ZMFheadphones Caldera

ZMF's much anticipated and lauded first Planar is finally here, and it is a beauty. If you don't want to read this review, then you can stop right here. This is my first 5 star review of any product. Nuff Said! The Caldera is emotional, fun, intelligent, comfortable, gorgeous in white oak, has incredible transience, fast decay; and all while still maintaining the trademark ZMF smooth, and fun sound.

I have not been compensated for this review. I would like to thank ZMF for the opportunity to spend this time with the Caldera. All thoughts are my own, and as usual this review will be a mix of food, music and the full engagement of our senses.

You will not find any measurements, there are plenty of those already. Hopefully, you will walk away feeling a little bit better about your decision to either own or potentially own a Caldera. It is WORTH every penny!

Accessories:
The Caldera comes with the normal ZMF accoutrement. You get a seahorse or wooden case, the headphone, two sets of pads (The Caldera Lambskin Perforated and Caldera Suede Perforated), 2 cables ( I received 2 braided spec cables, but have an OFC and other cables at my disposal), an Ownership Card, Lifetime Driver Warranty and a nice little bag for the cables.

As always, the Caldera arrived without any issue. The packaging is perfect. The headphones are secure and you always feel welcomed to the ZMF family. I cannot understate how important a factor this is in purchasing for me. I don't need the best deal, I just need to feel that my business matters. ZMF exemplifies this! They make every customer feel as if they are their only customer.

Driver's and Damping:
ZMF's first Planar is equipped with an 80mm Planar Driver encased in a carbon fiber baffle to keep weight down. In addition, it is equipped with several traces and pathway patterns all that are gold plated copper instead of aluminum. This seems to have a positive effect on overall weight, and therefore overall comfort. The Caldera tops out at 60 ohm's. In addition, the Caldera comes with the patent pending Atrium Damping System. The ADS reduces back-wave which helps to push air towards your ears giving you a more informed and developed pocket and musical space. In short, it increases the soundstage width and depth exponentially. However, the Caldera does not possess the otherworldly soundstage size as the Atrium, it does work beautifully and helps to create and extremely developed and accurate stage and image. This would make the Caldera the first Planar that I know of to use a damping system from a dynamic headphone. I don't know this for sure, but the addition of the ADS gives the Caldera a very unique flavor and tuning. It makes the jump from dynamic to planar such a comfortable space for a company that started modifying Planar T50's and then became known for their high impedance dynamic designs. To revert back completely in their own way, on their own time and with their own ideas makes the Caldera all the more special.

Comfort & Pads:
Every ZMF comes with their customary strap and crescent strap. They have recently changed to the crescent strap making weight distribution that much better. I can wear the Caldera for hours without feeling any hotspots or discomfort. Weight distribution is even and I have no issues wearing my glasses free of discomfort. The Caldera comes with their new Caldera Pads. Lambskin Perforated and Suede Perforated. They are smaller than the normal Universe, Auteur and Eikon pads. However, they don't feel any less comfortable and as always, pad roll to your heart's content. I personally prefer the Lambskin, just as I do on all ZMFs, but the Suede's offer a compelling sound signature. Per my usual, I find that the Lambskin’s offer a bit more linearity through the bass, with less 150hz hump and a cleaner move into the lower midrange. I also find the Lambskins to provide a bit more sparkle in the treble. I hear this especially with cymbal hits, wind instruments and vocal harmonies. Whereas, the Suede's counter with a more romantic sound. A bit rounder, slower decay and a fuller bass with more emotive vocal presentation. I also find the Suede's to be a tad bit darker coming out of the presence region into the lower treble. As always with pads, YMMV. This is just how I hear it, and what I prefer. Honestly, I love the Caldera with both sets of pads. The Suede's are admittedly a bit more comfortable, compressing into my ears a bit better lending to a smidge better seal. However, I still prefer the overall tonality and voicing with the Lambskin's.


Are these not GORGEOUS? I don't have much to say here, just couldn't waste this amazing shot. The grain is spectacular, the aggregated whole is just on point to my taste and preferences.

Customizing your ZMF:
I would be remiss if I didn't bring up the customization of the Caldera and all ZMF's. You can get an aluminum or magnesium chassis (for an up-charge), different color rods and grills. And the White Oak can be stained to look like vintage coffee with copper, brass or black. As you can see, the pair I have here are the standard Natural White Oak with all black. Sexy! In addition, you can upgrade your cable package. I believe the Caldera sounds best with a silver cable, but the OFC or 2k Copper will still provide you an amazing musical tour de force. I know some complain about their stock cables, but I have not found them to be anything other than easy to use and extremely musical. I love the OFC cable, and in most instances believe that the OFC is enough for a ZMF. However, my Audio Sensibility Silver Statement was the perfect compliment for the Caldera. It let the bass flow a bit lower, opened up the lower midrange, and gave the treble a small dose of sparkle that made the Caldera even more complete. Was it needed? No! Did I love it? Yes! You can also keep an eye out for Limited Edition runs (Kingswood currently), Canjam specials, and the twice yearly special that sends out B-Stocks, Stabilized Variants and woods that might only have 1 or 2 in that form. I am quite fond of all ZMF's in Camphor Burl. I would personally wait and try to score a Camphor Burl during the summer special or ZMF November. As for Janka Ratings, while the wood density will make a small difference, buy what you like the look of first and foremost. All Caldera's are tuned exactly the same and so ultimately buy what you find aesthetically pleasing. I always buy my artisan bread when their is a bit of browning or even a smidge of darkness to the crust. I know that the flavor isn't much changed, but I love the look and it makes it taste better to me. ZMF wood is no different. Are there small changes with wood densities? Maybe. Are you buying something you like the look of first? Definitely! The most important part of the wood will be weight. The denser the wood, the heavier the headphone. A regular white oak will come in around 490 grams. However, they could go as high as 550-575 grams if using an extremely dense wood. So, take into account weight as well while you are deciding on your custom Caldera heirloom.

