I don't write many reviews, but I feel like I need to for the HD 600. Practically everyone on this site has heard them at some point, and they have been around for over 20 years. The fact they have been a benchmark that many companies have tried to emulate for two decades is a testament to how good they really are.

Before trying the HD 600, I bought and reviewed the HD 580 back in 2014. I understood the hype from this Sennheiser HD 580/600/650 line, but there were a few things I did not like about the 580. It may have been my pair with their flattened ear pads, but they had basically no bass. This was at least when compared to the only other mid-fi headphone I had at the time, the Beyer DT 880. I sent them back, and I decided to try the HD 650 after much research here on Head-Fi. I noticed a huge difference between the 580 and 650, and I have since used the 650 as my daily driver up until a few months ago.

I now own the 6XX, 58X, and 600, and out of all of them, the 600 gets the most listening time. Over the years, I got used to the warm bass hump of the 650, and when I first tried the 600, I thought they were bass light. However, the more I listened and compared the 600 and 650, I found the 600 to have clearer and tighter bass. I also found the 600 to respond incredibly well to EQ in the sub bass, and actually got it to hit harder than the 650 with the right settings.

The mids are where the 600 outperforms every other near or above its price, in my opinion. I have tried other high end headphones such as the HD 800S and LCD-X, and I still prefer the smooth mids on the 600s. There have been many times where I thought real instruments were playing in front of me. The mids are that realistic and natural. I don't know what engineering magic Sennheiser did with these in the 90s, but they clearly did something right. In comparison to modern V shaped headphones, these will sound forward to the majority of people. However, I find them to be just perfect.

The treble, to my ears, is as good as the mids. I hear no grain whatsoever. This may come as a surprise, but I actually find the 6XX to have more treble sparkle than the 600. It may be unit variation, but from memory, I also remember my original 650 to have had more upper treble emphasis as well. This doesn't show up in measurements, so I don't know why I'm hearing it. Anyway, the 600s treble to me sounds perfectly flat and neutral, with no emphasis anywhere. Things sound just as they would in real life. And that is exactly what these headphones do best.

You can find hundreds of headphones that have a defining characteristic that makes them have their own "personality" if you will. Of all the headphones I've tried, the HD 600 does the best job at getting out of the way and just letting the music itself be the personality. I know that is a very cliche thing for reviewers to say, but I really mean it. The 600 is almost like a sound portal, where you just hear what is really there, with nothing taken away or given to the recording. With the exception of ultra low sub bass extension, everything that was recorded can be heard plainly with these, with no exaggeration or detraction. The HD 600s to me sound like they are not trying to be more than a simple pair of headphones. That may sound bad, but let me put it this way. I think many other headphones try to sound like something other than headphones, by making the imaging and soundstage super wide, or having over emphasized bass, or giving the treble more detail than what was in the recording. What makes the 600 so great in my opinion, is they focus mainly on replicating the natural frequencies of the music, and not attempting to change anything in the recording. I think what I'm trying to describe here is neutrality, and I guess one thing nearly everyone can agree on is how neutral the 600s are. In a way, the simplicity of the HD 600 makes it one of the world's greatest headphones in my opinion.

If there is one criticism I have for these, it is the dated design on the headband. I don't mind the speckled blue-grey marble most of the time, I would just prefer if it was a plain color all around. I think a refresh of the look of these would do Sennheiser a lot of good. Or, you can go crazy and paint them like Z Reviews.

Well, I think I've hyped these headphones up enough. Needless to say, these are currently my favorite headphones of all time, and I doubt I'm going to find a replacement for them anytime soon. Thanks for reading all this!

The FiiO Q1 is an easy recommendation for those on a budget. You would be hard pressed to find something that performs similarly for the asking price, below $100.
 
I don't usually talk about the packaging or build of products, but in this case I feel like I must. The build is exceptional, I believe it is completely aluminum all around. It is much sturdier and heavier than the FiiO E11.
You get a very short 3.5 mm cable to connect with any phone or portable device, as well as a USB to micro USB connector to use the inside DAC. That means you won't have to go searching around your house for the right connectors. 
Disclaimer, I take an objective approach to my audio equipment. I don't really give in to the belief than multi-thousand dollar amps or DACs sound "better" than budget amps/DACs. I have owned the ODAC + O2 for a while, and the Q1 gives me that sound in even a smaller package, so that says something. It is perfectly neutral, as a solid state portable amp should be. Same with the DAC. 
 
