I know that a lot of people compare the 6xx and the Sundara and wonder if they should get one or the other, so I thought I’d add my experiences in the hope that it might help someone. Also I’m dying to talk about how these two headphones sound compared to each other.
I’m a novice to audiophile gear, and have only a heard a tiny fraction of what’s out there to compare things to. My opinions here are all entirely subjective and my own and your mileage may vary etc. My ears will be different from yours.
I used both headphones with the same combo:
Dac: JDS Labs DAC+
Amp: Rebel Audio RebelAmp
Music Source: Qobuz via Roon
I have tried the Sundara on the Zen Can and the Atom Amp. As I note below, I thought the treble could be a bit harsh on the Atom Amp on some tracks, but the extra warmth of both the Can and the Rebel tamed them (with the Rebel sounding significantly better, but you’d hope it would for the price).
I’ve heard that the 6XX in particular can take on different characteristics based on the amp you use with it, but I don’t have anything else to test it on right now, so keep that in mind. Everything I say below might be different if you use a different DAC and amp.
I’ve owned a Sundara for a while now and decided I wanted another headphone. The primary reason is comfort–I love the way the Sundaras sound, but they’re heavy enough to become wearying after wearing them all day, which is what I’ve been doing since I’ve been working from home.
The Sundaras also seem to put too much pressure where my jaw meets the rest of my skull, which is particularly sensitive, and even after bending the heck out of the metal band at the top, it’s still noticeable especially after long listening sessions.
I was varying up the Sundaras with KSC75s which I modded with a headband and Yaxi pads. It doesn’t get much lighter than that, and they felt like air on my head. KSC75s sound amazing for the price, as is well known, and they’re obviously fine for Zoom meetings and such, but I just I wanted something that sounded better for long-term listening.
The obvious place to go here is Sennheiser, who make some of the lightest audiophile headphones around which are still considered among the best. It’s crazy to me how most audiophile headphones are so heavy, 350 grams or more, and its barely mentioned in reviews. And most of the time all this weight is not due to anything related to the drivers or performance, but just because they put metal all over the things to make them more durable and “premium”. And sure the metal on the Sundara looks cool, but personally I’ll take light plastic over heavy “premium” metal any day of the week.
I did have a little bit of a chip against Sennheisers, though, because there are people who hang around various audio Discords and actually bully people into buying them, and will put up vomit emojis if you say you like a headphone they don’t and tell you the Sundaras are bad and say maddeningly dumb things like “soundstage is for speakers”. (Fortunately, this forum seems to have kinder people than the Discords or some other places I could mention.)
Anyway, I shouldn’t let annoying people determine what I should and shouldn’t do with my life. And so looking into the line, the HD-6xx seemed like the right choice for me both for its relatively low price and its reputation as a relaxing and warm headphone.
I’ve already mentioned my issues with the comfort of the Sundaras.
The biggest problem with the Sennheiser from a comfort perspective is that the pads are just too hard, especially compared to the plushness of the Sundaras. I think I can get used to the pads around my ears, but the stock pads at the top of my head are just intolerably hard. So I replaced them with the Dekoni nuggets, and now they feel wonderful. This might create more hotspots, but I think it’s worth it overall not to feel like I have two elbows jammed into the top of my head. (As with everything here, YMMV.)
For the ear pads, since they supposedly wear out after about a year anyway, I think I’ll wait until that happens and then try the Dekoni ones to see if I like them any better. I know they might change the sound a bit, but what can I say-- I’m more precious about comfort than I am about tonality.
The Sennheisers are famous for having intense clamp force, and this is true, but I followed online instructions for bending the metal parts and got them to feel fine. Meanwhile the weight of them is everything I hoped for and there’s no uncomfortable pressure on my jaw at all. Altogether, I’m pretty happy with them.
I found the experience of switching back and forth between the Sundaras and the 6xx to be absolutely fascinating, in how good they sound in different ways.
I expected the “Sennheiser veil” effect to be subtle, given the way people talk about it and even insist that it doesn’t exist. It’s not subtle. You switch to the Sundara and instantly you’re hearing much more treble on the same track. Cymbals have a life and character on the Sundara that they just don’t have on the 6xx, as do high pitched synthesizers and strings. Maybe the effect is more subtle on the HD 600, maybe the Sundaras are just trebly, I don’t know. (I did try the DT1990 Pro in a store, and I can say that the treble on the Sundara is nothing compared to those, which I found unpleasantly trebly.)
That all said, as I mentioned when I previously had the Atom Amp, which is more “neutral” than the RebalAmp, I found the treble on the Sundara could get harsh, especially on distorted drums and synths. A song like “Time to Pretend” by MGMT which has a distorted synth line all the way through was almost intolerable to listen to. The warmth of the RebelAmp was a relief in this regard and really smoothed and warmed up those sounds and made them pleasant. However, I don’t think I would have had that problem with the 6xx since it’s so much warmer out of the box. Still, the 6xx seems to get along with the RebelAmp just fine, taking to its warmth and richness.
