In recent years, there has been an incredible array of new headphones launched into the market, pushing the boundaries of sound quality and fidelity. Of those, only a few have truly stood out for me and made me yearn for another listen, time and time again. The upcoming Tungsten headphones are one of those rare breeds and have emotionally moved me to share a detailed, in-depth, long-term review of my experiences with the headphone community.

Whispers of the Tungsten’s early prototypes have gradually amplified into a crescendo of anticipation within our community. My first encounter with them at CanJam Chicago earlier this year was unforgettable; the late prototype was not just one of my show’s highlights – it also introduced me to one to the industry’s most innovative developers.

Ryan Dietz (@Tulon ), founder of Modhouse Audio, has been modding Fostex headphones for years. These open-back planar magnetic headphones are his first fully developed headphones, designed by Ryan end-to-end, made in his (proverbial and literal) garage. If these are his first headphones, I can’t wait to see what the future holds for him!

Immediately after that show, I contacted Ryan to get a pair to listen to in my own chain. I have had the Tungsten now for over two months (including both the single- and double- sided magnet versions; more on that below). Since these are the first fully developed headphones from an upcoming developer and this (I believe) may be the first published in-depth review of the Tungsten, I wanted to take extra time and care in getting to know them thoroughly to provide thoughtful inputs (for all those waiting, thanks for your patience).

Per usual, my take is 100% subjective, based entirely on my hearing, taste, and gear. For a sense of my taste and reference points, please refer to my prior reviews.

The Tungsten are ultra-low sensitivity headphones that require significant amplification and thoughtful pairing (though, fear not, there are many options available for any budget). I have tested the Tungsten with numerous amplifiers, and therefore dedicated a full section further below to share my impressions of those I have used and tried, as well as explain in a bit more detail what these headphones require to be appropriately driven.

Most of my listening with the Tungsten was done in my home chain using Bricasti M3 DAC (sources: Nucleus+ for streaming, NuPrime CDT-10 for CD transport), and @L0rdGwyn ’s wonderful Aegis amplifier (tubes: Mullard EL73, Tung-Sol 6SU7GTY, Miniwatt GZ34).

My review will be based on the Double-Sided magnet version. In a separate section further below, I offer a comparison between the Single- and Double- sided magnet versions. I will state upfront that they are much more similar than they are different and, unless you have both on hand at the same time, if you liked one then you would like the other (and vice versa).

I’ve gone overboard in this writeup, as I sometimes do. In order to help you skip my diatribe, here is an index of everything I will cover, so you may skip and skim to your heart’s content:

• TLDR
• MODELS & SPECS
• BACKSTORY
• BUILD
• COMFORT
• SOUND IMPRESSIONS
  
  • Timbre
  • Resolution
  • Dynamics
  • Soundstage
  • Imaging/Layering/Instrument Separation
  • Attack vs. Decay
  • Frequency Response
• AMPLIFIER PAIRING
  
  • Technical Discussion
  • Amplifiers Tested
  • Bottom Line
• SOUND CUSTOMIZATION
  
  • Pads
  • Vented Adapter
• SINGLE-SIDED VS. DOUBLE-SIDED MAGNET
• COMPARISONS
  
  • Tungsten vs. LCD-4
  • Tungsten vs. Caldera
  • Tungsten vs. Susvara
• CONCLUSION
• BONUS TRACKS

TLDR

The Tungsten are superb headphones with a distinctly unique character. At a price point of $1,499 and $1,999 for the Single- and Double- sided magnet versions, respectively, they offer top-tier performance, providing perhaps the best performance-to-price on the market.

In my mind’s eye, the Tungsten are what the LCD-5 could have been, if they were a true upgrade of the LCD-4, rather than entirely different headphones. The Tungsten possess the creamy presentation of the LCD-4, but with a distinctly better tonal balance and technicalities.

With an exceptionally silky presentation, the Tungsten are neither dynamically aggressive, nor electrostatic lightning fast. Rather, they are exceptionally smooth, offering a very non-fatiguing listen while exposing everything in the music with great accuracy. They do not make you think about their capabilities, they let you sink into the music and enjoy yourself.

Unique in character, the Tungsten will not replace the Susvara, unseat the Caldera, or substitute any of your other top-level planar headphones. They were not built to copy any headphones. Rather, they were tuned to the ear of a great developer and reflect his taste, offering a distinctly unique character of their own. With a real emerging house sound, Ryan is set to carve out his own niche in the market, which I think will be rewarded with Modhouse building a dedicated following among headphone enthusiasts.

The Tungsten are high impedance planar headphones, a rather unusual combination. They are extremely insensitive, requiring high voltage amplification; but, when properly amplified, they scale remarkably and soar.

Finally, the Tungsten offer that certain quality and feel of hand-built headphones, with a distinct and beautiful design esthetic, and have excellent build quality. Picking them in my hands, I feel the happy pride of ownership reserved for buying headphones crafted by a boutique headphone maker.

MODELS & SPECS

The planar magnetic drivers of the Tungsten are based on 24k gold traces, with the custom-designed magnets made as thin as possible.

Both the Double- and Single- sided magnet versions are uniquely high impedance planar magnetic headphones. They both also have extremely low sensitivity. The combination of these factors requires thoughtful amplification pairing.

Specs

• Sensitivity: 78 dB/mW
• Impedance: 155 Ohm
• Weight: 515 grams

• Sensitivity: 76 dB/mW
• Impedance: 135 Ohm
• Weight: 520 grams

In the Amplifier Pairing section further below, I discuss their true sensitivity in the context of their impedance (dB/mW vs. dB/mV) and highlight high-voltage amplifiers that I’ve found work very well with the Tungsten.

Price

• Double-Sided: $1,999 / Single-Side: $1,499
• Included: 6’ OCC Litz cable by Viking Weave (@skedra )
• Optional: custom chassis color ($150), customer grill color ($99), travel case ($150)

The Tungsten are sold direct-to-consumer through the Modhouse website. They are also offered by Mimic Audio, which sells a Double-Sided version with a purple-colored grill for $2,099.

BACKSTORY

Years ago, at a time those were big and expensive, Ryan’s dad bought him a 3D printer with the hope he’d figure out a way to start a business around it. Ryan started making Grado mods and 3D-printed pad adapters, and then started modding Fostex headphones. After years of modding, Ryan decided to develop fully custom-designed headphones. This story of graduating from modding Fostex headphones into developing high-end headphones may sound familiar, perhaps reminiscent of the backstory of another great developer, Zach (@zach915m ) of ZMF fame. I can only wish for Ryan to follow in the big footsteps of this wonderful role model in building his boutique headphone business.

Designed and built in the US, the Tungsten are assembled in Ryan’s proverbial and literal garage. If the Tungsten sell as well as I think they may, I suspect Ryan will expand his operation to roomier pastures. The model’s name “Tungsten” is not based on the material used in its construction. Rather, it is a homage to Ryan’s chemist dad (and the reason that Ryan has been naming his products after elements in the periodic table).

BUILD

Overall
Built with great attention to detail, the Tungsten feel sturdy and well built. The gimbal and driver housing have a rugged finish, which initially felt odd, but conveys a comforting sense of ruggedness. The headband is made of hand-forged spring steel, with a thin and wide head strap hand-stitched genuine Alcantara. Stainless steel rods offer sliding adjustment up and down with very sturdy clicking. Driver housing fully swivels in all directions, making for an easy fit.

The entire design has modularity and serviceability in mind. Changing headbands or replacing grills is as simple as unscrewing a few Allen head screws, replacing them, and refastening.

Note that the design of the Single- and Double- Sided versions is identical in all regards. The only difference is the internal use of a magnet on one or on both sides of the diaphragm (total weight is practically identical, as Ryan was able to shave weight off the single magnet when designing the double magnets).

Packaging
The stock packaging is very secure and nicely branded. Nothing fancy, but just to the point. Should you want a pelican travel case, it is optionally available for $150 (I have so many of those from my ZMF headphones, I opted to keep things simpler for easier storage).

Grills
The highlight of the design is the beautiful grill, with sunray patterns around a Modhouse symbol. The stock grills are “Tungsten gray” made from colored aluminum, painted with Cerakote ceramic coating. For $99, you may choose from a wide selection of custom grill options, either other Cerakote coating colors, or a variety wood options. The wood grills are more fragile, but if you are careful with handling your headphones they should work well (and are easily replaceable). Some wood options, like Cedar, may have an actual natural smell, which you may either mind or find appealing. The weight difference between aluminum and wood grills is only 15g or so, which makes this choice entirely aesthetic.

Pads
The pads for the Tungsten are manufactured by ZMF (yes!) and are a variant of their Caldera pads. There are two pad options: Caldera Hybrid & Caldera Ultra Perforated. Pads are fixed onto a magnetic disc that snaps into place. One just has to note the proper alignment between holes in the back of that disc and screw heads on the driver side. There is only one proper alignment, with the pad stitches at the bottom (in theory, one could snap them at 90-degree rotational intervals, but the oval pad shape with tapering width from thicker behind the ear to thinner on the forward side, really lead to a single position).

Small note: to remove the pads, gently grab them anywhere and just pull them out. You will feel resistance: fear not, you are pulling against a somewhat strong magnetic hold and the pads won’t tear; they are firmly glued to their discs. Also, when you first remove them (if you do), you may see some glue strand stretching. Do not be alarmed. These are just some glue residue from the screw heads on the driver housing. Another note: the clamp force will let you put any pads you like (all ZMF and similar sized pads would fit) and just try them out. The mounting disc isn’t strictly required, except for normal long-term use. That is how in fact I first discovered the Ultra Perforated pads work well with these headphones (I normally use them with my Atrium Open headphones and was experimenting). So, possibly, more discovery may be afoot.

There is also a Vented Adapter, which magnetically snaps into place in between the pads and driver. It can be removed by prying it out carefully with a thin object (ideally non-metallic). Please do so carefully, as the adapter is slender.

For a discussion on the sound impact of pad choice and the Vented Adapter, please skip to the Sound Customization section below.

Cable
Hats off to Ryan on his choice of stock cable, no less than a cable from Viking Weave made by @skedra . As far as stock cables go, Sebastian’s handmade cables are as good as they get, an amazing inclusion for any headphone as stock cable. No upgrade necessary. The included cable is a 2-wire OCC copper Litz, terminated to your choice (XLR, 1/4", 4.4mm).

Personally, I used this opportunity for a cable upgrade and, instead, got from Sebastian for a fat and juicy 4-wire OCC, essentially the exact same cable, just double the girth. Walking around with this cable at CanJam SoCal, I got a lot of smirks (including from @skedra himself).

Headphone-side termination is a standard 3.5mm with a pinout identical to that used by HiFiMAN headphones, which lets you use any standard after-market cables.

COMFORT

Overall weight feels pretty standard. I’ve had no problem wearing the headphones for many long hours daily without any notice of their weight. Weight distribution is very good, owing to a decent clamp coupled with a wide head strap. They are really quite comfortable.

If I were to change anything, it would mainly be to reduce the clamp force. I find it a touch too much for my preference (my head size is average+). Clamp force is set, as the headband isn’t meant to be twisted and manipulated. It’s a thin springy steel band that isn’t malleable (like ZMF headbands are, for example). Ryan may perhaps offer some larger bands in the future (they are easy to replace). But after two months, the clamp hasn’t loosened, so what you see is what you get. However, the pads are very deep and plush and, therefore, the clamp force is absorbed by the pads’ “give”, making these headphones comfortable to wear for long listening sessions.

SOUND IMPRESSIONS

The Tungsten are one of the more tonally balanced headphones I’ve heard. They offer a touch of warmness, by which I refer to a more textured presentation, especially in the bass, which stands out more by the quality of decay than attack, offering a very satisfying thump rather than a sharp bite. The overall presentation of the Tungsten is smooth and silky, like a (much upgraded) LCD-4. Technically, these headphones punch way above their price point, offering true TOTL resolution and imaging, with exceptional instrument separation.

All music tracks referenced below are hyperlinked.

Timbre

The Tungsten renders notes with realism, offering a natural sound with perhaps a touch of sweetness. In the lower frequencies there is a hint of reverb, which reflects what low frequency bloom should sound like, in contrast to unnaturally fast decay in some fast headphones.

Isaiah J. Thompson’s piano in “The IT Department” and Martin Taylor’s guitar on “Stella By Starlight” are great example of acoustic instruments that showcase well-rendered natural resonances. Female vocals are particularly beautiful sounding on the Tungsten. South Korean singer Youn Sun Nah’s exquisite voice in “Lento” shines through with wonderful fidelity.

Perhaps the most beautiful example for great timbre can be found in Itzhak Perlman’s lead violin and David Garrett’s accompanying violin, on Shostakovich’s 3 Duets for 2 Violins & Piano, as adapted here for 2 violins and orchestra.

Resolution

The Tungsten is very well resolving, while not pushing details into your ears in an unnatural way. They resolve details effortlessly. Listening to “Alone” by Halsey, a track I’ve listened to many time, from min 2:20 to min 2:37 there is a high frequency hi-hats sequence that is captured in excellent detail. High frequency percussions are also wonderfully detailed on “Bobo” by Salif Keita, from start of the song and throughout. In “Prelude To Coup De Foudre”, Brandi Disterheft’s every intake of breath and plosive consonant can be heard. The drummer’s delicate, barely audible brush strokes can be perceived, adding that extra nuance for a complete portrayal.

Dynamics

An excellent example of the Tungsten’s dynamic responsiveness can be experienced listening to A.R. Rahman’s composition “Dacoit Duel” recorded by the Czech Film Orchestra. The beautiful melancholy of the pipa (traditional Chinese plucked lute) solo is followed by the massive impact of Indian dhor drums, concurrently with the lighter taps of Inidian tabla drums (this track, in its entirely, is a celebration of diverse instruments, and a feast for anyone who loves percussion; highly recommended). In the intro to the track “Black and White” by Michael Jackson, which I have played endless times, the Tungsten explode into the song’s rhythm 60 seconds into the track, a head bobbing moment if ever there was one.

