January 14, 2020 15 min read
By Andrew Park (@Resolve)
It’s easy to recognize the benefits of open-back headphones for those of us strictly looking for the best sound quality available. But it’s important to remember that the far more conventional use of headphones is to make the listening experience private, limiting your music to your ears alone and not inflicting it on people in your immediate surroundings. These days that quality is becoming even more salient, as we live, work and exist ever closer in proximity to one another. Closed-back headphones are in many ways the audiophile’s answer to living in urban environments, where the overabundance of city noise intrudes heavily on the listening experience for both speakers and open-back alternatives. And for those of us who sit at a desk next to a computer with fans that spin up regularly it becomes all the more important to find that perfect high-end closed-back headphone.
Unfortunately there’s not as much to choose from in the high end market, even if there’s likely more demand for them. This is likely due to inherent design challenges. It’s difficult to develop closed-back headphones that perform even remotely similar to their open-back counterparts. There are serious limitations that are introduced when closing off the headphone since the sound pressure isn’t able to easily escape like it can with open-backs. Moreover, because of the closed-cup design, it’s necessary to devise some way of dealing with standing waves, reflections, and cup resonances that would bounce around and return to the ear.
For this comparison, I’ve selected four closed-back headphones that have different ways of dealing with these challenges, namely the new Dan Clark Audio Aeon Flow 2 Closed, the Focal Elegia and Stellia, and the Sennheiser HD820. Each of these has its strengths and weaknesses, and depending on which qualities the listener is specifically looking for, it may lead them to different conclusions as to the best one. So the following comparison provides a ranking in line with my own requirements and preferences, as well as general descriptions from my experience with them. It’s also important to note that there are other closed-back options to consider like the ZMF Atticus, Eikon and Verite C, as well as the Sony Z1R, Denon D9200 and Audeze LCD-XC. I hope in the future I’ll be able to put together a comparison that includes some of those options as well, but for the moment I’ll focus on just these four.
Focal Stellia, Sennheiser HD820 and Dan Clark Audio Aeon 2C provided on loan for evaluation by headphones.com
The Focal Elegia, Stellia and the Sennheiser HD820 are dynamic driver headphones, meaning the standout here is the Aeon 2C for being a planar magnetic closed-back. Planar magnetic headphones are more commonly open-back, likely due to the difficulty in tuning them within closed-off enclosures. I’m led to believe this requires very careful driver damping to achieve the desired frequency response, and this can also lead to an over-damped sound as well - meaning it’s critical to find the right balance.
All four headphones feel quite solid, with the Aeon 2C feeling the most durable. The most “premium feeling” of the group, however has to go to the HD820. Just like with the open-back counterpart, the HD800s, everything about the HD820 feels highly engineered for each individual component. It uses a semi-concave glass covering on the outside of the cup that covers the driver. This appears to be part of Sennheiser’s solution to the closed-back design challenge mentioned earlier. The angle of the glass is intended to reflect resonances to an absorption system before they return to the ear. The Focal Stellia gets a close second here, mostly because it's the most luxurious looking headphone, and also has the softest and most comfortable padding for both the cups and the headband.
The Focal Elegia and Stellia are the heaviest, using their well-known M-shaped dome driver style similar to that of their open-back headphones, but even after a full day of using them, they still feel comfortable. Focal's unique solution to the closed-back problem is to design the inside of the cup like a room that's built to eliminate resonances. This ends up looking like an array of boxes on the inside of the cup that break up any standing waves or resonances that might reflect back into the ear otherwise.
For comfort, all headphones do remarkably well, however I have to give the edge to the Sennheiser HD820. This headphone has the ability to just disappear on my head, the pads are unbelievably soft and plush, and the clamp force is just right. Second place goes to the Stellia with its soft leather and luxurious feel. Both the Elegia and the Aeon 2C clamp with noticeably more force. Out of the latter two, I find the Elegia to be the more comfortable one long-term, but that may also be due to the fact that I have a slightly larger than average head, and I find the Aeon 2C's clamp to eventually be a bit much. For most people, however, I think whichever headphone you choose, you'll be happy with the comfort. They also all have a unique aesthetic to them that any prospective listener is likely to enjoy looking at as well.
