays tight and decays faster through these shifts on the DT 990. An as always the w1000x is a little slower with it's bass decay. K550 is as always nice and quick with it's bass.
Should be noted, the Dt 990 and K550 struggles a little bit with deeper acoustic bass notes. The w1000x is a little more natural with wooden instrument bass, than is the Dt 990 or k550. The extra decay of the w1000x bass is a big part in that, as woody bass has more decay than does synthetic or metallic bass.
8- Lenny White, Jamey Haddad, Mark Sherman -Seven [Binarual Recording] From _ (Explorations In Space and Time)
A percussion trio, this binarual recording has only one thing that makes it wonderful... imaging. The Width and depth of the recording is really wonderful, not to mention the dynamics of the track as a whole. A headphones Sound Stage, width and height are very important. However too wide a sound stage and the 3D imaging can get a little veiled.
          T-  Good energy in the drums and cymbals, but the lack of brightness and attack is a little missed.
Cymbal are wonderfully airy, great energy and the linear space is good, the 3D position, imaging how ever is not as nice as the w1000x.
          M- Good body on the drums, yet they lack a weighty tightness. Still very solid and enjoyable. Not to mention the placement in this track is not as 3D as one would like with the k550
w1000x added sound stage and over all forward and punchy mids are nice with this percusion tune. The 3D imaging is better as well, yet the K550 is still very enjoyable!
          B- Nice and tight, very pleasant!
Can't complain much here, both do a nice job with the drums bass
                   Dynamics- once again, pleasantly tight and quick.
Both cans do a nice job with dynamics
9 The Modern Jazz Quartet- Reunion Blues
A lovely classic jazz piece, what makes this such a great tune is the  balance of each instrument, as well as the placement of each in the sound stage. This song... is spilt literally into left and right. A soft Piano and Percy Heath's Double Bass to your right, with the drums and cymbals to your left, Also in the left channel is a magically warm and lush Xylophone! Best of all despite extreme stereophonic sound, the track as a whole is very balanced and incredibly enjoyable! Here a wider sound stage takes heed over a tall one.
          T- Lovely, cymbals have good extension and fabulous air.
But not as airy as the w1000x.
          M- the upper mids are excellent, as are the lower mids! The piano and Xylophone work together for a wonderful mid core!
Proving jack of all and master of none, the K550 is nice with jazz. Great balance but it again lacks the energy and airy brightness of the w1000x
          B- Excellent, tight,
Yet again the 3D imaging shows to be a little weaker than the w1000x, and the bass is a little too fast for the Double Bass, the lack of attack and extra decay do take away from the joy of the double bass in this jazz number!

                   Dynamics- As always, fast and accurate. Great for this classical Jazz piece!
[size=14pt]Sound [4/5][/size]
[size=14pt]Treble [3.8/5]- Very neutral, which isn't always my cup of tea. I miss the energy of slightly brighter cans. Not to mention the lack of air.[/size]
[size=14pt]Mids [4.2/5]- A beautiful tone to mids, with the right mix of body and a touch of weight to be enjoyed with all kinds of music.[/size]
[size=14pt]Bass [5/5] - Excellent bass all the time.               [/size]
[size=14pt]Conclusion- For $220 and around $170 used, it's one of my favorite all time closed cans! Great sound for almost all kinds of music and the bass lovers will enjoy it with everything! Good dynamics and fantastic build quality. A must have for any one getting into Audio Phila![/size]


Member of the Trade: Lachlanlikesathing
Pros: Comfortable, spacious open sound, great build quality
Cons: Very sensitive to seal, overall lean sound, somewhat raw treble, slightly heavy
Along with the summary below, I have posted a Youtube video review of the K550. If you like the video, check out my channel for more reviews :)

The AKG K550 has excellent build quality, with a great fit and finish and a solid, durable feel to the materials. The earpads are very large and may not fit everybody's head; despite being very comfortable and supple the earpads are sensitive to seal and small changes to positioning will affect the already quite lean bass. The headband padding is quite sparse and because they are quite heavy, after a few hours they may make the top of your head a little sore.
The AKG K550 has a very lean, dry sound. What is most noticeable is the spacious soundstaging and clean sound despite the closed design. The K550 has no real sense of congestion or anything characteristic of closed headphones. However the sound is very lean; bass extends very deep but there isn't much slam or warmth. The treble can be slightly raw on occasion. Overall they are balanced headphones good for a variety of music but on the leaner side of neutral and not to my personal preference. Fans of more analytical signatures may enjoy these.
These are well made headphones with a good sound, but the fit issues mean that you may need to trial these before buying them. The lean sound may also not please everyone, though I commend AKG for designing a closed headphone that sounds very much like an open one.
I have one of these. I totally agree with you. BTW, I love that post on your wall LOL


New Head-Fier
Pros: sharp looking, perfect bass for my taste, comfortable,
Cons: no detachable cord, long very long cord, maybe a bit too much treble
I am completely new to this forums and headphones; and not an audiophile at all. But I truly enjoy listing to good quality music.
I was looking for very very long time, scanning forums and all over internet trying to find the best headphones to start enjoying music with better quality.
I never tried any of the other headphones so I wont be making comparisons; but IMO this are great headphones to start with, I am very happy.
I confirm what others say about these not fitting right, way to wide, I do have a big melon as a head; and still they feel like just there, my wife has to press the cups to feel the difference. I've seen people bending the band, which I will probably do eventually.