For a great demonstration of the Tungsten’s macrodynamic i.e., how they handle big swings between very low and very high volume in original recordings with a high dynamic range, I’ve played Vienna’s Philharmonic rendition of Mahler’s Symphony, conducted by Leonard Bernstein. Part 3.4 of this composition, “Sehr Langsam”, showcases orchestral strings playing a quiet pianissimo which then explode into a beautiful forte around min 3:30.

When properly amplified (see below), the Tungsten handles voltage swings wonderfully!

Soundstage

Rather than placing the music around your ears, the Tungsten transports you into the room. There is no artificial sense of spacing, rather the feel is open, organic, and natural in size.

A great example is “Ixtapa” by Rodrigo y Gabriela. This entire track feels like a bottle of full-bodied red wine that was decanted and given a few minutes to breathe. The sense of openness is wonderful. The stage isn’t exaggerated but offers a genuine sense of the recording studio, as I imagine the recording engineer intended. The acoustic guitar duo’s reverb in space allows you to reconstruct the room size. It is a very believable rendering with a wonderful sense of space.

Beck’s “Heart Is A Drum (Album Version)” is another example for the Tungsten’s recreation of a natural soundstage, offering a very cohesive 3D experience. The music surrounds your head in all directions, both intimate and expansive.

Imaging/Layering/Instrument Separation

One of the biggest strengths of the Tungsten is its outstanding ability to render multiple instruments with complete separation and clarity, placing them in space accurately. Layering (depth) is simply excellent. There are so many great examples here, I will take some extra time to share with you some of these:

The multiple audible cues in the intro to Kiss’ “Detroit Rock City” is a great illustration. The voice from the transistor radio is projected from the slight left, while sounds of clanging dishes and cutlery under running water are placed clearly in the front and slightly to the right. A door bangs to the hard left as a car engine revs. As the car radio comes to life, it sounds layered further in the background, while the protagonist hums along directly in your headspace, positioning you right in his car seat.

The wonderfully recorded blues track “Walking Blues” by Pete Alderton, offers a great demonstration of the Tungsten’s excellent imaging at the start of the track. Footsteps can be heard clunking to the left. As the song begins, the harmonica then plays to the far right, with the singer up front and center. The bass is slightly to the right, while electric guitar is far back to the left, offering a true sense of depth relative to the singer.

Separation technicalities are evident in Buck Dharma’s “Wind Weather and Storm”. I can make out each of the backup vocals in the space along with the lead vocal. Sax, drums, and bass are concurrently clear, and the added ambient rain pattering does not detract from any of the detail. Another great example can be heard on “The Windmill of Your Mind” by The Tierny Sutton Band. The sound of a clock, voiced by the drums, is distinct and layered behind the singer. One of the more challenging tracks for vocal separation is the wonderful cover of “Moon River” by Jacob Collier. There are so many vocals layered in this track to create the wonderful harmonies this musical marvel has reimagined. In specific, the very end of the track (after min 7:10) adds low bass vocals to numerous others. Listening to it on the Tungsten is a treat. Michael Bublé’s cover of “Nobody But Me” renders percussive and brass instruments, and accompanying vocals, with superb clarity, making the track so enjoyable.

There is nothing like big-band jazz to stress test soundstage, imaging, and separation. “Moanin’” performed by the WDR Big Bang Koln with drummer Bernard “Pretty” Purdie is presented with a natural-sounding soundstage in both width and depth. When the trumpet solos, it is pinpoint on the left side of the orchestra, and the trombone solo is clear on the right. All instruments are clearly distinguishable.

The gentle reverb of electric keyboard in the first few seconds of “Only Girl In The Room” by ISYLA creates a great of sense space. The low volume of bass guitar is one of the subtle nuances on this track which the Tungsten presents especially well. The distinction between lead vocal and acoustic guitar placed at the center, backup vocal to the left, and drums to the right is very well articulated.

Finally (as we must move on), “Down to the River to Pray” from the movie soundtrack of “O Brother, Where Art Thou?” showcases all of the above. This sublime a cappella piece blends a chorus of female and male vocals. The Tungsten’s presentation of timbre is natural, their resolution is minute, and their soundstage accurate. Most notably, I could clearly place the lead female singer within the ensemble, just as I could pinpoint the position of each and every chorus member. What a feat!

Attack vs. Decay

The Tungsten’s presentation stands out more for its decay than its attack. These headphones do not voice with an aggressive attack like a Focal Utopia nor with the delicate and fast decay of the Susvara. Rather, the Tungsten offer a natural balance, merging the technicalities of top-tier planar headphones with a lingering sense of the notes and a touch of reverb, resulting in a natural decay rarely found in such headphones. To my ears, this leads to a presentation that doesn’t seem designed merely to impress, but instead delivers notes in a manner that feels innately natural. It’s especially well-suited for extended listening sessions.

Let’s take two examples: first, how the Tungsten renders drums; then, acoustic guitar:

In “Lion” by Kodo, a Japanese professional taiko drumming troupe, the deep reverb of the lowest bass drum notes is especially notable. Higher percussive notes show the speed of the Tungsten, yet their trailing ends are soft rather than abrupt, which enhances the sense of acoustic realism.

When a guitar string is plucked, the initial attack is full of harmonic overtones and, as the sound decays, the higher harmonics tend to decay faster than the lower ones, leading to a warmer sound as the note fades. In rendering this instrument, decay therefore will influence the perceived timbral character of the instrument, and the Tungsten strike a very natural balance when presenting acoustic guitars. I can’t think of a better demonstration of this than when listening to my favorite currently living acoustic guitarist, Tommy Emmanuel. I’ve had the rare pleasure of hearing him performing live in NYC last month. In between his more virtuosic solos, he played a wonderfully musical cover of “Somewhere Over The Rainbow” (if you can ever catch a live show, I can’t recommend it enough; meantime, check his numerous YouTube recordings). Listening to the recording of this track rendered by the Tungsten in my system, I am struck by the natural decay (for example, in the arpeggios he plays around min 2:40) and the wonderful timbre of his acoustic guitar. It transports me right back to that live concert; I am grateful to be able to relive it in my home system: it is as true to the source as I could hope for.

Frequency Response

Sub-bass
Sub-bass extension is exceptional. To test this, I played several standout gospel tracks by Kirk Franklin, starting with “Love Theory”. From min 1:10 to 1:18 in this track, the bass guitar reaches so deeply that only headphones boasting superior low-frequency extension can truly capture its detail and physicality. The Tungsten handles this with aplomb. I then switched to “OK”, which consistently showcases these deep sub-bass notes, notably from min 1:03 to 1:17. While many higher-end planar headphones falter in reproducing these challenging notes, the Tungsten excel.

“Fall In Love Alone” by the upcoming singer Stacey Ryan serves as another testament to the Tungsten’s impressive sub-bass resolution. At min 0:45 to 1:07, the deepest bass guitar notes introduce delightful texture and depth. For those familiar with these other models, in terms of physicality, I would place the Tungsten’s sub-bass above the Susvara but below the Caldera. However, in terms of sub-bass resolution, the Tungsten surpasses both.

Bass
Low bass is thick and weighty. A great example for this is found in “Farolito” by Alondra de la Parra. When the orchestra chimes in with the thunderous low tuba and drums, you can feel the diaphragm pushing massive air against your ear drums. The result is very satisfying.

If you are familiar with the ZMF Atrium, the Tungsten shares a similar bass quality – more of a deep thump than a snap. While they can undoubtedly hit with speed and force, the Tungsten's presentation leans toward being rounded with reverb, rather than sheer aggression (though it remains fast). This characteristic positions the Tungsten as a prime choice for rock enthusiasts. Tracks like Shinedown’s “Simple Man [Acoustic] [Live from Kansas City]” with its quintessential rock drumbeat or Muse’s “Uprising” exemplify this punchy yet lingering bass. I typically favor lower volumes, but I can't resist turning these tracks up—it's just so satisfying! This thunderous drumbeat quality is equally evident in Alicia Keys’ “Girl On Fire [Inferno Version]” (the version featuring Nicki Minaj). The drum decay on the Tungsten feels incredibly organic.

Lower mids
Male vocals are lovely. If I looked for a singular adjective for the quality of their rendering, it would be resonant. Gregory Porter’s voice on “Don’t Be A Fool” is sonorous with a touch of vibrato that gives his silky voice an extra dimension. Tony DeSare voice in his original song “Lover’s Lullaby”, a quiet and diminutive ballad, is wonderfully smooth.

Upper mids
Female vocals are slightly forward and very well resolved. Carla Bruni’s raspy voice on her beautiful cover of “The Winner Takes It All” is intimate, with every nuance of her breath captured to completion. Kenny Washington has an unusual upper-register male vocal that is always surprising. On “S’Wonderful”, the Tungsten present his voice with finesse and sweetness.

The Tungsten's characteristic sweetness can also be observed in how it smooths the edges of notes. For instance, while trumpet blasts can often sound aggressive, the trumpet accompaniment to Martina DaSilva’s vocals and Dan Chmielinski’s bass in “I want To Be Happy” is rendered with exceptional smoothness by the Tungsten

Treble
Treble is very well-resolved, yet smooth and pleasant. In “Window” by Bonefield there is tremendous amount of percussive detail in the treble region, and the Tungsten expose all of it while keeping a relaxed listening experience. This is a trait that I think many will appreciate. An edge case example is violinist Nigel Kennedy’s arrangement and rendition of “Rhapsody in Claret & Blue”. The violin high notes on this track are definitely not for the treble sensitive (I am not). The Tungsten will not change the nature of the track but will make it more accessible.

To test treble resolution, I first played Boz Scaggs’ “Desire”. There is a high pitched “crunchy” sound (which I believe is a ratchet) from minute 2:01 and on, audible from the left. The Tungsten delineates it very well. That same instrument is clearly resolved and separated in “A Girl Could Get Used To This” by Kandace Springs. The Tungsten offer very good clarity while maintaining a smooth presentation.

AMPLIFIER PAIRING

For anyone who has been following the chatter around Tungsten, you may already know that the they have a very low sensitivity and require serious amplification to be properly driven. When looking to purchase a pair, you are well-advised to consider whether you have the right amplifier on hand. There are some considerations here that are worth understanding. The good news is that there are plenty of good options that will work well. Please understand, though, that an average amplifier is unlikely to work well, and proper planning is prudent. There are plenty of affordable options, so breaking the bank isn’t necessary to get an awesome experience!

Technical Discussion

I am not an engineer but, to the limit of my knowledge, I would like to start with a short technical discussion in order to put into context the objective amplification needs of the Tungsten. They are both substantial, and unique for planar magnetic headphones.

The industry is accustomed to quoting sensitivity in dB/mW. However, this results in apples-and-oranges comparisons when compared across headphones with varying impedance levels. When the Tungsten’s sensitivity is converted to dB/mV, one can appreciate the high level of voltage that is required to properly drive them.

Making layman calculations, I arrived at the following:

• The Double-Sided (DS) magnet version, rated at 78 dB/mW @ 155 ohm, has a sensitivity of approx. 86 dB/V.
• The Single-Sided (SS) magnet version, rated at 76 dB/mW @ 135 ohm, has a sensitivity of approx. 85 dB/V.

For context and reference, consider this:

• Susvara, notoriously power-hungry headphones, are rated at 83 dB/W @ 60 ohm, which is approx. 95 dB/V.

Therefore, the Tungsten would require an amplifier with a much higher voltage output than the Susvara.

How much is enough?
If we set a goal of 115dB, with ample overhead for peaks and transients, we would need 28V for the DS and 33V for the SS. If we set our goal at 110dB, we would need 16V and 19V, respectively.

Therefore, as a general guideline, amplifiers capable of producing over 20V at 150 ohms might be a good starting point. Most amplifiers provide their output power specifications in Watts for a given impedance level. To calculate the voltage at that impedance, simply multiply the power (in Watts) by the impedance (in ohms) and then take the square root of the result. If no specifications are available at 150 ohms, you can extrapolate based on the trend observed at lower and higher impedance levels to make an educated guess. Alternatively, it's best to ask the manufacturer directly.

Some of you may have incredible amps for Susvara. However, not every amplifier that works for those headphones would work with the Tungsten (the Susvara needs ~10V when setting a goal of 115dB; amplifiers driving them need to provide lots of current, but not necessarily voltage).

For those curious how much current the Tungsten will draw, at 115 dB, the Tungsten would draw 0.24A and 0.18A with the SS and DS, respectively (and at 110dB, 0.14A and 0.10A). For comparison, Susvara will draw 0.16A at 115 dB (0.09A at 110dB).

As you can see, the right amp will have a very high voltage supply and drive quite a bit of current. With great power comes great responsibility.

However, the universe for Tungsten amplifiers is not more limited relative to the Susvara, it is just different: there are amplifiers that work with the Tungsten but not with Susvara. For example, amplifiers with high output impedance, such as very powerful OTLs (which I tested) or, potentially, vintage receivers (which I have not). The Tungsten’s high impedance may allow it to be properly damped where the Susvara’s lower impedance will not.

There are always exceptions. I have tested amplifiers with 20V @ 150 ohm that weren’t sufficient, while testing one with 10V that worked well. Rules of thumb are helpful in narrowing the playing field, but circuit design and implementation often produce unexpected synergies. At the end of the day, sometimes the only way to know if something works or not is to just to insert a plug into a socket and find out.

I’ve done just that with a wide array of amplifiers. Here is some of what I’ve found out:

Amplifiers Tested

The Tungsten headphones are amp picky. They also scale magnificently with good amplification. It's been a joy experimenting with different amplifiers to discover the ideal matches. I will detail what worked, what didn't, and the reasons why. My aim is to offer helpful guidance on which types of amps might be worth exploring.

My Chain
I spent the first month listening exclusively to my amps as I first got to know the Tungsten intimately.

