Dan Clark Audio Stealth – Closed-back High-End Headphones Redefined

Dan Clark has done the seemingly impossible in making a pair of high-end headphones that re-define what is possible with portable audio.

If it were only so simple to say that Dan Clark has made a flagship pair of closed-back headphones. Four years in the making, Dan Clark has turned the talents of both himself and his team into making the Stealth, and simply gone above and beyond what we’ve seen in a pair of headphones before.

Fundamentally, if you think about what headphones were originally designed for, the intent was that a single person could listen to communications or music exclusively — both without disturbance from outside and, without disturbing others.

One might say something like Sony’s WM1000XM series are the ultimate headphones, at least in that regard. However, for many of us, we seek high fidelity, for which the goal of isolation seems to be fleeting. Simply put, super-light drivers used in the most resolving headphones do not lend themselves to being enclosed.

For example, put on a pair of HiFiMan Aryas or better, and play some music. If you put your hands even a foot out from the back of the enclosure, you can hear the effect on the music of sound reflecting off your hands and back onto the drivers.

If you cup your hands over the back of the headphones, the result is just a disaster. Thus, manufacturers have gone to great lengths to produce designs that can be closed-backed, yet maintain both a sense of soundstage, as well as fidelity.

What is more, enclosing planar drivers, of the type used by the Stealth, has significant effects on the frequency response, most noticeably in the mid-bass region, lowering it significantly, and making the headphones sound “bright”.

Dan, wishing to make a closed-backed version of the Ether 2, ran into so many problems that he decided to start from scratch, and thus, the Stealth was born after years of intense labor.

Design

If one’s immediate reaction to seeing a pair of Stealth headphones is to think that they look like a more sophisticated-looking pair of Aeons, then one wouldn’t be too far off, at least externally. Nitinol wire, which will retain its shape regardless of deformation, makes up the remarkably simple headband. However, rather than the head pad being on sliders, it now resides on high-quality elastic, allowing for an instant fit. Should the head pad elastic wear out, it is easy to replace, as only two hex screws hold it in place.

An Aeon-style organic-looking folding mechanism makes up the yokes. Push down on the headband, and it folds neatly, ready to fit in the included case.

The ear pads are thick and comfy, and designed not to deteriorate and deform as many of us have seen happen on headphones. Like the cups, they are ear-shaped, sit comfortably with sufficient firmness, and are held on by glue that wont damage them if temporary removal is required.

A clearly hand-made cable is included, with the usual medical-equipment-grade Hirose connectors, which are designed for years and thousands of connections, and click satisfyingly in place. If anything, the slight bulkiness of this cable makes it a bit of a tight fit in the case.

For those who care, the overall design looks attractive, both on one’s head and off. The somewhat discrete black with red accents colour scheme means that those people not in the know, wouldn’t likely guess at their value.

Technology

For much of the following, I recommend both watching the Head-Fi interview with Dan Clark, as well as Dan’s presentation at CanJam on headphone measurements. The following is a brief summary of both, with my own perspective.

Whether we are aware of it is not, much of the sound that enters our ears is not direct from its source, but reflection. This, whether we’re outside or inside, going about our daily lives or listening to music.

This is most apparent if you enter a recording studio with heavy sound dampening, and most extremely, an anechoic chamber which has near zero reflections. If you have not experienced either, watch even a few seconds of Dan Clark talking at CanJam, and you’ll clearly hear his voice reflecting around the venue.

In aiming for increased fidelity, whether in the recording studio, a concert hall, a listening room, or even headphones, damping reflections is of great importance. Just as Dan’s voice has considerable echo in the video, likewise, something like a band playing at full volume in a small space would result in an unlistenable recording in such a space if no damping was used.

Similarly, modern, high-tech concert halls use a variety of methods to both damp, and direct the sound from the stage to the audience. If you do an image search for “concert hall acoustic damping” or similar, you’ll see a variety of designs used for this purpose, some with links to technical information about them.

In the same way, in a room used for listening with speakers, damping reflections, either with considered furniture placement, or the use of products such as bass traps is necessary for the speakers to work most effectively.

