I've listenend to all the top offerings from Denon, Beyer, Audeze, AKG, Hifiman, Ultrasone & Sennheiser and this is one of my personal favourites. It is a true reference headphone that is very natural sounding, albeit leaning ever so slightly towards a darker tone. The sound is detailed, smooth and richly textured, especially drums and vocals come alive amazingly well. It has no problem spanning all the way from the deepest bass to the highest highs with supreme control and plenty of muscles to spare.
 
For the money I think this is a real audiophile bargain; the HD650 exists on that plane of ultimate performance where musical enjoyment no longer becomes a factor of sound quality, but rather personal taste. It really doesn't get much better than this no matter what you pay. The HD800 has better resolution, speed and spacial presentation - but can be a bit cold, analytical and unforgiving. The LCD-3 is arguably a higher-performing heaphone, with amazing resolution, extension and control, but in my humble opinion it can sound a little dry and laid-back compared to something like a HD650, Grado, Hifiman or D7000 which are more "fun" and energetic and with a more "forward" sound.
 
So in short - the HD650 I think is truly great, not unbeatable in specific genres but an amazing allrounder. It should however be said that it only truly begins to show what it can do with top notch source and amplification - I wouldn't recommend driving this beauty with anything like a phone or Mp3 player due to its rather high impedance and revealing nature.
 
Although "revaling" is also a relative term since they are infinitely more forgiving towards bad recodings than a HD800 or LCD-2/LCD-3. It should also be said that I do think they exhibit a slight veil (this eternal debate) but ONLY at low listening levels - so that those who find themselves always listening at very low volumes might want to also consider something along the lines of a grado reference headphone which are known for their "intimacy".
 
All in all the HD650 is a superb headphone that comfortably matches, or beats, competitors at more than three times its price (not joking). A superb allrounder with a fun and energetic play-style, detailed but not too unforgiving - not to be overlooked! Seriously.
 
Edit Sep 2016: I've increased these back to 5 stars again. After changing DAC and some other system tweaks I managed to elevate my HD650's to a yet another plane of performance. They just scale like crazy and completely unlike any other headphone in this price range with the exception of the HD600. Sorry for the confusion.

one of the best sounding headphone.

These are a great pair of cans all around. Very few complaints. Fantastic value. I've been driving them with E17 / E09k - it may not be perfect but it sounds great to my ears!
 
These are the kind of headphones you forget you are wearing because they are so comfortable. The rolled off treble is great for long listening sessions.
 
I find that I tend to use them when I want my experience to be a little bit hands-off. The sound, the feel, etc. is all very comfortable. The bass is a little bit underwhelming, but it fits the 'comfortable' experience.  They are nonetheless quite detailed. They aren't bad at really low volumes, but I am more likely to reach for my grados if I want really low listening volume with clarity. 
 
The build quality is quite good. I am worried about the paint chipping though. 
 
They are a massive step up from entry level headphones and IMO about 75% of the way to hi-fi headphones (e.g. LCD3). 
 
In my opinion they work quite well with all genres of music, but are a little bit too laid back for rock. 

Thumbs up! 

My reference for reviewing the HD 650 is the AKG K701. I've used the HD650 with various amps and sources including the Nuforce HDP, Headroom Ultra Micro Amp (now discontinued), the Beta 22 (2 channels), Musical Fidelity M1 and the ALO Rex MKII. Sources included Marantz CD5003, Ultra Micro DAC (discontinued), Ultra Desktop DAC (discontinued) Nuforce HDP and Centrance DACPort LX.
 
I think many reviewers have already talked a great deal about the characteristics of the HD650. Most of them have better experience and probably are more capable of discerning the pros and  cons. I only wanted to add a few points regarding classical music listening.
 
Some listeners shy away from the HD650 when listening to classical for their dark sound and lack of airiness but for my ears they are suitable for the genre. First of all they have a beautiful natural tone for strings and winds, in comparison to the K701 which has an anemic neutral to bright tonality. The HD600 has a similar tonality to the HD650 but IMO the latter is more refined, less grainy and enjoys a better sound stage and imaging. The only drawback is the HD650 need for a neutral to bright system to sound their best. With some set ups it can sound too dark and dull. I heard them at their best with the Beta 22: a very big and tall soundstage with exceptional depth and detail. 
 