L0rdGwyn Aegis
Of all the amps I have on hand, the Aegis is the best match for me with the Tungsten (it also happens to be my favorite pairing for another uniquely high-impedance planar headphone, the LCD-4).

The synergy is sublime. The rich, creamy, and silky sound of the Tungsten, paired with the refined, airy, and wide soundstage of the Aegis, offers an exquisite result. The Aegis uses EL34, KT88, and similar variants as output tubes, making it rather powerful (tubes used: Mullard EL37 output, Tung-Sol 6SU7GTY input, Miniwatt GZ34 rectifier).

Auris Nirvana
This amp is an EL34 based power beast. It drives Susvara wonderfully and handles the Tungsten with similar aplomb. However, it wasn’t among my favorite pairings for the Tungsten. The Nirvana is an amp with a very well-defined and focused center image, and a deeply extending bass with a fast attack, but it lacks the airiness which the Aegis has to complement the Tungsten. While the power matching was good, the synergy left me indifferent. If you have the Nirvana already, then you can comfortably get the Tungsten and enjoy them with it; but I wouldn’t get the Nirvana for them. I didn’t get into tube rolling as I already had too many variables to test for this review, but that may definitely change things up (tubes used: Mullard made EL34 output, Siemens 5814A input).

Decware ZMF Reference OTL (preamp) into Decware Taboo SE84TS+
This combo is my favorite for the Caldera. It is extraordinarily holographic and sweet sounding. It was sufficient to drive the Tungsten if not with maximal headroom. Whereas this combo fits well the more dynamic and aggressive Caldera, it was a touch too saccharine when combined with the Tungsten’s smooth presentation (tubes used: OTL - Tung-Sol 5687 output, RCA 6BQ7A input, Miniwatt GZ34 rectifier; Taboo - Reflektor 6P15P output, Telefunken G73-R input, GE 5Y3G rectifier).

Glen OTL
A wonderful surprise. I plugged the Tungsten in expecting an OTL surely would not drive it. And it blew my mind. The GOTL (alas, no longer available, but with very patient hunting it may be hunted down) is an unusually powerful OTL that also has a bit of an oomph and a grunt; an in-your-face presentation, if you will. With the Tungsten’s high impedance, damping was good. In contrast to the Aegis, notes are slightly softer here and a smidge thicker; but, to mood and preference, this is an unexpectedly great option (tubes used: Sylvania 7236 output, Brimar 13D1 input, Raytheon 5CU4 rectifier).

Decware FMF Reference OTL
There was no real chance this would work, and it didn’t. It simply couldn’t generate a listenable volume.

And, in general, it would be a safe assumption that OTLs would be a poor choice for the Tungsten. This represents the expected outcome. OTLs are built to drive high-impedance dynamic headphones.

Violectric HPA V281
Bingo! An outstanding match that I highly recommend. The V281 drives the Tungsten easily and beautifully, with tremendous headroom. It controls the drivers very well, offering a bite coupled with thickness in bass. The V281 delivers a weighty presentation with a touch of reverb that offers a sense of spaciousness. Digging into the V281 spec sheet, one can see that it supplies increasing voltage at higher impedance levels; at 150 ohms, the V281 supplies approx. 25V (see technical discussion above).

A limited reissue of this storied amp was just announced so, for the moment, one can be ordered new. Consequently, at the moment, some used ones are coming to the market. Per @ArthurPower , the owner of Power Holdings and developer of the V281, the reissue is the same amp (save for changes in input/output choices and volume implementation).

CFA-3
I have just sold my wonderful @Dukei built CFA-3 (it was very hard to let it go but I ran out of space in my rack). Fortunately, I’ve had it for most of my time with the Tungsten, and it is another excellent choice for the Tungsten. The CFA-3 has lots of voltage on tap and offers great resolution in the higher frequencies, a snappy bass, and an overall tight and fast presentation. It fits the Tungsten very well.

Beyond ordering from custom builders (@Dukei is warmly recommended), the CFA-3 in now also sold by Headamp if you are looking for a standard purchase experience (I demoed their build at CanJam Chicago and @justin w. 's design sounds very good).

Simaudio MOON 330A
I use this power amp with the Susvara. It delivers 125/250 Watts at 8/4 ohms. It had sufficient power (pre-amp volume 10-15 dB higher compared to the Susvara for same volume) but it wasn’t a great fit: it is a warmer amplifier, and the Tungsten lacked some clarity and openness.

CanJam SoCal Demos
I brought the Double-Sided Tungsten with me to CanJam SoCal and dedicated most of the show to testing amplifiers with it. Here are the highlights of amps which I demoed at the show:

Woo WAS23 Luna
Excellent fit. Gobbs of power, delivered with speed and control. It is an excellent match!

Schiit Mjolnir 3
I tried this newly released amplifier and, regrettably, it was not great fit (it may be great with other headphones, which I didn’t try). It lacked headroom and sounded anemic with the Tungsten.

ampandsound Red October Rev2
I listened to the Tungsten prototype on the ampandsound Nautilus Rev2 at CanJam Chicago and found the pairing outstanding. I was curious to try it with the Red October. I previously heard this 300B amp before with the Susvara and Verite Closed and loved it. I was delighted to find it was as exquisite with the Tungsten. Just, wonderful. If I had the space to park this beast somewhere, I’d sell a couple (or five) of my amps and get one (a unit will set you back a neat $13,000).

Kallyste Amethyste
Continuing to rub elbows with the upper crust, I tried this newly released amplifier, priced somewhere in the $16,000-18,000 neighborhood. The manufacturer only quoted power spec is 15 Watts @ 8 ohms (a rather low impedance for headphone relevance). TLDR; this amp lacks the juice to command the Tungsten drivers. I’m sure it is great with other headphones, but not with this one.

Zahl HM1
This smallish chassis packs massive power and is very well engineered. The HM1 has some kind of crossfeed adjustment knob that allows one to adjust the soundstage in the analog domain; I love that feature! I heard this amp previously with the Susvara and that is a truly outstanding combination. However, the HM1 is not a good fit for the Tungsten, lacking the “grip” to properly drive them.

Viva Egoista 845
The 845 took a nosedive with the Tungsten. This isn’t meant as a takedown, as I heard this amp previously with other headphones and thought it was awesome. But my experience with the Tungsten was illuminating, so I will detail it – when the Viva was fed with a source line voltage of up to 6V, it lacked the gain to bring the output voltage to a sufficient level to drive the Tungsten, sounding distorted at listenable volume levels. When I tried a 9V source, the amp’s gain became sufficient, and it then worked well. For reference, most DACs will output 4V balanced and 2V single-ended. A few will provide 9V (more commonly used in pro audio).

Ferrum Orr
It’s great with the Tungsten! This super small little amp packs a big punch. Every time I demo it, I like it. I was happy to find that it worked well with the Tungsten, offering a very dynamic and engaging presentation. At around $2,000 it is a great option which I can comfortably recommend.

Mass Kobo 465
This amp is extraordinary, boasting pristine and linear amplification. Crafted by hand, it sits at the zenith of the uber-expensive tier with a price tag of $17,000. And even if you're in the market for one, its scarcity is assured, as the designer constructs merely a few units annually (a great tale for another occasion). Will it pair well with the Tungsten? Absolutely! You’re in the know now.

Riviera AIC-10
Sticking with aristocracy, the AIC-10 was my CanJam SoCal show highlight and the best amp I've heard with the Tungsten so far (the only amp that bested my Aegis). This Italian-made amp has an MSRP of around $18,000, and on a fortunate day, you might find a used one in the $8,000-10,000 range. I don’t want to mince words, so here's the bottom line: the AIC-10 paired with Tungsten is the stuff my dreams are made of. This hybrid amp – featuring a tube input stage paired with a robust solid-state class A output stage – marries immense power and driver control with outstanding musicality. It has secured a top spot on my suppressed bucket list.

At this point I want to take a moment to sincerely thank @zach915m for letting me come into the ZMF room before the show started to demo his incredible array of amps (if you ever go to any CanJam, do yourself a huge favor and, before anything else, make it your top priority to visit ZMF: they always have a dedicated room with the most amazing selection of headphones, some of which I have reviewed here, as well as the best selection of amps to demo them with; they are also the nicest people in this business). Anyway, courtesy of Zach, I also tried the Tungsten with the following amps:

Feliks Envy
Very good fit for the Tungsten. Lots of clean power, ton of headroom, and neutral in presentation, it lets the Tungsten shine, passing whatever the source had to give. A great option .

Holo Bliss
I had high expectations, but it didn’t come through here. The synergy was good but the Bliss, a pretty darn powerful amp, lacked headroom to drive the Tungsten to its potential (when cranked up to the max, it was still listenable, if not pleasantly so). I calculate it as offering 19.4V @ 150 ohm, which supports my impressions 20V is roughly the cut-off point for good power supply for the Tungsten.

Wells Milo
Returning to amps for the hoi polloi, this $1,700 is a fantastic option. Always fun, dynamic, and aggressive, the Milo delivered. It hits hard with the Tungsten like it does with anything else I ever tried with it. Another excellent option!

Enleum AMP-23R / HPA-23RM
Two different models – one a desktop amp, the other a mobile one. To my ears, they didn’t work well with the Tungsten. There is something loose and relaxed about these amps’ voicing in mid frequencies. The already smooth Tungsten needs a more grippy amp to drive it. These amps lacked the authority and bite to make them an ideal pairing.

Cayin C9
I love surprises, and sometimes the only way to find those is to stick a plug in and see what happens. The C9 is a powerful portable amp. Still, it delivers only 10V into 150 ohms. But rules of thumbs are sometimes meant to be broken, and I found this was a wonderful exception. If you want a portable(!) unit for the Tungsten, or just a super-small desktop amplifier, this $2,000 little unit is a marvel to me.

Moving on from ZMF’s room, I tried two more amps...

PrimaLuna Evo 100
I couldn’t get a sufficiently audible listening volume.

Patho InPol Ear
A quirky-looking amp priced at $5,000, it supplies about 18V at 150 ohm. It works ok with the Tungsten, but lacked some headroom and it is not an optimal option.

Bottom Line

I found some great amps in the $1-2k price range (Well Milo, Ferrum Orr, Cayin C9, used V281, used GOTL), a few crazy top-end amps (Riviera AIC-10, Mass Kobo 465, ampandsound Red October), and some in between (Aegis, Woo Luna). The conclusion I hope to offer is that there are amps for the Tungsten at nearly any budget for someone who is buying headphones at this price point. The key is to look for high voltage output at 150 ohm (over 20V is ideal, but there are exceptions).

For the best synergy, I would recommend looking for amplifiers that are either more airy, dynamic, or aggressive in their presentation.

SOUND CUSTOMIZATION

Pads

There are currently two pad options: the Caldera Hybrid, and the Caldera Ultra Perforated. The Hybrid pads are perforated suede along their inside and head-facing rims, with solid lambskin on the outside, while the Ultra Perforated pads are perforated lambskin leather across all rims.

I believe Ryan may still determining which would be offered as stock/default options (possibly, Hybrid for the Single-Sided and Ultra Perforated for the Double-Sided) but, in any case, with the option of ordering the other set for $99.

The most significant change I noticed with the Ultra Perforated pads was a more open feel and an expanded soundstage, along with enhanced imaging. I didn't perceive any drawbacks compared to the Hybrid pads. While the Hybrid may provide a bit of extra warmth or perceived body for some listeners, to my ears, they are identical in that respect.

In the pop song “The Way You Make Me” by Korean artist Cloud, the Tungsten imparts a welcome sense of space with the Ultra Perforated pads. It sounds equally good with the Hybrid pads, but with a touch more intimate soundstage.

Similarly, in the “End Credits” from the soundtrack of Star Trek Into The Darkness, the orchestra has much more room to “breathe” with the Ultra Perforated pads. At the same time, the thudding low drums and low brass notes are equally articulated with both pads.

I spent the first month listening with the Hybrid pads, and the second month with the Ultra Perforated pads. I developed a clear preference for the Ultra Perforated.

Vented Adapter

The Vented Adapter is a thin metal disc appendage that snaps into place in between the driver and pad. It has the same honeycomb pattern to match the pad mounting disc, with the only notable feature being a few parallel gaps at its bottom, through which a smidgen of extra ventilation is afforded. As of this moment, I believe it is only meant to be included with the Double-Sided magnet version.

This is the least consequential element in terms of customizing the Tungsten’s sound. With the Vented Adapters in place, the upper mids are slightly elevated, whereas the lower mids seem slightly reduced compared to listening without the adapters. The difference is nuanced, and personally, I'd be content either way. In terms of sonic impact, this adjustment is subtler than changing the pads or, even more significantly, switching amplifiers.

SINGLE-SIDED VS. DOUBLE-SIDED MAGNET

After early Single-Sided (SS) prototypes, Ryan also decided to introduce a Double-Sided (DS) version to create a stronger and more uniform magnetic field, aiming for higher performance than what the single-sided magnet array could achieve. Consequently, both SS and DS versions are now available.

Identical on the outside in every aspect, these two variants of the Tungsten differ in only two respects: (1) the presence of either a single magnet on one side of the driver or double magnets, one on each side, and (2) the price, with the Double-Sided Tungsten costing $500 more ($1,999 vs. $1,499).

These two headphone versions are more alike than they are different. Unless you have both at hand for a direct comparison as I do, if you evaluated and liked one, you would likely appreciate the other just as much (and vice versa).

Overall, I've found the DS to be somewhat more refined, with a larger soundstage than the SS, which offers a more intimate experience. The DS also tends to be more relaxed and non-fatiguing – though the SS is non-fatiguing in its own right. When I compare them closely, the SS seems to have a subtle V-shaped sound signature relative to the DS's neutral tonality, but it would likely strike me as neutral in isolation. Those who favor a rawer edge and more aggressive dynamics might lean toward the SS. In contrast, the DS seems more resolving and technically sophisticated, which makes it my personal preference.