I found this EQ profile for the 6xx on Head-Fi and I like the extra treble and sub-bass it gives to the 6xx:
6xx EQ profile:
I also tried Amir from ASR’s EQ settings on my Sundara, but found it sucked the sparkle out of them so stopped using it. Maybe I can try a different one some time, but I like the stock sound of the Sundara so much I’m not sure I care.
The 6xx had a wider soundstage than I expected given the reviews, but it’s still nothing compared to the Sundara which puts the sound all around you so you’re just floating inside of it. The Sundara also has so much more clarity and airiness, you notice and can pick out each instrument in a way you can’t on the other headphone.
One place where the 6xx excels is “punch and slam”. Songs with driving rhythms just rock on it. And what people say about the tonality of the midrange of the 6xx is true too, vocals sound stellar. This is especially true on songs that focus on vocals, like Joni Mitchell’s “Both Sides, Now” which has a fullness on the Sennheisers that it just doesn’t on the Hifimans. The punch and midrange of the 6xx can make the Sundara sometimes feel lifeless by comparison. And while cymbals and strings have more character on the Sundaras, bass instruments have more character on the 6xx and become much more noticeable.
Sometimes the 6xx’s punch can be off-putting, though. There’s a strangeness of getting a thumping kick drum on a delicate folk song like Simon and Garfunkle’s “The Boxer”, for example. I had the same issue with “Cruel” by St. Vincent, where the kick drum just became overbearing, while these songs sound great on the Sundaras.
Lots of other rock albums though, like Little Fictions by Elbow sounded distinctly livelier on the 6xx, while the Sundara felt a little washed-out on it. And an album like The Fall of Chronopolis by Hedersleben I found boring on the Sundaras and super fun on the 6xx, and I feel like the headphones have given this album to me.
Moving to the harder stuff, on something like Tool’s “AEnema” the power and muscle of the 6xx really shines. It almost sounds like two different songs between the two headphones–on the Sundaras you get this beautiful effect where the toms are spread out all around you and you pick up all these little details of the recording, but everything feels detached and distant. The 6xx, on the other hand, just thunders through and gives you that head-bobbing effect.
A mellow Jazz song like “So What” by Miles Davis sounded better on the Sundara’s, making you really feel like you were in the room with the musicians playing all around you. I also seemed to like “Plainsong” by the Cure better on the Sundaras with its sweep and grandeur, which surprised me–the 6xx made it sound too muddled and the instruments too same-y. I put on “Reflektor” by Arcarde Fire and it sounded better on the 6xx, but “Joan of Arc” from the same album sounded better on the Sundara. (Actually it’s not even that neat–the first 60 seconds of “Joan of Arc” sounds better on the 6xx, but as soon as the strings, synths, and backing vocals kick in, the extra treble from the Sundara changes everything. In the end, I actually think I could be happy listening to the song on either headphones.)
And something like Pink Floyd’s “Dogs” which is not particularly hard but still depends on this driving propulsive feeling, it’s more active and compelling through the 6xx. “The Chain” by Fleetwood Mac also sounded better on the 6xx for similar reasons.
I was surprised when I put on a Grateful Dead album ( Blues for Allah ) and liked it better on the 6xx, but put on a Jethro Tull album ( Thick as a Brick ) and found I liked it better on the Sundara. Most jazz and orchestral soundtracks/classical I tend to like better on the Sundara, but classical music with a single instrument, like a piano sonata, I like better on the 6XX where the tonality is front and center and the soundstage matters much less.
The 6xx also seems to be more forgiving of suboptimal mastering, while the clarity of the Sundara exposes everything, good and bad.
At its worst, the Sundara sounded washed out and lifeless compared to the 6xx. And at its worst, the 6xx sounded like a muffled cave compared to the Sundara. This depended not only on the genre, band, mastering, and individual track, but also sometimes just on my mood, which goes to show how subjective and weird “what sounds good” can be. And at their best and with the right music (and mood), both headphones could be breath-taking and shiver-inducing in how excellent they sound.
I can see why some people talk about these two headphones complimenting each other. They bring out different things in the music you put through them. It can even be tough sometimes when you’re listening to a song and realize one part would sound better on one headphone and one part would sound better on the other. Of course, now I’m dreaming of something with the punch and mid-tone of the 6xx but the soundstage, treble, and clarity of the Sundara, but I’m betting I would have to climb pretty far up the price chain to find anything like that, assuming it even exists. I just don’t have the pockets for a Susvara or HD 800 S or whatever.
In the end, while I’ll use to the Sundara when I want to listen to certain music or just vary things up, the headphones that will probably stay on my head all day are going to be the 6xx, and it’s because of that one killer feature that most reviews barely mention in passing: the weight and comfort. We should have more headphones that weigh 260 grams.