When listening to orchestral music on the HD 650 there is more weight and impact. The experience is closer to live performances in comparison to K701. There is also more emotional involvement, using the K701 is like reading the notes, while both HD600 and 650 reveal the mood and the feelings of the piece. In other words, listening to the HD 650 is like being in the concert hall, while the K701 experience is closer to being in the studio. 
 
The HD650 is more forgiving with older recordings. Classical gems like Arrau's recordings of Beethoven's piano sonatas or Oistrakh glorious recordings of Prokofiev and Shostakovitch can't be rendered with revealing headphones like the K701 or the HD800.
 
It's also much easier to match the HD650 with the right DAC and AMP in comparison to the K701. Actually the HD650 is an excellent performer with high grade equipment and a steal at its current price (around $300 used). For the K701 it's very hard to find the right amp to pair with it, it sounded at their best on the Luxman and MF M1 HPA amps. 
 
The K701 is definitely more airy, with a wider sound stage, but the warm tone of the HD650 provide a solid placement of instruments in space. Sometimes I feel the K701 too thin sounding for complex passages compared to the HD650. 
 
This review was done on mid fi gear involving Cetrance Dacport Lx and ALO RxII. 
 
Update 03/28/14
 
I did an extensive comparison on the current set up: Flac and Aiff files played by Audirvana plus on a Macbook computer. The macbook is connected by optical cable to Headroom Ultra Desktop DAC. The UDAC is connected to Musical Fidelity M1 headphone amplifier via DiMarzio RCA cables. 
 
On this set up the AKG Q701 is performing very well indeed. The highs are smoother and the sound is more open, with fuller, richer and clearer mids. The imaging and the depth of the soundstage have been immensely improved. In short I feel that the Q701 and the MF M1 amp are very good combo, much better than the HD650 combined with the same amp. Probably the M1 being slightly warmish works better with brighter headphones like the Q701 and the HD800. 
 
The HD650 is certainly more fun to listen to, but the Q701 is more detailed with a wider and bigger sound stage, better imaging and more extended treble. But the tonality of the HD650 is more true to life, where K701 sounds pale in comparison. When listening to the HD650 you feel like living inside the music, while the Q701 is more objective and cold. The mid on the HD650 is rich and has a palpable presence, compared to the thinner mid on the Q701.
 
 
Of course these observations are purely subjective, and based on my experiences with different set ups. 

These headphones are a true classic!  Even if they are bettered today by some in technicalities, their sound signature and non-fatiguing nature remain a must hear in today's very crowded mid-fi range.  However, you'll need a good source (they're quite forgiving on the quality of the recording though) and an amp that can drive them to their full potential since they scale very well with high end amplification (in my case the ALO PanAm dac/headphone amp).

These headphones are superb in their presentation of rich, harmonic tones. They are not in your face headphones... the bass doesn't have the visceral impact of other headphones, and the highs are not cutting or piercing in any way. These headphones are smooth in a way that other headphones just can't match... they flesh out the tonality of the music, and present it as if you were sitting in the tenth row. You're left to close your eyes and take it all in, without it being pushed at you the way newer, more exciting headphones may do.
 
The midrange can be lush, organic and supremely holographic with the right gear. The bass is controlled, slightly emphasized compared to completely flat headphones, but in my opinion, there is just enough emphasis to keep things sounding balanced. I'm not left focusing on the impact of the bass, or the sparkle of the treble. There is some of that, but the real star of the show is the smooth, romantic tone. Guitar and vocals really shine for me with the 650's, in a way that is just so natural and smooth. The long listening sessions without any kind of fatigue make these headphones a true classic.
 
