Guys, my expectations have been exceeded with the HD 6XX, which I avoided like the plague since they came out. But people grow and mature, and I matured, so I decided to hear them with my own ears. While other people are not wowed by them on first listen, I was the opposite. Coming from the Beyerdynamic and Audio-Technica camp of bright sound, I was wowed since the first second. INSTANTLY. I felt cheated on by myself. How could I live without this sound for so many years? I always thought that bright treble was like...the right way to present music. The HD 6XX sat me down for a mature talk like an experienced elder counsels a disoriented youngin'.
What did I hear? Reasonably tight, weighty bass that digs deep, smooth, speaker-like mids without being too upfront, and refined, anti-aliased highs that reveal even more detail than they'd suggest on first listen. The stereo image is well outside the head and to the rear of the ears. There is a lot of frontal depth, and every sound is in its own layer on the field. This always depends on the DAC and amp used, but no matter what I use on the HD 6XX, they sound way more open than I've read about them. They do sound the widest, the clearest and the most holographic with the MIYO DAC/amp. The aural image is just more...visual. I came to this world equipped with a mild form of synesthesia , so I apologize if this doesn't make sense. If number four is green to you, then you know what I mean.
The HD 6XX just have an unusually clean, clear sound that just makes me smile. Musical and satisfying. Perfect recipe to my ears. As good as most people say they are. What I noticed is that they remove unneeded harshness, making one think they're less detailed on first glance. But listened closely, all the detail is left, allowing one to hear deeper into the music. I produce music for my own enjoyment, so I know my tracks like they're my babies. Every little nuance and detail I've intentionally put in them is presented with clarity on the HD 6XX. While not as bright as my other headphones, I don't consider my pair dark sounding or veiled.
If I have to mention darkness, reverbs do sound darker and less open. That's as bad as it gets. Just reverbs. Everything else sounds at the least as clear and at the most, even more clear. As a matter of fact, because of their smooth highs, I can hear some details and nuances way more distinguished here than on my brighter headphones. They're like polarized glasses, removing certain aspects of the visible light to allow you to see better.
Compared to my HD 58X, which are my favorite cans for enjoying music, these are the better headphones to my ears. While the bass on the HD 58X is punchier and thumpier, sometimes it's too much to my ears, and I listen mostly to gospel reggae. The bass on the HD 6XX is balanced just right with the mids and the highs. I wouldn't want any more, and I'm a rehabilitated basshead. The mids on the HD 6XX are not as upfront and zoomed-in, presenting a more expansive sound stage. They're not as aggressive, and are so smooth, the Jubilees, which are smooth themselves, sound harsh to my ears when wearing them right after. Same with the highs. I feel relief taking off the Jubilees and wearing the HD 6XX. This is just a comparison. The Jubilees are very smooth compared to most headphones, and I consider them baby HD 650.
The HD 6XX are just more refined-sounding, more revealing headphones to my ears. They give me more detail than the HD 58X even if those are funner in terms of dynamic presentation. Although the HD 6XX don't have excessive high-frequency sizzle, all the macro and micro details are evident. I don't consider these cans relaxing or boring at all. To me, they're as exciting as my T90 and SRH1840, which are shoutier and more fatiguing, even if those are on a higher echelon of technical audio performance. I won't deny that. The HD 6XX are on a lower echelon, but that means nothing to me in the sense that they're basically on the border of diminishing returns. The HD 6XX could be the highest end you could go and you wouldn't be missing a lot. They're already up there in objective technical ability. That people deny that to justify spending more money is a different subject.
What would I want to be improved on the HD 6XX? NOTHING. I love them just the way they're. The mids are as good as people rave about them. They just dig deep and present music, not just sound. Now I understand why they've attained such legendary status and are considered an audiophile benchmark. They truly give me all the detail with none of the fatigue. Nothing I own has mids as delicious as the HD 6XX. I have to say it. Whatever hyperbole you have read about them is really no exaggeration. The general consensus, and I agree with it, is that the HD 650/6XX are on a category of their own. In my opinion, the Jubees with their similar sound signature cannot touch them detail retrieval-wise and sound signature-wise. Not taking away from the incredible value of the $149 Jubees, spending $50 more for the HD 6XX is worth it.
By the way, I don't know if my pair are factory freaks, but the bass is dynamically impressive, the mids are not dark, and the highs are not rolled off. There just seems to be a removal of high frequency harshness, but all the treble detail is there, just with none of the annoying sheen and sizzle. Some trebley tracks still bother me on the HD 6XX. Anyway, if you think about it, real life instruments or percussion are not sparkly or sizzly. Their treble never sounds in person as sharp and tizzy as it sounds with bright headphones. The HD 6XX sounds like real-life treble to my ears.
One more thing: Just to test, expecting the worst performance, I plugged them to my Denon DA-300USB, which has the weakest amp of all my gear and the most easy-going sound. WOW...at -30dB, which is the highest I go without feeling cerebral alert, it's plenty of volume and dynamic vividness. I would've never imagined they would sound so good here. The polite, gentlemanly Denon is rocking the HD 6XX with authority. I would've NEVER imagined.
Now, with the Asgard 2, the level of performance is higher. They sound brighter and clearer than I expected. That Schiit amp is smooth up top, but still, it managed to open up the Sennheisers way more. The Mimby/Asgard 2 combo here makes everything sound so realistic and alive. I have never heard my Asgard 2 sound so musical before; it is in my opinion a great companion to the HD 6XX . I think for the first time in two years of ownership I get to really listen to my Asgard 2.
What an impressive pairing. The depth into the sounds is astonishing me. I'm REALLY hearing the sound of every sound with the HD 6XX. I've never been taken so far with my Asgard 2 before. This is synergy, guys. I never noticed PRaT much before or cared about it, but I'm totally perceiving it clearly with this combo and it's a relevant thing in my opinion. It matters as much as the sound signature, because I'm understanding now why some combinations sound good but boring. It's like a perceivable micro time envelope.
Anyway, coming from bright headphones for so many years, I honestly and without hyperbole say that, to my ears and brain, NOTHING is lacking on the HD 6XX's sound, and NOTHING needs to be fixed or improved. They don't leave me wanting to reach for my brighter headphones, and they even reveal a lot of nuances that my pricier headphones obscure due to their high frequency sizzle.
For $199, in my entire lifetime, this has to be the highest value to price ratio I've ever experienced on audio equipment. What headphones would I buy next regardless of price? I have no clue. I mean...why keep going? If I wouldn't have bought the HD 6XX last, I think I still would've reached the conclusion that regardless of price, they're on a category of their own. My ears and brain just classifies them as the superior headphones in terms of musical enjoyment. Do I own better headphones than the HD 6XX? Yes. Do they better the HD 6XX? No. So what is better then and why does it matter?
Thanks for reading and God bless you!
EDIT: [November 18, 2019]
A year later, I still agree with every word in this review...AND I haven't purchased any more headphones!
EDIT: [January 9, 2020]
I got curious about the beyerdynamic Amiron Home and decided to order them. I received them yesterday. They sound amazing, technically better than the HD 6XX, but guess what I'm wearing RIGHT NOW? I know...it's crazy!