I found that the slight difference in the specified sensitivities between the headphones was indiscernible to me. When I connected both headphones to various amplifiers side by side, setting the same volume level on the amp, the audible volume was consistent for each pair. When deciding which version to purchase, I recommend you proceed with the understanding that your amplification needs will be similar for either version.

COMPARISONS

With the Single-Sided and Double-Sided versions of the Tungsten priced at $1,499 and $1,999 respectively, one might expect comparisons with other headphones in this price range. But I must state upfront that, in my view, the Tungsten surpasses them all. Consequently, comparing it to its immediate price peers felt like juxtaposing a lion with sheep. Instead, to properly contextualize their performance, I found it more informative to compare them with TOTL planar headphones. This approach serves as a testament to the remarkable accomplishment of Ryan, whose dedication has brought these exceptional headphones to market.

Tungsten vs. LCD-4

Although no longer the latest model, these headphones can still be found, and offer a useful point of comparison that many audiophiles may already be familiar with, which helps in describing the Tungsten's sound characteristics.

My initial impression of the Tungsten was that their silky and smooth presentation most reminded me of the LCD-4, which is another uniquely high-impedance planar. However, whereas the LCD-4 delivers a darker presentation, the Tungsten extends well into higher frequencies and presents them with clarity.

The Tungsten also extend lower with more rumble in the sub-bass. They are overall better balanced tonally. In “Royals” by Lorde, the Tungsten’s sub-bass extends with more articulation and rumble. It simply “out-basses” the LCD-4. Yea.

The Tungsten headphones are notably more resolving and technically superior across the spectrum – a significant feat considering the LCD-4 were Audeze’s top performers until just two years ago. While the LCD-4 sound impressive in isolation, they can seem somewhat veiled when compared directly with the Tungsten, which provide a clearer sense of air, space, and superior note separation. Dire Straits’ “Brothers In Arms” showcases the Tungsten’s superior imaging and instrument separation: male vocals, drum rimshots, electric guitar, bass guitar, and electric keyboard are all clearly delineated. These can also be well discerned on the LCD-4, but bass guitar notes were not as distinctly clear as on the Tungsten. In Michael McDonald’s cover of “I Heard It Through The Grapevine,” the drum hits are crisper on the Tungsten, which are faster than the LCD-4. The lowest bass guitar notes throughout the track are equally audible on both headphones, but the Tungsten separates these notes better with overall improved air and space between instruments.

Female vocals are really lovely on the LCD-4. Adele’s “When We Were Young” is silky, and the presentation is comforting and non-fatiguing; I could listen to it for hours with joy. In comparison, the Tungsten presented Adele’s voice to me a touch more energetically and forward. I suspect that may be a perception due to the Tungsten’s higher resolution and better separation of vocals.

The Tungsten feel like what the LCD-5 may have been like if they were made as an upgrade to the LCD-4 (rather than the departure in direction they are).

Tungsten vs. Caldera

As great as the Tungsten’s stage and separation are, I do find that the Caldera edges them out a bit in this department. On jazz pianist Tommy Flanagan’s wonderful album “Lady Be Good… For Ella”, when using “Cherokee” as a test track, the placement of instruments by the Caldera is just a touch more exact (we are talking about the difference between great and greater).

However, the Tungsten edges the Caldera in low-end extension. Whereas the Caldera’s lower bass is more physical, the Tungsten extends a hair deeper and is more resolving in detail. In “Suite from ‘Romeo and Juliet’: I. Montague and Capulet (Live) 1936” conducted by Riccardo Muti, the low grunt of tubas is more flushed out in the lower reaches on the Tungsten. That qualitative difference between these headphones is also evident on the previously mentioned track “Desire” by Bozz Scaggs. The Caldera presents the low and sub-bass with greater physicality, while the Tungsten reaches a touch lower and exposes a touch more detail. Which you may prefer – Caldera’s physical sub-bass vs. Tungsten smoother presentation – is a matter of personal taste. I love both.

Paavo Jarvi’s wonderful interpretation of Beethoven’s Symphony No. 5 first movement is another demonstration of the difference between these headphones. Overall, the Caldera headphones offer superior dynamism and a slightly more expanded soundstage, while the Tungsten offer great resolution and extension with a smooth and refined presentation.

I’d like to point out something – the fact that Tungsten is able to even get admission to this club and be contrasted with headphones twice its price is an accomplishment in itself. The Caldera’s place in my collection, and in my heart, is firmly lodged. But for any Caldera owner, the Tungsten would be a wonderful complement to your collection, owing to its different style of presentation.

Where the Caldera reigns supreme as the most dynamic, exciting, and visceral planar headphones, the Tungsten offers the smoothest and most non-fatiguing presentation of the TOTL planar lineup.

Tungsten vs. Susvara

Sara K.’s wonderful song “Blind-Hearted” has a luscious bowed double bass in its opening. The Tungsten offers a meatier presentation here that offers an extra texture on that bass notes. However, the Susvara's overall clarity, soundstage, and instrument separation are superior.

“New Oldie” by Snoop Dogg, Usher, and Eric Bellinger combines sparkling treble notes with a deep punchy bass, along with multiple male vocals. To my ears, the Susvara treble extension is a touch superior, while the Tungsten bass is a touch meatier, though both excel across both frequency extensions.

Before we continue, I’d like to pause again and acknowledge that we are entering the realm of products that retail at the $6,000 mark. That such a comparison can be useful is, in itself, yet another triumph. The Susvara remains the king of technicalities among planar headphones and, when both of these hard-to-drive headphones are amplified to their fullest potential, the Susvara edges out the Tungsten in technicalities. But my advice to Susvara owners would be similar: the Tungsten offer something truly special and complementary and would be a wonderful addition to your lineup.

Where the Susvara is known for its “ethereal” presentation – wonderfully delicate and super-fast – the Tungsten offers a fuller and sweeter voicing with comparatively more decay on its trailing notes, providing a smoother and more relaxing listening experience.

CONCLUSION

The Tungsten headphones deliver exceptional performance with a distinct character. They do not attempt to outdo the Susvara, imitate the Caldera, or follow any other established path. Instead, they resonate with the unique ear of a designer who has a clear vision of his preferences and the expertise to realize them. I have a deep appreciation for innovators with the courage and conviction to carve out their own signature sound.

Tonally balanced with a touch of warmth, the Tungsten provide fantastic extension into both the lowest and highest frequencies. Their signature feature is a silky smooth, non-fatiguing presentation. Combined with a beautiful design and quality build, these headphones are crafted for many hours of enjoyable listening. For the past two months, they have been my primary headphones while working on this long-term review, and they are poised to maintain a high position in my listening rotation.

Selecting the right amplifier for the Tungsten is crucial, as they require a considerable output voltage to truly shine. When properly powered, they deliver a superlative sonic experience. Should you get them? Emphatically – and without any reservations – my answer is yes.

It is nothing short of astonishing that an emerging boutique brand could launch such a remarkable product as their first fully in-house design. The fact that Ryan, essentially a one-person operation, can source and produce these headphones independently is just remarkable. The Tungsten are reshaping an entire market category, surpassing competitors in their price tier, and comfortably knocking on the doors of the upper-market echelons. This is a prime example of how competition benefits consumers.

The Tungsten may very well be one of the most pivotal headphone releases of the year, undeniably redefining the cost-to-performance ratio in the marketplace.

Modhouse has not just entered the audiophile neighborhood – it constructed a permanent residence in it. Indeed, Modhouse now has a signature house sound!

BONUS TRACKS

Say what?

Yes, the review is over. If you’ve stuck through it and made it to this point, here is a little easter egg as a bonus. There were so many tracks I enjoyed on the Tungsten. In preparing the review, I earmarked many of the following to reference, but ended up with more tracks than I could squeeze into this long writeup. So, in no particular order, here is a mish-mash collection of tracks across genres with no logic or rhyme, except that I have loved listening to them, so why not share the love?

“City of Stars” by 王OK
“Slow Dance” by Ana Popovic
“Lonesome Road” by Madeleine Peyroux
“Africa” by TOTO
“Sunset City Theme” by Soulpersona & Princess Freesia
“The Crown Main Title (Faithless Remix)” by Hans Zimmer
“Howl’s Moving Castle – Merry Go Round Of Life” by Gissini Project
“Earth Song” by Michael Jackson
“Lowdown” by Boz Scaggs – high hats (treble, imaging to left)
“Romeo and Steve” by Iiro Rantala (read these liner notes while listening)
“You Are The Sunshine Of My Life” cover by Ida Landsberg
“Ascent” by Art Hirara (the EP 2022 recording)
“Logos / Pranking The Natives” from the soundtrack of Star Trek Into Darkness
“Angel” by Sarah McLachlan
“Caravan” from the soundtrack of Whiplash
“4ware” by deamou5
“Recomposed by Max Richter: Vivaldi, The Four Seasons (2012)” by Max Richter
“Hey Nineteen” by Steely Dan

The long anticipated ZMF and Decware amplifier collaboration was first confirmed by Steve Deckert last year. As he then posted on the Decware forums: “A CSP3 with full anniversary mods comes close, but this is noticeably better, and it should be... If you live in your headphones and want a reference OTL headphone amplifier/line stage, I seriously doubt you'll find anything that sounds even close for the money”.

I have had the rare pleasure of testing this output transformerless (OTL) amplifier over the last four months across several design iterations and, a year after this promise was first made in public, I can enthusiastically concur. The final result is absolutely superb.

Some discerning folks might have caught a glimpse of this amp at ZMF’s room at the recent CanJam in NYC, where it was doing a quiet trial run somewhat under the radar.

Dubbed “Decware ZMF Reference OTL” (catchy), this exciting new amplifier is now, at long last, ready for launch! Per Zach, it will be available later this month, on or around the launch of the new Atrium Closed headphones. It will retail for $3,999 and will also be available for $3,799 bundled with ZMF headphones.

For simplicity, I will refer from here on to the Decware ZMF Reference OTL as the “Decware OTL”.

A noteworthy anecdote: the current waitlist for Decware amps is close to two years (not a typo). This may be both an opportunity to get assertedly the best OTL Decware has made, and an opportunity to get it directly from ZMF upon its upcoming release.

SPECS

Tubes

The Decware OTL uses one gain (input) tube, two driver (output) tubes, and a rectifier tube. It offers extensive tube rolling options:

Input Tube
A tube roller dream, this amp will accept most 6V dual triode tubes, including: 6DJ8 (ECC88), 6922 (E88CC), 6BQ7A (ECC180), 6N1P (6Н1П), and 6N5P (6Н5П). It will also work with 7V tubes, such as 7DJ8 (PCC88) and 7ES8 (PCC189). The stock tube is the 6N1P.

Output Tubes
Stocked with a pair of 6N6P (6Н6П) tubes, the Decware OTL’s circuit design is optimized around these tubes' electrical characteristics.

You can also roll in 6922 and similar tubes per above; however, note that these would increase impedance and cut down output power by about 3x which is not ideal.

Rectifier Tube
There are many options here. All of the following rectifiers are supported: 5AR4 (GZ34), 274B (CV684), 5Y3, and 5U4. You can also use the USAF 596 with an adapter.

Power

1800 mV in cathode resistor mode.
2000 mV in cathode bypass mode.
More on that, further below.

BUILD & FEATURES

Design

The Decware OTL has a classic Decware design. An old-fashioned design, it offers a heavy dose of authentic nostalgia, with a hint of retropunk or quirkiness, depending on your esthetics. Like drinking a glass of excellent single-malt scotch, it is served straight up.

Encased in a beautifully minimalist wood casing, it will sit harmoniously alongside your ZMF wooden headphones. The Decware OTL also has a very small footprint at 8” wide x 15.5” deep. It is also very light (you can easy pick it up in one hand, even if you’ve never done a bicep curl in your life).

What’s What

Volume Control
Up front, we have the black volume knob. It is smooth, and offers excellent and fine volume control, with perfect channel balance from the very lowest volume.

Headphone Outputs
You will note two XLR headphone outs to each side of the volume knob; and if you look further toward the back of the amp, you will notice two more 1/4" headphone outs (behind the blue capacitors, to each side of the black transformer). There are a total of 4 headphone outs which work concurrently. So, if you usually invite 3 friends over to listen to headphones together (with exactly the same headphone sensitivity and personal volume preference) then good news! You now have an amp that can do that.. Note that since the amp is single-ended, the choice of XLR vs. 1/4" offers a welcome convenience, but otherwise has no significance to your listening.

VU Meters
The Decware OTL has VU meters. They look beautiful and glow in soft orange, adding to the fun analog aura of the experience. Like all VU meters, they have no practical use, but that’s not the point, is it?

Cathode Bypass Switch
In between the VU meters you will see a small switch. It is one of the more notable features of this amplifier: a cathode bypass switch. When pulling the switch toward you, the amplifier will bypass the cathode resistor. I do not have the technical diagram of the amp (nor the technical expertise) but, in layman terms, in cathode bypass mode, the line-in signal would reach the gain tube’s cathode via a capacitor connected in parallel to the cathode resistor, which is being bypassed. Bypassing the cathode resistor should reduce some of the negative feedback caused by the resistor, resulting in both increased gain and improved dynamics and frequency response.

This switch has a real and meaningful impact on the sound signature. The Decware OTL sounds great in both modes. With the cathode resistor engaged, the sound is more focused and centered. With cathode bypass engaged, beyond a small audible increase in gain, the music is rendered more holographic and, at least in my mind’s eye, there is a feel of slightly more second-order harmonics and reverb, to taste. That is my preferred mode.

Tubes
Behind the cathode bypass switch you will see the input/gain tube, behind it follow the two output tubes, and further back is the rectifier (in between the two blue capacitors). The large black transformer follows. All line-in and line-out connections are further behind it.

Preamplifier
On each side of the transformer, behind the 1/4" headphone out ports, you will two RCA outs. These are the L and R channels of the variable line-out, which is controlled by the volume control contemporaneously with all headphone outs. The line-out and headphone outs are all “hot” (no switching in between headphone and preamp; if the wire is in, it gets the juice).