Sound Impressions:
The Caldera sounds huge, snappy, fast, and balanced. It isn't as fast as my Soltaire P-SE, or the Susvara, but it is also more emotionally charged. It is incredible with Psychedelic Rock, Jazz, Bluegrass, and good ole' Rock n Roll. It is powerful, and the ADS provides front to back depth that enables an incredible sensation, where instruments and vocals are separated within the sound field.

Image Specificity, especially instrumental separation is top notch. All instruments can be heard in their exact space on stage, with enough room and air to discern their exact location. If you have been to Red Rocks, the Caldera provides a similar feel to being at the Rocks. After the rain dissipates, and the stars come out, a warm wind swirls through the amphitheater creating resonance as the sounds bounce off the rocks and back at your ears. The Caldera is doing the same thing. Sounds are swirling around you, the image solidified by the resonance of the wood and the stability of the driver and ADS where the acoustic soundscape makes its way back to your ears accurately and oh so pleasantly.

Like most TOTL planars today, vocals remain upfront in the mix. They aren't as gritty as the Atrium, but they are still emotive with wonderful focus. This I imagine is helped by a treble presentation that is more uplifting than downward sloping.

As always, ZMF goes their own way when it comes to their version of the Harmon Target and Frequency Response. I wouldn't call the Caldera "ZMF Neutral", but it definitely goes its own way. They aren't trying to follow a curve, they are trying to create the most musical, enjoyable and fun headphone that you want to continue to pick up over and over. They do this on their terms, and with the Caldera it works as well as any headphone I have heard. It is not as detailed as the Soltaire P-SE, it is not as fast and ethereal as the Susvara, but I just can't stop listening to it. Their is a noticeable lift around 2-3k and a dip between 4-6 to my ears, which mitigated by a peak around 8k gives the Caldera that finishing touch of sparkle and openness.

The Caldera's most impressive feat is the move from bass to midrange. It is extremely linear all the way down to 20 hz or so, and so clean as it enters the presence region. I don't hear any scooping, just a smooth transition into the midrange. ZMF continues to impress with an articulate, open and beautifully rendered midrange. On Radiohead's "High & Dry" off their album Bends, the guitar is both subtle and gritty simultaneously. Vocals are extremely present, yet emotive. All instruments are placed perfectly and the sound is whole. The peaks and valleys of the song are paced perfectly. There is no slog. It is an effortless reading of a gorgeous song. The same can be said for the Roy Ayers tune "A Tear to a Smile", the titular song off this amazing album. Roy's vibraphone playing is impeccable, its tonality is spot on, and it sounds like a waterfall of sound coming out of every direction, firmly planted in the middle of my head. The sounds are coming from everywhere, yet the Caldera still anchors you to the pacing and rhythm of the bass and down beat drumming. Roy's vibraphone playing must be heard on the Caldera. It is so powerful, evasive and subtle; while remaining completely up front. It is so good, it is all you can discern.

I continue to move through my Roy Ayers collection with the Caldera. Next up was Mystic Voyage. Another song with a funky bass pocket, instrumental subtlety coming from left to right and front to back, and as always, you get a Roy Ayers Vibe's solo that will knock you out of your chair. Thank you Caldera for rendering Roy's Vibes perfectly. I can feel his hands moving, his mallets hitting the metal bars with perfect decay and transience.

Timbre/Tonality:
As with all ZMF's Timbre and tonality are right at the forefront. Timbral Coloration is slightly north of neutral giving the Caldera a beautiful harmonic balance. It is charming, rhythmic, with beautiful pace and timing. Tonality is accurate and the Caldera sounds like music. Is there any better way to describe a headphone than to say it sounds like music? I know when I make a new dish, all I want to achieve is for it to have balance, aesthetics and for it to taste like what it is. The Caldera sounds like how great food is supposed to taste. Accurate, with a bit of alchemy where the customer has to ask themselves; how did you do that? Generally the answer is easier than what people think. Good technique, and a connection to your senses. The Caldera's timbral abilities are exactly that. A bit of science and a bit of magic. All that matters is that the Caldera sounds right.

Staging and Imaging:
This has become my favorite part of all ZMF headphones since the inception of the ADS. There is so much room for the instruments to play patiently and within their own space, that the stage is accurate, lifelike and generally takes on the size of the room. What else can you ask for? I don't want my music to sound like it is being played at MSG when they are at the Fillmore in San Francisco. The staging must be able to take on the instinctive feel of the room size and the space between the musicians. Both the Caldera and Atrium do this in spades.

What I like even more is how well the Caldera handles image specificity. The Accuracy of the instruments, their location on stage, the accuracy of how they come out of each channel, and the balance which gives each instrument its own unique tone and the air necessary for it to have the proper decay and transient snap. Caldera, CHECK!

