I have the 6XX @frudogg and love them, the 6 series from Sennheiser is hard to beat for the money!
Been listening for 3 days now, with these HD600’s…usually I am listening with Focal Clears…but I was rotating thru the three tube amps I have and its day 3 of just absolutley marvelous listening with a Bottlehead Crack with the Speedball CCS update.
Very, very good pairing with these cans…the only other pairing that is really good is the Schiit Vahalla 2 on High Gain. IMO.
Its a light saber, totally enjoyable, musical experience.
As far as punching above the level, these cans are it for sure…Folks compare to 650s and even 800s and some even like these better than the higher cost cans!!
Says somthing for cans to be around for 20+ years!!
Alex
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Can you actually hear the valves distortion on high gain or is it just a matter of more power?
There is no distortion on high gain with the V2 and HD600s.
Its a better impedance and power matching setting for the V2 and the 600’s.
Remember the V2 is still and OTL amp and it works better with high impedance cans…so the HIGH gain setting is best for this pairing…
So in simple terms its more about a efficient power transfer with the higher impedance load.
The LOW gain settings I have used for headphones with 55 - 100 ohms impedance and in one case a 32 ohm headphone…and its not too shabby.
Schitt did some circuit design improvements to make this OTL amp work better over a more broader range of heaphone loads…
Still not for your IEMS!
But with the 600s’ its heavenly IMO.
Alex
NOTE: Schiit has these for $299 in the B-stock DEALS section!
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Thanks for the heads up. My interest in tubes is more to the colors added to the sound than impedance-wise motivation. But it’s always good to have some info on what works and what doesn’t.
The good thing about HD600 is that the majority Amp manufactorers will use these cans for QA/QC testing when developing or troubleshooting the product. Therefore, it is expected to be a good pairing with pretty much anything – as long as power requirements are respected, of course.
To my current listening levels (SPL) though, I can probably even drive my HD600 with my Radial ProD2 direct box in reverse, routed from my balanced Scarlett 6i6 interface jacks. Good experiment to try in these confinement days. 
Revisiting The HD 600 and HD 650 in 2020
Written by Chrono
Introduction
Sennheiser’s HD 600-series is undoubtedly one of, if not the most, successful and beloved audiophile headphone line-up ever created. For many years after their release, the HD 600 ($399) and HD 650 ($499/$220 [DROP 6XX]) were considered by many to be the standard for reference-class headphones; enamouring listeners with a sound that is often described as highly musical, natural, and remarkably accurate. Now revisiting them in 2020 and considering the current headphone market, I want to find out: do the HD 600 and HD 650 still live up to their legendary status?
NOTE: The DROP X Sennheiser HD 6XX is essentially an HD 650 that’s using the older-style HD 600-series chassis and a midnight blue finish. Aside from those aesthetic changes the sonic characteristics of the HD 6XX and HD 650 should be identical.
Sources and Music Used in Listening Tests
The Amplifier/DACs used in this review were the SPL Phonitor XE (with built-in DAC), Grace Design SDAC + Topping A90, and the JDS Labs Element II connected via USB to my desktop computer. For the listening tests I used music from a wide variety of genres including Rock, Jazz, Classical, Acoustic, Hip-Hop, and latin. I played tracks from my own FLAC library as well as from Qobuz streaming service played via Roon (exclusive mode).
What’s in the Box?
Unfortunately, in the latest HD 600 and HD 650 revision, Sennheiser has ditched the rather nice, large case that used to package the HD 600 headphones; the packaging is now identical to that of the DROP X Sennheiser HD 58X Jubilee.Regardless, you still get the same accessories you would have with the previous revisions. Whilst, both headphones include a 3m cable that terminates in Sennheirser’s dual-sided proprietary connectors for the headphone side, theHD 600 terminates in 3.5mm with a thread-on ¼” adapter, and the HD 650 has a ¼” termination and a very short ¼” to 3.5mm cable. Additionally, I think that it is worth noting that the HD 600’s cable specifically is different from that included with the HD 650 and HD 660S. The HD 600 still includes a cable that is very similar to that which Sennheiser originally packaged with it back in the late nineties, and it feels somewhat frail and prone to tearing when compared to the more robust cable that is included with the HD 650 and HD 660S
Power Requirements
Both the HD 600 and HD 650 use a very similar 300 ohm driver, however the HD 600 is rated at 97db/mw, and the HD 650 is rated at 103db/mw. Without a doubt, you will need an amplifier to drive these and get them to sound right. With that being said, I do think that most amplifiers will suffice in cleanly driving these, as they sounded pretty good on entry-level sources like the JDS Labs Atom set to high-gain.