If you're looking to drive these headphones to their full potential, I would recommend a good OTL amp. The Bottlehead Crack, Woo WA2, or the LaFigaro 339 are probably the three that really bring out the best in these headphones. If you're looking for a cheaper solution, go for a DAC/amp combo that uses a tube... the Aune T1, or the Project Ember. Without one of these, you'll most likely find the 650's to sound somewhat unexciting, especially if you compare them with newer headphones. This is usually why a lot of people end up selling these headphones, moving on to better gear, and then buying them back. You've been warned! For the low price they're selling at now, they are well worth keeping and enjoying.

I love my HD650 for rock, jazz and weightier orchestral pieces. The sound is very detailed but somehow dark (which is good with some recordings). This headphone never sounds obtrusive or hard. It is very comfortable. I have it as a companion to another great headphone, AKG k701, and they work great with their parts of my record collection.

Superb headphone, that has excellent detail, amazing soundstage, very nice highs, mids, and a very tight and detailed bass....but to get quality like this, I'm using a blue dragon v3 headphone cable, little dot mk3 tube amp, and playing CDs though them....but even with a modest setup, you will still greatly appreciate the sound that these headphones can put out! Give the hd650's about 100 hours of break-in time, and you will truly hear what they can offer....all in all, STILL one of the best headphones out there....buy a pair, and enjoy! today I started using my hd650 headphones with a full sized CD player, with built I'm dac, and other very high end parts...NOW I'M REALLY IN AUDIO NIRVANA!! DOESN'T GET BETTER THAN THIS!

I am by no means experienced in this field. I am a poor 18 year old who spent a lot of time dishwashing in order to support his unreasonable obsession with great sound.
 
When searching for my perfect headphone, I narrowed down my choices to two headphones: The Sennheiser HD650 and the HifiMan He-400. I originally picked up the HifiMan He-400s and spent a month with them before parting. They sounded great and were built like a tank, but I knew that the ortho sound wasn't for me. The sound was too fatiguing, and this was exaggerated by the poor comfort that they provided.
 
My next step, obviously, was to pick up the Sennheisers. As soon as i put them on my head, i knew these were right for me. Comfort was above (my admittedly high) expectations. I could sleep with these babys on, and the sound exceeds their comfort. The smooth, romantic sound woes me in every time. These are the cans that you could listen to for days. 
 
The Sennheisers gave me what I ultimately wanted. And that was to have sonic nirvana poured into my ears for hours on end. I can slip these on and do my homework without being interrupted or l can critically listen to some vinyl.

e
 

After owning the HD of 650 for two months it is time to do a review. With that time I was able to get the Vallah 2. I was using the Magni 2. The OTL tube amp is a game changer for this headphone. I wish I had a better solid state amp to do a better comparison in sound quality. The OTL amp makes everything sound richer,slightly warmer, and more soundstage with the HD 650.  

To begin this review of the HD 650, I listen to a variety of music (classical, EDM, theory, rock, and animation to name a few) preforms well in these genres of music. Overall I enjoy the sound of HD 650. Imaging on this headphones are extremely. Soundstage great; it does wonders with live recordings. Bass on these are exceptional for an open dynamic headphone which makes it a worthy upgrade from the HD 598. Mids are awesome on these amazing. Highs on these are solid --not too much harshness on them (2.5k and 7k region).Details on these are amazing . For an example, I can hear the way of a guitar is strummed and hear the room. Thus, I find the tone of the headphone very well balanced for my sensitive ears.       

Comfort on these are very good. The headband is very comfortable. It has little pressure to no head pressure on them because of the  headband spectacular design.  Earpads are alright. It also has a light clamp. These headphones are so comfortable that I can listen for hours at a time with these on. 

My final thoughts of these headphones that they are very solid pair of headphones due to the great sound that they can produce as well as the great comfort. These headphones changed the way I proceed sound. In my opinion, I believe everyone should try these out.  

Awesome headphones. Perform a lot better with good amplification. Good for almost every genre of music. Bass response is already good, can get even better and tighter with amp. Extremely lush sound signature. You can spend hours with it without getting fatigued by sound. Treble, though sparkling, sounds bit rolled off but that's how they can be so relaxing to keep listening forever. Only area where these headphone leaves you feeling want more is build quality. Plastic used is strong but at the price tag doesn't justify the use of plastic.I really liked to see what Sennheiser done with Momentum they could have done similar with looks department of these headphones after all its almost 10 year old design.