However, inside the small spaces between the driver and one’s ear, a headphone is dependant on the material both in front of, and behind the driver, as well as the ear pad to manage the acoustics. This tiny space is less than ideal, and leaves most headphones with a considerable amount of internally reflected sound, lowering fidelity.

Thus, in much the same way Sennheiser used a single, round, Helmholtz resonator in the centre of the HD800 S to reduce some of the treble, Dan Clark came up with a similar concept, though more akin to an idea found in high-end KEF speakers, which he calls AMTS.

Much as a concert hall, recording studio, or speaker room might use differently shaped and sized materials to absorb different frequencies, the honeycomb-like AMTS system sits between the driver and the ear, and through selectively leaving certain ports open and certain ports closed, acts both as a waveform guide (like the Ether Flow) as well as a series of Helmholtz resonators to absorb unwanted reflections of select frequencies.

As the AMTS guide is a removable, 3D-printed part, small changes in the design are readily possible. It may also be possible to design AMTS attachments for 3rd party headphones.

While it seems wrong to place an object between the driver and one’s ear, the result of using the AMTS system is, seemingly counter-intuitively, incredibly effective in its goals.

Listening Impressions

If you look at the frequency response measurements of the Stealth, then of another pair of planar headphones, such as the Meze Elite, you may be surprised that the Stealth seems to have greater bass, with the slope rising down towards 20 Hz. It does — BUT, here is where the confusion lies: The Elite may look like it measures flatter, but it sounds like it has more bass. This is where we are comparing direct, versus reflected bass, as well as “flat” in a headphone measurement not being “flat” perceptively.

That’s because a frequency response measurement is done with a tone sweep, not music. Just as putting in a bass trap behind speakers in a room will reduce the reflected bass, the internal cup design has the same effect in the Stealth.

However, a typical headphone tuning that shows as being flat through from the bass to the mid-range (20 Hz to 1 kHz) has, perceptively, somewhat of a mid-bass boost. This, consequently, has long confused people attempting to reconcile what they hear, with typical measurements found online.

The Stealth has been tuned to the Harman curve, intended to represent what one would likely hear listening to high-end speakers with a flat response in a well damped room, the result is — exactly that kind of sound. With a touch of mid-bass added back in, to prevent the sound being too sterile, one’s initial impression is that they are somewhat mid-forward, with a lighter-sounding mid-range than Audeze’s LCD-5.

Initially, one is tempted to think of them as “bright”, but a touch of what seems like roll-off in the treble prevents that — the Stealth doesn’t have that exciting treble that, say, the HiFiMan Arya does. This, on the one hand, makes the Steath seem less exciting, but after some listening, they aren’t as fatiguing as the Aryas can be.

As the Stealth doesn’t have the kind of mid-bass bloom many planar headphones have, they can, initially sound unexciting, depending on the music. Initially, I wanted to push the cups in sometimes to increase the bass. However, after some weeks of use, the pads must have softened slightly, as the situation didn’t seem as severe as I remembered it.

What results isn’t going to be for everyone’s taste. The Stealth are rather like high-end Chord gear — you either gel with it or not. But what the Stealth does well is reflected in the incredibly low distortion measurements, which are better than some amplifiers, in that it brings the music to you, near absolutely unadulterated, and with an incredible amount of low-level detail. That isn’t always a good thing.

The term “brutally revealing” could be mistaken for a bright headphone that actually has mid-range or treble distortion that accentuates imperfections in the music. This is wrong meaning. The Stealth are brutally revealing of the music — you get what you get, savagely so.

That means the best recordings — David Chesky’s works, Decca masters (Julia Fisher comes to mind), classic Gain 1 system recordings, such as Muddy Waters, are absolutely glorious. The mid-range — timbre in general, is spot-on. With other, less well-made recordings, you hear every fault and imperfection.

Unexpectedly, the Stealth do not give you the impression of listening to closed-backed headphones, at least for the most part. With less complex music, such as classic jazz, solo guitar and other simpler, more intimate works, the result is an insight into the music itself, with the greatest subtleties completely revealed, as far as your equipment is capable. And, if your equipment isn’t up to the task, its faults and coloration will be absolutely revealed.