Select Comparisons:

Caldera vs. LFF Code X
I am going to compare the Caldera to my all time favorite headphone. The LFF Code X. I just recently picked up an original Code X. All is well in the world. Does this headphone compare to the Caldera from a technical standpoint? No! Does it compare with a natural tone and timbral quality? Yes! The Code X's super power is how incredibly musical it sounds. It doesn't have the most technically advanced driver, and the modification is 7-8 yrs old, but this oldie still stands the test of time. The Caldera counters with a faster sound, a better sense of stage presence and overall it is just a more proficient headphone. That being said, the Code X is so good I have a hard time picking a winner. So, a tie it is. This is more heart than head, admittedly.


The Caldera vs The T+A Soltaire P-SE
This one is tough. The Caldera is a more musical headphone with a more physical and enchanting sound. The P-SE is lightning quick, and resolves as well as any headphone I have ever heard. Every aspect of the P-SE is perfectly balanced. Its main fault being that the sound isn't as weighty, and I tend to like my music to be physical. However, when I switch the P-SE from the CFA3 to the Icon Audio HP8 a lot of that physicality becomes more present. It is tough to say which headphone wins. The Caldera has such an alluring sound, but the P-SE is so technically on point that saying one is better than the other is a futile effort. How do I decide if I like the food at The French Laundry better than a Roasted Chicken and Tuscan Bread Salad at Zuni? I can't, I can only appreciate each for their brilliance. Result : Tie!

Atrium & Caldera

I am not going to do a huge comparison between the Atrium and Caldera. They are so different, and if you want to read my thoughts on these two headphones, please read my review on the Atrium. I go in depth and give a detailed explanation of what makes each headphone so unique and great. I will say this. The Soundstage is bigger on the Atrium, but more accurate on the Caldera. Decay is slower on the Atrium and faster on the Caldera. Transience follows the same logic as decay. Which do I like better? The Atrium is my favorite headphone for every day listening. The Caldera is a better headphone technically.




Amplification Select Comparisons:
Before I begin, can you believe the grain on that Caldera on top of the Audio-GD R28? Wow, what a beautiful headphone.

CFA3:

As much as I love Caldera with my normal psychedelic rock, when you hear the Caldera on the CFA3 listening to the Terry Callier show Alive and his tune "Lazarus Man", I realize that the 5 star rating is more than adequate. Terry's vocals are emotive and the performance is transcendent. Flute and Sax solos have fantastic tonality and the song is supercharged by the strong bass, and full band articulation. This album still remains the seminal live work available to Terry Callier fans. This album, this song and the CFA3 with the Caldera is nothing short of spectacular.

The CFA3's dual mono design, golden reference power supply and 16 watts into 50 ohms is overkill for the Caldera. However, the pairing is perfect. The top end resolution is refined, bass is palpable, and the midrange opens up like an Orchid on a May day in San Francisco. Listening to Michael Kiwanuka's album "Love & Hate" is an absolute wonder. You realize what a talent Michael is. The Caldera and CFA3 perfectly render the somber mood, his cautious optimism, and political commentary. The song Love & Hate sounds so good I want to hit replay over and over. The CFA3 helps the Caldera open up, providing accurate ambience, perfect stage presence and the exact amount of air between instruments to evoke the full sensation of being in the studio as Polydor produced this amazing album. Bottom line, the CFA3 and Caldera are an absolute must hear. Top End Resolution is as good as I have heard.

Icon Audio HP8:
I was surprised how much I liked this combo. I felt the 60 ohm Caldera would prefer my SS amps. While the CFA3 is a study in Solid Stage perfection with the Caldera, the HP8 provides a beautiful, soulful, weighty, and powerful performance. Top end resolution isn't quite to the same standard, but the midrange and bass are hitting on all my preferences. I am using a pair of Sylvania 6SN7WGTA Brown Base 1955's and a RFT Rohre 12AT7 driver tube. A perfect compliment for the Caldera. Tonality and Timbral accents are slightly warm, and the music flows like a warm summer breeze. I keep using this sentence when describing the HP8 and it is borrowed from John Grandberg. But, the sensation is exactly how the HP8 sounds and the Caldera only further exemplifies why this pairing is worth a serious listen. They have phenomenal synergy.

Audio-GD R28 AIO:
This was the biggest surprise for me. The R28 is a wonderful balanced AIO. It has an R1 R2R DAC and a NFB-1 balanced headphone amp that is pushing 9.5 watts into 25 ohms and 8 watts into 40 ohms. More than enough power for the Caldera. The best part of the R28 is the R1 DAC inside. The sound is robust, weighty with just enough resolution to satisfy even the most discerning audiophile. I had about a 2 week period where the R28 was my favorite pairing with the Caldera. I love the sweetness of the vocal presentation, the physical nature of the bass, and the impeccable instrument placement. Especially with keys/piano and drummers. Listening to the Goose show from 1/15/2023 from Play Del Carmen with Bob Weir is a pure joy. Their new song Hungersite has phenomenal PRAT, and their reading of Peggy-O with Bob Weir is spectacular. Bob's voice sounds soulful, gentle and his ability to turn this Jerry tune into his own vocal experience is wonderful. Rick's voice counters with a more clean, young and reverberant experience. The R28 and Caldera are simply a special combination. I would say that a high end R2R DAC would be the best pairing for the Caldera.