100+ Head-Fier
Pros: Excellent bass extension & mid-range clarity. Smooth & grain-free treble. Spacious soundstage.
Cons: Treble rolls off a bit early. Lower-treble a bit too forward. Mid-range and bass could both use some additional body. Sound imaging a bit indistinct.
Comparison Review: ATH-A900X, AKG K550
Two years ago, when I was looking to upgrade my aging ATH-A9X, I came across the AKG K550 and the ATH-A900X, both then newly-released, with several head-fiers reporting that they are tonally-similar headphones. Unable to decide which one to get, I bought both to do a comparison. I ended up keeping the K550 for myself and giving the A900X to my wife (who still uses it and loves it).
Below are my thoughts regarding how these two cans compare.
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Craftsmanship & Comfort
Audio-Technica ATH-A900X
  1. The A900X isn't a bad-looking headphone, but lacks K550's elegance. That said, comfort level is excellent and I in fact prefer it over the K550 in this department. The AT "winged" headband design makes putting them on and taking them off a breeze, and the angled drivers do not press against my ears even after my prolonged use (whereas the K550 causes discomfort).
  2. One particular thing another reviewer complained about was the "poor quality" of the wings on the A900X. I looked into this issue, and did not personally find this to be true (relative to previous models). Below are my observations:
    1. On the old model A9X/7X/5X, the wings only pivot in one direction (let's call it the Y-axis), which is up and down.
    2. On the A900, AT implemented the "3D Wings" which pivot in two directions (X- and Y-). The way they achieved this is by making the wings themselves into a 2-piece design - there's an "outer rim" that pivots around the Y-axis (like the old wings), and an "inner piece" that pivots back and forth (X-axis).  This is actually a fairly intricate design and I imagine, harder to manufacture.
    3. On the A900X, AT simplified the "3D Wings" to ease manufacturing process while still retain pivots in both directions. The wings themselves are now back to a 1-piece design and pivots up and down (like the old wings on A9X), but the T-shaped joint where the wings are clipped onto the arms now pivots back and forth (in the older models, this joint is fixed). The joint on the new system makes the wings feel loose, giving the appearance of flimsiness, but having owned this headphone for two years I can attest that the construction quality on the wings are solid.
  3. Material quality on the A900X is decent but not great. It's a step up from the A900 (which had the cheapest pleather possible and several plastic bits just look like sub-$100 headphones), but it's not at the same level as its older cousin, the A9X (which had supple protein leather earpads and wings). The earpads on the A900X is a durable-looking pleather that feels a bit on the hard side, and the wings remain fabric-covered like on the A900.
  4. One nitpick: The stereo plug on the A900X is the exact same one AT has been using since the mid-90's (starting with the old ATH-AX series). It might have looked ok in the 90's, but looks a bit gaudy by today's more understated aesthetics.
AKG K550
  1. The K550 is simply one of the most tastefully-designed headphone I've seen. The construction, materials, and appearance are all superb (my photos don't do them justice).
  2. Comfort level is good but there are some nitpicks here... The earpads could be a bit deeper. The top of my ears do press against the drivers because the foam used in the earpads are extremely soft. The earcups are a bit stiff when it comes to pivoting, so they may not conform to the shape of your head without manual adjustment. The clamping force of the headband feels a bit loose, especially if you have small heads (and this is a headphone that already has sealing issues)
  3. The plastic used for the signal cord, while fairly high-quality, is still more prone to tangle and deform in comparison to Audio-Technica's fabric-wrapped cords, which retain their shape better. I personally prefer AT's implementation.
  4. One material nitpick... The headband padding is pasted onto the headband using basically a double-sided tape. Unfortunately the adhesive becomes a black goop as it ages and, in my case, actually started oozing out from the headband and making a mess on whatever surface I leave the headphone on. I ended up tearing out the padding, cleaned off all the adhesive, then glued it back using a glue gun.
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Sound Quality ​
Several Head-Fiers have claimed that the A900X and K550 are tonally similar, which was the reason I was interested in these two cans to begin with. They turned out to be very different-sounding cans, heh.
FR Graph of ATH-A900X (Left) & AKG K550 (Right)
Audio-Technica ATH-A900X
  1. Treble: The A900X has a fairly clear and resolving treble. It appears to be tuned to offer sparkle without being offensive or sibilant (there's a dip at 7K which, I suspect, was intentionally introduced to reduce sibilance). Extension is absolutely brilliant, going full up to 20KHz. The only complaint I have is that it's noticeably grainy-sounding compared to the K550, whose treble is simply silky-smooth in texture.
  2. Mid-Range: The A900X's mid-range is thicker, fuller, and more engaging than the K550. It is definitely a more engaging presentation (more "musical" if you will), but clarity suffers a bit here. The K550 in comparison is more clean-sounding.
  3. Bass: The bass is my biggest gripe with the A900X - there's quite a bit of mid-bass bloat and the control isn't particularly tight. Bass extension isn't very good either - the rolloff starts at 50Hz, which means there's not much sub-bass compared to the excellent extension of the K550. Without any earpad mod, the A900X has a bit of a consumer sound to its lower end (I personally found that swapping the pads for the oval-shaped ones from the A1000X helps dial the bass down a bit)
  4. Soundstage: The A900X has a very wide sound stage, likely owing to its excellently-resolving treble. Imaging is likewise excellent - I feel this is one area where it has a definite upper hand against the K550, whose soundstage - while large - feels a bit indistinct.
AKG K550
  1. Treble: The treble is a bit of a problem area for the K550. Many users have complained about it being "peaky" or "sibilant". I don't find this to be the case, though the lower-treble is definitely too forward, causing the slightly unnatural treble presentation noted by many reviewers (a problem compounded by the thin-sounding mid-range. Both issues were addressed in the K553). I also wish there were less roll-off in the higher octaves, as the K550 could benefit from better extension (it's rolled off from 1.5KHz onward). Complaints aside, clarity is good and treble texture is superb - there is absolutely no grain on the K550.
  2. Mid-Range: The mid-range on the K550 has excellent clarity, which I really love. However it is sometimes dominated by the lower-treble, which as I mentioned, is too forward. Additionally it could use some additional body - the overall presentation does sound a bit bright & thin.
  3. Bass: The bass on K550 has excellent tightness and extension, however it could likewise benefit from some additional body. I personally do find K550's bass to be thin-sounding due to the lack of mid-bass. There's ample amount of sub-bass and upper-bass, but the mid-bass is intentionally recessed. A 2-3dB boost in the mid-bass would provide a more balanced bass presentation (exactly what the K553 did).
  4. Soundstage: The K550 is well-known for its spacious soundstage, and I do agree it feels very wide and airy. However, I feel the imaging is a bit fuzzy and indistinct. Watching movies and playing games, it's much easier to tell where a sound is coming from on the A900X.
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Final Thoughts ​
The A900X and K550 are both good headphones with distinct personalities. Neither are perfect, though. I would say the A900X is the more balanced-sounding of the two and more versatile when it comes to musical genres and other usage (games & movies).
The K550 offers better clarity and may be more desirable for analytical listening and editing tasks, but it's not as musical as the A900X and many will find its treble presentation to be problematic.
very great review :D
Just got the a900x last week and have had K551 for about a month. One thing I noticed immediately is the sound stage on the a900x is much better than the 551. The a900x also has a lot more resolution than the K551. a900x sound stage is deeper, more three dimensional but not fuzzy or blurry at all compared to the K551. Positioning of instruments is easier to hear for me. On busy passages of music the a900x manages to maintain separation and detail in instruments where the K551 misses things all together. The K551 is not bad by any means and in this price range I'm very surprised to find something (a900x) that I consider an upgrade and not a side grade.
Interesting review, but I disagree with your statements about the A900X. The A900X is a much better headphone. More comfortable, much better bass, better mids, and the soundstage is way better. Your ears must be very different than mine, and I don't know what amp you use, but the A900X is great bass to me. It is tight, controlled, and has a good punch. The only area that the K550 would be better, is in the treble area. Which is a matter of debate. I like the treble in the A900X, it has no sibilance, has good timbre, and detailed enough, it sounds good. It is a closed-back anyway. The treble is not super airy, or super detailed, it is good though. The A900X is just an awesome headphone, end of statement.