Line In
You can connect up to 2 different sources to RCA line-in connectors at the very back of the amplifier. Small switches, one to the left and one to the right, let you choose which of the connected two L channels and which of the connected two R channels are used (in short, you have to move two switches to change a source). There are 4 small black knobs, one next to each of those line-in channels. These let you control the gain of the line-in, before it reaches the gain tube. These are controlled separately for L and R channels.

The on/off switch is tucked in between the transformer and power outlet. Speaking of which..

Quirky Design
When turning the power on, you carefully insert your hand vertically from above, in between the various interconnect cables that jut upwards. When turning the power off, you will now also have the warm transformer to keep you company.

The cathode bypass switch is right next to the gain tube, so just make note not to touch it.

In practice, nothing is really too hot, and nothing is too sensitive. Retro design, retro Ux. A throwback to a more genteel time. It is really part of the charm of using this amplifier; and this design oozes with charm.

SOUND!

Chain Used

In the specific context of this writeup, I have used the following chain:

Roon Nucleus+ ➤ CAT 7a ➤ Audioquest Cinnamon RJ/E ➤ Bricasti M3 (power cable: Cardas Reflection) ➤ Moon Black Dragon (RCA) ➤ Zynsonix custom switchbox (silver cabled) ➤ Moon Black Dragon (RCA) ➤ Decware ZMF Reference OTL (power cable: Audio Sensibility Testament SE | power source: IsoTek EVO3 Aquarius) ➤ Decware Decware Taboo SE84TS+ (power cable: Audio Sensibility Testament SE | power source: Transparent PowerBank 6)

Overall Sound Signature

When one conjures up the sound of a great OTL, a few things come to mind. The Decware OTL offers these all in spades: it is holographic, natural, and smooth sounding. The sound will naturally be highly dependent on the headphones used. However, I have found the Decware OTL to impart the following consistently:

Lushness
This amplifier has a beautifully sweet sound, with a smooth and velvety voicing that washes over you like refreshingly cold water on a hot summer day. I don’t have the gear to measure harmonic resonances, but I imagine it would show a dose of second order harmonics in cathode bypass mode.

I find this essence of sweetness and lushness of sound most alluring with acoustic vocals. A great example for male vocals is Al Jarreau signing of “Breezin’” which sound as smooth as silk. For female vocals, Laufey voice sounds especially sweet on “Street by Street”. OTL saccharine without overdose. Really breathtakingly beautiful voicing.

Sense of Space
There is a real impact on the soundstage when switching to the Decware OTL, with a wonderful sense of diffusion of sound into a very large space coupled with a nuanced reverb. As if the music played within a large cathedral hall with the sound softly echoing across the faraway stone walls and vaulted tall ceiling arches.

On “The Wind That Shook The Barley” by Dead Can Dance, listening with the Atrium Open, I found the already incredible soundstage of this recording and that of the Atrium further expanded, echoing far and wide in the endless distance with a sense of beautiful resonance, while remaining organic and natural sounding.

Thumpy Bass
Not the most scientifically objective adjective, but if I would try to convey the feel of the bass with the Decware OTL, I would say that it is a lush and warm thump. It hugs you like a comforting flannel blanket. A wonderful example is the collaboration of Taj Mahal and Keb’ Mo’ on “Don’t Leave Me Here”. On this track, the bass is rich and thick. On Dominique Fils-Aimé’s wonderful song “Birds”, the Decware OTL offers a bass that is clear and transparent, while lending a sense of gentle decay to the low drum kicks and handclapping rhythm. At the moment, I am listening to “Good Morning Gorgeous” by Mary J. Blige on my Vérité Open headphones, and just caught myself bobbing my head with a full on stank face. Shut the front door!

To offer a sense of comparison, my beloved transformer coupled Auris Nirvana provides a more focused and crisp sound, with a blacker background and a more centered image. In contrast, the Decware OTL offers a wider sense of space, resonance, and organic timbre. If I borrowed an analogy from the ZMF headphone universe, the voicing of the Nirvana and Decware OTL offer a similar Yin and Yang contrast in the signal chain as would the Caldera and Atrium headphones, respectively.

Synergies

There is a common rule that suggests one should pair red wine with meat and white wine with fish. OTL amps are meant to drive high impedance dynamic headphones, and the Decware OTL does so wonderfully.

I practically love the pairing of the Decware OTL with the Vérité Open, Atrium Open, and Sennheiser HD800s. These combinations are magical. In all cases, the amp offered the value added sound attributes I described above, imparting its smooth, spacious, and harmonic sound signature. If I put one of those headphones on, they stay on for hours

I have also found the Decware OTL an excellent match to the Atrium Closed and Vérité Closed.

There is also wisdom that suggests that one can drink any wine with any food, and that the aforementioned rule is meant to be broken. I’ve found that keeping an open mind can sometimes be rewarding, and that some unique cases that do not make sense on paper, work great against all logic. These included the AT L5000 (45 ohms) and MDR-R10 (40 ohms), both of which I found to be remarkably well controlled by the Decware OTL, including an unexpectedly tight bass. I can’t explain it. And, as expected, some other low impedance headphones were poorly controlled. So you should get this amp for your high impedance headphones but, if you do, don’t be afraid to experiment..

Tube Rolling

I have tried numerous tubes for the input gain and found that all worked great. A 6922 (Sylvania JAN 1970) and a 6BQ7A (RCA 1957 black plates o getter) both offered clarity, and a Telefunken PCC189 offered a tighter bass, possibly a good choice for heavy rock, metal, or other bass heavy genres. My current preference is the 6N1P tube, the very one which comes as the stock tube. I have found it offers the most holographic and smooth sound. An excellent choice for this amp imho.

For output tubes, I have stuck mostly with the 6N6P. I have yet to do more significant tube rolling here, but given these tubes are more powerful than the alternatives as I explained in the spec section above, I am not sure if I would end up changing these.

For rectifier, I have roll in a Philips Miniwatt GZ34 (Sittard brown base), GE 5Y3G, and a Raytheon 5Y3GT. I settled on the GZ34, having found its low voltage drop (lower sag) pairs best with the amp’s organically smooth OTL character, offering the best transient response and dynamic performance.

As a preamp

I tried the Decware OTL as a preamp to my solid state CFA-3 headphone amplifier, and to my TC Auris Nirvana headphone amplifier. In both cases, it provided a clear and neutral line stage with excellent and quiet volume control. The resulting sound characteristic was true to the amplifier used. I haven’t done extensive tube rolling in listening to these combinations.

However, there is one notable exception that was a true revelation.

In fact, this combination was so exceptional, it may be one of my all-time favorite amp configurations:

Decware OTL + Decware Taboo
A quick note: I have an older Taboo model (SE84TS+ from ~2011). However, @zach915m has the current Taboo (IV) and, as we’ve exchange notes on this, we have both found a very similar experience: when using the Decware OTL as a preamp into the transformer coupled Decware Taboo amplifier, the resulting sound is absolute magic. As best as I can describe it, it is like taking all the goodness of a tube amp, multiplying it by two and applying an exponent. I recall the first time I tried this combination. My jaw dropped to the floor!

On this combination, the Caldera headphones were as good as I have ever heard them. Insanely holographic and musical, it is the ultimate amplifier chain for these headphones. I also tried the Susvara, and it may have been the most melodic I have heard them, though the headroom with those would make it more of a specialist combo for specific genres only.

CONCLUSION

Our decisions in life are often guided by a blend of rationality and emotion. The Decware OTL is the embodiment of that duality. It offers great technical performance but, first and foremost, it offers a uniquely emotional experience. As your hand hovers above its beautiful casing to adjust the volume, you note the impractical VU meters facing upward and the warm tube an inch away from your fingers. You smile knowingly, just as the music washes over you and as you rediscover your headphones, as sweet and harmonious as you have ever heard them. The stirring notes tug at your heartstrings are the ones that amplify your life, transcending mere function to create a truly unforgettable experience. Yes, the Decware OTL will make even a poor writer want to wax poetic..

In a stack alongside several other amplifiers that I love, I have found that I can now not only select the headphones to match my mood or genre, but I can tailor the amplifier to the occasion.

Finally, after having had this amplifier on a very long and extended loan for review, I realized that I needed it to stay with me. I loved it so much that I bought it. I am not sure how many of these will be available, but I suspect they will be gobbled up as fast as they are offered. If you are considering getting an OTL, keep you eyes peeled for the upcoming launch of the Decware ZMF Reference OTL (and, don’t blink!)

ZMF's latest headphone, the Atrium Closed, is one of the most widely anticipated upcoming headphone launches. A closed-back version of the immensely popular open back Atrium headphones launched last year at CanJam Chicago, this sibling is expected to make its debut at the upcoming CanJam NYC and become available to the public in the coming weeks.

Following are my first pressions of these exciting new headphones. Please note that these are first impressions only, based on several days of listening. As always, I may come back later with updates as I get to know these headphones better and as my own impressions evolve. Realizing that many community members are eager to learn more about the Atrium Closed, I am consciously expediting this writeup.

For simplicity, I will refer from here on to the Atrium and Atrium Closed as AO and AC, respectively.

WHAT’S WHAT?

The Atrium Closed is a ZMF headphone through and through, with the familiar warmth, richness, and fullness of sound one has come to expect from ZMF. But I think that the definition of the “ZMF House sound” is becoming less homogenous with the expansion of their product portfolio.

Many who may read this note would be intimately familiar with ZMF’s headphones (and possibly own a pair or few). But Zach has been busy launching new models at a dizzying rate (with more to come), and so, let me make a quick intro statement to help put these into quick order.

We now have several distinct ZMF product family groupings. At the top of the line, these include:

• The Vérité family, offering a wonderfully natural timbre coupled with fast attack; these headphones have fast dynamic drivers.
• The Atrium family, offering a lush sound and slow decay, coupled with holographic soundstage and imaging; these headphones incorporate the ADS damping system.
• The Caldera family, offering exceptional technicalities and frequency extension, stemming from its new planar driver, CAMS magnetic array, and new pads design (note: Caldera Closed headphones are in the offing).

TLDR

The AC enjoys the same beautiful slow decay and addictive lushness of the AO. If you are looking for the analog presentation of the Atrium in a closed-back version, you will be find it here.

The AC shares the ADS (Atrium Damping System) used in the AO, adapted to a closed-back setup. While it shares the beautiful analog sound of the AO, which many users know and love, the AC has a distinctly unique tonality.

Most notably, the AC has a rumbling sub-bass and a clearly elevated lower bass (those of you who remember the L3000 and were waiting for a worthy bass-y closed-back successor, take note). In addition, to my ears, the AC’s upper mids are more forward than the AO. This is notable, for example, with female vocals. So the AC are not strictly downward sloping frequency response headphones, and do offer clarity in the higher registers (depending on pads choices).

The AC are not closed-back headphones that feel like open back headphones. They simply feel like great closed-back headphones. Seal and passive isolation are exceptional. My wife has startled me more than once over this past weekend tapping on my shoulder

BUILD & COMFORT

The Atrium Closed share the exceptional build quality of all ZMF headphones and are very comfortable. They will be initially offered in Cherry wood for the stock model (the same wood offered for the AO stock model) and Olive wood for the limited edition option. The stock model weighs approx. 500 grams (about 30 grams less with a Magnesium chassis). Weight distribution is very good on this headphone. The headphones feel light and can be comfortably worn all day. Olive wood would be a little heavier.

The AC have a much thinner profile than the Vérité Closed (VC), not much wider than some larger consumer headphones, and a slightly more angular line. I think that this is probably what an MDR-R10 headphone would look like if it were photoshop-ed to look thin

Per Zach, the driver on these headphones is the same 300 ohm driver used in the AO. It sits a little further back in the cup (3mm further compared to the VC) which, coupled with its damping system, allows these headphones to offer a real sub-bass experience (more on that further below). I also noted that the venting ports at the top of the cups are about half the length of those on the VC (though seemingly a bite wider).

SOUND CUSTOMIZATION

I would normally save a discussion of wood choice, pads, and amps to the tail end of a review. However, I have found that these can have a significant impact on the AC’s presentation, so please humor me as I take a moment share my experience here before jumping into the details of my listening impressions. My purpose it to provide a proper context for my impressions that will follow. If you’d rather skip the tedium of these details, skip down to the “SOUND IMPRESISONS” section.

Wood
As you read the notes below, please keep in mind that Cherry wood is softer and will offer more decay, reverb, and lushness; while the harder Olive wood should sound a little faster and snappier in comparison, with more speed and resolution in the bass. My impressions below are based on my listening to an AC review unit in Camphor Burl wood, which Zach told me is similar to the Cherry in its presentation. Therefore, my listening impressions are based on a soft wood listening experience.

Pads
The AC stock pads are the Caldera Lambskin Thin pads. Caldera pads are perforated on the outside and head-facing rims, and solid on the inside rim. Given the elevated lower bass sound profile of these headphones, this “semi closed/semi open” pad construction allows some release of excess energy from the cups through the outer perforations to better control sound wave dissipation, while the solid interior retains the closed-back characteristics and seal of solid pads.

I will share upfront that, while I have always preferred ZMF’s stock pads for all their headphones to date and have always preferred lambskin pads in general, I decided to try the Caldera Suede pads (which I happen to have at home as alternative pads for my Calderas), and I much preferred them.

I do love a great bass. However, the soft wood coupled with the Caldera Thin pads had too much bass reverb which I found a little too elevated and bleeding into the mids. I am pointing this out upfront, as I know that there are folks that would, in fact, prefer and love this presentation (I’m talking to all you bass heads). For me, the Caldera Suede pads tightened the bass and offered a very clean transition to the mids, while also taming some of the upper mid forwardness (which some ZMF fans may prefer) and extending the treble, and materially improved the soundstage.

The Caldera Suede pads are therefore me my reference point in what follows, unless otherwise specified.