My only complaint is the power. The E11 does have a tiny bit more power on high gain compared to the Q1, at the expense of more audible hiss noise. It cannot fully power my HD650s when listening to Classical, or any other very quiet music. With other genres, it does fine. One thing I am impressed by is the noise floor, which is basically non-existent. It is so dead quiet, even when turned up all the way at high gain with my sensitive IEMs. Very impressive improvements by FiiO. Also, it is extremely simple to set up. Just plug in your computer, and no drivers are required so you can just start playing music right away.
 
For IEMs and low impedance headphones, this amp/DAC may be all you need. For stuff like planar magnetics or Sennheisers, look at a desktop solution. Not that you would get a portable amp/DAC just for hard to drive headphones. Overall, one of the best portable amps for the money IMO.

By now, I'm sure almost everyone on Head-Fi knows the company Meze. After such a huge positive response to their full size 99 Classics, Meze has now made new IEMs, the 12 Classics. 

 

Before my review, I would like to give a huge thanks to Meze for giving me the opportunity to participate in their Meze 12 Classics Review Tour. 

 

Since there are already detailed specs and pictures in the first review, I will not be posting those. Instead, I am going into detail about how good these sound, especially for the asking price.

 

I have been on the lookout for good balanced sounding IEMs for quite some time. For reference, so far the IEMs I have owned or currently owned are:

Shure SE425

Klipsch X10

Klipsch X20

Hifiman RE-400

 

So, I do not have much experience with many IEMs yet. However, I know what good sound is, and I know what kind of signature is for me. These Meze 12 Classics, in short, are pretty much perfect for me. I really like warm bass, but not overbearing bass, and the Meze's have it. I like natural sounding midrange, and the Meze's have it. I also like flat somewhat recessed treble, and you guessed it, the Meze's have it. Honestly, the only fault I see with the Meze 12 Classics are the ear tips. I have smaller than average ear canals, but the smallest tips size was too small and the medium tip size is too big. But that is not Meze's fault, because I just have weird ear. Using the provided Comply foam tips fixed that problem for me easily. 

 

I forgot to talk about build quality; it is very well constructed. For $79, I can't believe the attention to detail they put in. The cable looks beautiful, and feels sturdy too. I think the wooden casing around the driver is a very nice touch. I have not had it long enough to test durability, but these seem like they can take a beating.

 

I have since gotten rid of the Klispch X20 and Shure SE425, so I only had the Hifiman RE-400 and Klipsch X10 to compare the Meze's with. Overall, I would describe the sound signature as north of neutral and warm. In terms of bass quantity, it has more than both the RE-400 and the X10. It does have the best sub bass out of the three in my opinion, and kicks hard when you need it. I am a huge fan of the Sennheiser HD650, and while the 12 Classics have more perceived bass, the same amount of mid bass warmth and balance of the 650s is there. I'm already a huge fan of the bass these give. 

 

The midrange is great too, and sounds just as good as the X10 for me. It also sounds more natural than the RE-400, as the RE-400s seem a little too analytical and flat in the mids for my taste. I think the midrange is the Meze’s strong point, in my opinion very natural and open. This makes the soundstage bigger than what you would expect from a typical IEM too.

 

Now, the treble is sort of the thing that makes or breaks a headphone for me. The 12 Classic’s treble is definitely recessed in the upper response past 10 khz. But, I don’t think that takes away from the overall performance. You can still hear plenty of detail, but it’s not in your face. The response in the treble reminds me of a warm pair of vintage speakers. It does an amazing job of taking away the harshness from many of today’s less than stellar recordings. This is what I like to call a “fun” IEM. And really, isn't that the point of music listening? To have fun?

 

I am overall very pleased with the Meze 12 Classics, and for $79, I don’t think there is much competition. It is a more enjoyable listen than the Hifiman RE-400, and a good dynamic driver alternative to the Klipsch X10, which sounds very similar but more expensive. I very much want to buy these after having the chance to try them out for the review tour. Once again, thank you Meze for these amazing IEMs!