Conclusion:
The Caldera is simply a phenomenal first planar by ZMF. It is powerful, subtle, emotional and technically adept. I cannot think of much that I would change, and that is rare for me. I have never given an audio product a 5 star rating, but the Caldera is worthy. The bass is deep and taut, the midrange is open and articulate, and the treble is sparkling without ever crossing over into sibilance. Pairings definitely change the headphone, and for those who like EQ, the Caldera takes very well to EQ. I, however, do not feel the Caldera needs EQ. I think ZMF nailed it and that is enough for me. There are a lot of options out there fighting for your hard earned dollars. You have several Planars that compete in the same price point, so what separates the Caldera? For me it is customer service, overall tonal balance, aesthetics, staging/imaging and a powerful sound. A most hearty recommendation.

​

ZMF Caldera Review: Thoughts After Two Months​

Opening​

A couple of months ago, ZMF’s new flagship, the Caldera, was launched. As per Zach’s explanation, Caldera is a pinnacle of accumulation of all the lessons Zach learned in his journey as a headphone developer: The Caldera incorporates a great deal of noble headphone design that is either new for this product (e.g., magnet structure) or proven in his previous works in moving-coil dynamic headphones (e.g., Atrium back damping system). Given how tastefully ZMF headphones performed to me, I don’t doubt that bodes well for the Caldera. However, with the highest price tag ever attached to a ZMF product, the new-born Caldera must prove itself in practice instead of riding on prior success. That brings us to this review where I’d like to discuss how much those advanced designs have added up based on my two months of intensive evaluations.

Disclaimers​

There are two things to make clear before diving in further:

• Preference/History: I’ve been a very enthusiastic ZMF owner for years (owned Eikon, Aeolus, Auteur, and Verite open; reviewed Atticus, Atrium, Auteur Classic, and Verite Closed) but I wanted a little high capability in terms of technicality as well as more neutral balance thus moved on. Then I entered a totl planar/ortho game a couple of years ago and settled down to the Stealth-Susvara swap.
• Loaner: The pair I evaluated in this review is generously loaned to me by Zach. I don’t have any financial conflict of interest with Zach or ZMF. Zach did not require anything but my honest opinion. Nonetheless, readers should be still cautious because I am not immune to biases resulting from favorable memory and generosity.

Build / Aesthetics / Comfort​

I’d go brief about aesthetics, build, and comfort. I really don’t have much to say as Caldera shares a lot of design languages from other ZMF products. Excellent as usual ZMF. The same goes to comfort. The demo pair weighs 525g without cable in my scale. That’s more or less comparable to previous ZMF headphones. The weight was well distributed over the large surface and did not give me neck pain even with long listening sessions. It won’t be hard to find discussion about these points elsewhere.

Method and Associated Gears​

Below are gears I used in my Caldera evaluation

• DAC: SMSL M500 mk3 (usb in, xlr out), Gustard X18 (usb in, xlr out)
• Amp: SMSL HO200 (xlr in, 4 pin xlr out), Topping LA90 (xlr in, thorough banana-to-4p xlr adapter)
• Headphones: Hifiman Susvara, Dan Clark Audio Stealth

The demo pair of Caldera was made of American White Oak (stock wood). I also tried out lamb, suede, and cowhide perforated pads tailored for Caldera. I preferred and converged to suede pads eventually but my claims apply to any of these three pads I tested.

Caldera was mostly paired with M500.3 and HO200 for evaluation convenience -- easier to isolate headphone-specific effects from chain confounders and/or moderations. And because I didn’t focus on gear synergy much, readers should be aware that different pairings may draw different conclusions from my findings.

Subjective Analysis: Tonality​

While neutrality in tonal balance might be highly debatable and subject to various confounders, I’d confidently say Caldera has one of the most neutral tonal balances among the ZMF lineup both in perception and measurement. Let’s concentrate on the perception part in this section.

As usual for high end orthos, Candera’s bass extends down to the lowest register moderately. I might nitpick Caldera had mild attenuation in the lowest sub bass occasionally (e.g., audible with pipe organ tracks), which is alternatively perceived as a tiny hump around the upper subbass. It’s not a show stopper and likely attributable to my head’s sculpture rather than driver limitation because (1) I found the seal was very slightly broken behind the lobes and (2) bass extension was improved when I pushed both cups inward. So, how low Caldera can go must be a function of individual head shape, I believe. I also think that stronger clamping would result in better seal therefore better extension at a cost of sacrificing comfort a bit.

It is worth noting that other ZMFs I tested (Auteur Classic, Atrium, and Verite) have more audible roll-offs and stronger humps in higher frequency (100-120 hz). Caldera feels significantly more linear to me regarding bass responses.

Interestingly, compared to the energy level in mids and highs, I hear Caldera’s whole bass is gradually up-shelved, roughly by 3db or so. Put differently, Caldera’s bass sounds audibly warmer, which I believe makes Caldera sound more ZMF-ish.

While this differentiates Caldera’s bass from many other orthos (i.e., more ZMF-sounding) and I do appreciate it in many tracks, those coming from leaner orthos (myself included) may recognize it as being a bit too fat or thick. Fortunately, I found alternative ear pads or leaner-sounding amps could mitigate this to some extent.