Please note! It is quite possible that with harder wood varieties, the Caldera Lambskin Thin pads may work better than the Caldera Suede pads, as the harder wood will likely sharpen the AC focus and slightly lower its reverb. Therefore, your pads of choice should take into account both your personal taste, as well as your choice of wood.



Amps
I have tried the Atrium Closed with 6 different amps and narrowed down my listening to the Auris Nirvana (transformer-coupled tube) and CFA-3 (solid state) amplifiers. These performed the best from what I’ve had on hand, and they are also my most familiar references.

With the soft wood and Caldera Thin pads, I found that a solid state amp offered the necessary clarity to tighten up the bass, increase treble clarity, and expand the soundstage a little. However, once I switched to the Caldera Suede pads, a tube amp was the perfect complement, adding in turn more bass texture and warmth.



Cables
I tested the AC with the following cables: ZMF 2K Copper, ZMF Letrik S, Underwood Linx Diamond, and ZMF Vérité Silver. I settled on the Vérité Silver. I am skeptical whether I would pass a bind taste but, at the moment, I perceived a slightly tighter bass and more airy presentation with the silver cable.

SOUND IMPRESSIONS

The Atrium closed timbre is very similar to that of the AO: the slow decay of the Atrium Damping System yields a very satisfying slow decay that provides a lush and organic presentation and a sweet timbre. But the AC has a distinctly unique tonality. Most notably, it has an elevated sub-bass and lower bass, and a forwardness in the upper mids to lower presence region. Let’s jump right into the detail!

All music tracks referenced below are hyperlinked.

Frequency Response
Sub-bass
This is one of the lowest extending dynamic drivers I can recall listening to. If you like sub-bass, you will love these headphones. Especially with the Caldera Thin pads, the AC exhibits a sub-bass presence that is normally reserved to the domain of planar headphones. It is more subdued with the Suede pads, though still present. For example, on the track “Null” by South Korean indie artists eAeon and Jclef, a sub-bass rumble begins at 0:13 seconds and stays present throughout the track. I have heard it before but never noticed it as much until now. Relative to the rest of the frequency curve, I perceive the sub-bass on the AC to be more elevated than on the Caldera headphones (though the Caldera’s sub-bass resolution is superior). Put Kenrick Lamar’s “King Kuta” on the AC, and the sub-bass energy will shake your bones.

Lower Bass
The lower bass follows the sub-bass, offering a continuum of elevation in the lower spectrum of the FR. Thick, heavy, and lush. If you like to eat a pint of ice cream with a spoon in a single seating, you will have a blast with the Caldera Thin pads. For my taste, they were a little too elevated and muddied, but with the Caldera Suede pads I got great clarity and joy. These headphones were designed for slow decay. Where their Vérité brethren offer a crisper attack, the AC offers a slower decay. This creates a lingering reverb, for example, with low bass guitar notes on tracks such as Mary J. Blige’s “Good Morning Gorgeous” and Scary Pockets cover of “American Boy”. At the same time, the AC can offer a very crisp rhythm when required. For example, on @warrenpchi ’s personal favorite track, “Kiss Me More” by Doja Cat (), the lower drumbeats and electric guitars are very tight and exact. Male bass vocals, such as on The Fairfield Four’s a cappella track “These Bones”, are beautifully creamy and resonant.

Upper bass
Warm and clearly articulated, the soft thump of drums sounds especially satisfying and organic on the AC. Terri Lyne Carrington’s drum kicks on “Nothing From Nothing” (supporting pianist Tim Ray) had my foot happily tapping and my head bobbing. The damped decay results in a wonderfully natural drum timbre. Drums are also well resolving and enjoyable in highly rhythmic tracks, like “Sunset City Theme” by Soulpersona & Princess Freesia (a mix between soul and electronic dance music). On Björk’s wonderfully quirky jazz track “Lukta-Gwendur”, the slow decay of double bass notes almost defies gravity, gently lingering in space (btw, this unusual album is one of my little guilty pleasures).

Lower Mids
ZMF’s dynamic timbre shines through. Lower mids are a hint laid back, and to my ears offer a very natural presentation of male vocals. I think that male vocals sound especially good on the AC. Gregory Porter’s rich baritone on “Hey Laura” is sonorous, while Allan Taylor’s voice on “The Tennessee Waltz” is smooth as silk (check out the beautiful acoustic guitars on this wonderful track).

Upper Mids
The Atrium Closed sweet timbre carries on, but it is more forward in the upper mids and presence regions. Female vocals are quite forward but non-fatiguing, making the presentation very intimate. Jo Harrop vocals on “I Think You’d Better Go” is melodic, forward, and immersive. The track “My One and Only Love” by Polish duo Wojciech Myrczek (male vocals) and Paweł Tomaszewski (piano) is simply exquisite. In French classical guitarist Thibault Cauvin’s acoustic rendition of Bach’s Toccata and Fuge in D minor, called simply “Toccata” (from his latest album released last week), the guitar is right up front and close, yet each pick of the guitar decays slowly around you. This forwardness, coupled with the AC’s decay, creates a uniquely intimate experience.

Treble
The Caldera Thin pads offer the more traditional ZMF tuning with a recessed and slightly rolled off treble. On the other hand, the Caldera Suede pads offer a very good treble extension, keeping it neither forward nor relaxed, just perfectly level (to my taste), with excellent resolution. One of my all-time favorite jazz vocal performances is by Danish singer Sinne Eeg. On “Jeg Snakker Med Mig Selv” (singing in her native Danish the translation to the jazz standard “I’m Singing to Myself”), hi-hats are clearly articulated and presented equally along the vocals and piano on this track.

Soundstage
Pad choice made a significant difference here. I found the AC with Caldera Thin pads to have a narrow soundstage. With the Caldera Suede, the AC has more sparkle, resulting in a greater sense of space without a finite end. To be sure, these are closed-back headphones, and you will not mistake them for open back ones. However, with the Suede pads I quickly forgot that, and my brain adjusted to the sense of space offered.

In both cases, soundstage depth is good (more detail on imaging follows below). On Till Brönner’s rendition of “Come Dance With Me” the drums are placed further behind the singer, offering a sense of depth, even as the width is more limited.

With the suede pads, soundstage width expands enough to create a facsimile of the familiar Atrium Open 3D presentation, packaged in smaller dimensions. I’ve listened to “Goliath” by Woodkid and the soundstage on this track is wonderfully holographic. The slower decay hangs the notes in the air for a moment longer, which then dissipate and gradually dissolve. That wonderful, familiar presentation repeats with Allan Taylor’s “Colour To The Moon”, with rich vocals and guitar picks reverberating in space.

Imaging/Layering/Instrument Separation
The Atrium Closed do a very good job placing instruments in space. On “Hunting Wabbits” by Gordon Goodwin’s Big Phat Band, the placement of the big band instruments is exact with a fantastic instrument separation between all brass and percussive instruments. “Love Mad” by singer-songwriter and guitarist Tamar Eisenman is a song that I’ve had the chance to recently hear her perform live in NYC within a small club setting. The AC faithfully reproduced this track to my recollection, with low drum kicks reverberating off the imaginary walls of the recording venue. A more traditional imaging test track, “Flamenco Sketches”, from Miles Davis’ Kind Of Blue album, stress tests the AC’s imaging and layering. Miles’ trumpet comes clearly from my 1 o’clock, while further to the right at 2 o’clock, Cannon Adderley’s alto sax joins in. The piano accompanies them to the far left of the stage. Drums are placed right and further behind Adderley, as Coltrane’s tenor sax enters at 11 o’clock, perhaps with a touch of height. I cannot tell in all honestly how true this is to the original recording, but it is consistent with how I have heard this track since I first bought the album 30 years ago, and it is very believable.

Resolution
In comparison to the Caldera, the best resolving ZMF headphone, these headphones keep up close behind. I've started with same track I used in my Caldera First Impression: Yoko Kanno’s “Tank!” (from the Cowboy Bebop album). While the Caldera pulls ahead in its resolution of the lower frequencies (a challenge for any closed-back headphone to compete with), the AC treble extension and resolution kept up impressively close to the Caldera's high benchmark (contingent on my use of the suede pads). On German soul/jazz singer Jeff Cascaro’s live recording of “Roots”, the faint sound of cymbals in between minute 0:45 to 1:05 is very well captured.

COMPARISONS

Atrium Closed vs. Vérité Closed
These two closed-back headphones by the ZMF offer some distinct contrasts. In many ways, they each excel in different areas.

Starting with soundstage, to my personal preference the VC has a wider and superior soundstage to the AC. When I put my VC on, if feels open after a while. The AC will sound airy and spacious with the Caldera Suede pads (less so with the Caldera Thin pads), but it is not as wide. For example, on Simone Dinnerstein’s superb performance of Bach’s “Concerto for Harpsichord No 5. In F Minor (Allegro)”, the VC recreates the grand feeling of Concert Hall 1 at the Funkhaus Berlin.



In bass, the AC and VC offer clear contrast and choice. The AC offers a notably superior sub-bass to the VC, and a more elevated bass level overall. The VC, in contrast, offers more speed, with a snappier and more resolving bass.

The AC offers a slower and more organic sound, while the VC offers a more incisive presentation. On “Concerto for Trumpet” by Lucienne Renaudin Vary and the Luzerner Sinfonieorchester, the VC’s attack offers superb clarity to the lead trumpet notes, while the AC offers a beautiful and organic presentation of the overall brass ensemble that feels more cohesive. Another example is offered by the wonderful female vocal and double bass duo Frau Contra Bass. On “Ich Liebe Dich Uberhaupt Nicht Mehr”, the double bass is much clearer and better resolving on the VC and more saturated on the AC; while the AC presents a superior timbre for the female vocal.

In the mid frequencies, the AC is truly a Yin to the VC’s Yang. Relative to each other, the VC’s lower mids are a little more forward, while upper mids are more recessed. At the same time, the AC’s lower mids are neutral, while the upper mids are decidedly more forward than the VC’s.

Which headphone you may prefer will depend on your listening preferences; and if you are lucky to have both, on your mood

Choices, choices.

Atrium Closed vs. Atrium Open
The AC and AO share the same 300 ohm driver, and both use the Atrium Damping System with some adjustments. The essence of the Atrium is preserved in its closed version: slow decay, reverb, lush and organic presentation, and a beautiful timbre. Nonetheless, these two headphones offer some distinct differences in tonality.

Most notably, the AC offer a sub-bass that is superior to the AO, and their bass is more elevated. For example, on “Hotline Bling” by Drake, the AC present a constant low bass rumble beyond the lower reaches of the AO.

As open back headphones, the AO offer a clearly superior soundstage. The extent to which their famous holographic presentation is preserved within the confines of the closed-back AC depends on one’s choice of pads. With the Caldera Thin pads, I found the soundstage width limited, akin to traditional closed-back headphones; with the Caldera Suede pads, the essence of the Atrium presentation is preserved, naturally on a smaller scale.

The AC upper mids are more forward to my ears than the AO, which are not recessed to begin with. That means that female vocals are presented much closer on the AC.

Atrium Closed vs. Audio-Technica ATH-L3000
I dropped a mention earlier, didn’t I? Well, I’ve started this writeup early yesterday morning, and with a growing sense of expediency to get this review out, I’ll keep this short. A comparison here would have no practical consequence, as the L3000 has been out of production for nearly 20 years. But for the benefit of those who are familiar with it, here are couple of quick anecdotes.

First, the Atrium Closed bass extends lower into the sub-bass region and is overall more elevated compared to the L3000 (yes, more bass..). In contrast, the L3000 provide more balance in the upper frequencies and an overall more relaxed presentation. Naturally, the AC’s dampened sound is entirely unique, while the L3000 offer the more traditional, faster, dynamic driver rendering. In broad strokes, it is much closer to the VC than it is to the AC.

CONCLUSION

For those of you who have read through to this point, kudos for your stamina. For those of you who jumped right down here, naughty you. In seriousness, I have written this more comprehensive account because the Atrium Closed are not headphones which should be summed up in a snippet. They offer many nuances and choices. That said, I shall try to summarize:

The Atrium Closed are wonderfully enjoyable, preserving much of the open Atrium’s lush and beautiful timbre in a closed-back setting. In contrast to their open cousins, the Atrium Closed offer a real sub-bass and an elevated lower bass. While lower mids are neutral and balanced, the AC offer a more forward and intimate presentation in the upper mids.

Choice of pads has a significant impact on the overall presentation of the Atrium Closed. The Caldera Thin pads are a Basshead’s dream. No EQ needed, sub-bass and lower bass will reign supreme. With an overall clockwise tilting FR, these pads provide a more traditional closed-back soundstage. In contrast, the Caldera Suede pads present a tamer version of this elevated bass, with more air and sparkle, and a more holographic soundstage.

ZMF's superb build and comfort are now par for the course. The Atrium Closed feel light, with an excellent weight distribution. You could comfortably wear them all day long.

If you are looking for your next closed-back headphone, ZMF’s new Atrium Closed should right in your scope!

I’ve never previously owned a Grado.

There are many factors that go into my process of selecting new headphones, and they are mostly focused on sonic presentation. While I value tremendously well-built headphones, I will make the occasional tradeoff in chasing a new and exciting sound. However, I will never buy headphones I cannot comfortably wear for many hours.

And that is why I have never previously owned a Grado. Until now.

When I saw a brand new Grado GS3000x offered for sale at steep discount, I decided to challenge myself: could I get that set and use less than that discount value to put back together a comfortable version of this Grado?

TLDR; yes!

Heads up Grado fans and other gentle spirits. This writeup starts with some honest criticism for its stock build, but I promise a happy ending. I am writing to share my rather simple journey reaching design nirvana, with the hope it can serve others.

