The summit of hi-fi headphones has usually been occupied by open cans. But the past few years has seen companies like Focal, Audeze, and Sennheiser attempting to turn some of their best open headphones into audiophile-grade closed cans.
Over the new few months, I’ll be reviewing a few of these new entrants into the closed-back market. Today, we’re going to start at the top, both in terms of price (U.S. MSRP of $2,399) and in terms of expectations, with Sennheiser’s HD820.
As Sennheiser’s lead designer Axel Grell has explained, “Open type headphones are better by principle because sound that is radiated by the diaphragm to the rear can leave the system and the sound that is reflected from the ear can also leave the system.” As a result, Sennheiser’s closed cans have traditionally been aimed at professionals like studio musicians and DJs who require isolation, while their audiophile line has focused on open cans. According to Grell, the aim of the HD820 was to create a “closed-type for audiophiles.”
The path to the HD820 began in 2012 with a simple attempt to close the company’s flagship open-back, the HD800. After testing different cup materials, Grell and his fellow designers settled on Gorilla Glass due to its rigidity. They made the Gorilla Glass panels in the cups convex to direct reflections into dampened chambers so that “reflected sound waves have virtually no chance of disturbing the movement of the HD 820's advanced 56 mm transducers and of compromising the precision of the audio reproduction,” as Sennheiser puts it.
Underneath its fancy Gorilla glass exterior, the HD820 shares much in common with Sennheiser’s open flagship HD800 and its revised incarnation, the HD800S (U.S. MSRP $1,699), which I’ll be reviewing in this piece to provide a comparison with the HD820. The HD820 uses the same 56-mm “ring radiator” as the HD800S. Both have the same nominal impedance (300 ohms) and nearly the same sensitivity (103 dB for the HD820 and 102 dB for the HD800s).
Physically, the HD820 also resembles the HD800S. If you like how the HD800S looks (and I do), you’ll also appreciate the HD820’s black-and-silver color scheme and build that mixes high-strength plastic and aluminum. While the added cup material causes the HD820 to weigh in at 360 grams compared to the HD800S’s 330 grams, neither is a heavy headphone. Like the HD800S, the HD820’s clamping force is minimal, and with proper adjustment both the HD820 and HD800S are comfortable over long listening sessions.
Like the HD800S, the HD820 comes in a rigid storage box. Befitting its extra cost, Sennheiser has included three cables (rather than the HD800S’s two) with the HD820: an unbalanced 1/4-inch stereo cable, a balanced XLR-4 cable, and a balanced 4.4mm Pentaconn cable.
If the HD820’s build and presentation share much in common with the HD800S’s, its sound is where it deviates.
In his 2018 CanJam presentation, Grell graphed the frequency response of the HD800S and the HD820, which was still just a prototype at the time, to illustrate how the HD820’s response would deviate from the HD800S’s. The HD820, according to Grell, would have a small dip between 150hz to 200hz in order to compensate for the resonances of closed-back cans, allowing the the HD820 to possess the extra bass thump of closed cans without “blur[ring]the mid details.”
While everyone agrees there’s a dip, its size has been debated. In some measurements it’s as much as 15 db. In others, it’s as little as 3 db.
Given the debate about the HD820’s dip, I was anxious to measure the HD820 with my MiniDSP EARS. While there’s reason to be cautious about any oddities found in a budget measurement rig like the EARS, the EARS acquit themselves fairly well in comparison to much more advanced measurement gear.
For the HD820 (red) and HD800s (green) measurements below, my EARS were calibrated with a slightly modified version of Marv from SBAF’s compensation curve, where a flat frequency response is represented by a flat line:
With the EARS, the the HD820’s upper-bass/lower-mids dip appears to be what the kids call “lorge.” However, the size of the dip as captured by the EARS is in line with other other measurements of the HD820.
Also very apparent in the measurements is the HD820’s bass quantity. Especially in comparison with the HD800S, which exhibits a mostly flat frequency response except for a slight boost in the highs, it’s clear that the HD820 isn’t tuned to be a neutral set of cans.
If your preference is for a (mostly) neutral set of cans (as mine is), the bad news is that the HD820’s dip is clearly audible when listening to frequency sweeps. (Grell’s claim that the HD820 is “good and linear” enough to be used audio professionals strikes me as unlikely.) The good news is that the HD820’s dip doesn’t sound quite as large as it measures.
Nonetheless, the upper-bass/lower-mids dip of the HD820 clearly affects how it reproduces music. I listened to the HD820 over four weeks and compared it to the HD800S and several other cans using a Schiit Yggdrasil/Ragnarok stack, with lossless files played via the OSX version of Audirvana Plus. (While I put the HD820 and HD800S through the paces using a variety of music, from jazz to pop to rock, I was in a Who mood when writing this review, so the examples in this review will be drawn from their early-‘70s catalog.)
Like any daring and controversial deviation from neutrality, the pros and cons of the HD820’s unique presentation become apparent very quickly.