More complex music, and some recordings where sounds came from far out seems to reveal limitations to the design that simply couldn’t be overcome, with the sound seemingly not wanting to go as far out from my ears as is possible with various other open-backed flagships.

Equipment-wise, the low impedance and low sensitivity make the Stealth demand the best equipment. While they can be used with portable gear, you’ll be wanting the serious gear, such as the Chord Hugo 2, iFi Diablo and FiiO M17 for best results in that realm. The Cayin N8ii, for example, while able to make good music with them, was clearly outclassed by the more heavy-duty amplification of other devices.

Desktop equipment, as far as one can afford is the go here. On hand I had the Audio-gd R-27HE, Chord TT2/MScaler, Headamp GS-X mini and ALO Audio Studio Six, the latter of which the Stealth revealed its superior driving ability over the R-27HE’s already excellent amplification. While they aren’t “get a serious speaker amp” level of difficult that the Susvara can be, they are rewarded by equally price-serious equipment.

Music Impressions & Comparisons with Other Headphones

Dunedin Consort - Air "I Know That My Redeemer Liveth"

From: Chord TT2 + MScaler

Audeze LCD-5 – Best dynamics

Missing the last bit of air for preference, making the sound feel a bit closed-in. The vocals come close to clipping in this track at a few points, which at at louder volumes comes across as clipping. Otherwise, the delivery has a wonderful clarity, the beauty of the vocals exceptionally apparent, delivered with almost a kind of magic.

Final D8000 Pro – Best soundstage

With the brighter treble, the atmosphere is more audible than with the LCD-5, that tended to mute it. The vocal clipping points don’t come through as aggressively as they did with the LCD-5. The singer seems to be a bit further back, and more in a space of her own, though with a slight loss of intensity compared to the LCD-5. Violins seem a touch artificial.

DCA Stealth – Best timbre

The Stealth seems to bring the lighter sound of the D8000 Pro, with the intense vocals of the LCD-5. Larger stringed instruments seem to benefit from the tuning. Violin timbre seems more natural than from the D8000 Pro. The soundstage comes through in a slightly odd way, somewhat more smeared, with the location of the singer less clear.

The Durutti Column - Nina

From: Chord TT2 + MScaler

Audeze LCD-5

Reveals the imperfection of this track pretty straight-up, with a mid-range that is a bit odd, being that it comes across more forward than with other headphones.

DCA Stealth

The Stealth puts the contents of the mid-range in a form of blob in the middle as well, but with less warmth. Like the LCD-5, it reveals the imperfections in the music.

Final D8000 Pro

Thicker in the bass with a more relaxed sound, which is more forgiving of the imperfections.

Gotan Project - El Capitalismo Foráneo

From: Chord TT2 + MScaler

Final D8000 Pro

The perceived soundstage is more between one’s ears with most of the sound in one’s head, except the dog barking, which comes out from somewhere outside. As with other tracks, there is a gentle balance of warmth, soundstage and detail that makes listening both easy and enjoyable.

DCA Stealth

The bass was more audible, but it, along with the soundstage, seemed quite closed in a narrow, with the barking dog barely making it out to the edges. Some dynamic peaks in the mid-range sounded like they were clipping.

Massive Attack - Blue Lines

From ALO Audio Studio Six (with a warm tube selection) via Chord Hugo TT2 and Mscaler

DCA Stealth

Spacious and with just the right amount of balance between the bass and sounding spacious. However, they do come across as a bit thin-sounding sometimes. Instrument timbre is excellent.

El Chicano - Viva Tirado

From ALO Audio Studio Six (with a warm tube selection) via Chord Hugo TT2 and Mscaler

DCA Stealth

The hiss in the background is very audible, which was a surprise. While giving this track and overall brighter sound, instrument timbre is again, excellent. The Stealth gives this track a degree of fantastic sharpness, bringing out the guitar with great intensity.

Massive Attack - Paradise Circus

From ALO Audio Studio Six (with a warm tube selection) via Chord Hugo TT2 and Mscaler

DCA Stealth

Some very subtle background percussion was revealed from this track unexpectedly. Listening reminds me of the first time I heard Blue Lines on a proper hi-fi system, and heard the instruments separated for the first time. I’ve listened to Paradise Circus numerous times — it is one of my favourite Massive Attack tracks, and to have it elevated to yet another level was unexpected.

