650 has the original pads and the 600 has oem recently purchased pads for reference. They look relatively identical to me. No audible difference either.
1 Like
@kcrack That could very well be true. Iâm going to get a pair of stock pads and keep them in a closet as extras for when these get old and feeble. It would make sense that they change to that color in time depending on the environment. My place is very dusty and we constantly dust so I can see mine turning a shade of that color over several years.
1 Like
INTRODUCTION
Iâve had the HD6XX for about a year. I wanted to get a review of it up here on HFGF. Because the 6XX/650 is such a well-known headphone I thought it would be useful for HFGF readers as a baseline reference. Also, this headphone has been around long enough that there are dozens of reviews out there. This review will then give readers an idea how my opinions and tastes compare and contrast with many other reviewers. I have tried to make this review âscale-ableâ by making it clear what parts are targeted to newer audiophiles and readers who havenât read my other reviews on this forum and which parts are more useful for more veteran audiophiles. Alright, letâs get to it.
KNOW YOUR REVIEWER (skip this if youâve read lots of my posts on this forum)
My preferred genres are rock/metal and classical/orchestral music. Iâm getting to know jazz more and enjoying quite a bit. I also listen to some EDM and hip-hop. My hearing quirks include a high sensitivity to midrange frequencies from just under 1KHz to around 3Khz, give or take. My ears are thus quick to perceive âshoutinessâ in headphones in particular. I describe âshoutinessâ as an emphasis on the âouâ sound of âshout.â Itâs a forwardness in the neighborhood of 1KHz and/or on the first one or two harmonics above it (when I make the sound âooooowwwwwâ into a spectrum analyzer the dominant frequency on the vowel sound is around 930Hz, which also means harmonic spikes occur again at around 1860Hz and 2790Hz). In the extreme, it can have the tonal effect of sounding like a vocalist is speaking or singing through a toilet paper tube or cupping their hands over their mouth. It can also give instruments like piano, but especially brass instruments, an added âhonkâ to their sound. I also get distracted by sibilance, or sharp âsâ and âtâ sounds that can make ssssingers sssssound like their forssssssing esssss ssssssounds aggresssssssively. Sibilance does not physically hurt my ears nearly as quickly as shout, though. Itâs distracting because itâs annoying and unnatural. Readers should keep these hearing quirks in mind as they read my descriptions of sound.
Prior to owning the 6XX I had the V-Moda Crossfade M-100, Beyerdynamic DT990-32ohm, and Monolith M1060. After the 6XX Iâve also acquired Dekoni Blue, HiFiMan HE-4XX, Ikko OH-10, Tin T3, Beyerdynamic DT880-600ohm, HiFiMan Edition XX, and Fostex TH-X00 Purpleheart. Iâve also used the 6XX on combinations of the following amps, dacs, and amp-dacs: Schiit Magni 3, JDS Labs Atom, Monolith Liquid Spark, Loxjie P20, SMSL SP200, Darkvoice 336SE, Schiit Asgard 3, Schiit Modi 3, Topping D10, SMSL M100, SMSL SU-8, Fiio E18, Topping NX4-DSD, iFi Hip-Dac. Iâve even used a Nobsound/Doak Audio tube buffer in the signal chain with 6XX as well.
HD6XX INFO (for beginners)
If youâre shopping around and considering the HD6XX you should know that it is just a Sennheiser HD650 with different cosmetic styling (just a different color), Massdrop branding, and a lower street price. Oh, the Massdrop cord that comes with the 6XX has a 3.5mm (1/8 inch) plug with 6.3mm (1/4 inch) adapter where the 650âs stock cable has a 6.3mm plug only. Other than that, they are the same headphone.
BUILD (if youâre familiar with Senn HD6?? series build, move along, nothing new here)
I donât have much to say here other than âdittoâ to the host of other reviews. The plastic build initially feels a bit chintzy but in time reveals itself to be quite durable. The clamp force is a bit much, but can be effectively stretch it out by putting the headphone over a yoga block for an extended period of time. The earpads are a bit stiff initially but do break in. Itâs also a light headphone. I never noticed any hotspots from the headband.
