A Bio-Dynamic Adventure: AudioQuest NightOwl, Fostex TH610, ZMF Eikon

Two channel systems with loudspeakers, or “stereos” as my childhood friends and I called them, and headphones have always run together, side by side—my earliest memories of listening to playback include both. I recall sitting on one end of our couch in the living room with some big 70’s headphones on, leashed (with the coiled cable) to an 8-track player like a tetherball (skinny kid/big head) to a pole. I was most likely listening to the Star Wars soundtrack. Or Elvis. Yep. I was eight. My first loudspeaker was not two channel, but instead a single speaker in a small red briefcase, with the 8-track slot on the side and a microphone. I can’t recall the exact model, but this looks like it…

I went mono before it was cool, uh, again. Heh, No. Of course, music (making it or playing it back) is not a sport. Also, not a race. Mono was benched to make room for stereo years before I was born, and, I suspect (hoping, actually) there has been a Loyal Order of the Monophonic since the industry made the switch. Today, we know many who continue pursuing (I’d like to experiment with a mono cartridge, well, because I want to know, and information isn’t knowledge.) mono playback, and with verve. The pendulum swings…

The Verve 1995 stereo reissue – found it at Stinkweeds

As time passed I came to prefer two-channel over headphones for its scale and power, and still do. That said, I have spent ever more time with headphones in recent years, and now with my reference system, find the trade—primarily, a much smaller listening space—to be an equitable one. With headphones, we lose the scale, full body immersion, and some social aspects, and in turn, get a more direct and intimate sound that removes the influence of a listening room.

One point I’d like to make here is that even those dedicated to two-channel playback and maybe a less modern hifi sound can find satisfaction in personal audio.

The current mainstream trends in headphones lean more toward HiFi, or what I might describe as hyper-real playback. The latest luxury products are primarily high-priced planar magnetic and electrostatic designs with which the builders have driven measured performance to Olympian levels (Focal’s headphones are one exception) . I’ve not heard the Meze Empyrean ($2999) yet, for example, but it has received several glowing reviews. WHIle my experience with planar headphones (I had the Audeze LCD-XC for a time) is limited, it left me wanting. Just me. Yes, they are fast, and they deliver scale, low distortion, and power in ways most dynamic headphones cannot. I am, for a couple of reasons, willing to trade a small measure of that world-class performance for other things.

AudioQuest driver design – from their site

This is a complex issue; we all have our unique experience and references for defining excellent playback. The cues that trigger my own feeling of hearing lifelike playback are closely tied to my experience watching and playing music live. Naturally realistic tone, immediacy, and lifelike dynamics tend to get me there before ultra-high resolution, pinpoint staging, and extreme reach in the frequency extremes will. Of course, all of these things are important to an engaging musical experience – we may simply prioritize them differently.

My favorite headphones are those with bio-dynamic drivers. Using a bio-cellulose diaphragm, voice-coil and rubber surround, they are a step or two closer to their dynamic floor-standing siblings than some other headphone designs. This also means that they do need to settle in, much like a loudspeaker. The surround is stiff and will become more pliant over time. I have found the drivers in the AudioQuest headphones took quite a long time to get there. AudioQuest designed their own driver, and the Foster/Fostex drivers are used in the TH610. I wasn’t able to confirm who designed the Eikon’s driver, only that it was custom built for ZMF. I like these designs because, like the big paper/pulp drivers in my Altec Lansing loudspeakers, they deliver the most convincingly lifelike tone and dynamics that I’ve heard at home.

In this installment, the first of what I would like to be a two-part survey, we are talking closed-back bio-dynamic designs by AudioQuest, Fostex and ZMF. I am looking to add others to the list, like the Klipsch HP-3 and Fostex TH909, for the open-back group. Stay tuned.

My reference: the Toolshed Amps Euphoria 45 headphone amp


I own and have lived with most of the headphones I’ll be talking about for months and in some cases years, the exception being the ZMF Eikon, which I had for a few weeks. I primarily used my Toolshed Amps Euphoria 45 DHT amplifier for this comparison. Some of the time, I used my great budget desktop system—the Cavalli Liquid Carbon amp and Schiit Modi2 DAC, which is connected directly to my computer. Roon, Tidal, and Qobuz are feeding the stream via the SonicTransporter i5, and Sonore microRendu.

I have several different headphone cables: the Moon Audio Blue Dragon and the new AudioQuest NightBird (more on that later) for their respective ‘phones, and an after-market copper cable with a 4-pin balanced termination for the TH610. I used the stock ZMF 4-pin balanced cable for the Eikon. I have a Moon Audio Blue Dragon 4-pin to 6.3mm adapter/cable so I can run any of them single-ended or balanced.