Moving on to the midrange, I think Caldera leans toward the laid-back side. Its lower midrange is relatively recessed compared to its upper bass (as described above) and there's an even more energy cut around 1.5 kHz by a couple of decibels. This scoop is not as severe as that found in many HFM orthos including Susvara. I do prefer Caldera’s mids to Audeze LCD5/MM500’s forwarding presentation, too. But to my ears Caldera is not as spot-on neutral or full-bodied in midrange as DCA Stealth/Expanse, Seen HD6X0, or ZMF’s own Atrium.

The highs are surprisingly more present, refined and smooth than I typically expect for ZMF headphones. They maintain an appropriate energy level in presence as well as brilliance regions, and extend very well to the top octaves. I really like how crisply Caldera renders tenor sax overtones, female vocals, and hi-hats with good sparkles. While it took some learning curves (due to its elevated bass level), I found Caldera’s treble was more satisfying than LCD-5 which is mildly withdrawn, or Susvara which is a bit too sharp and edgy. It’s also easily the best ZMF treble I heard to date.

Subjective Analysis: Technicality​

Caldera is doubtlessly the most capable in technical prowess among all the products Zach has ever created. After two months of intensive listening, I am pretty confident to say Caldera is right up there and stacking well against any TOTL orthos money can buy today. Caldera surprises me in that it achieves an extremely high level of technicality without losing much ZMF-style presentation (which I believe somewhat conflicts with modern standards of high-fidelity).

When first putting on Caldera, the most immediate thing wowed me was soundstaging ability. Since Susvara joined my collection, it’s been very difficult to find headphones with acceptable soundstage in terms of both size and quality. Stealth was better in some areas (less distracting and more accurate spatial definitions) but slayed in the most areas that make headphones holographic. Caldera was the first pair of headphones that didn't make me feel relatively claustrophobic right after switching from Susvara: almost equally grandeur feeling, possibly better positioning for vocals and many core instruments, and great reproduction of characteristics of recording venues. I may nitpick Caldera is still more diffusing than Stealth and less airy/lively than Susvara. But none of those hurts enough for me to discredit Caldera’s holographic soundstages.

Caldera resolves tiny details (delta in frequency) and nuances (delta in amplitude) as superbly as any contemporary high end orthos costing 4k usd or more. Maybe a few ticks behind Susvara or Stealth on some occasions. But after carefully adjusting against perception tricks of tonal balance, it is nearly impossible to find out what specific components in tracks are unheard with Caldera over more revealing competitors. One may argue such a tiny difference is also caused by higher resolution and I don’t disagree. My point is they are pretty damn close in dealing with microstuffs. All the musical cues and information are equivalently resolved but presented differently across headphones.

Like many solid and matured high-end performers, Caldera’s weaknesses may be mostly a matter of gaps between personal preferences and intended voicing, rather than real performance issues. Nonetheless, I would like to point out a couple of Caldera’s behaviors where some buyers may feel disappointed.

I’ve recently seen an audiophile who found Caldera’s bass underwhelming. After listening to him explaining a bit more about why he heard that way, I realized people having a set of expectations about how orthos should sound used to look forward to hearing macrodynamics (dominantly characterized by tight, slamming, or hefty impacts) in certain ways. While I don’t think Caldera is shy of anything I listed, it’s also true that Caldera presents them with less squarer and less overshooting transients than contemporary high-end orthos. It’s possibly due to moderately damping on both sides with ZMF’s proprietary metal mesh and backwave damping system respectively. Or esoterically shaped magnets might play a role in air flow restrictions. These, confounded with thicker bass tonality, may not align with certain directions of expectation.

Also, I do think Caldera might not be the perfect replacement for other ZMFs like Atrium or Verite mainly because of timbre. While timbre might be an umbrella term for a set of multifactorial phenomena, I think one important factor in the technicality context is how sounding bodies excite mutl-order harmonics. ZMF’s prior drivers with biocellulose and Beryllium (vaporized) had their own respective harmonic excitation and Zach tastefully leveraged them to make reproductions sound more life-like, cohesive, and breathing -- which as a whole I often call ‘organic’. However, I don’t quite feel the same organic level with Caldera although it sounds more organic to me than any other orthos I experienced. Maybe Zach wanted to avoid making Caldera just an ortho-version Verite/Atrium or pursue different directions such as transparency (input signal fidelity) or less coloration. If so, I totally get it and it’s indeed one of the reasons I’d take Caldera over any other ZMFs for myself, but current ZMF lovers who want a full exclusive transition to Caldera should be aware of gains and losses before making irreversible decisions.

Subjective Analysis: Comparisons​

During my evaluation, I mostly compared them to the two TOTL orthos I had in the house: Hifiman Susvara and DCA Stealth. As I already made some comparisons in prior sections, I’d focus on noteworthy commons and differences.