Where do I start? These honestly sound like the HD600/650 in IEM form. My previous go to IEM was the Klipsch X10 ($100), followed by the Klipsch X20i ($539). What is amazing, is that the RE-400 sound smoother, are more realistic, have better treble extension, AND have better soundstage than the X20i. And these cost just $79! I am continually impressed by these the more I listen to them. They seem to work with every genre too. For classical, they bring out every instrument texture to make them sound realistic. For pop and EDM, they have decent impact and sub bass extension, but are not for bassheads. I would describe them as neutral, and very slightly warm. Some may say they don't have good sub bass, but I disagree. If you are used to Hifiman's planars like the HE-400i and HE-560, you will notice these have extremely similar bass presentation. Mids are fantastic, very realistic and right where they sound be. Maybe slightly elevated compared to most IEMs, but only very slightly. Treble is so smooth, no peaks at all. I must say, the tonal balance is smoother and more realistic than many over ear headphones such as the Beyer DT800 and T1, Hifiman HE-400i, and Shure SRH-940, and sound very similar to the Sennheiser HD600/650 in the mid and treble regions.
The only con I can think of is the supplied ear tips may not fit people with smaller ear canals like me. The smallest size is ok for me, but doesn't seal as well as foam tips, and the next size up is too big. So I ordered Comply foam tips (the TS-400 size) and hopefully those will get a better seal. However, even without the best seal, it doesn't seem to affect the sound that much, because they already sound fantastic. 
Considering these sound significantly more balanced and natural than what the Klipsch IEMs have to offer, at under the $100 price point, is a huge accomplishment in my book. You probably wont find a better sounding audiophile IEM under $100, or maybe even up to $300. I wouldn't be surprised if these match the performance of the king of dynamic IEMs, the Sennheiser IE800. Hifiman sure knew what they were doing with these, and I can't recommend them highly enough!

EDIT: 
9/12/16
This review was done before I realized I may have gotten a defective pair, and that is why I was experiencing almost a veil like sound from these that makes cymbals and high hats sound distorted. Once I try another pair of X20i's, I will update this review to confirm if I really did try a defective pair. 
 
The Klipsch X20i is Klipsch's flagship IEM, which has a dual balanced armature driver system packed in. Klipsch claims that the addition of a dedicated BA "super tweeter" driver makes these sound like over ear model headphones. That is a bold claim, but I definitely agree these compete with many over ears around this price. 
 
I find the sound of headphones the most important factor above anything else, so if a headphone is ugly but sounds amazing, I will still keep it. However, with Klipsch, these IEMs look stunning, and really look more like a piece of art than an IEM. Build quality alone, these are reflective of their $500 price point. The "surgical grade injection molded steel" according to their website feels so high quality, it feels like a tool. I won't go too much into detail about the build quality, but it is very impressive.
 
When it comes to the sound, I had an interesting experience. At first, I could have sworn they sounded worse than the Klipsch X10. I was very sad if this was the case, as I thought maybe I got a defective model. But no, what actually happened, was a seal problem. The stock ear tips that were on the X20i's where too big for my ear canal, and didn't get a solid seal, and therefore the treble extension suffered drastically. However, when I installed the small ear tips and got a proper seal, my goodness these sounded fantastic. So make sure you get a good seal well within your ear canal for the best possible sound. The treble extension really does sound like over-ear headphones. And they blow both the Klipsch X10 and the Shure SE-425 out of the water when it comes to detail and realism. The bass is very extended and present but not to the point of being super rumbly and overbearing. These sound very fast in the bass and are very punchy. These honestly sound like a typical monitor speaker frequency response. I guess this is what Klipsch intended, as they are a speaker company. I would characterize these as warm sounding, with neutral mids and treble, and very flat above the initial warmth of the bass and lower mids. According to the frequency graph at Innerfidelity, these extend all the way to about 17 Khz before rolling off. http://www.innerfidelity.com/images/KlipschX20i.pdf
These have incredibly low distortion too, only bad 5% distortion occurs after playing at 100 db, but who the hell would play that loud unless you want permanent hearing loss?
 