Now, I do not think it is possible to talk about the HD 600 and HD 650 without discussing their ability to scale with the source equipment used, and from my listening experience with them they definitely did scale when paired with higher-end amplifiers. When powered by, for example, the SPL Phonitor XE, the HD 600 and HD 650 saw a rather significant and sincerely impressive increase in midrange and treble resolution, getting fairly close to the level of detail and clarity that I would expect from something like an LCD-2.
Build Quality & Comfort
Minus some aesthetic changes in the latest revisions of the HD 600 and HD 650, the build on these headphones has remained virtually unchanged since their original introduction over twenty years ago, and with good reason. Despite being built almost entirely out of plastic, the HD 600-series’ design is one of the most reliable and durable out there. I have owned a couple of HD 600-series headphones over the years, and I have never run into any build quality issues–no cracks in the plastic, no loose parts, and no unbearable creaking. The only part of the build I can really flaw is the pads, which tend to wear out very quickly and will likely need to be replaced once or twice a year depending on your usage.
Out of the box, I feel like the HD 600-series headphones have a little too much clamp. However, after giving them a couple of days worth of wearing them, they ease up quite nicely. Thanks to the mostly-plastic construction, these headphones are extremely light at 260g; they never feel like they are weighing down on your head. The pads may look a little shallow, but I never really felt as though my ears came in contact with the driver, and they do actually provide a bit of room for your ears to fit in. After you give the clamp a bit of time to go away, I think that these become some of the most comfortable headphones you can buy, and I feel like I am able to wear these headphones practically all day without feeling fatigued or sore; I really doubt comfort will be an issue for anyone on these.
Sound
The HD 600 and HD 650 were designed to be “neutral,” reference-listening headphones–and I think most listeners would agree that Sennheiser succeeded in meeting that design goal.
For the most part, the HD 600 and HD 650 have a similar sonic signature; both possess an exceptionally natural-sounding tonal balance that is delivered in an intimate presentation with a great sense of speed. However, they have distinct traits that set them apart and could make you choose one over the other, or even encourage you to own both as contrasting flavors. In this sound section, I will be sharing how the HD 600 and HD 650 compared to each other in my listening experience and how they stack up against more modern headphones.
Bass
The bass is one of the regions where the HD 600 and HD 650 differa fair bit and sets them apart from each other. They do have some similar characteristics in the bass, but listening to them side-by-side it is very clear that the HD 650 has significantly more presence in the lows, whilst the HD 600 delivers a flatter bass response. Both the HD 600 and HD 650 see a bump in the mid-bass at around 150hz, and while I do not think that it is that noticeable on the HD 600, it is a prominent quality of the HD 650’s tonal character. The bigger emphasis on the HD 650’s midbass lends its bass response a considerable but tasteful amount of warmth that adds an enjoyable fullness to it without ever feeling overbearing or intrusive of other frequency ranges. No whilst I do like both the HD 600 and HD 650’s bass tunings, I do have to admit that, to me, they do seem to lack the precision and technicalities that more modern headphones have to offer in this region of frequency response. The bass on the HD 600 and HD 650 never sounds undefined or lacking in structure, but it definitely does not strike as being presented with the same level of control and articulation that headphones like the Beyerdynamic DT 1990 Pro and HiFiMan Sundara can achieve. Furthermore, the bass on the HD 600 and HD 650 is missing quite a bit of depth in the sub-bass region; to me they sound as though they roll-off quite steeply under 80hz, especially on the HD 600. Nonetheless
Mids
The midrange is what the HD 600 series is mainly known for, and it is the definitely the star of the show. The HD 600 and HD 650 both feature a nearly-identical midrange presentation; and for my tastes and preferences, I can only describe their mids as ridiculously realistic in their tonality and extremely natural in their timbre. I find that both of these headphones really do have a beautiful voicing in the midrange that delivers extremely organic vocal and instrument tones. There is, however, one very slight difference present in the mids between the HD 600 and the HD 650, as the HD 650 does seem to have a little added energy at around 300hz. This added emphasis at 300hz gives the HD 650’s lower mids a subtle, but present boost that enhances their tonal richness and empowers vocals and low instrument tones. If there is one complaint I have with the HD 600 and HD 650’s mids is that, to me, they sound just a little bit too forward in the upper midrange for me, particularly at around 3.5K. This elevation in the presence region can make electric guitars and brass instruments in particular come across as shouty and occasionally harsh. Aside from that, the midrange tonality on these really is spectacular, and I still think that it is one of the best midrange tunings I have heard from any headphone. Resolution is also great in the midrange, as I personally think that the HD 600 and HD 650 both possess some of the most transparent and resolving mids of any headphone in the sub-$600 price range, and in this regard they only get better when paired with higher-end gear.