Compared to HFM Susvara, I found:

• They both are excellent at emotional excitations.
• Caldera is thicker and richer but less delineated in bass. I often hear better details with Sus but notice finer volume gradation with Caldera in quiet but complicated passages. The difference is subtle for both aspects.
• Susvara’s midrange has been slightly ambiguous to me because of certain colorations and laid-backness (likely caused by acoustic designs such as cup interactions with minimal damping). Caldera’s midrange is also recessed due to different reasons but there’s not much evident ambiguity. As a result, vocals and main instruments are clearer and more articulate through Caldera.
• Soundstages are equally large and slightly diffusing on both. Instruments were separated more convincingly and understandably with Caldera. But Caldera is not able to reproduce as lively and open stages as Susvara.
• Overall, I like to pair Caldera with small ensembles, operas, and big band jazzes. Symphonies with large orchestrations are better enjoyed with Susvara. But they both have zero problem in switching genres I specified above. Needless to say, they’re also good at any other genres I didn’t refer to.

Compared to DCA Stealth, I found:

• Caldera isn’t as analytical as Stealth -- Caldera is more inviting and intimate in presentation while Stealth enables me to accurately and carefully capture sonic cues.
• Stealth’s complicated resonator array and overdamping enables almost zero coloration in both fundamentals and harmonics but introduces a sense of artificiality. Caldera opts out that route but is still well-controlled yet focusing on more entertaining, natural, and emotion-oriented sounding by comparison.
• Caldera is more holographic in soundstaging, exhibiting better lateral and depth sizes. Stealth is less diffusing and more accurate in layering and placements.
• Interestingly when I switch from Stealth to Caldera, everything sounds bigger and more organic. Reversely, switching from Caldera to Stealth feels like enhancing clarity and articulation.
• Stealth exposes me to the stream filled with overwhelming information and enforces me to maintain higher tension that leads me to relatively more fatiguing for longer listenings. Caldera let me take back, stay relaxed, still enjoy beautiful details.
• They both exhibit generally round and soft transients although Caldera sounds squarer between the two.

Notes on Amplifications​

I’m not chasing headphone amplification rabbit holes these days as much as I used to be. I still believe amps make differences.. But, beyond certain points, not proportional to the benefits I’d expect for the price deltas. I’m also a little disagreeing with general underpowering concerns when it comes to orthos/planars. I am rather concerned with overpowering cases because surplus current does more harm than good to me.

That being said, Caldera has not shown any hints of underpowering with moderate SS amps I hooked up with. Caldera required way less current than things like HE6 or Susvara. Hence, I believe Sonic synergies or flavor alignments should be prioritized in choosing amps for Caldera. I did try out a few exotic tube amps my friends had. Some sounded fairly impressive. But not enough listening to make bold claims. Anyway, I do recommend not to rule out Caldera solely because you don’t have monster-power amps.

Measurements​

My measurements were taken with the MiniDSP EARS at 95db SPL@300hz with the homebrew hybrid compensation target curve that mixed HPN, HEQ, and additional adjustments based on B&K Room Curve.

Please note that my frequency responses are averaged results based on 5 different positions (center/up/down/front/back) to control positional variance. Results from optimal positioning might differ even with the same measurement fixture/rig.

Highlights below:

• Slight sub-bass attenuation is attributable to suboptimal seals: I found the bottom of the pads was a bit loosely attached to EARS's silicon plate. As argued in the subjective analysis, I also had this issue with my real head although respective reasons for broken seals were different.
• The 4.5 kHz peak suggested by the graph is likely an artifact, too. It seems associated with internal resonance created by my ear coupler’s cylindrical ear canal, Caldera’s earcup geometry, or etc. Not very audible in the way it is presented.
• Slightly recessed region around 1.5 kHz is consistent with what I found in the tonality analysis. It looks like HFM scooping pattern but with a narrower bandwidth and less intensity. Fortunately, this relatively boosts 1 and 2 kHz separately to prevent too much loss in vocal clarity.
• Bass and lower midrange are slightly emphasized, which I believe is correlated with Caldera subjectively sounding closer to earlier (T50rp mod era) ZMF tone than more recent Verite or Atrium.
• The measurement confirms what I hear in highs: not overly bright but spot-on neutral.

I’m also attaching other measurements I took.

Conclusion​

While $3,500 is not a small sum of money for a single pair of headphones and there’s plenty of competition out there in cost-no-object orthos, Zach really surprised me with this fantastic debut product entering the summit-fi planar headphone market cluster. Surely in mostly good ways.

Caldera comes with a pack of great sound qualities (some being spectacular) that many other competitors with similar or higher price tags often fail to achieve: one of the two best treble responses I have heard through headphones, top-level soundstage and resolution excellence, and many many more. Of course this doesn’t mean Caldera is perfectly flawless. It’s actually not. There were some sounding behaviors such as midrange scoops that didn’t fully align with my preference. Nothing critical though.

All things considered, I can think of two clusters to recommend to shortlist or audition Caldera. One is the group of ZMF owners who want to add a solid technical performer to their collections. Caldera’s sheer detail-nuance retrievals and neutral tonality must be giving them a better chance to discover unheard sonic cues in many musics. The other is the group of hipster ortho buyers who pursue different sounding from mainstream high-end planars yet at the same performance level. As I claimed in this review, from technicality perspectives, Caldera does almost everything no worse than any other high end headphones I heard. And the presentation is drastically different from what I used to hear from orthos and rather close to ZMF moving-coil dynamic products.

Please let me know if you have any questions. Thanks for reading!