Note that this is not a proper headphone review. If I may share some superficial sound impressions further below, these are anecdotes at best. This writeup’s sole purpose is simple: to offer 3 quick steps to transform the Grado GS3000x into comfortable headphones. Here we go…

STOCK FORM

After receiving the GS3000x, I noted 2 key problems:

• Pads – the stock “G Cushion” pads are a medieval torture device that was cleverly concealed as a consumer product. A cheap, scratchy, synthetic foam that is neither over-ear nor on-ear, managing a uniquely cruel middle ground. No doubt there is “a head for every pad”, so others may find it blissful; alas, I have not. I imagine the audiophile endurance test version of a hotdog eating competition would feature a row of Grado users at a desk, battling for maximum endurance measured in listening time achieved.
• Cable – headphones that come with fixed, non-detachable, cables are a minor felony. In this modern age, in which users want the flexibility to fit their own after-market cables, fixing your own cable is a blatant disregard of consumer demand and limits consumer choice. That said, I can appreciate how a quality obsessed boutique, such as Spirit Torino, may pursue this path in pursuit of extreme sonic quality control. Their saving grace is that their cables are ergonomic and very well made (though, personally, I’d still prefer a detachable setup). However, the Grado GS3000x fixed cable is neither ergonomic nor well made. Microphonic, heavy, and stiff, its kinks and bends never go away. The cable proudly floats mid-air, daring gravity while assisting gravity.. Did I say heavy? Measured separately, I can report this cable adds 153 grams, a 40%(!) in extra weight.

I also noted one minor opportunity for improved comfort:

• Headband – beautifully thin and minimalist, the original headband is designed with a really nicely stitched leather. I quite like it in fact. However, it does not offer any cushioning. Frankly, I could live with that if I needed to. But, I don’t.

”Before”…

MODS

After doing some research and legwork, prowling user communities and reaching out to quite a few vendors, I have proceeded with following 3 simple changes:

• Pads – there are several good options (please see further below for more info on the various pads I’ve tried and my impressions of them). I chose the Large Hybrid pads made by Silvian from Beautiful Audio in New Zealand. His pad design is clever and executed with extra care. Big, soft, over-ear pads that are supremely comfortable (shipped to NYC in 4 days, wow). One down!
• Cable – finding someone who will perform a full detachable cable mod on this was very hard. There are only a handful of folks who undertake such mods for Grado (or in general) and, out of those, most did not want to touch these slim delicate wooden cups out of fear of risking damage. In the end, UK based CustomCans was happy to take on this challenge. I believe this was their first time working on a Grado wooden cup model of this type, and James, who worked on my headphones, did a wonderful job. We assumed that these small headphones would require 2.5mm ports, but it was a pleasant surprise to find out in real time that they could comfortably accommodate 3.5mm ports, allowing the use of one of the most ubiquitous and easy-to-use cable terminations. Two down! One to go…
• Headband – Beautiful Audio came through again. Silvian has an ingenious, magnetically closing, headband. It fits perfectly, and it is very soft and plush. Wonderful workmanship.

and ”After”…

BASIC LISTENING IMPRESSIONS

As I mentioned at the outset, this is not an in-depth headphone review. I don’t feel that I have enough listening time to offer one yet (nor sufficient context to appreciate Grado’s other headphones properly). That said, in brief, here are my basic listening impressions in speedy bullet-point format. Aa always, YMMV:

• FR
  
  • Treble – well resolving, forward (hi-hats sound great, yet elevated)
  • Mids – sweet sounding
  • Upper bass – well-defined with a natural decay
  • Lower bass – recessed
  • Sub bass – rolled off
• Pros
  
  • Life-like, airy, open, and bright
  • Vocals are particularly clear sounding, with a very enjoyable presentation
  • Very easy to drive and revealing of the chain. Different amps sound rather differently, allowing ample room to synergize
• Cons
  
  • Sibilance on some tracks (not always)
  • Complexly layered tracks are not well resolved
  • Does not respond well to EQ

These headphones have a sound signature that is quite different to what I’m used to. It took me a few hours to adjust to them, and I am not done doing so. That caveat aside, my hunch is that they will be best suited for intimate acoustic recordings and live-concert vocals. Tine will tell..

PADS

As previously mentioned, the stock “G Cushion” pads are outright uncomfortable to me. Sound wise, I will say that, for the brief time I used them, they sounded lively and enjoyable. However, the nearness of the driver to the ear was a bit too much and sonically fatiguing.

Here are the pads I tried, ranked in my order of preference:

Best Option

Beautiful Audio – Large Hybrid – 5/5

• Excellent clarity, offering the best resolution from all pads
• Airy, with a natural and gradually diffusing soundstage
• Beautiful timbre
• Tonal balance
  
  • Treble – sparkly, rich with detail; forward, but exposes detail pleasantly
  • Mids – beautiful and sweet timbre, presenting a feeling of a live concert
    
    • Upper mids – female vocals are forward
    • Lower mids – male vocals are naturally positioned in space
  • Bass – medium speed, recessed
• Construction: perforated leather on the outside rim, solid Merino on the inside
• Convenience: soft, complete over-ear, these pads are extremely comfortable
• As a nice bonus, these pads are shipped with an extra pair of insert foams, which can replace the foams shipped inside the leather/merino pads cover. The inner foam replacement process is a really clever design feature and super easy to do (with a helpful YouTube clip). The default foam, aka “white” foam, is the one I reference above. The other “pink” form is less dense, trapping less energy inside the pads and offering slightly lower bass.

Viable Options

Dekoni – Fenestrated Sheepskin – 4/5

• Fastest transients of all pads
• Soundstage is smaller than the Beautiful Audio pads, but imaging is good
• Tonal balance
  
  • Treble – well resolving, airy
  • Mids – very forward; female vocals are sweet & beautiful
  • Lower bass – excellent: rich and snappy. These pads offer the best lower bass from all pads, a notable plus for this headphone’s default tuning. It almost made it the obvious choice.. except..
  • Upper bass – bleeds into the lower mids. For example, double bass plucking or bowing, lower male vocals, or lower piano notes, are diffused and lacking coherence in the presence of lower bass notes. I really wanted to love these pads for its successful lower bass presentation, but this issue put it safely in second place. Perhaps to be revisited one day
• Construction/convenience: these leather pads are similarly shaped and offer comparable comfort to the Beautiful Audio pads
• I may give the Dekoni fenestrated a second listen in the future to reassess my initial impressions

Dekoni – Custom Velour – 3/5

• Softer sound profile: offering a more gradual attack, these pads are less snappy than the Dekoni fenestrated
• Soundstage is smaller, and imaging is a bit less clear than the Dekoni fenestrated
• Tonal balance
  
  • Treble – a bit forward
  • Mids – very forward, similar to the Dekoni fenestrated
  • Bass – high in quantity, but the resolution is not great
• Construction/convenience: made of velour, they are otherwise identical to the Dekoni fenestrated pads in build and comfort

Do Not Attempt

Shipibo – 2/5

• These pads I believe may have been designed with other Grado models in mind. They fit physically. But don’t fit this model sonically. Like listening through a veil, these pads get fuzzier and fuzzier the lower the frequency
• There is a total collapse of soundstage
• In summary: barely listenable
• Construction/convenience: these are less deep and less wide than the Beautiful Audio and Dekoni pads, so they offer a partial, but not complete, reprieve compared to the G Cushion pads. The material is a course synthetic textile (as far as I could guess), offering medium comfort.

Dekoni – (Solid) Sheepskin – 1/5

• The sound is completely muffled. Clearly these pads were developed for other Grado models.

CONCLUSION

This has been a fun journey with a happy conclusion. I now have a wonderfully light and comfortable pair of Grados in my collection and can start spending time listening and getting to know this critter. I look forward to it!

If you’ve always been “Grado curious” and too afraid to try, fear nor. With a little will, there is a simple way.

There are a few things one should try at least once: see the world, start a business, make love under the starlight, and try a Grado. Now you can.

Happy listening!

I have now had the Caldera in my hands for a week and, while it is obviously too short a time for a serious review, I am sharing my first impressions knowing that many community members are eager to learn more about the Caldera in advance of its upcoming launch.



TLDR

The most resolving ZMF to date, the Caldera offers a densely textured timbre with a palpable “weight” behind the notes. Most notably, it has an excellent bass, the kind that moves you both physically and emotionally, without being artificially elevated. ZMF signature mids. And a lower treble energy, in line with ZMF warmer tuning. The Caldera is energetic, snappy, and exciting. Overall presentation is more intimate and forward. It commands your attention.

The Caldera is extremely engaging and enjoyable. Every time I thought of taking some notes I blinked, and 3-4 hours passed by as I got lost in the music. There are a couple of more resolving (and expensive) headphones out there, but the Caldera’s presentation is entirely unique. It is engaging and tactile. Once you put it on, it refuses to come off.

In advance of my impressions, I am sharing some detailed notes below about my chain and personal reference points, as well as some notes on packaging, build and comfort. Skip down to “SOUND!” if you want to get to it, or to the “COMAPRISONS” or “CONCLUSION” further below for an even shorter read

BACKGROUND NOTES

My Tastes
I have an eclectic collection of music across most genres. I gravitate more toward acoustic and vocals in general, but I will mix jazz, classical, rap, rock, blues, R&B, and anything else that simply moves me.

My current favorite headphones are the ZMF Atrium, Audio-Technica ATH-L5000 (with ZMF Universe Lambskin solid pads), Hifiman Susvara, and Stax SR-X9000.

Chain Used
Roon Nucleus+ ➤ CAT 7a ➤ Audioquest Cinnamon RJ/E ➤ Bricasti M3h (power cable: Audio Sensibility Testament SE) ➤ Moon Black Dragon (XLR) ➤ Zynsonix custom switchbox (silver cabled) ➤ [1] Moon Black Dragon (XLR) ➤ Auris Nirvana (power cable: Nordost Heimdall 2) , [2] Kimber Kable Carbon Interconnect (XLR) ➤ Simaudio MOON 300A (power cable: Audio Sensibility Testament SE) | power conditioner: IsoTek EVO3 Aquarius

At Zach’s suggestion, I am listening to the Caldera with ZMF’s silver cable.

3 Caveats
(1) I have only had the Caldara with me for a week. Including two weekends, I’ve logged approx. 50 hours of listening time. My impressions may, and likely, will change further.

(2) I am not a professional reviewer. My knowledge and experience are limited to that of a deeply passionate consumer. I am a community member who enjoys headphones, and I am deeply passionate about discovering and listening to great music. If it sounds good to me, I like it. If it doesn’t, I don’t. Sometimes I can explain why. Sometimes I know why. Often, neither it true I will do my best to explain myself and offer examples wherever I can.

(3) I am typing this review in a single sitting. The NYC Marathon passes today a block away from our place, giving me the perfect excuse to stay home on this unusually warm and beautiful November day and to commit to this promised writeup. I may come back here later once or twice to fix a typo or correct any small error or omission I may have missed in this writing sprint.

Reference Headphones
When listening to the Caldera, I have mostly used the following headphones for comparative reference:

• ZMF Atrium (ZMF Letrik S cable)
• Hifiman Susvara (Linx Diamond silver cable)

I have made select comparisons to these headphones in various sections below to help draw contrasts and highlight Caldera’s unique presentation characteristics. I have also referenced one or more additional headphones. In my summary comparison notes, I have also included the Vérité Open.

Reference Tracks
I have drawn my impressions from tracks I am very familiar with that span a wide variety of genres. I included links to all the referenced tracks.

FIRST IMPRESSIONS

Packaging
The Caldera I received is the Kingwood LTD, which comes packaged in a beautiful wood crate. The unboxing experience is the usual ZMF affair, with great attention to detail and, as always, feels very premium.

Build
I am referencing the Caldera Special Kingwood LTD. Per Zach, these will be offered at launch as a limited edition alongside the oak and golden coffee stock models. The Kingwood are a stunningly beautiful, glossy, darker wood (a hint of reddish hue is seen under direct light and in photography; in real life, they are a more of a dark brown rich wood color).

The build is ZMF exceptional. Wood, leather, magnesium chassis. It’s a joy to hold in your hands. It feels what it looks.

The Caldera are identical in their excellent build and comfort to all other ZMF headphones. They feel perhaps a touch heavier than other equal weight ZMF headphones (my 609g Caldera feels similar to my 624g VO blackwood). I am guessing that the weight distribution has changed a little as a result of the driver magnet weight and the new pad design. After a week, I wear them happily and comfortably. But, if you are sensitive to weight, consider the stock models, which I believe Zach indicated will be running around the 500-550g range.

Pads
The Caldera’s new pads, per Zach, will be called (wait for it..) “Caldera” They are made of leather (lambskin?) which feels great. I have always loved ZMF leather pads. The Caldera pads seem to have a bit less surface area on my face compared to the Universe pads. They do however offer an excellent seal. Two additional pads will be available, including suede and cowhide. They will undoubtedly change both sound and comfort, but I have not had a chance to test them yet.

SOUND!
The Caldera shares the Atrium’s damping system, and they are both unmistakably ZMF-tuned headphones. But they do sound rather different from each other. Where the Atrium’s slow attack and beautiful decay offer a lush and organic presentation, the Caldera is distinctly faster and snappier (it actually reminds me much more of the VO in that regard). The Caldera mids are also more forward relative to the Atrium. The Caldera’s sound signature is definitely not relaxed... but I have certainly found myself relaxing and getting lost in the music.

Bass
The Caldera’s most distinct feature for me is its amazing bass. It may be my favorite, across all headphones. ZMF’s first planar offers a clear distinction here compared to its dynamic brethren, but it also stands apart from other planar headphones. The Caldera bass extends low. It is deep, textured, and physical. It moves you, figuratively and literally. It is not one of those cases where it is a “headphone feature”, like the Abyss 1266. It is neither exaggerated nor elevated. Bass quantity depends on what the recording calls for. Opinions about the Susvara’s bass differ, but I love the Susvara’s bass as voiced through my power amp. In comparison, the Susvara’s bass is a bit more “open” and effortless, while the Caldera’s bass is “denser” and physical. This distinction is generally representative of their respective voicing, which are distinctively different.