I bought these used in near mint condition and they were already burnt in.

The so called Sennheiser veil won't bother you that much. You might notice highs rolling slightly off on instruments like harps. Some headphones might make Loreena McKennitt's harp playing almost pinch your ears, but on HD650 it's a pleasure to listen to.

I have never owned headphones of this quality before and it was something of a revelation to hear FLAC files through these headphones. Suddenly I heard details and sounds never heard before even though I have owned some of my CD's for 23 years.

These headphones obviously needs a separate headphone amplifier whether you're going to use them on your portable rig or on your stereo. Ordinary portable mp3 players can't play the HD650's high enough and the headphone amps built into CD players and pre amps might not be of good enough quality to take fully advantage of the HD650's.

I had several of those (balanced and unbalanced) and I liked them alot.
I can't remember if they had the newer "silver" drivers.
I compared them with the HD600 and they sounded better.

From a post of mine:
I realized something about the HD650, now that I'm listening to my 2nd pair (rebought ~6 years after selling my 1st pair): an immature listener might completely under-appreciate what they do, how they present recordings, have no idea and then just sell them like I did. It took me that many years to understand what I want and what I hear... It's hard to explain but at the moment I feel like these bastards will only be sold if I go deaf. They're just so competent, they shift my attention to music. The detail level is really good and the way they image is sorta enigmatic but competent and engaging. I can't say that I miss the soundstage or sub-bass of my bass-port modified Q701. It's like when you listen to HD650 you're in a world where other headphones don't exist, or the things that HD650 are incapable of are just irrelevant or don't matter. This second pair smells exactly the same as my 1st (I wonder what psyche-manipulating stuff Senn puts into that fragrance...).

BTW I think it's important to maintain the pads in good shape, replace them once they compress and especially replace them right away on a newly acquired used pair (mine is ~12 years old).

 

Massdrop x Sennheiser HD 6XX Headphones​

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Let me start of by saying this is not what I would call a real review. This is more like a Tribute to a headphone that, while controversial, has been and is irrevocably deemed a classic reference headphone. Not just my posts but many reviews have referred to it or used as a headphone to compare it to.  The disclaimer is that I have known about this release for a while now and have been sent  a pair. Even so, given my long relationship with several pairs of HD650's I have no reason to shill these along side the fact that they will sell out very quickly anyhow. 
 

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I have had 6 pairs myself with the HD6XX being my seventh pair. I have bought and sold this headphones for a myriad of reasons. It always seems to end back up in my stable because I have come to know it as consistently more spot on in tonality than just about every headphone I have heard. Some of the reasons for me selling them so many times was because I sold it them to help fund a new piece of gear or was in a honeymoon phase of something new that outperformed it in a particular attribute. Then later when I knew I had lost my bearings on how things were supposed to sound I would repurchase it again. 
 
Why were people asking if the Focal Elear was the super 650 they have always wanted?
 
Why do people ask if the the new ZMF Atticus are the closed back HD650's they have been longing for?
 
Why when the Audeze LCD 2 was released was it called the planar magnetic super HD650?
 
Could it be because  they are more expensive headphones with a darker than neutral signature? Well if so then why is it much less popular for someone to ask for a super Beyerdynamic DT880? or a super Hifiman HE-500 even? Such an opinionated and categorically diverse thing as music can't possibly have one tuning unanimously crowned as champion can it? Uhhh... well if it did, love it or hate it, like it or leave it, buy it or sell it, the Sennheiser HD650(or even HD600) is unequivocally the closest thing to having that crown as far as headphones go. Sure the HD800 is technically better but just because the prince is younger, brighter,  and faster doesn't make him king. The king would have to die first and as far as that goes the HD650 is apparently immortal. Relatively, the 600 is the more even tempered queen right by his side. 
 
Let's take a look around the web shall we:
This is without searching specifically for the HD650 but rather "best reference open back headphone". Some have their preferences but there is one consistently present. 