I’ll start as I usually do with sincere thanks to ZMF for allowing this amazing headphone to go out on loan. They were generous enough to allow a considerable amount of time in order to put it through it’s paces and I sincerely enjoyed my time with them. There’s a lot of info already out there about the Caldera's development and construction, I think it's worth reading & watching:

https://www.zmfheadphones.com/caldera-acoustic-design
https://www.zmfheadphones.com/measurements


Fit, Comfort and build

ZMF has a reputation for making headphones that are on the heavier side, and the Caldera is no exception (490 - 560 grams in current stock wood). IME ZMF also makes these headphones as comfortable as possible with their well padded headbands and suspension straps. Personally I've found that they never disappear on the head, but I've also never had an issue wearing ZMFs for hours at a time.

Like all ZMFs I've seen to date, the Caldera is simply beautiful for my tastes. The craftsmanship is impeccable, and the design is appealing. I'm always surprised how aesthetically pleasing I find each new ZMF release, but I probably shouldn't be. Zach and company have been at this for a while, and the quality of parts as well as the overall care in assembly is evident.
(Obligatory bad photo)


Review Details

Before I offer my listening impressions, I’ll start with a little about myself and other points of interest. I’m over 50 years old and have less than perfect hearing. I’ve been a music lover for as long as I can remember, and my preference leans toward the warm side of neutral. I’m a huge believer in the “my ears/your ears” axiom, and I believe the signal chain makes a difference. Feel free to liberally add as many mental IMOs and YMMVs as you want while reading.

My chain for playback is various WAV, FLAC, & MP3 files from my refurbed HP Elite Desk via USB to a Bifrost 2 to either my ifi Pro iCAN (1st version) or ZMF Pendant (also 1st version). The Caldera sounded wonderful from both the Pendant as well as the ifi, but I had a slight preference for the Pendant and did the majority of my listening utilizing that amp. No need to burn in during this go around since I have it on good authority that it has a couple of hundred hours on it already.

Sensitivity

For a planar the Caldera is fairly efficient with about 95db efficiency and 60 0hm impedance. As mentioned I only used my ifi Pro iCAN & Pendant which can drive them easily, but you can probably get decent results from many lower and mid tier priced rigs. I'd wager synergy will play a part here, but that is usually the case IME. If you're going to invest in a headphone of this caliber it makes sense to play it on a chain that'll maximize performance, but it's good to know that it's not a requirement for enjoyment.

Sound

When you hear the Caldera it is easy to hear the ZMF roots in the sound. I appreciate Zach's commitment to creating something unique with each headphone, which is evident when listening to the 1st fully in house designed ZMF planar. I only had one set of pads on hand which I can only assume were the stock lambskin pads, and I had no issues with them sound or comfort wise.

I think I understand why others have noted that the Caldera doesn't sound like a stereotypical planar. There is a recent trend (that seems to be thankfully changing) of utilizing the thinnest micro-nano-quark-sized diaphragm chasing the fastest transients and the lightest airiest sound. The stereotype speaks more to that trend than to planar technology itself. Obviously a planar can be tuned differently just as any driver out there. Hopefully the caldera will help to hasten the demise of this unwarranted bias.

Even though ZMF doesn't incorporate the thinnest most agile driver here, there is plenty of speed for my tastes. It is definitely faster than any beryllium drivers I've heard, but it's certainly not trying to sound like an electrostat. The flip side of that sonic coin is that there is a certain amount of heft & weight to the notes that you also wouldn't necessarily associate with the current crop of planars. Combined with the novel magnet structure and ADS (Atrium Dampening System, patent pending at the time of writing) the result is something fairly unique, which I believe was Zach's goal.

Bass

If you like the ZMF house sound I think there's a lot you'll like here. Being a planar, sub bass reaches low and it also has decent impact. More importantly there's texture and nuance to the bass; uprights don't sound electric, finger and pick plucking is audible, and electronic music is a joy.

Mid-bass is more subdued but is still full, rich and present. The emphasis is slight here, not bombastic, overblown nor bleeding into the mids. It's still a ZMF so probably more than many would describe as neutral, but Caldera sounds rather even throughout the spectrum to my ears.I found it easy to hear into busy passages, not just in the bass level, but I did notice it the most there.

Mids

The mids sound a bit more dry than I'd expect from a ZMF, but it's far from sterile or brittle. The slight recess around 1khz that others have mentioned didn't bother me in the least and wasn't particularly noticeable for me, unless that somehow contributed to the sense of dryness I noted. Either way vocals, both male and female, as well as all manner of brass & strings had plenty of detail and presence without edging into being perceived as shouty, shrill or overdone.

Treble

The treble is not your embellished over emphasized ear dagger by any means, however I found there to be more sparkle than I'm used to enjoying without fatigue. Despite this I has no issues listening to Caldera for hours on end without discomfort.There definitely could be a YMMV here given hearing loss. Also notably Caldera nails the timber of cymbals and such better than many other planars I've heard.

Detail

Detail retrial is quite good, I'd say among the best I've heard. It's not what I sometimes call hyper-revealing where the presentation is all about magnifying details, but I found plenty of sonic information when I listened for it. I found that if I did concentrate I could isolate many hidden gems in the music, but more often than not I found myself getting lost in the song itself. I think detail is important when it's lacking but at a certain point that emphasis can be distracting for me. Caldera straddles that line without ever crossing over.

