Closing time!

Excepting only the HE 1 Orpheus successor, the HD 800 has since 2009 represented Sennheiser’s top-of-the-line headphone, “reference class” they call them, “crafted for perfection”. In 2016 a new version arrived, the HD 800 S, with variations including the support of balanced symmetrical cables, along with the release of dedicated Sennheiser headphone amplifiers suitable for driving them to their best advantage.

Both the HD 800 and HD 800 S headphones are open designs — their drivers spill their sound outward as well as inward to your ears. And while open headphones are still considered to rule the roost for the ultimate in unrestrained performance, they have clear limitations on use. You need to be alone.

Enter the HD 820. At first glance the move here seems obvious enough — Sennheiser has sealed the earcups behind a cover of tough Gorilla glass. What was open is now closed. Tada, a closed version of the HD 800s.

But that raising of the glass alone would be expected to change the sonic signature of the headphones unpredictably, as the sound from the driver is reflected back into the headphone. How does Sennheiser handle that?

Nice curves
Rather cleverly. It’s hard to see from the images of the headphones but the glass is neither flat nor curved outward — it is actually concave, the bulge curving inward. And crucially the curve is carefully calculated to redirect reflected sound to a dampened outer chamber where a new absorber has been fitted. With reflections thus minimised, Sennheiser claims the outward-travelling sound waves are effectively “gone”, just as they would be in the open version of the headphone, but without spilling into the environment. In other words, these are closed headphones which should sound like open headphones.

This use of absorbers extends an idea pioneered in Sennheiser’s IE 800 in-ear phones, where the goal was to reduce low and medium frequency resonances that could obscure the reproduction of higher frequencies. Absorbers were used in the 2016 HD 800 S as well, though it wasn’t clear exactly where they were positioned. In the new HD 820 we know the absorber forms a ring around the transducer, in effect isolating the driver from the reflections.

So that’s the new stuff, while longstanding essentials of the design remain. The unusually-shaped headshells are still shaped not in a circle, nor an oval, nor an ear-mimicking sculpture, but as two curves of differing radii joined together to form a bulging letter D, within which the now-closed circular acoustic port sits surrounded by its skeleton of supports around the source transducer, which is embedded in a specially manufactured stainless steel gauze. While the HD 800 S switched the original’s silver finish to black, the closed HD 820 is even more black, with a new striated black cover to the formerly open casing section. 

The diaphragm is the same legendarily large 56mm ring design, rather than a cone-type. This has various potential benefits — instead of sound emerging as from a point source, the ring radiator delivers a more planar wave, which may allow the ear and brain to better localise different sounds, while in distortion terms a ring dramatically reduces cone break-up. Sennheiser quotes these as having a frequency range of 12Hz to 43,800Hz (-3dB), or 6Hz to 48kHz within a 10dB envelope.

The earpads are a luxurious microfibre fabric, and fit is both balanced and light — they weigh 360g without their cables, and there’ll be no wear fatigue preventing the long listening sessions which their performance will, as we’ll hear, encourage.

The HD 820 comes with a trio of three-metre cables which connect to each headshell using the same circular connector as used on previous HD 800 series headphones — this is made by ODU, a German-based connector specialist with impressive credentials, supplying as it does to medical, military and security companies where signal integrity might be considered even more crucial than from our own audio perspective! You may need your reading glasses to line up the little notches on plug and socket, but it makes a solid connection, no twist-to-lock required, so that only a firm tug (firm enough to be a bit worrying first time you try) is required to release them.

The cables themselves are low-capacitance silver-plated oxygen-free copper, shielded and reinforced by para-aramid fibres (Kevlar is one example of para-aramid material), coated with a rubber-type plastic from the ODU connectors to the Y-split, where the separate ear feeds combine into a chunky braided cable down to the final plug. The three termination options (shown above) are standard unbalanced quarter-inch (6.35mm) headphone plug, a four-pole XLR balanced connector, or the increasingly popular Japanese-developed audiophile balanced 4.4mm ‘large minijack’ 5-pole connector from Pentaconn, championed as a new standard by JEITA. No minijack option here, and the 300-ohm impedance makes them unsuitable with portable devices anyway.