Listening to “Baba O’Riley” from the clear and dynamic mid-1980s mastering of Who’s Next, the tonal contrast between the HD800S and the HD820 is marked.
With the HD800S, Sennheiser has fixed the treble peak that marred the HD800 and sent modders searching for solutions. Freed from the sometimes piercing high end of the HD800, it’s easy to enjoy the HD800S’s impressive soundstage (or “headstage”), which is arguably the widest and deepest of any set of cans currently available. On “Baba,” the opening synthesizer line is crisp and tonally accurate on the HD800S. When the band enters, Keith Moon’s cymbals project far left and Pete Townshend’s guitar far right without any sense of exaggeration. While the HD800S is still a slightly bass-light headphone, its low end has enough heft to render Moon’s kick drum and John Entwistle’s bass accurately.
Compared to the Focal Clear (U.S. MSRP $1,500), which is arguably the HD800S’s clearest (pun intended) competition in the open-back audiophile category, the HD800S (green) is slightly brighter, while the Clear (blue) is slightly warmer:
The Clear and the HD800S are remarkably close when it comes to factors like transient response, dynamics, and overall clarity. The Clear’s tonal balance is more neutral than the HD800S, which still leans bright. Despite the Clear’s extra bass, its bass is also cleaner than the HD800S’s. However, the HD800S is slightly better than the Clear in retrieving microdetail (even accounting for the HD800S’s brighter character), and the HD800S’s significantly more spacious soundstage also allows for better separation between instruments than the Clear can muster.
In short, with the HD800S, Sennheiser has turned the flawed HD800 into a more balanced, more competent all-around headphone that now has to be the go-to set of cans for audiophiles seeking out the best detail and soundstage possible.
Switching to the HD820, it’s immediately clear that Grell and his team at Sennheiser succeeded in one of their top goals, which was creating a closed set of cans with the soundstage of an open pair. The HD820 projects incredibly wide and relatively deep, rivaling (and even exceeding) the soundstage of many good open-back headphones.
As Sennheiser intended, the controversial upper-bass/lower-mids dip reduces muddiness in most (but not all) recordings. Instruments and voices are easily placed in space and are remarkably clear, likely owing to the HD820’s remarkably low distortion.
However, the effect of the HD820’s dip on tonality is serious. Electric guitars lose some of their fullness, string articulation on bass guitars is lost, and drums sound hollow.
The opening synth line of “Baba O’Riley” sounds “scooped out” on the HD820, suppressing harmonics that are usually front-and-center and revealing others that are usually inaudible. As the piano and drums kick in, the impressive bass slam of the HD820 becomes obvious, but so does its somewhat disjoined presentation. The dip creates a separation between the bass and the mids that, besides affecting tonality, leads to a notable sonic incoherence.
While the dip seems to accentuate the instrumental separation and reduce muddiness with well-recorded, well-mixed material, the HD820’s unique frequency response makes some sonically less-than-stellar material even cloudier. Keeping with The Who, the Mobile Fidelity mastering of Quadrophenia presents that somewhat murky mix at its best. On most headphones – even warm ones like the ZMF Atticus – the murkiness is evident, but not overwhelming. But the HD820’s elevated lower bass and upper-bass/lower-mids dip renders Quadrophenia a bassy mess. Switching to a more neutral set of cans, including the HD800S, is a sonic breath of fresh air.
Like any non-neutral set of cans, the ear becomes more accustomed to the HD820’s presentation the longer you listen to it, making it easier to appreciate its strengths. However, there’s a good case to be made that world class headphones shouldn’t have a flaw that you need to acclimate your ears to before you can fully enjoy them. That’s even more true when those headphones come with the HD820’s hefty price tag.
There’s also the fact that, despite being a closed can, the HD820 (red) don’t isolate better than vented closed cans like the aforementioned Atticus (orange), which lacks the HD820’s soundstage, microdetail, and low bass extension, but bests the HD820 on overall dynamics, smoothness, and (crucially) tonal balance:
Whereas the HD800S can now stand toe-to-toe (and often best) any open can in its price range, the HD820 are hard to recommend over another warm-leaning closed can like the Atticus, which (at a U.S. MSRP of $1,099) happens to come in at less than half the price of the HD820.
So, just as Sennheiser has nearly perfected its flagship open can by revising the HD800 into the HD800S, it’s also introduced a technically impressive but tonally flawed top-of-the-line closed can in the HD820.
Hopefully, as was the case with the HD800, Sennheiser will release a revision of the HD820 in the not-too-distant future that remedies its flaws and keeps its strengths.
About the Author
Josh Mound has been an audiophile since age 14, when his father played Spirit's "Natures Way" through his Boston Acoustics floorstanders and told Josh to listen closely. Since then, Josh has listened to lots of music, owned lots of gear, and done lots of book learnin'. He's written about music for publications like Filter and Under the Radar and about politics for publications like New Republic, Jacobin, and Dissent. Josh is currently a postdoctoral fellow at the University of Virginia, where he teaches classes on modern U.S. politics and the history of popular music. He lives in Charlottesville, Virginia, with his wife and two cats.