For isolation, the Aeon 2C in particular shines, largely due to the deep leather pads that create a seal around the ear. For noise escaping, the Aeon 2C is also impressively minimal. It appears to have a small notch on the bottom side of the surround, and this is likely the porting mechanism required to let the pressure out. For the Elegia and Stellia, the porting mechanism is actually the logo on the outside of the cup, but they both do a reasonable job at keeping sound in so as not to annoy your neighbors. The HD820 on the other hand doesn't seem to do as well as the others in either category, but it will still do well enough to block out the sound of a computer fan spinning up.
The Aeon 2C is far and away the most portable of the bunch. The Focal Elegia and Stellia each come with a nice carrying case, however the Aeon 2C's folding yoke mechanism allows it to collapse to half its size, and it fits in a very small compact case as well, taking up only a fraction of the space that the Focal offerings do in a backpack. On the flipside, the Aeon 2C also requires quite a bit more power than the Focal headphones, as it's a somewhat inefficient planar (despite its low impedance). So you'll need to consider something like an iFi XDSD, if not a higher end DAP for portable use. The HD820 is not very portable at all since the cups are rather large, it's a 300 ohm headphone, and it doesn't include a carrying case - at least not one that could be put into a bag or backpack.
The perception of detail is often the combination of a number of factors (including speed, decay, and frequency response), but in an effort to isolate this description as it relates strictly to technical ability, I'll characterize detail retrieval with the following attributes:
While frequency response and tonal balance for certain treble frequencies are integral to the perception of detail retrieval, what I'm talking about here can be isolated on its own. It's the headphone's technical ability to render nuances and textures in the music that makes it more life-like and ultimately more enjoyable. It's what makes something like an Audeze LCD-4 stand out from the crowd, even though its tonality isn't doing it many favors.
In this case, it's also important to note that the Aeon 2C is the standout planar magnetic headphone, and given that planars often have a very different type of sound from dynamic driver headphones, it can be difficult to make detail retrieval comparisons across transducer types. With that in mind, to me the Aeon 2C does a capable job at the description above.
When listening to music with busy passages with a lot of complexity, the HD820 seems like the most capable - at least, it gives the perception of being able to analyze the music more clearly and cleanly (for most of its frequency response). But for the description of detail retrieval given above, I find that the Focal Stellia is categorically superior, as it benefits from the stiffness and rigidity of the solid beryllium driver. The Elegia and the Aeon 2C are both not far behind, and may even rival that of the HD820, again given the description above, but when comparing with the Stellia it becomes obvious that, just like the open-back Utopia, it does a better job of detail retrieval.
For the HD820 and Focal Elegia, I like to think of this as the same distinction between the open-back Focal Clear and the open-back Sennheiser HD800s. The HD800s provides a greater sense of image distinction or space between the images, but there are times when the Clear feels more detailed.
So while I find that the HD820 may make it easier to analyze different musical layers, my feeling is that this is due to its stage and space between the images, not strictly its internal detail capabilities. The bottom line is that the Stellia is a cut above the rest in this category, and the others simply do a different yet equally capable job at detail retrieval.
For speed, all four headphones are tight and immediate for the initial leading edge, however the Stellia and Elegia are the best in my opinion beating out the Aeon 2C and HD820 slightly. While the Stellia isn't quite as tight in the bass (even though it's highly detailed), it has some of the cleanest and most immediate decay I've heard due to the self-damping properties of beryllium. The formerless M-shaped dome style driver of both Focal headphones allow for minimal mobile mass, ultimately leading to a snappy, punchy sound. The Aeon 2C being a planar also has a bit of an advantage. I tend to find that planars in general are tight and well-controlled - often more so than dynamic driver headphones, especially for bass frequencies. Tight, well extended, planar bass with low distortion is a lot of fun, so it's a close second.