Highs
The treble region is where–again–the HD 600 and HD 650 differ a little bit more significantly for frequency response. Starting with the HD 600, I find it to have an adequate amount of energy and sparkle in the highs; I personally did not find it to be veiled in any way. Additionally, the HD 600 has fantastic treble extension, with good air qualities above 10K that add a nice texture and glisten to the highs while also enhancing the overall perceived resolution from the headphone. For the most part I found the treble on the HD 600 to be very inoffensive, although to me it did sound like it could be a little peaky at two different spots. For me, 6K could come across as just a little forward and introduce the slightest bit of sibilance in the low treble. I also found that to my taste, 10K has just a little too much energy; cymbal crashes and drum strikes had a little more zing than I would personally prefer. On the other hand we have the HD 650, which has a treble region that I would describe as being very warm, and very smooth. The overall treble level between 6K-10K sounds to me like is set 1dB-2dB lower than that of the HD 600, so it is quite a bit darker, and I can see how it could earn it the title of veiled. However, I still think that the HD 650 has a fantastic tuning that whilst being very smooth and relaxed, does remain capable of conveying all the tonal nuances in the highs.For resolution, I think that the HD 600 and HD 650 are both very resolving in the treble region, sounding cleaner and more transparent in their delivery than the HiFiMan Sundara and DT 1990 Pro. Also very important to mention is that–like the midrange–the HD 600 and HD 650’s detail retrieval capabilities in the treble range scaled with the source used, and they again reached higher levels of performance when powered by the Phonitor XE.
Soundstage, Imaging, and Layering
The soundscape created by the HD 600 and HD 650 is a very intimate one, with a very forward center stage and fairly closed-in lateral images. While I do not think it has a claustrophobic presentation, this lack of width is, for me, one of the drawbacks of the HD 600 series, and it is a category where many of the other headphones in their price range such as the DT 1990 Pro and Sundara perform better. Imaging and sense of directionality are, unfortunately, also a little lackluster as the HD 600 and HD 650 since both seem to have a slight gap at front-left and front-right; resulting in a soundstage that is focused mainly on the center, left, and right images. Instrument separation and layering, however, I think is fairly impressive on the HD 600 and HD 650 when you consider the small soundstage that they are working with. Even during complex musical passages, I never feel like vocals or instruments get lost or drowned out–they maintain a well-defined space of their own within the stage. In this regard I think the HD 600 and HD 650 actually perform better than the DT 1990 Pro, and are about on par with the Sundara. Lastly, I would also like to mention that, to me, the HD 600 sounded ever-so-slightly more “open” than the HD 650, which is likely due to the HD 600 not having the additional bass presence filling up the space like it does on the HD 650, or the 300hz boost that elevated the sense of intimacy from lower midtones.
Dynamics
Dynamics is a category where I think that the HD 600 series headphones perform decently well. Whilst they do not have the strongest sense of punch and slam, they still provided a decent kick behind bass notes, and when listening to acoustic guitars, strings were reproduced with a nice top-end attack that gave them a decent feeling of tension and presence. Overall, I found the dynamics to still possess a good impact and strike that made them fairly engaging to listen to.
EQ
Both the HD 600 and HD 650 are extremely natural-sounding headphones that I really do not think need EQ at all, but I have made profiles for them that bring them just a little bit closer to my personal preference, and to be more specific, target the upper midrange which was a little too forward for me. If you would like to try out my preset for the HD 600 and/or the HD 650, these are the settings that I used:
HD 600
Low Shelf at 85hz, +3dB Q of 0.7
Peak at 3500hz, -3dB Q of 2
Peak at 6000hz, -2dB Q of 4
Peak at 10000hz, -3dB Q of 3
HD 650
Low Shelf at 85hz, +3dB Q of 0.7
Peak at 200hz, -3dB Q of 1.2
Peak at 3000hz, -2dB Q of 2
Conclusion
I am sincerely impressed every time I get the opportunity to re-listen to these two headphones. With their incredibly natural tonality, good technical performance, great comfort and build, HD 600 and HD 650 have, without a doubt, stood the test of time and still remain one of the best options under $500, it is then just a matter of choosing the flavor that is more to your liking: Do you prefer a slightly warmer headphone with a sense of fullness in the bass, strong, tonally-rich vocals and a smooth, relaxed treble range? Go with the HD 650. Looking for a headphone of which tonality feels remarkably true-to-source, has present mids, and highly-articulated highs? Then the HD 600 is the Sennheiser headphone for you. If you want to get a taste of what many listeners, including myself, consider to be the reference sound, then I do not think you can go wrong with either of these two headphones—they offer a fantastic listening experience at a great price.
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Great review, @Chrono.
Did you just run them with stock cables? Have you tried the balanced output as well? Thoughts? That Phonitor amp looks like a beast. 