The Border Patrol SE DAC and Clearaudio Concept turntable with Soundsmith Carmen MKII are my main systems sources.

The Headphones

AudioQuest NightOwl Carbon
Fostex TH610
ZMF Eikon

These headphones are not new and have had plenty written about them, so I’ll try to keep it short. The above links will take you to their product pages with specs and any additional information provided by the manufacturers. If you’ve not browsed Audioquest’s personal audio site, it’s worth a look; they supply an incredible amount of detail.

I will lead with the fact that these headphones all share the qualities that the bio-cellulose drivers are known for: natural tone, speed, and very low distortion. Of course, each is implemented in different ways and with unique materials. The AQ headphones use liquid wood for their ear cups, Fostex uses black walnut, and ZMF use a variety of woods—my Eikon’s were made from Padauk. Each designer was working toward their sonic ideal so I view my goal here as being to talk about how these different approaches translate into my listening experience.

ZMF Eikon. photo credit: ZMF

Fostex and AudioQuest have published similar specs for their headphones: 25ohm@98db. ZMF rates the Eikon as 300ohm@98db. Physically and sonically, the Eikon stands out as the muscular one of the group. I dig the vintage-inspired metal and wood construction, though I did struggle to get comfortable with them. They are more comfortable than the Audeze LCD-XC, the heaviest headphones I’ve had here. The NightOwl is the most comfortable of the three, while the TH610 are close but don’t quite reach that level of plush fit. The Eikon with Padauk cups weighs 530g, the NightOwl 346g, and the TH610 comes in at 375g. All three feature removable cables, allowing some room to tune their sound as well as offering more flexibility with setup.

Fostex TH610. photo credit: Fostex

In addition, there are replacement ear pads available for all three. This can simply extend the life of your headphones, but may also provide another opportunity for tuning. The ear pad defines the listening space, so changing the material and/or shape can affect the sound. I used the stock pads with the Eikon and TH610 and used AudioQuest’s Classic pads on the NightOwl. These are made up of a combination of protein leather with a microsuede interior. In my system, they provide the best balance overall and the clearest midrange. The protein leather pads also offer better isolation but in turn feel more closed. The Eikon have the largest pads, the NightOwl’s pads are deeper than the TH610’s, which provide the least amount of isolation. Like the Eikon, the NightOwl is vented or a semi-closed back design versus the TH610’s fully closed approach.

AudioQuest NightOwl. photo credit: AudioQuest


I am impressed with Fostex’s ability to make a sealed design sound so relaxed. The TH610 feel less dynamically compressed and has a wider, more shallow stage, as compared to the NightOwl. The Eikon throw a large stage, and due to the 300ohm impedance, take less power to reach the top of my comfortable listening levels. Tube amps, like my Euphoria 45, tend to mate well with high impedance headphones. The solid state Cavalli amp has an impedance switch (High/Low), and I did need to use it to get similar results. The TH610’s high frequencies and midrange are perhaps the most sophisticated and nuanced, but overall have a similar voice to the NightOwl. The bass is ample, and less linear, though I don’t hear it bogging down the mids. In this regard, the NightOwl is leaner sounding, though they also deliver a touch more sparkle, which increased contrast.

The Eikon are less sophisticated, with uneven performance in the upper mids and highs. The Eikon’s sub-bass boost detracted some from the natural mids. The TH610 are more immediate than the NightOwl. At the same volume setting (6 on the dial or 12 o’clock) on the Euphoria 45, I get a bit more output and dynamic drive from the Fostex TH610. I suppose this could be the shallower pads in concert with Fostex’s damping techniques. The NightOwls stage is deeper and thinner  but these are subtle shifts.

I switched back to my reference, the original open-back design AudioQuest NightHawk, and they are, obviously, the most open and dynamic.

Only Lovers Left Alive (2014)

On the soundtrack (streaming via Tidal) for Jim Jarmusch’s Only Lovers Left Alive, (performed in part by Jarmusch’s group, SQURL) there’s a great instrumental track , “Spooky Action at a Distance,” a mid-tempo tune, with big swells of distorted guitar washing over additional layers of guitar, bass or keyboard, and drums. Paired with the NightOwl, this track is a rust-dusted, dense, and insular experience. The intimate presentation suits the music. Outside the ping of the ride cymbal cutting through the mix, the guitars are in focus—especially those panned harder left and right. Skipping ahead to “Hal”, performed by Yasmine Hamdan, which is from one of my favorite moments in the movie, the overall vibe remains. Her voice is in focus, tucked between the guitar drone, and the NightOwl’s subtle high frequency shimmer draws the edge of the vocal effects forward, as well as the rhythm of the percussion parts toward the end, creating an edgy groove.