100+ Head-Fier
Pros: Transparency, soundstage, treble
Cons: Comfort, perfect seal
This is my first review so please be gentle!
When you first put on this closed headphone, you'll be stunned how wide the soundstage is. Compared to my open Sennheiser HD600, the soundstage is equivalent! (though the HD600's soundstage is slightly deeper).
The K550 also trumps the HD600 in so many aspects including transparency, clarity and dynamics. On the other hand, the HD600 trumps in bass slam and comfort.
There is plenty of bass in the K550, but it's not as textured as the HD600 and as for comfort, the cups are really comfortable but the headband requires more padding.
The amp I used to to compare the HD600 and K550 was an Aune T1 with 6922 tube. I've only just upgraded the tube to a 6H23N-EB and the K550 sounds even better, but unfortunately I don't have the HD600 handy right now to compare on this new tube.
The value of this headphone is unmatched given how good it sounds and is possibly the best sounding closed headphone that is still in production. It's currently my favourite headphone for music, and in case you were wondering, this is my headphone preference:
AD700 < M50 < FA-003 < DT770Pro LE < HD650 < HD600 < K550 baby!
I think that your order of ">" is incorrect. (opposite).

I would be surprised if you find the M50, AD700 surpass the HD600s!
Thanks Chimp, now corrected :)