Comfort wise, they are just as comfortable as the X10s, if not more so. The steel housing is shaped like the inside of the ear, and feels much more comfortable than the typical IEM design. They come with 5 different tips including the ones already installed on them. They come with the same tips as the X10: small, medium, and large oval tips, and a small and large double flange tip sizes, except this time they are black colored. For me, the small fits the best, as I have smaller than normal ear canals. Anyone should be able to find a nice fit with one of these tips. 
 
Compared to my Sennheiser HD 650, which are open over ear headphones, the Klipsch X20i is not as open or airy, but that is a typical limitation of IEMs. Given the HD650 and X20i are both around the same price point, the Klipsch's compete very well against open back headphones around their price. For example, these sound more natural and real to life than the Beyerdynmaic DT-880, and the Audio Technica ATH-M50, at least to my ears. In fact, I would say these sound a lot like the Sennheiser HD650, but in IEM form, and they have more bass. However, $549 is a pretty steep price even for the excellent sound these give you. Another con is the cable, which has a volume control that I never use, so it just gets in the way. Luckily, the cable is detachable, and Klipsch has stated there will be more cables available from them in the future. All in all, they are the best IEMs I have heard so far, definitely better than the X10 and Shure SE-425. If you love the X10s, you will definitely love these. At the time of this review, they are on sale for $439 on Amazon and Ebay, and I'd say that is a very fair price for what you are getting. Great job Klipsch!

I am coming from limited headphone experience compared to most on Head-Fi, however I've had my fair share of listening to headphones over the years. I have listened to the following open back headphones: Senn HD-650, HD-580, AKG K712, AKG K240, Beyerdynamic DT 880, and Beyerdynamic T1. Out of all of these, I have to say I prefer the HE-400i over even the HD 650s, which were my favorite for nearly the 2 years I have had them so far. While I love the laid back sound of the Sennheisers, I could not really experience many of the "hidden" things in recordings and other details. The HE-400i's have a way of making instruments sound super realistic, and in my opinion they are amazing at instrumental and classical music. In some pop songs, this extra detail means slightly heightened treble because of compression and mixing for those rock and pop genres, however it is not so much that things become sibilant. Comparing to the Beyer T1, these have not nearly as bright treble, and I much prefer these over the T1s.
 
Bass extension is AMAZING on these. Sure I haven't listened to the other Hifimans or Audeze planars, but I have never experienced planar headphones before the 400is. Compared to everything I've heard, these win in bass extension hands down. They have the perfect amount of bass for me, I would call ever so slightly more than neutral, which I like. I just love the detail and the way they make things sound. The mids are great, but I do prefer the HD 650 mids over these. They are very close to the 650 mids, a little less smooth however.
 
I have 2 minor complaints for the HE-400i: the cable, and the fit. The cable terminated to a 90 degree angle 1/8th jack, which is very odd considering most headphones like this have a straight jack. But, the quality of the cable makes up for it, being completely cloth covered until the end of it. The fit for me is ok. I have a taller head than most people, so I have to click the headband adjuster all the way up for the pads to fully cover my ears. If the adjuster had one less click from the top, I would not be able to pull the pads down over my ears. So if you have a large head like me, see if you can try them before buying, because what's the point of having a headphone if it doesn't fit. The build quality however is extremely impressive, these feel more like $800 headphones than the $499 listing price.
 
If these sound so good, I can't wait to hear the HE-560s. I had my doubts about Hifiman before, but these guys are the real deal and make excellent quality headphones. I got these open box for $389, and even for the listing price of $499, I'd say these are well worth it. 

This is my second actual IEM purchase, and I have to say, I'm very surprised. These have a more enjoyable and pleasurable listening experience compared to the Shure SE425, which sounded dry and lifeless in my opinion.
The Klipsch X10s have bass extension to die for. These things pack a bigger punch and impact than the Sennheiser HD650s. They are perfect for rock, pop, and pretty much anything else. One thing these really shine at are binaural recordings. Ive noticed with listening tests that IEMs do a better job recreating a binaural experience than open back headphones, at least for me. This is probably due to the way binaural is recorded, with the mic near or inside the ear canal. So, they sound extremely realistic, and very balanced.
Some people complain these have too much bass, but for me they are absolutely perfect in that regard. They resemble the overall sonic signature of the Sennheiser hd 650, which i love. The only thing i would list as a con is the pressure you feel when getting a seal, but thats for every other iem i suppose.
Even for $200, these are worth it. I got them for $125 on Amazon. Highly recommended!