The Fostex TH610 provide a bit more space for the music, while its slightly lower center of gravity has me feeling the groove. The vocal effects on “Hal” are tucked back behind her voice, drawing even more focus. The drones drift higher, and Hamdan sings within a slightly larger space. When the groove drops in, it has more impact, and better balances the percussion and other low frequency rhythmic parts. The Eikon brings everything forward, slightly exaggerating the upper mid/lower treble range, so that everything else floats along on that deep, growling bed of rhythm.

Dangermouse, David Lynch and Mark Linkous

Dark Night of the Soul (2009)

Mark Linkous’ final project, with Brian Burton (Dangermouse) and David Lynch is special for this Sparklehorse and Lynch fan. This project was nearly lost in legal shenanigans, and unfortunately was not officially released until after Linkous’ death. I’ve got the box with CDs, LPs and some prints of Lynch’s work.

Listening to the stream, the first track “Revenge” features the voice of Wayne Coyne of The Flaming Lips (Linkous wrote the tunes, but wanted a guest singer on each track). The recording is a touch hot way up top, and the NightOwl accentuate the sibilant vocals. That said, the higher contrast otherwise delivers a nicely balanced sound. The TH610 don’t obscure the sibilance, but are a tad more relaxed up top. Focus is drawn to the thuddy kick drum and nicely textured bass line that support the electric piano, atmospheric guitar, and keyboards. With the Eikon, the kick drum and bass dominate. No surprise, given both the songs and headphone enhanced sub bass.

Bill Frisell Live (1991)

While I am hoping Bill Frisell Live—a fantastic performance from my favorite Frisell trio—will be released on vinyl,  it’s only available on CD. This is a fast, open, and dynamic live recording. Very nice. The more refined and immediate TH610 balance the micro and macro dynamics very well, keeping up with Joey Baron’s lightning quick phrases and cymbal work without disturbing the overall flow. With the Fostex TH610 I get a bit more of Kermit Driscoll’s bass, the anchor tethering the band to the stage, which let’s me admire the subtle nuance of his performance. The Eikon deliver a more dramatic view of this show, highlighting Driscoll’s low end support and Baron’s punctuation of Frisell’s lyrical lines. The Eikon’s are also quite detailed, so I get both the broad strokes and nuance, though at times the spatial cues were confusing—their cavernous stage and tuning build a subtle caricature of the performance.

the AQ Nighthawk remain my reference for truly convincing tone and dynamics.

How’s it end?

In my system, and it can’t be said enough, so I’ll repeat—the amp/headphone pairing is critical, I hear the qualities—organic tone, stellar dynamic expression and immediacy—I look for from the bio-dynamic drivers in all three headphones. Better yet, they each add a unique character to the experience; there is something here for everyone.

In terms of comfort, the AudioQuest NightOwl are the most plush and comfortable of the three. The Fostex TH610 are close in this regard. The ZMF Eikon are less comfortable and may not be the perfect mate for those seeking comfort and long listening sessions. Audeze fans may not be bothered by their weight.

The NightOwl and TH610 are closely matched overall. The Eikon exaggerates some, and are for those wanting the extrovert (upper presence and sub bass boost) in their life. The TH610 are buttoned down in comparison, though like the NightOwl, are more inviting and erudite. If thrilling dynamics are first priority, then the Eikon or TH610 are recommended. Again, I am impressed with the TH610’s lack of compression and cupped sound for a fully closed design. The Eikon are the most detailed and deliver more high frequency excitement in addition to their sub bass boost. The NightOwl’s sophisticated sound differentiates itself with the sparkle up top and a slightly leaner—though not lacking—low end. Again, we’re talking subtle differences.

If you, like me, are looking for paper-cone tone and lifelike dynamics in a closed-back form, all of these headphones are worthy of an audition. They each do the bio-cellular thing and they all scale like mad mountain goats—strap them to high quality power!

Thanks for listening.

AudioQuest NightOwl Carbon
Price: $399.95

AudioQuest HQ
Location: Irvine, CA
Telephone: 800.747.2770

Fostex TH610

Fostex Company– a division of Foster Electric Co., Ltd.
1-1-109 Tsutsujigaoka,
Akishima, Tokyo,
Japan 196-8550
Tel: +81 42 546 4974

ZMF Eikon

ZMF Headphones