A quote from one of all of our favorite sources:
 
- "Well...they've changed their tune a bit with the just announced Massdrop Sennheiser HD 6XX because in this case they didn't change the headphone's tuning it at all. (Measurements show the HD 6XX and HD 650 essentially identical within measurement errors.) No, there is really no reason for them to re-tune the Sennheiser HD 650. They've done their homework. They know that this is widely considered amongst headphone enthusiasts the standard by which all other headphones are compared. I've reviewed them and love them. Yes, there are better sounding high-end headphones, but none deliver the price/performance ratio of this icon."

Read more at http://www.innerfidelity.com/content/if-it-aint-brokethe-massdrop-sennheiser-hd-6xx#qLHs1kALCTYimQT2.99

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Looks / Comfort / Build​

1. Ear pads out of the box are slightly firm but deep and create a healthy distance between the driver and the ear.
2. The ergonomics have proven to be timeless and are a succession of previous designs used by Sennheiser
3. I won't mention the names of other manufacturers but I dare you to find a 650 that was delivered broken through shipping. If it does happen it is a lot more rare than with ____. You fill in the blank. 
4. The clamp pressure can be a bit imposing out of the box. 

 
 

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Sound ​

1. Very dynamic and punchy without sounding aggressive. (Amp dependent so results may vary)
2. Good Microdynamics
3. Great Details
4. Non Fatiguing
5. A chameleon with down stream and upstream gear so heavily manipulatable. 
6. The treble can be grainy and/ or slightly dark to some but is smooth in balance with good resolution and extension
7. Wonderful midrange from the lower midrange all the way through to the lower treble
8. The bass is a bit rounded with a slight mid bass elevation for healthy kick drums
9. The sub bass can sound ill extended at times but for the most part is capable of handling even sub bass saturated genres(yet not effortlessly)
10. Can be modded to have very tight and controlled bass, even better clarity and cleanliness (very easy to mod)
11. Can sometimes sound slow and veiled to some when not properly amped or in stock version. 
12. Very scalable and reportedly becomes competitive with Top of the Line headphones when used with uber quality amplification
13. Soundstage can sound narrow to some but maintains adequate depth and layering for  relatively deep insight into recordings. However, in the grand scheme of open back headphones it usually sounds less wide and is said to have a small soundstage. Again, amping really helps the depth of soundstage increase. 
14. Though some believe it is a darker sounding headphone, It really works well with OTL tube amps and is revealing of system changes and improvements. 

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​

 
 

MODDING​

 
 
There is a coin mod to be done by using a quarter to cut out a portion of the foam covering the drive; a removal of the back cover and adding Dynamat in specific places; and a  removal of  the foam from the back of the driver. (please put the cover back on). Be sure to scour the internet for more specific instructions. Rest assure that these mods are all VERY VERY easy. There are all sorts of mods..even some to make it brighter. 
 
The mods can give the following improvements:

1. Increase of bass control and perceived reach
2. More satisfyingly visceral bass slam
3. Increased speed
4. Faster Decay
5. Crisper and livelier sound
6. More openness and clarity

 
There may be more improvements and mods to do so this is by no means exhaustive, and again just a little boost to get you started. I personally heard the HD6XX and thought that they changed the tuning until measurements confirmed that they actually are the same HD650. I had become acclimated to the tuning of my modded 650 so upon arrival I was very disappointed with the stock bass in comparison as well as felt the headphone sounded slower. For 199 the HD6XX is a no brainer and a modded 650/6XX one will become legend if it already isn't by now...the stock version most definitely is. 

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Amps I have heard the 650 on and personal rankings (of the pairings not the amps themselves)​

• Apex Teton
• Trafomatic Head 2
• Ifi iCan Pro 
• Bottle head Crack and Speedball upgrade/ Schiit Jotunheim 
• Cayin iHA-6 
• Airist Audio Heron
• Nuprime HPA-9 (a bit dark for it but good body)
• NFB - 28

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 HD6XX VS HD650​

 
The aesthetics and accessories are the only thing to compare here really. But eh..why not?