I find the HD820 to be reasonably quick for its upper frequencies as well, but the bass isn't quite as tight, and there are some areas of its frequency response (in the midrange) that occasionally get a bit muddier as well.
What some describe as macrodynamics or 'slam' can often be difficult to compare because an elevation in the bass can enhance the perception of that impact, punch, or slam quality. Often the headphone that has the best excursive capability, or has a particularly large driver doing the work, will end up having the best punch when you EQ the frequency response to similar energy levels. In this case both Focal headphones are the clear winners. The Elegia has a solid sub-bass slam, largely due to the excellent transition between bass and midrange, and the Stellia's upper bass elevation gives it the most impressive impact. Both Focal headphones have drivers that provide some of the best in class punch and impact, perhaps only bested by a closed-back ZMF in this category.
At first listen the Aeon 2C also comes across as having decent impact, but this is largely due to the bass elevation around 100hz. This may not be an issue though for anyone who doesn't feel the need to EQ the bass down by a few dB because the perception of increased intensity is still there. The same feels true for the HD820, where I always found the open-back model would slap rather than slam, the HD820 is only a bit better because of extra bass presence that increases that sense of impact and intensity.
This is where the Sennheiser HD820 shines. The 'ring radiator' driver has always been able to deliver an exceptional soundstage, and while not on par with its open-back counterpart, the HD820 is still a very spacious and speaker-like presentation for a closed-back headphone. The one detractor is that due to the closed nature, you often feel like it should be more open sounding, but the images do throw quite wide on an expansive stage, and you also get some of the best available separation and distinction between all the images.
The Aeon 2C excels at stage depth, however it's focused more left and right, where the center image is noticeably more intimate. Both the Stellia and Elegia have a slightly larger than average stage for a closed-back, with a slight edge given to the Stellia. They're both more expansive for the center image than the Aeon 2C, but only the Stellia provides a strong sense of depth and distinction like the HD820.
Once again the HD820 does an exceptional job at imaging and image distribution. This time, however, it's matched by the Elegia's perfectly even image distribution across the front of the stage. What it lacks in depth it makes up for in spatial accuracy. I find that the Stellia has the same capability, however it also has more lateral presence and definition, with a better sense of distinction between the images than the Elegia. Due to the Aeon 2C's more intimate center image it lags behind the others here.
The main drawback of Focal headphones is that they often come with a description of a 'metallic' timbre. I personally don't find that to be an issue, but for anyone sensitive to that, the Aeon 2C and HD820 don't exhibit this whatsoever. If anything the HD820 renders music with the most 'normal' sounding timbre - notice I didn't say 'natural' so as not to confuse this category with frequency response-related sound characteristics. Keep in mind that the answer to this question is a very different one, and the HD820 is certainly not as 'normal' sounding in that department. The Aeon 2C gets 2nd place here because it is still noticeably a planar, but as far as planars go it's one of the least distinguishable in the timbre department, and to some that may be welcome news.
It should be mentioned that all of these headphones are particularly sensitive to seal, and so for anyone who wears glasses with thick sides, you may hear these as having less bass than the way someone who doesn't wear glasses experiences them. This is another common issue with closed-back headphones.
The following measurements were taken with the MiniDSP EARS rig, which is not industry standard. Also note, the Focal headphones us an angled driver, which emphasizes coupler artifacts in the lower treble. Use this for a sense of general tonality, not an accurate depiction of frequency response.