The HD 650, is it a brand new one? Where is it made? Romania?
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Yeah I tried them balanced as well. Also, yea this is a Romanian-made one. It sounds exactly like my 2016 Ireland one, though.
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Great review!
Own both and still really enjoy them. Especially with OTL headphone amp’s.
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Do any of you happen to remember whether the hd600 cable was plugged into the headphone the way the hd650 appears to be out of the box? I just ordered from amazon for a low price and am wondering whether I got an open box/returned headphone, because the packaging is really bad (expected), the box is beat up, and the cable wasn’t plugged into the headphone. It also had sort of a funny smell to it, kind of like a hotel room. Fairly pleasant smell, thinking it could be someone’s shampoo but unlikely since it was so strong. Thinking it’s probably just the factory smell (really the foam).
Mine are plugged in label side out (L and R out). I bought an aftermarket cable sold for the 600 or 650, and the same cables are routinely sold for both models. The left cup is marked at the top with 3 braille dots.
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@generic Thanks for responding. Just to be clear, I’m asking whether the hd600 came brand new with the stock cable already plugged in. I’m pretty confident it’s a genuine 2019 hd600, just not sure whether it’s returned/open box or new.
My left cup does indeed have the 3 braille dots at the top.
I bought my HD600 a long time ago and am almost positive the cables were pre-installed. I recall that they were so stiff coming out the first time that I thought I might break the connectors. However, mine is from the former Ireland factory so they could have changed the packaging with the move.
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Yes, the entire packaging is much worse now (although it’s not a big deal to me as long as I still got a brand new headphone). However, even in the new 2019version packaging the hd650 at least seems to come with the cable pre-installed. I have yet to find any information on the state of the 2019 hd600’s packaging, however the fact that the cable was installed in the older version and the fact that the new 650 comes with it installed do not bode well. However, the 650 and 600 cables are different, which perhaps could have something to do with it.
Did you get the Romanian version? Weird. I was looking at my pictures and the HD600 was one that I haven’t taken any pictures. 
The HD660S came with the cable attached:
This video should answer your question though:
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I did get the Romanian version. And yeah, that video does answer my question, although it was not the answer I was hoping for…
Thanks for the help.
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This does indeed seem like a Return/Open Box to me. If it were me I would send them back.
Just to answer your question though. Yes my cable was plugged in already. Good luck. Oh and welcome.
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Impressions and Comparison: HD-600 vs. HD-6XX vs. HD-58X
I’ve owned the Sennheiser HD-600 for many years, and it was my first set of serious headphones. I’ve used the HD-600 with all sorts of amplifiers and signal chains, ranging from phones and PCs on up to nice equipment. In 2021 I bought Drop’s HD-58X and HD-6XX when each was on sale. This post summarizes my impressions of all three headphones. While I’ve moved on to the technically superior Focal Clear and other headphones, I continue to use the HD-600 for smooth and relaxing background music.
All three products use the same chassis, connectors, and basic design. One has to look at the name and color to determine which model is in use. I swapped my aftermarket balanced cable when testing on my balanced sources.
Experience Summaries
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HD-58X: This is definitely a technical step below the 6 series, and it does not scale much or at all. Sounds tend to be distinct when present, but details I know from the HD-600 routinely disappear (i.e., binary, digital, mechanical). It works well on low end, low power devices. As such, if I keep the 58X I’ll use it for ultralight travel, practice sessions with my guitar amplifier, and other scenarios with inherent quality limitations.
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HD-600: I’ve owned this for many years, and heard it generate both terrible and quality output. It’s the most amplifier dependent of all three, and can either perform worse or better than the other two. On a weak or noisy DAC/amp it becomes hissy, harsh, bright, and screechy. On a “well matched” DAC and balanced or single-ended amp (E.g., Rebel Audio RebelAmp), it sounds great. Bass performance becomes reasonable (never excessive, nor satisfactory for a bass-head), and the tone neutralizes. It remains the most natural sounding and my favorite of all three, hands down.
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HD-6XX: This sometimes sounds identical to the HD-600 (e.g, when the source has little or no bass), and sometimes pretty different (e.g., substantial bass content with vocals). The HD-6XX boosts lower mids, whereby male vocals become husky, and also bass guitars and some drums tend to dominate upper vocals. The mid bass is dominant, throbbing, and insistent (i.e., focus of attention). Simultaneously, the upper mid range is degraded, resulting in roughness, grain, and a binary character similar to the HD-58X.
I’ll certainly keep my HD-600, but am undecided about the other two. So far I don’t see where I’d use the HD-6XX much at all, as I own solid supporting hardware and prefer the naturalness of the HD-600. However, if one did not own a dedicated headphone amp, its bass boost may be needed and welcome.
More testing to come.
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