1. The 650 comes with a longer cable terminated in XLR and an adapter for 1/8 jacks
2. The 6XX comes with a shorter cable terminated in 1/8 inch and has a 1.4 inch adapter. Why... possibly to be more compatible with portable amplification and transportable systems. Because by no means is it competitive with 'Beats' since people with those headphones most likely wont be using any amplifier
3. The 650 will still have the more luxurious or classy paint job as the 6XX is a plain midnight blue that can look black depending on the lighting used. 
4. Through and through the build quality is the same and they measure the same as well 

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Conclusion​

When I started the "Massdrop Collaborations...What If?" thread almost a year ago I expressed how my choice would be for a 650 collaboration. While not quite black, I am sure Sennheiser had their reasons and I am very happy that this headphone is available at price lower than I have ever paid even for a used pair. These are good times to be an audio enthusiast. Not to mention the most recent release of the Schiit Jotenheim, now Music lovers can have a system I used to dream about for a lot less than a new 650 and Bottlehead Crack w/ Speedball upgrade would have costed you back then. I feel very humbled to have been able to witness this re-launching of an industry legend and know tons more people will be smiling from ear to ear as they listen to music "the right way" lol.. just playing anyway you choose is the right way for you.

This is my second-time owning the HD650, and I've taken a bit of this review from a post I made in the HD650 impressions thread.
 
I have some detailed analysis of findings my first time around of the HD650 in comparison with an LCD2 that can be read here:
http://www.head-fi.org/products/audeze-lcd2-planar-magnetic-headphones/reviews/13729
 
I'm going to keep it brief as by now you've probably read gushing reviews, and for the most part they are true. This is a great headphone. Perhaps all one ever may need.

Save yourself and your wallet, get the HD650, a decent amp / DAC and run far away from head-fi and never speak of it again. 

But if you are still here, you may need a bit more convincing. So I have a set of excellent classic LCD2s that measure and perform very well. In my second time owning the HD650, I've pitted them up against these high-end headphones for this review.  
 
The HD650 in my possession, a silver driver variant, is very very close in signature to my LCD2 classic, just a bit more mid forward, and lacking that extreme low-end extension. 
 
My LCD2 have more clarity, and you can really tell with bell tones.  There is a more separation between sounds, the HD650 takes on a slightly bit more of blurred sound in contrast.

But really, I'm splitting hairs. These are exceptional headphones, and damn they are much more comfy and lightweight. 
 
One test I was excited to put them through again was listening to binaural nature recordings, particularly rain, canyons, and deep thunder. Many people talk about sound stage with headphones, but its a mute point to me as the majority of music will have a proper stereo field only with 2-channel speaker setups. Both the HD650 and the LCD2 are capable of rendering 'holographic' spatial reproductions of binaural recordings - with the LCD2 taking the prize in reproducing the low ranges, but the HD650 just edges it out in naturalness on the upper registers, it just seems smoother on the high-end while still retaining detail. LCD2 has more depth though, you can hear 'further' into the soundfield. I've mentioned this in my comparison on these two headphones before, but the 650 has the edge here (it may have a bit to do with the distance of the drivers to the ear, with the 650 being a bit closer than the LCD2). It says a lot for their presentation. Yes, the 650 may lose in some technicalities, but for the most part its presentation is incredibly life-like and natural. Switching, back and forth between the 650 and the LCD2, the 650 just has a bit more 'air' on the top-end that when listening to sounds of wind rushing through a valley, leaves rustling around you, it just creates spine chilling realism. Listening to a recording of  the pitter patter of rain hitting the roof of a tent, something we've all heard at one point, the 650 has the right treble tilt to make this recording a bit more lifelike and 'above your head' than the LCD. Combined with its better ergonomics and light weight, and I'd have to say that the binaural experience on the 650 - the headphones just disappear. 
 