Patricia Barber - This Town

ALO Audio Studio Six (with a warm tube selection) via Chord Hugo TT2 and Mscaler

Final D8000 Pro

While the piano travels around the back of one’s head, the double bass plucks away nicely slightly to the left, with cymbals slightly to the right. Everything is sharp and clear without overwhelming, no doubt helped by the Studio Six. The overall effect is warm and enjoyable, yet with just enough air to the treble to make Patricia Barber’s voice open and clear.

Audeze LCD-5

The double bass takes on a thicker quality. Patricia Barber’s voice takes takes on more depth and the overall soundstage has a better, more spherical shape, though the relative positions of the instruments remain the same.

The treble is slightly duller, and is offset by the stronger mid-range presence, a change which can be slightly disconcerting. Bass delivery is as precise and delicious as can be.

DCA Stealth

The Stealth sits somewhere in the middle, having a strong focus on timbre. The high treble is slightly reserved. Patricia’s voice sounds a bit lighter than with the LCD-5, yet with bit more of the lower registers than the D8000 Pro. The double bass is sharp and clear, but impact feels a bit reserved compared to the other headphones, with plucks not registering as clearly. The soundstage feels more diffuse and the overall effect seems like the music is a bit more blended together.

Lucinda Williams - Are you Down

ALO Audio Studio Six (with a warm tube selection) via Chord Hugo TT2 and Mscaler

Final D8000 Pro

As usual, the Final delivers the feeling of the song nicely, with a touch of airiness to the treble and the singer slightly back, but not so much that the impact of her voice is lost.

Likewise, the guitar is the same, though the 4k frequency drop does mute a touch of the vocals and instruments, giving them their slightly step-back-from-the-mic quality.

Audeze LCD-5

Switching to the LCD-5, you get a feeling of more of a small radio speaker quality to the vocals, as the treble is reduced in favour of the mid-range and the “monitor” tuning, which isn’t designed to editorialise the music. The organ (electric piano) comes through rather sharply in the mix — to much so for taste.

DCA Stealth

The organ comes through sharply, but a touch back from the forwardness of the LCD-5. The bass notes don’t seem to have as much impact as with the other headphones, and seem to overwhelm the sound to a degree, whereas with the D8000 Pro, the vocals maintain their separation from the rest of the sound.

Third World - Jah Glory

ALO Audio Studio Six (with a warm tube selection) via Chord Hugo TT2 and Mscaler

DCA Stealth

It is very easy at the start to imagine the stage and performers. The vocals come through quite strongly, and, I feel are a bit overwhelming of the sound.

Audeze LCD-5

Guitar and vocals are equally, or even a bit more intense than with the Stealth.

Final D8000 Pro

Vocals are less intense and consequently, there is less overwhelming of the rest of the music.

All India Radio - Sula Guin

ALO Audio Studio Six (with a warm tube selection) via Chord Hugo TT2 and Mscaler

DCA Stealth

The music floats out with an effortless, if bright smoothness, bringing out the magic of this track. The lack of fullness that I often prefer from headphones such as the Meze Elite isn’t a problem here.

David Chesky - The Girl from Guatemala

The Stealth reveals out the spaciousness of this track. I get the impression that the mid-range isn’t as clear as it could be, and the sharpness of the mid-range and treble can overwhelm the rest of the music a bit. As well, the overall soundstage width seems a bit closed in, and the overall sound feels a bit congested, though a lot of that is the recording. However, the bass is fantastic and precise, Chesky always known for creating his music with plenty of it.

Cascading notes are delivered with fantastic speed and precision.

Final Thoughts

The Stealth are a masterful pair of headphones, with the contradictory requirements of offering hi-end performance, but in a portable form. Indeed, I’m acutely aware of the imperfections of other headphones now, from the resonant sounds, through to inferior timbre. The Stealth have revealed things I cannot un-hear. Yet, I’m not about to let go of my other headphones. Sometimes, perfect is not what I’m in the mood for.

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