EDIT: 7/7/16
 
I am redoing this review I posted in 2015 because it was too short. For this review of the HD650, I will be going into much more detail about the sound, pros and cons, certain tracks that make these headphones shine, and how DSP plugins can make this headphone (or pretty much any headphone) come alive.
 
First, let's go over the build quality and comfort.
 
The HD650s are completely plastic on the outside, except for the metal grills and metal adjustment band. For the 2 years I have had them so far, there have been no paint chips or places where the paint has rubbed off from use. Keep in mind, I have taken extremely good care of them, and made sure to never place them on hard or rough surfaces. If you do that you will find the paint will come off eventually as others have said in their reviews. I really like the gray color all around, and personally like it better than the HD600 and HD580 design and color.
 
These are the second most comfortable headphones I have owned, right behind the Beyerdynamic DT800/T1. The clamping force is tight at first, but over time it loses that tightness and stays comfortable. I have a narrower and taller head than many, so I need to click the headband adjustment down 9 clicks in order for it to fit over my ears. These also weigh very little, and there have been times where I've worn them for 4+ hours and forgot they were on my head. I used the original pads for about a year before I replaced them, and then recently replaced them again a few month ago, but they have compressed quicker than the other 2 pads for some reason. I suggest before you buy replacement pads for these, make sure they aren't fake and are from an authorized Sennheiser seller or from Sennheiser themselves, because I may have gotten fake ones since they got flat in less than 5 months. Flat and compressed pads really affect the sound negatively and caused my pair to have more bass in one cup than the other.
 
For reference, I am using the JDS Labs ODAC with the Objective 2 amp. Yeah, many people on this site will criticize me for using such a “lowly” source and amp, but they sound good and are neutral and flat, as they should be. The O2 powers my HD650 very well. Also, I do not believe in cables making a difference in sound, so I am using the stock cable, which is plenty durable enough for years of use. Let's just say I'm a bit objective when it comes to audio tech.
 
 
If I were to describe the HD650s sound in one word, it would be natural. Very natural, smooth, and non-fatiguing. I remember first listening to these, and saying to myself, "FINALLY! A headphone I can LISTEN to!" These have no exaggerated lows, mids, or highs. I keep telling people that these remind me very much of high quality speakers. In general I like the way speakers portray music more than headphones, but I am starting to rethink that as the HD650s immerse you even more than speakers in my opinion.
 
Starting with the lows, these have a somewhat relaxed bass tone. The sub bass is definitely there, but is not emphasized, and may be very slightly rolled off. Compared to planar magnetics, these lose the sub bass battle, but I am ok with that. I have experimented with EQ in the 25-50 Hz range, and found if I raise this area by about 4 decibels, the sub bass is more present and not distorted at all. The mid bass and low mids are raised ever so slightly, giving the headphones that lush and warm feel I love so much. Yet, it does not affect the rest of the frequencies, and makes recordings with little information in this range sound smoother and and less analytical.
 
The mids are where this headphone beats pretty much every headphone I have tried ever. The mids are incredibly realistic and natural, and makes instruments sound like the instrument they are supposed to be. Compared to other headphones such as the Hifiman HE-400i, Beyerdynamic DT800, and even the T1, the mids outclass them all because of how natural they sound. I feel with those other headphones, the mids are overshadowed by the higher treble response giving the impression of the mids being sucked out. They have more of a V and U shape response as opposed to the HD650s flatter response. Yes, many will say the mids in the HD650s are emphasized and too lush, but the very reason I have fallen in love with their sound signature is because of the smooth mids and treble. Many headphones just sound too analytical and sharp in the mid to treble region. Not so with the HD650s.
 