Apart from a bit of a recession in the upper mids and lower treble, the Focal Elegia has a mostly 'neutral' frequency response with a slight midrange emphasis. Some hear the Elegia as bass light but it really depends on the music you listen to. For anything that makes use of the full frequency range, the Elegia has an appropriate amount. There's a bit of a dip in the transition between the bass and the midrange, and this causes certain tracks that don't reach the lower registers to sound lean. But I find for well-recorded music this dip is actually a desirable quality as it helps add definition and distinction to the bass as it comes across in your music. Treble is non-fatiguing and it doesn't suffer any unnecessary elevations throughout the consonant range, in fact I'd say it's quite a bit smoother than the open-back Focal Clear, but it also doesn't have as much energy around 3-4khz, so that's a good place to add a bit of energy if you do feel inclined to EQ.
The Stellia has a very agreeable frequency response for the most part, however it does have quite a substantial bass elevation around 100hz (comparing measurements across units also reveals that the bass elevation isn't always at the same spot, but it's generally around the upper bass). This makes it sound a bit more 'V-shaped', where the midrange isn't as prominent as it is on the Elegia. Still, the Stellia's technical ability allows it to get away with this, where lesser headphones might not. In spite of the bass elevation, lower frequencies don't get muddied up, and the rest of the frequency response retains ample clarity. The Stellia's treble is also well-extended but not fatiguing in the slightest. This is the more laid back and relaxed Focal headphone that's simply a joy to listen to for the widest range of genres.
The Aeon 2C is somewhat 'U-shaped' with a bit more of a bass boost and extra treble splash. This will likely do better with more modern genres like pop, rock and anything that doesn't take full advantage of the full frequency range. That's because the elevation for the bass sits a bit closer to the midrange. Still, there's acceptable distinction between the bass and mids, even if the bass has a bit more energy than I'd ideally want. The Aeon 2C also has an upper midrange cut between 3-5khz that pulls back resonances for piano recordings, but at the same time this can actually be desirable for anything with electric guitars as it prevents any unwanted shout or shrillness to them. Lastly, the treble can be tamed by using the tuning filters provided by Dan Clark Audio (I prefer the soft black ones).
The HD820 has possibly the strangest frequency response of the group. With notable exceptions to be discussed, it has a general shape similar to the consumer curve (unlike its open counterpart, which they've called "loudness diffuse field" equalized). So there's more bass emphasis with the closed-back version, but there is also a very dramatic dip around 300hz. My guess is that it was tuned this way in order to avoid unwanted resonances. If you've heard the HD800s (or the older model), you know that it has extreme image separation and distinction, and this is only possible if resonances are appropriately kept under control. With the open version, it's clear they were able to do that, but closing it off introduces those very real design challenges when trying to achieve the same image separation and distinction qualities. But, the frequency response they ended up with does allow for the perception of this effect at the very least. So if your key requirement is image distinction and separation at all costs in a closed-back then this is likely on the radar. I find this transition into the midrange to emphasize the upper mids more, causing an occasional congested sound to the mids. Still, this does help the bass distinction, I just find the dip to be a bit excessive, and much more tastefully done on the Elegia.
For me, each of these headphones has some key strengths. If stage, image distance and a speaker-like presentation are the most important requirement for you, the Sennheiser HD820 is probably your best bet, but personally I prefer the two Focal closed-backs. Don't get me wrong, there is absolutely a time and place for the the kind of ability the HD820 has, I just find myself being drawn to other qualities more. I love the punch and balanced image distribution of the Elegia, and I love the internal detail and instrument separation of the Stellia. If I were to require something ultra-portable, it would have to be the Aeon 2C, and its technical ability for detail - especially in the treble - is also not something to overlook. But given my current priorities, I find the Focal Stellia to be the clear winner, followed by the Elegia and the Aeon 2C for portable use. I can easily see someone preferring either of the other two for the various strengths they have, but if I had to choose one, it would easily be the Stellia. For a more modest budget, the Elegia is my preference, but that's more based on my priorities, music preferences and use case.
The following is how I rank the closed-back headphones in this shootout. This ranking is based more on my key priorities than any definitive statement on which one is the best. So for example, if your key requirement is soundstage and a speaker-like presentation, or portability, then this list would likely look different.
Check out the full video comparison here:
- Andrew Park (@Resolve)
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