SOUND
Signature:
The 6XX has a neutral-warm signature with pretty even performance until about 2KHz where the upper-mids and treble start to slowly roll-off. There is a slight audible emphasis on the 100Hz-250Hz which give is that warmth, though. The treble roll-off can at times make it sound lacking in detail; giving it that âSennheiser Veil.â In my listening though, this effect goes away after a few minutes of listening.
Detail Retrieval:
The 6XX is not a detail monster. It tends toward a more relaxed sound, but it would also be a mistake to say itâs NOT detailed. It pulls out a lot of subtle details, itâs just not in-your-face about it. I think midrange suffers the most for detail retrieval, though. The mids can sound excellent until there is a lot going on. They can simply be overwhelmed and lose the ability to separate different instrument and vocal sounds in the mids. This isnât common, but it is notable. A ready example is the song âThe Poet & The Pendulumâ by Nightwish. Somewhere between 7 and 8 minutes into this track, there is a dueling solo between an electric guitar and a violin. Thereâs a full orchestra behind it, a full drum & bass rhythm section under it, and a choir on top of it. The 6XX struggles in this kind of sonic environment.
Spatial Performance:
Um, yeah. If a wide soundstage and pinpoint imaging are what youâre after, look elsewhere. The soundstage is narrow and intimate. The imaging also has a noticeable â3-blobâ effect where thereâs sound in the left, the center, and right, and seemingly not much in between. The intimate soundstage can be beneficial for some music, though.
Timbre:
This is where I have to get controversial. The 6XX â indeed the whole Senn 6?? Series â is widely lauded for its timbre, particularly in the mid-range. There are aspects of the midrange that are really good. Most snare & tom drums sound excellent. The lower and higher registers of pianos also sound quite good. The issue is right around that 1KHz range. The 6XX crosses over into âshoutyâ too often and with too much magnitude for my tastes. This shoutiness breaks the otherwise good midrange timbre. It doesnât just affect vocals either. Some drum tunings can sound overly hollow. Some piano keys get emphasized more others. Brass instruments in particular can become ear daggers. Miles Davisâ trumpet can be very uncomfortable for me at what is an otherwise very listenable level. This shoutiness can be mitigated a fair amount by amp quality and type. The 6XX is very amp dependent and that shows up most in the midrange.
But If You Tube It:
IMO, the 6XX is a good headphone on a solid-state amp for its price, but nowhere near the best option at the price point. What it does on a tube amp though changes the equation significantly. They really wake up on a tube. The bass in particular gets deeper, punchier, and more powerful. Thereâs still not a lot of sub-bass rumble, but from about 50Hz on up there is lots of oomph. The treble also perks up, but not quite to the extent the bass does. To my ear, moving from solid-state to tube amplification takes the 6XX from being a neutral-warm signature to something more U-shaped with the left side of the U being much taller. The soundstage widens out a fair amount as well. They never sound wide like a large planar can, but they donât sound as claustrophobic anymore. Imaging also improves on a tube with some fleshing out of the âholesâ between center and each side. Even so, the 6XX still canât be accused on being pinpoint imagers. At any rate, because of this big change in sound from solid-state to tube amps we need to talk more about:
AMP PAIRINGS
Out of the amps Iâve tried, the best solid-state amp for the 6XX was the Asgard 3. The Liquid Spark was also pretty respectable. Both of these amps keep the shoutiness fairly well in control, but they arenât cures either. The Liquid Spark does have a bit less treble sparkle because it rolls off the highs a bit. This might get sticky for some listeners because the 6XX does not have much treble sparkle to begin with, but some of that treble can be recovered by using an ESS-based DAC. Amps with op-amp amplification like the SP200 and the Atom do awaken the 6XX treble a bit, but donât rein in the shout near as well as the Asgard or Spark. Interestingly, the Fiio E18 did a pretty respectable job driving them despite being a bit power limited. The Hip-Dac is NOT a good match because its Burr-Brown dac chip sucks all the treble life out of the 6XX. I got pretty good results by going DAC-> tube buffer -> Atom, though. The added warmth and bass plus the treble extension the tube buffer added masked some of the shoutiness present on the Atom â but again didnât cure it. The Darkvoice, an OTL tube amp, is by far the best amp I have for the 6XX, though. The 6XXâs reputation for tubing well is no joke.