Caldera’s lower bass region is magical. This is notable in acoustic music. For example, in the deep and richly textured bowing of the double bass on “Blind-Hearted” by Sarak K. (Water Falls - https://open.qobuz.com/track/87979534), or in the beautiful classical rendition of Valenyn Sylvestrov’s “Wedding Waltz” performed by Hélène Grimaud/Camerata Salzburg (The Messenger, Extended Edition - https://open.qobuz.com/track/126195369) where the occasional vibrato of the double bass and the lower piano register notes are beautifully resolved. I particularly like the rich plucking of the double bass on jazz tracks, such as on Ron Carter and Houston Preston’s duo “Love Is Here to Stay” (Remember Love - https://open.qobuz.com/track/51156776).

For those who enjoy the planar slam of drums, the Caldera has it, in spades. For example, the fast attack of drums on Michael McDonald’s cover of “I Heard it Through the Grapevine” (Motown - https://open.qobuz.com/track/13650307) offers a very satisfyingly, crisp articulation; and the hard-to-resolve bass guitar in Boz Scaggs’s “Desire” (Dig - https://open.qobuz.com/track/96893171) rumbles beautifully.

Sub-bass
The Caldera’s sub-bass doesn’t extend as low as the Susvara’s, but it is a little bit more forward and physical. For example, on tracks such as “Blinding Lights” by The Weeknd (After Hours - https://tidal.com/browse/track/134858702) or “New Oldie” by Snoop Dogg/Usher/Eric Bellinger (Snoop Dogg Presents The Algorithm - https://open.qobuz.com/track/138711392) I felt the satisfying feeling of a subwoofer shaking my core. For those who enjoy that, you are in for a treat.

Relative to each other, the Caldera provides a more hard-hitting bass and sub-bass, while the Susvara provides a more neutral presentation and a lower extension. However, the more poignant comparison here would be between the Calendar and Atrium. The Atrium will highlight more the mid bass as its lower bass will naturally rolls off, while the Caldera will draw your attention to the lower bass register, extending deep into sub-bass with a more forward and linear presentation.

Mids
This is a ZMF, through and through. The Caldera’s unique trick is bridging the natural timbre that is normally associated with dynamic headphones with the speed and bass extension of planar headphones (perhaps it is the combination of its planar magnetic drivers with the Atrium damping system. I am sure there is much more to it, including pad design and a very painstaking driver tuning process).

I am a sucker for vocals. It is the main reason I have had several ZMF headphones. However, the Caldera and Atrium do sound different here. The Atrium voices female vocals softer and rounder. It is a sweet and caressing, velvety tone, the kind that wills you to close your eyes, lean back, exhale and lose yourself in the music. The Caldera “opens up” the sound with a more crisply resolving, clear, and forward presentation. It asks you to lean in, grabbing your attention.

When listening to Sabina Sciubba & Antonio Forcione’s vocal/guitar duo cover of “Estate” (Meet Me In London - https://open.qobuz.com/track/59943654), the Caldera separates the vocals and guitars with great clarity, while the Atrium soften the notes. The guitar plucking is better resolved on the Caldera. On the other hand, on Samara Joy’s cover of “Stardust” (Samara Joy - https://open.qobuz.com/track/151697608) I prefer the softer and more rounded presentation of the Atrium.

Compared to the Susvara’s more ethereal presentation of the mids, the Caldera’s mids are more densely textured and weighty. They are both beautifully and exquisitely resolved.

Treble
The Caldera is tuned a touch warmer than neutral and there is certainly less presence in the treble region. This may be welcome by those who are treble sensitive, and in this regard, it is similar to the typical ZMF tuning with a gentle treble roll-off. I noted that with its reduced treble energy, it is also less resolving in the treble region than the Susvara. For example, in Michael Frank’s “Now that the summer’s here” (Time Together - https://open.qobuz.com/track/121160413), the hi-hats and maracas are more clearly resolved and more distinctly layered on the Susvara which extends more linearly into the higher frequencies.

Soundstage
This is where I find the Atrium shines and has a distinct advantage over the Caldera. There is something special about the Atrium’s staging, a certain holographic presentation that surrounds you, which is entirely unique. The Caldera’s soundstage is done well but feels more traditional 2D (horizontal left to right).

For example, on a live track at a small jazz club, such as in Sheila Jordan’s rendition of “Comes Love” (Winter Sunshine - https://open.qobuz.com/track/168305625), the Atrium gives a sense of sitting inside that small jazz club in Montreal, surrounded by the soft echoes of the brick walls around. The Caldera here sounds great on this recording but presents the stage more like a perfectly mastered studio recording than a reflection of that live club setting.

In recordings from big wide venues, the Atrium offers a wider stage, whereas the Caldera is narrower in comparison. For example, in Eric Clapton’s live recording of “Wonderful Tonight” (Forever Man, Deluxe Edition - https://open.qobuz.com/track/23361774) or Sara Bareillles cover of “Goodbye Yellow Brick Road (live)” (Brave Enough: Live at the Variety Playhouse” - https://i.imgur.com/fGFaGiK.png) the Atrium’s presentation is placing you closer to the front of the stage with the sound surrounding you and dissipating around and behind you, while the Caldera puts you further back in the concert venue, perceiving the sounds coming from the stage in a narrower dispersion which would reflect such a perspective.

In the Oscar Motet Choir’s famous 1976 recording made inside the Oscarskyrkan church in Stockholm, listening to “Hossiana, Davids Son” (Cantate Domino - https://open.qobuz.com/track/4410172), the Atrium captures the height of the church, whereas the Caldera presents a more focused soundstage.

Imaging
While the Atrium provides more spatial cues within the soundstage, the Caldera’s speed results in much clearer and superior instrument separation.

On “Wild Women Don’t Have The Blues” by Cécile McLorin Salvant (Dreams and Daggers - https://open.qobuz.com/track/43459125), the Caldera offers a much better separation between Cécile’s vocals, piano, bass, and drums; at the same time, the Atrium creates a better image where in the space these instruments are positioned.

Resolution
Caldera is, notably, the best resolving ZMF headphone. It can also handle complex tracks with ease. I have benchmarked it against the highest resolving headphone I have on hand, the Stax SR-9000X, and I was surprised to see how well it has held its own. With the exception of treble frequencies (see above) where its detail is more recessed, the Caldera is otherwise a resolution monster. It almost matches the X9K resolution in the mids and is superior to the X9K in the bass(!). That is quite a fit. On a complex track such as Yoko Kanno’s “Tank!” (Cowboy Bebop - https://open.qobuz.com/track/96723118), the Caldera effortlessly renders the details, making for an incredibly enjoyable listening.

Amplification
Regarding how the Caldera is impacted by, and scales with, amplification, I can only offer very limited insight at this point. This requires much more listening time, as well as more gear than I currently have on hand. But I can offer the following anecdotes:

My Caldera listening was almost exclusively done on the Auris Nirvana, a powerful (6.5W) transformer-coupled tube amp characterized by very clean and linear power amplification (for those interested, currently rolled in are a 1974 Siemens 5814A drive tube, and two Sophia Electric EL34-ST power tubes). This has been my daily driver for all ZMF headphones, and the synergy with the new Caldera has been excellent.

I tried briefly two other options.

First, I tried using the solid state amp built into the Bricasti M3h (I otherwise use it purely as a DAC). It is not overly powerful. Based on a couple of available data points, I am guessing (very crudely) that it provides about 0.5W into 60 ohm, so not exceptional headroom. The amp is quiet and proficient. It drove the Caldera easily and well. Switching back to the Nirvana, I felt the expected richer tonality and weight on the notes, but this was not a massive change. The Caldera is not an exceptionally power hungry planar headphone. But it will benefit from improved amplification.

Which gets me to the juicy second anecdote.

I couldn’t resist the temptation of trying the Caldera on the power amp setup I use with the Susvara, plugged into my Moon 330A speaker outs (125W into 8 ohm, SNR 100dB at full power) with volume control through the Bricasti’s pre-amp. My experience to date on this specific chain has been that only my Susvara (83 dB) and Arya V2 (90 dB) were insensitive enough to work well in this chain, and with all planars in the high 90s and up, the noise floor became audible. At 95dB, the Caldera offered an edge case. I found that the Caldera soared! Soundstage expanded significantly, and the overall presentation became more dramatic and exciting than it already was. Yet, it is still borderline. When the music is paused, the noise floor is just, slightly, audible. It disappears with the music, but it is enough for me to likely continue using the Nirvana as my daily driver. But I suspect that much of the lore of Susvara owners, filtered through a different sensitivity lense with a much greater emphasis on exceptionally low noise floor, can lead to some interesting discoveries and exciting possible synergies. Entirely anecdotal and speculative.

COMPARISONS

Reminder, for those who have jumped down here skipping all the detailed notes above. These are first impressions only. With that, let’s get to it…

Caldera vs. Atrium
This question seems to be highest on everyone’s mind. Two new ZMF flagship headphones this year, one dynamic and one planar. If I already have one, should I get the other? If I have neither, which one should I get?

I wish I had the simple answer you are looking for, but I can only offer an “it depends”. Personally, I will definitely be keeping both as they are highly complementary and really quite different in their presentation.

The Caldera is more resolving (but when I listen to the Atrium on its own, I do not feel like I am missing any detail). The Caldera also extends better into the lower bass and sub-bass frequencies, where it is more visceral and outright physical. The Caldera is also a faster headphone, resulting in a much faster attack. For example, on Counting Crow’s cover of “Big Yellow Taxi” (Hard Candy - https://open.qobuz.com/track/61540069), the slam of drums is much crisper and more exciting than on the Atrium’s. And Terri Lyne Carrington’s quick drum beats on “Come Sunday” (The Mosaic Project: love and Soul - https://open.qobuz.com/track/54351500) are rendered with better speed and clarity.

If there were a single word to describe the Caldera, it would be “Exciting”.

The Atrium, in kind, offers a much more unique soundstage presentation. The slower Atrium offers an incredibly organic and lush sounding decay. Both of which can be heard on Aaron Copland’s famous “Fanfare for the Common Man” (Copland 100, Minnesota Orchestra - https://open.qobuz.com/track/5164109). On this track, the horns’ blast echo in the wide concert hall, and the low bass beat of the drum decays beautifully and naturally, giving a sensation of being present in the venue unlike any other headphone I know.

On “Deadwood” by Tony Braxton (Sex & Cigarettes - https://open.qobuz.com/track/47776201), each of these headphones highlights different strengths: the Atrium presents the lush decay from the bass, making the sound feel organic. While the Caldera’s voicing of the drums is crisper, with a clearer separation and a better layering of vocals and instruments.

If there were a single word to describe the Atrium, it would be “Analog”.

Put differently, the Atrium offers a more relaxed, lean back, lush sounding voicing. While the Caldera commands your attention, presenting you with highly resolved detail, speed, and physicality.

Caldera vs. Susvara
This seems to be the second most popular question at present. How will ZMF’s first planar fare in the uber competitive top-tier planar market? In specific, how would it compare against the Susvara?

The simple answer here is that these headphones are so far apart in voicing, it is almost an academic question. Except in technicalities, the Caldera is much closer in its presentation to its dynamic siblings than to other planars. Given they were tuned by the same ear, it makes sense.

Comparatively, the Caldera offers a warmer tuning, and its voicing sounds thicker and fuller, lending an extra weight to the notes. In contract, the Susvara offers its famous ethereal light touch and effortless resolution. The Susvara’s overall resolution still reigns, and it offers soundstage and imaging that (from the headphones I have experienced) can only be rivaled by the X9000K (note that both of these headphones retail at nearly double the Caldera’s price). However, if you like ZMF’s presentation of vocals and mids, you will likely gravitate to the Caldera.

These headphones simply offer a very different presentation.

It is a choice between the most dynamic-sounding planar vs. the most electrostatic-sounding planar.

Caldera vs. Vérité Open
This was somewhat surprising to me and a little counterintuitive, but I found the VO closer in its presentation to the Caldera than to the Atrium.

Where the VO is a bit more aggressive and faster than the Atrium, the Caldera is even more so. While I plan to keep both, I can see some folks viewing the Caldera as a possible upgrade path from the VO, especially those listening to more energetic music. In genres such as hip-hop/rap or rock, the physicality, bass extension, and planar speed of the Caldera may prove to be winning attributes.

However, if you have vocals and acoustics in high rotation in your listening, the VO may offer an edge in this comparison, providing the beautiful and more natural timbre of the ZMF dynamic sound, while still keeping you very satisfied with its bass and aggressive attack.

The Caldera’s resolution is superior (to that of all other ZMF headphones), while the VO’s timbre is a bit more organic. Both ways, I am close to splitting hairs.

For example, on Haley Reinhard & Jeff Goldblum enjoyable rendition of “My Baby Just Cares For Me” (The Capitol Studio Sessions - https://open.qobuz.com/track/131263909), I prefer the VO’s vocal presentation, and find the spatial cues to be more natural, while the Caldera offers better instrument separation and a more mid forward presentation.

If I were to keep only a single ZMF headphone, it would probably be the VO, as it offers a perfect middle point between the classic ZMF organic timbre, and the attack and speed of the Caldera.

If I could keep two, I would take the best of both worlds, which for me are the Atrium and Caldera.

Either way, you can’t go wrong!

CONCLUSION

If you paid attention earlier and noted that I have logged 50 hours of listening time on the Caldera in a week (including 2 weekends, to be fair) and have done some mental math, you may have realized that the Caldera have been on my head for pretty much most of my waking hours this past week. This wasn’t for the purpose of this writeup (to which I committed solely this beautiful Sunday), but entirely for my personal pleasure. The Caldera is just one of those extraordinarily enjoyable headphones that once you put them on and start the music, you realize that bedtime was a few hours ago…

The Caldera is a really unique headphone. It shares the beloved ZMF sound signature, warm tuning, and beautiful mids. To that, it adds excellent speed and resolution, and a truly exciting, well extended, visceral bass.

I suspect that, in the long run, the Caldera will gain a massive following. Count me as one of its very first…

…and now, please let me get back to the music