Speaking of treble, these have probably the smoothest treble I have heard from any sound reproduction device, speakers included. There are no peaks in the treble, and that is why these sound so smooth. These are never fatiguing, and are perfectly suitable for even the worst recordings (examples of which I will add to the music section). And with that note, there is something very important I need to address about the HD650s: the dreaded “veil”. Simply put, these have no “veil” and I don't understand why people keep saying they do. The high frequencies are present, and do NOT roll off. The treble extends all the way to 20 Khz, and frequency graphs support this. Perhaps before these headphones got revised in 2007, they had some sort of veil. But this new version has just as much extension as the HD600. So, these have plenty of treble detail and extension, just enough for me to not get fatiguing. Sure, compared to the T1 and Hifiman HE-400i these have less treble quantity, but the quality is exactly the same in my opinion. Even if the treble is less present than many headphones, I find it strikes a perfect balance between natural and realistic.
 
 
Now, I will list a number of music examples that I find bring out the HD650s strengths, and maybe a few of it's weaknesses:
 
 
 

 
 
This is a very well recorded piece of classical music, a genre I find the HD650 to excel at. In the beginning and in the middle of the piece there is a timpani on the right side and with the right headphones, sounds incredibly realistic. The HD650s make me sometimes believe that the players are in the same room! Just goes to show that with well recorded music, headphones sound their best.
 
 

 
No doubt everyone has heard this electronic piece from the 80s. This is one of the better recorded versions, and really shines with headphones with extended bass. The HD650 doesn't do as well in the sub bass as say planar magnetics, but I find them to be at a realistic level of what the mastering room would have heard the recording. If I want a little more bass, I just EQ the 25-50 hz range up a few decibels. Also, there are subtle treble details in this composition that the HD650s bring out beautifully.
 

 
Bet you saw this one coming, an extremely popular song that sounds incredibly good on good headphones. In particular the vocals are without sibilance and the drums are at the perfect level. The HD650s bring so much out of this recording, including the detail in the drums. Why can't music be mastered like this anymore?
 
 

 
I put this one on here because it is a harsher recording. The solo vocals were obviously recorded with a lot of compression and sounds like someone turned the treble all the way up on their big chunky 80s equalizer. On the Hifiman HE-400i and Beyer DT880, this song is almost unbearable. But, the HD650 tones down the harshness just enough, but still is revealing of the harshness.
 
 

 
Yes… I know… It's a Backstreet Boys song, but bear with me here. I chose this song solely for the only reason to show how the HD650 makes harsh recordings sound better. This one, in my opinion, is even harsher than Broken Wings. At the 0:48 mark, there are cymbals and really harsh vocals that have a lot of presence. I've listened to this on the AKG K712s, and it is downright PAINFUL. Thankfully, the HD650s save the day once again, and turn down the harshness just enough without sacrificing detail.
 
 
 

 
This is an incredibly beautiful rendition of Pachelbel's Canon in D. And, it is spectacularly recorded too. With the HD650, it's easy to get lost in the sea of the ambiance this piece has. The slight mid bass bloom the HD650s have make this piece incredibly immersive and lush. And everything sounds very realistic, especially the strings and plucked instruments. 
 
 
 

 
This is extremely impressive on any headphone, but especially the HD650s. The cello on the left at the beginning is so darn realistic because of the binaural recording that Dr. Chesky did. Really, you can't go wrong with any of the binaural tracks that Dr. Chesky has made, because they are meant for headphones and make you feel like you are really there.
By the way, I didn't purposely pick videos that have the same music album info layout, those were just the best quality I could find on Youtube.
 
 
 
Next, I want to talk about how you can squeeze every ounce of sound quality out of the HD650s: Digital Signal Processing.
 
Many people are very much against DSP plugins, but if you use them the right way, it can be a transforming experience.
 
There is a software plugin called Sonarworks Reference 3. Used mostly by recording engineers and music producers, this plugin takes your headphones or speakers and calibrates their frequency response to be reference monitor flat. Basically, the program equalizes the response of your set of headphones, and makes them suitable for mixing and mastering in a studio.
 
 

 
 
 
As you can see here, the program takes the average frequency response of the HD650 and corrects any deviations from whatever curve you select, whether it be flat, B&K curve, or your own custom curve. The blue line shows the average response of the HD650s, and the green line is the correction curve. It claims to have an accuracy of +- 3 db across the whole range, and it certainly sounds like it to me. They also have an option to send in your headphones to be measured and calibrated, having an accuracy of +- 1 db. This is a very good option for those who want the convenience of headphones, but have the sound of accurate studio monitors. Or, like me, someone who want the most accurate sound possible. I have also tested the AKG K240 Studio with this software, and to my surprise they sound strikingly similar to the HD650 when calibrated, at a significantly lower cost. The correction curve makes the HD650 have great sub-bass response, less mid bass bloom, and even smoother more present treble. Even with the default calibration, this program makes the HD650s sound like speakers, and that is what I've always wanted in headphones.
 