COMPARISON TO OTHER HEADPHONES
Two other popular open-back headphones in the ~$200 price range are the Beyerdynamic DT-880 and the Massdrop + HiFiMan HE-4XX. Iâll use the 600 ohm DT-880 in this comparison. Signature-wise, the 6XX is neutral-warm, the 880 neutral-bright, and the 4XX more W-shaped. Compared to the 6XX, the 4XX and the 880 can both suffer from some sibilance issues; the 880 moreso. Sibilance is almost never an issue on the 6XX. The 880 offers better bass extension than the 6XX, but not more bass quantity. The 4XX has similar bass extension to the 6XX, but more bass quantity. Both the 880 and the 4XX are overall more detailed, with the 880 leading. The 4XX offers the widest soundstage of the 3, followed by the 880. The 880 images far better than either of the other two, followed by the 4XX. I have to give mid-range timbre and detail to the 880, though. The 880âs mids make voices sound more like voices, pianos sound more pianos, trumpets sound more like trumpets, etc. Plus, the 880 resolves busy midrange much better than the 6XX. The 4XX also has more detailed mids than the 6XX, but does not have the timbre. The 880 and 6XX also both change their characters a lot on a tube. They both get more bass extension and quantity and a sweeter, more natural sounding treble. The change is bigger for the 6XX than the 880. If I could only pick one of these three headphones to have for all of the music I like, the 6XX would be hard to turn down. The 4XX is more enjoyable and engaging for rock, metal, and EDM. The 880 is more realistic and engaging with classical and jazz, and its spatial abilities make it awesome for gaming. But the 880 has an Achilles heel in its sharp treble for rock and metal and the 4XX doesnât have the timbre that jazz and classical really need. The 6XX would be my second choice for each of those cases, (except gaming where the 4XX would be #2), especially on a tube. And on a tube, the 6XX is probably better for rock and metal than the 4XX on solid state (4XX doesnât tube well) for a lot of recordings.
FINAL THOUGHTS
I really struggled with this review and took my time on it. The struggle is with how well-respected the 6XX/650 is in the audiophile community, particularly with its mid-range timbre. But, it shouts too much too often for me, struggles with resolution with busy midrange, and is very amp picky. As my list above shows Iâve tried many different amps and amp types under <$300. The 6XXâs midrange performance changes a lot; enough so that I do believe those lauded mids can really show up with more expensive amps, but I have a hard time justifying buying an amp for a particular headphone that costs twice as much or more than that particular headphone. At that point, I think you should spend more on headphones that match your tastes. However, this particular mid-range issue may be just one for me with my mid-range sensitivity. For many listeners this shoutiness may not be an issue at all. If youâre one of those people, the 6XX becomes a very compelling headphone at its price. For ~$220 you get a good all-arounder headphone. And then you put it on a tube amp and it becomes an excellent all-arounder for the money. In some sense, if you have both solid-state and tube amplification on hand, the 6XX is like buying 2 good-to-excellent headphones for ~$220, for anyone who doesnât have my level of mid-sensitivity. Even with the midrange issues, I spent several months genuinely enjoying the 6XX. Itâs another headphone that Iâve learned a lot from. It was a worthwhile stepping stone in my own audiophile journey, and because of how well-known it is, makes for an excellent point of comparison for a lot of other listeners.
I look forward to any conversations you all want to have about this review. Cheers, all. Enjoy the music!
15 Likes
Great write up, love my pair. I think they are a great companion to my 600âs, canât wait to get my BottleheadâŠ
1 Like
Interesting review. I never found the 6XX shouty. If I had to describe it in one sentence, I think itâd say the 6XX is the pair of headphones I put on if I want to forget Iâm wearing headphones. Thatâs after bending the headband open, of course. Before it felt like it wanted to kill me 
However, Iâve also found that our ears tend to get used to the sound over time, so I might just have gotten used to it, like Iâm almost used to the DT 770âs treble after a week of listening to them.