▲ Balanced and unbalanced driving options a-plenty from the $3799.95 HDV 820 headphone amplifier.

We used the 4mm balanced connection for most of our listening, and it gave us a lesson in the benefits of a good headphone amp, as well as the balanced connection. That’s because we listened first — and let them run in — through the normal jack plug cable into the headphone output of a Classé amplifier, a solid enough headphone stage. We listened to the alluringly-titled Stoned Soul Picnic by Fifth Dimension: quite a complex arrangement, with ping-pong elements, some key vocals hard left, harmony and orchestral overdubs right. The HD 820 quickly established its claims to an open rather than closed sound — a bright blue-sky presentation with every element in its place, perhaps a little light-sounding, though this characteristic was not unexpected from the HD 800 variants. Such unemphasised bass may bemuse those used to the throb of many consumer headphones; most, given time under their spell, will come to appreciate the flatter balance here.

Another selection, Morcheeba’s Rome Wasn’t Built in a Day was equally open and detailed, but Skye Edwards’ breathy vocal was betraying a little excessive sibilance. We decamped to the music room where we had attached Sennheiser’s HDV 820 headphone driver (see above) via USB to our Mac Mini, where it was running under Roon control. We switched to the 4mm balanced headphone cable, and replayed the Morcheeba track. The sibilance was tamed right to a level at which it was revealed as mere presence to deliver cut-through over the mix.

This balanced delivery from the HDV 820 provided a truly sophisticated sound, and was astoundingly revealing of detail and ambience. The 24-bit DG release of piano music by Benny Andersson was delivered with more dynamics than might be expected from his softness of touch, but also revealed the soft chuff of his pedal releases, and more (on Chess we heard what sounds like a metronome for four beats around 0:53, and even a little dribbling over the final note before the end of the recording. Almost too revealing!). Jazz fans will love this abiitiy to delve into detail while appreciating the ensemble; we loved the magic crispness the HD 820s gave to the tight harmonies of Chet Baker, Art Pepper and Richie Kamuca on Tynan Time, and the extraordinary sharp-edged guitar rendering on Passion, Grace and Fire by John McLaughlin, Paco de Lucia and Al Di Meola.

Classical fans will similarly swoon over the tonal detail and separation granted orchestral material. It distinguished individual sections within the soft string surge opening the prelude to Tristan und Isolde (Karajan/Berlin Phil; the 1974 recording), and as the depth and complexity grew to its height around eight minutes in, another quality of the headphones (and the HDV 820 amp) were revealed — no matter the level, no matter the complexity, there was no audible distortion, no struggle for dominance among the individual elements. Just sweet music, or mildly ominous in the case of this prelude. 

We confess we expected that light approach to bass to preclude quite the enjoyment with rock. Not so. Whether it’s the reinforcement of the closed design or something else, there was plenty going on downstairs. The electric bass a little off-centre on The Doors’ Hello I Love You was full, nicely toned and beautifully integrated with the clavinet and guitar on either side. Bic Runga’s Hello Hello had its big central wallop of kick drum and bass delivered fully. Wilbur Bascumb’s bass was nicely resonant under Jeff Beck’s soaring electric on Goodbye Pork Pie Hat. It was only on recordings where bass was underplayed — notably 1980s digital transfers — where the Sennheisers underplayed bass, and of course, that’s just telling it like it is. The HD 820 headphones are not about to hide the truth, they are revealers of such things.

What did you expect? The Sennheiser HD 820 headphones do exactly as claimed — they deliver the sound of Sennheiser’s top designs in a more usefully private closed-back model which betrays not the slightest compromise to the open performance of the earlier incarnations, indeed giving an additional solidity and attention to bass, as well as benefiting from the option of a balanced connection, especially when served by the excellent HDV 820 headphone amp. They become an instant reference product for any competitors in these heights of headgear, against whom their revealing accuracy and grace under pressure will be their first weapons of near-unassailability.

Sennheiser HD 820               

Price: $3499.95

Type: closed, over-ear, dynamic
Driver: 56mm ring radiator
Impedance: 300 ohms
Sensitivity (SPL): 103dB at 1kHz, 1V
Quoted frequency response: 12Hz-43,800Hz (-3 dB), 6Hz-48kHz (-10 dB)
Weight: 360g without cables