 
 

 
 
The fun doesn't stop there! I have been using the ToneBoosters Isone VST plugin for about a year, and it wasn't until I used it with Sonarworks that I was blown away by it. Essentially, this plugin gives you the option to emulate a 2 channel studio environment, complete with room size, reflections, and even an anechoic chamber. I use this plugin mostly for it's crossfeed settings, but with the addition of the Sonarworks software, the results are shockingly convincing. After adjusting the HRTF to meet what I find my head and ear size to be, I could swear there are speakers in front of me producing the sound. This is what I imagine a poor man's Smyth Realiser would be. In fact, I would go so far as to say it sounds better than a really good 2 channel speaker system, because you have a controlled simulated environment without any room imperfections or resonances. Technology has really come a long way with these plugins, and I wouldn't be surprised if 3D audio became a mainstream thing in the years to come.
 
Comparisons:
 
Vs. HD580
I bought the HD580 2 years ago before I had the HD650, but I remember the sound well enough to describe the comparisons between the two. The HD580 did not have enough bass for me, and they seemed to roll off to my ears in the upper treble. The HD650 is more extended at both ends, is warmer, but has pretty much the same midrange. Since the HD580 and HD600 are similar but the 600 is an upgrade, I would assume the HD600 has just as much extension as the 650.
 
Vs. Hifiman HE-400i
These headphones were amazing when I tried them. I was floored by their flat extended bass all the way down to 20 hz. In the end I returned them because they were too analytical sounding for me. There was enough bass, but the midrange was overshadowed by the treble peaks and made things sound unnatural in the end. However, these do have better treble detail than the HD650, but it is directly a result of higher treble response, not of treble quality. In fact, I have experimented with EQ to raise the HD650s treble higher, and got a very similar result of higher treble detail. So, these beat the HD650 in sub-bass only for me. Also, I would say the HD650s have better soundstage than the 400i.
 
Vs. Beyerdynamic DT880 + T1
It's been a while since I have had these two headphones, because I have sold pretty much everything since I started using the 650s. Both Beyerdynamics have great treble detail and clear crisp sound. However, I did not like either for long listening sessions, because of the painful treble peaks Beyers are known for. Compared to the 650, both Beyers have less lush mids, more treble, and about the same bass, but both are more extended. These both are on the list of the Sonarworks software, and I have yet to try them with it, as I am sure the software will tame the peak very well.
 
Vs. AKG K712+K612
Again, it's been a while, but I remember the AKGs excelling in soundstage only. The K712s had slightly more extended bass, but lots of mid and treble peaks that made things sound weird. The K612 had less peaks, but the midrange was a bit unnatural and analytical. Again, the K712 is on the Sonarworks plugin list, so these can be corrected to sound flat and probably maintain that better soundstage.
 
 
Final thoughts:
 
 
I have gone through at least a dozen headphones in the past 3 or so years I got into the hobby. I have since sold pretty much all of the ones above $200, except for the HD650. That should tell you how good they are, that they even outclass the flagship Beyerdynamic T1 in my opinion, at least when it comes to natural and realistic sound signature. I have yet to try the HD800, but if I were to make a prediction, I probably will still like the HD650 better. If you are into lots of treble detail, these will probably not be for you. But, if you like a smooth sound without peaks across the whole frequency range, these should be on your list to try. Thanks for reading!
 
 
 
 
 
 
 
 
 

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

Today I got scared a little because this $50 portable amp sounded pretty much on par with the O2 amp. Yeah, really, it did! 
I bought this thing last summer, and I didn't realize how good it was until I compared it to my recent purchase of the Objective 2 and my two vintage receivers. Bass is nice and controlled, mids and treble are right where they should be. Overall, a very nice balanced sound. And best of all, it can drive pretty much anything up to 300 ohms. It even sounds great with the Beyer DT 880 and Senn HD 580. 
 
For $50, this is a STEAL, highly recommended!