I think itâs an amazing entry point for anyone looking to get into good quality headphones at a reasonable price. Iâve had them for almost two years and Iâm only now starting to use something else more (Sundara). The only other alternative I can think of at the same price range, that Iâve heard, is the X2HR. It is actually cheaper than the 6XX these days. The Beyers are also great, but I find them to be an acquired taste, the signature and brightness might be hard for a n00b to swallow. I havenât heard the 4XX.
Hey, thanks for the response. I canât disagree too much with many of your points. Although, I do think the Beyers can be a good starting point for a noob provided the get an amp. But thatâs also a requirement for the 6XX. The thing about the 6XX, is it doesnât do much to reach out and grab your attention. But it also - excepting the shout for me - doesnât do a ton to distract you either. Cheers 
2 Likes
Great review! 
I cannot wait to try the 6XX with a tube amp.
3 Likes
Hi everyone! I am thinking of getting the hd6xx from drop. The cable they offer with the 2.5mm is worth it? I plan to buy the balanced 2.5mm cable and the 2.5mm to Xrl adapter.
I would not recommend that. Just get Hart Audio cables. They have a pretty cool interconnect system for any future terminations you may need.
Or if you just need one cable, just get a single Dual Sennheiser to XLR balanced cable.
2 Likes
Any other recommendation besides hart cables and periapt cables? I eventually going to order some hart cables for the future (When I have more gear). For the moment i just need a fast shipping alternative.
If you wanted fast shipping, Drop wouldnât be my recommendation to begin with lol.
Whatâs wrong with just getting a Sennheiser XLR cable off of amazon or ebay?
You got me wrong. I donât mind waiting for the headphones, cable and adapter from drop. Hart cables are good, but just for two headphones at the moment doesnât seem worth it. I will have to order another cable for my t1.2nd ( more money). I just wanted to know if the drop cable was worth it compared to other cable from amazon and ebay for the price 40 if buy together with the headphones. I will definetily buy hart cable if I decide to keep this and have more gear.
Thank you!
In some ways, you might end up saving money by starting with Hart/Capistrano earlier. One interconnect kit allows you to connect to pretty much any source, then just the headphone portion, which arenât generally much more than a half decent full cable from Amazon. I probably could have saved some money that way myself, rather than ordering balanced cables that I no longer use after getting Hart.
6 Likes
Thank you!
Hi, I plan to buy hd650 this month and in the next month amp or balanced cable for my shanling m6. My question is how much power these headphones need because I will be using them for a month with my dap unbalanced and Iâm afraid that my dap wonât be able to power them enough to sound good.
Canât speak to that dap directly but plugged into an iPhone with the volume maxed out (or close to it) I think they sound good enough to tide you over to your cable or amp purchase 
I have recently took off the Dekoni Pads I got sometime after I purchased the 6XX because the stock pads were squeeking and I was in for more bass (normal as a beginner I guess).
Now I understand why itâs said that Sennheisers should stay on stock pads. The 6XX sounds so much better now. Much clearer. The bass region was completely muddy and bass was overshadowing the mids the some extend. At least this is how I feel. They are so much more natural with the stock pads. I guess I simply couldnât get it 2 years back. Happy that I have learned 
4 Likes
Is this the right place to talk about the 6XX? I just want to know if you guys think they sound good off a solid state amp (liquid spark)
Yep! Fire away.
Theyâre ok off solid state. I prefer them off a tube amp but theyâre decent off solid state too. Liquid Spark will handle them fine. The spark rolls off the treble just slightly which you may or may not like with 6xx.
Thanks, I am debating between these and the 58X. For what I heard the 6xx are technically superior but DMS said that âyouâre doing yourself a disservice if you listen to the 6xx without a tube ampâ which just worries me that without a tube amp the 6xx might sound worse than the 58x.
1 Like