I would love to get a chance to listen to Stax SR007 again or even 009 and run them through some of the above tests. I'm sure I'd be impressed. But one has to marvel at high-quality, especially at the bargain price you can get these headphones for used. If you can afford new, they are still worthy as its hard to find this quality and comfort in its class-range. If you want to spend less, the HD598 is not bad, but lacks the resolution, doesn't quite display audio as natural as the HD650. There are many great and excellent headphones, but myself and many head-fiers, the 650 just fits. I find myself just sinking into these. 

Getting these back again is a real ear opener. They are everything I remembered and even more so. Absolutely (still) world-class. 

If you are looking for a great audio experience and are willing to pay a little bit more than typical price. These headphones are open back, so if you are listening in noisy areas they loose alot of their ability, but in the same light the sound quality is excellent in quite areas. If you plan to buy these headphones then consider using them for home use where you can get to a quite area that you are willing to listen to pretty much just listen to music. Also these headphones are not for everyone, I say this for one simple reason : YOU HEAR EVERYTHING! Literally I was entranced when I first these headphones for a simple guitar riff. Since I play guitar I heard every little imperfection in the note played. But overall these are one of the best headphones that money can buy.

Sennheiser HD 650 
 
COST: $370
 
Background
 
This headphone is well known by many people. With that being said, it is not a "new" model, its been released for a while. It has also been dropped on massdrop as the sennheiser HD6xx, once again returning our attention to the greatness of this headphone. There is also this big question whether they will drop the HD6xx again or not with over 50,000 people requesting it ! 
 
SPECS
 
- frequency response of 10 - 39,500 Hz (-10 dB) 
- High-power neodymium magnets
- Lightweight aluminum voice coils
- 300 ohms 
- SPL: 103db
- THD: less than 0.05%
- Open back
 
Review
 
Design
The headphone is not the stylish headphone but remember these are open back and are intended for home use. It comes in one single silver color although the limited massdrop edition (HD6xx) comes in a midnight blue finish
 
Build Quality
Mostly plastic and the wires can feel cheap but everything works well and most of all comfortable 
 
Sound Quality
Now this is where we talk about the most important thing in a headphone. The sound quality in these headphones are superb. Scratch what you've read from other people because we all have difficulties describing this headphone especially when it comes to the sound qualities. It is the best neutral with extended bass YET still not boring... 
 
Overall is it worth the money?
Absolutely, if you can buy one headphone and you are buying something other than this, you are doing it wrong !
 
AMP/DAC?
yes I highly recommend you use one with these. some recommendations are some schiit products or O2/ODAC 
NOW keep in mind these are "some" and there are countless more others recommend depending on preferences
 
I personally use the DARKVOICE 336SE tube amp with my OPPO HA 2 SE as the dac
 
FEEL FREE TO KEEP THE LIST GOING DOWN BELOW IN THE COMMENTS
 
Mods
there are various mods online that can be done easily to improve bass etc, shoot me a message if you have any questions or difficulties
 
 
SOULSIK LAB SAYS
 
Want me to compare x headphone to these? feel free to message me for extra help ! OR better yet try my pair before you buy them ! HOPE THIS HELPED 
 
review provided by soulsikreviews.com (more detailed review available on the website)
 
video for reference only
 

The HD 650s do just about everything right. Extremely forgiving yet detailed, it makes all music sound gorgeous. Absolutely dreamy, you'll find yourself lost within your music. Much of the sound attributes have been said before, e.g. the warmth and laid-back signature, so all I want to say is that if you ever had to buy a pair headphones solely for the enjoyment of music, pick the 650s. It's an absolute bargain at it's current price.

My only complaint is in aesthetics. If only it would look as beautiful and elegant as it sounds. Although, not really a complaint as the sound takes precedence and it's really not that ugly. Could use less plastic though.

Everything sounds great, extremely clean and extremely detailed on the HD 650.
 
Fantastic clean sound, fantastic resolution, fantastic tone, warm, extremely well balanced, great bass (not boosted), very detailed sound, well separated instruments, very present sound, great sound stage, the highs and mids are smooth, clean and sound very musically.
 
And how about the infamous veil of the HD 650? It, definitely, does not exist. Perhaps on the old models, with the black drive, it could be true. On my new model, with the silver drive, there is absolutely no veil.