I've had these for a few months now, and more recently have got to try them with the ODAC+O2 amp dac combo. 
With the O2, I am extremely impressed by the detail and lifelike presentation the Beyer brings. Sure it may have recessed mids, but I'm actually a fan of the V shape sound sig. It brings more excitement and makes things less boring to listen to. However, it sacrifices a fuller sound than some headphones to achieve this. 
I have also tested this with my Nakamichi CDP-2A + TA-2A receiver, and it makes the Beyers even more fun to listen to, while adding more mids to make the experience even better. 

When I compare these to the newer Studio K240s, these win by a long shot. Not only in neutrality and detail, but in build design too. 
The Studios have a big mid bass hump that makes everything sound boomy. But the Monitor version has a very balanced frequency response that sounds almost perfect. To me, the treble is very good, but I dislike the spike most AKGs have in the 8-9 kHz range, these included. Although not as apparent with classical music (which these are great for btw), rock and pop and singing definitely is sibilant after a while. That being said, the treble adds to the detail retrieval, which may be why these are meant for studio monitoring use. I also LOVE the mids on these, and they are the phones strong point. Mids are better than the HD 600s IMO. That being said, the soundstage is kind of small compared to many headphones, but still ok. 
I also have noticed the bass could be a little more, as it rolls off quite a bit in the sub bass.
 
EDIT: 6/3/14
I have tested these with both the ODAC+O2 combo and my vintage Nakamichi TA-2A + CDP-2A. Sounds amazing with both of course, but I prefer the Nakamichi as it powers it better and gives a little extra bass boost and it also smooths out the treble a bit. It's also meant to be driven from those kind of sources. With the ODAC+O2, its a little sibilant and bass could be a little more, but this is because of the neutrality the O2 brings. This headphone would do quite well with warm dacs and amps. 

This is my first review, but I will try to make it fast and straight to the point.
 
I just received the HD580s from ebay, and before I bought them I did some research and found out these have the same drivers as the HD600s. However, that doesn't necessarily mean they sound exactly the same. But, I don't own the HD600s, maybe in the future I will. 
 
I opened them up, and while they are used, they look very lightly used, except for the ear pads, which are filthy (and smell.....ewww)
But anyway, they came with the stock cable, and without the 1/4 adapter unfortunately, so I couldn't hook it up to some good amps yet.
 
I plugged it in to the FiiO E11, which is connected to my ipod. First thing that I noticed was how amazingly balanced the sound was! I own the Beyer DT880, AKG K240, K550, ATH-M50, and the Shure SRH-940, and it is more natural sounding than ANY of them. That is what I look for in headphones, a nice, clear natural sound. It's almost like sitting in front of speakers, just enjoying the music, rather than complaining about how there's "not enough bass" or whatever. For once, I could just enjoy my music. 
 
That being said, people who prefer super detailed highs need to look elsewhere. These will not do that. I suggest the Shure 940s for emphasized treble detail retrieval. However, I think these are very detailed throughout the whole frequency range. 
 
Edit: 3/22/16
I have sold these headphones shortly after I did this review in order to try the HD 650. The main difference between the HD580 and the HD650 is the bass quantity. It has been about 2 years since I have heard the HD580, however I remember the bass not being as present with them. The 650s change that, with more bass from 200hz downward, giving more impact. The highs surprised me a little, as I remember the highs actually being less present in the 580s than the 650s. This may be because there are more forward mids in the 580, giving the impression of laid back treble. But to my ears, the HD650 has more treble extension with better detail. None of this "veil" people go on about.  I want to eventually buy the HD580s again to compare directly, for the price you can get them they are honestly a steal, and you are probably getting 95% of what the HD600 is for more than half the price. I have never heard the HD600, but I believe between the 580, 600, and 650, it is a difference in your preferred sound signature rather than sound quality. I do prefer the HD650 sound however. 
If you want a comfortable, neutral headphone with enough detail for critical listening, or just sitting back and listening to music, these are for you! Highly recommended!  
 
edit: 5/29/14
I have tried these with the ODAC and O2 amp, more detailed but still the same natural presentation I felt with the E11. I think the ODAC and O2 bring out the best of the HD 580, while adding some more treble detail some might find missing in the HD 580 and 600.