Compared to Atrium

I don't have a planar on hand that would be a good comparison here (just the HiFiMan 400i & a memory of some time spent with the D8000 - not the pro) so I figured the Atrium would be a good side by side despite the drivers being different tech. Note I'm using the stock Universe pads with the Atrium & the solid mesh (I'll have to try the perforated mesh one day since many people I know that have heard both seem to prefer it).

Comfort

Despite being about the same weight (cherry Atrium is also supposed to be 490g), I found the Atrium to feel a bit lighter. IDK if it's because of clamp or weight distribution, but it was noticeable for me. Keep in mind I had no comfort issues with Caldera, but it's worth noting.

Bass

Caldera bass definitely reaches lower with a more even mid-bass, and the Atrium has a more pronounced mid-bass accentuation. Atrium sub-bass does roll off yet it is still audible if not as forceful. Caldera is tighter, Atrium looser though no where near flabby or indistinct. Atrium definitely slams harder though Caldera is no slouch.

Mids

Caldera mids are slightly dry and Atrium comes off as more lush yet both presentations I found extremely engaging. Caldera had a bit more lower mid presence and the Atrium a slight push in the upper mids in comparison. Neither sound too forward nor too recessed to my ears, though my mids preference seems to lean toward the Atrium overall. I'll note here that overall I found the Atrium to be more forgiving of sub-par recordings, and the mids may have a bit to do with that I think.

Treble

As mentioned treble is indeed not my strong suit, but from what I can hear Caldera is less rolled off and more even and airy up top. IDK if it's related to the treble but I found that Caldera was more resolving overall in comparison to the Atrium though not by a huge margin. Detail was easier to discern, and I found that especially so in the treble region.

Headstage

Headstage is wide deep & coherent. The Atrium bests it to my ears, but Caldera definitely has a great sense of width & definitely depth. Height isn't lacking, I just didn't find it to be on par with with the other axes, and I didn't find it to be distracting. There is still a great sense of space and "realness" that I don't often find with other headphones. Both headphones draw me in like few others I've heard, and though the Atrium does seem to have an advantage I wasn't turned off by the Caldera staging at all.

End Words

After comparing the two I'm not sure I could pick one over the other, both the Atrium & Caldera are an absolute pleasure to listen to for my tastes. When going back & forth comparing songs I found myself having a slight preference, but it was never for the same headphone. I always enjoyed what each headphone brought to the table, and it was always track dependent. If I didn't already own the Atrium I could definitely see myself saving for a Caldera since the sub bass reach and overall detail appeal to me. Owning the Atrium already I don't feel I'm missing anything, and the Atrium's strengths align well with my preferences. If I had the money, I would more than likely have them both in my stable. IMO Caldera is definitely worthy of it's co-flagship status and is worth checking out.

I always look forward to new headphones from the gang at ZMF. I was in the market for a new pair of planar magnetics and I asked Zach for a recommendation. Seeing as he started with modded T50's, I assumed he had probably heard most planars out there. I own two pairs of ZMF's, a pair of Cocobolo Eikons and a Walnut Burl Aeolus so I am reasonably familiar with the ZMF house sound and I trust Zach's opinion. Instead of recommending a one of the the headphones I had asked him about (Hifiman Arya or Audeze lcd X), he mentioned that he was developing his own High End Planar Magnetic headphone, and that he would be willing to let me try them out if I was willing to wait. I was, indeed, willing wait and a month or so ago a pair of ZMF Calderas showed up on my doorstep. Thank you Zach for the chance to try these out.




I have been listening to the Calderas for the last month connected to both tube (Cayin HA-3A, with Baldwin/Sylvania 12au7's and matched NOS 6V6GT Westinghouse tubes) and solid state (Audio-gd NFB-1) amps. Each connected balanced to Geshelli J2 DAC's via Blue Jeans Cables XLR cables. I also used only the balanced outputs on both amps.




While Zach made it clear that no review was necessary, I thought I would post my impressions anyhow.

Build quality and comfort – Long a hallmark of ZMF, the build on my Calderas is immaculate, no creaks, no loose nuts or bolts, nothing to indicate that these are hand assembled. By any visual measure, these are perfect. It is no lass than I have come to expect from ZMF, but I marvel each time I pick them up at how solid and sturdy they feel without feeling simultaneously heavy and awkward. The pads are soft and deep and my admittedly large ears fit comfortably with with only the bottom of my earlobes touching the bottom of the cups.

The new comfort strap and padded headband are a noticeable improvement over the previous stock headstrap while the rest of the hardware is reassuringly solid and allows for easy adjustment without fear of slippage.

One last note regarding the physical build. The slightly concave mesh grill on the Calderas is beautifully machined and sits perfectly flush with the wood. The concavity is, I assume either a function of the new drivers, or a nod to the name Caldera. Either way, the cups are approximately the same size as the Aeolus, and by definition smaller than my Eikons. The grill also lacks any visible mounting screws, which lends itself to a cleaner overall aesthetic than the Aeolus. I will have to note, for the record, that from a purely visual standpoint, I prefer the grill and wood of the Aeolus, with is marvelous gleam texture. The Caldera also sports 2 and a half pressure release vents around the grille. This is in contrast to the 5 full vents on my Eikons. As the Eikons are closed back, I assume these are necessary to relieve the pressure while the Calderas are open-ish and need less venting. I say open-ish because less sound escapes these than the Aeolus or, for example, the very open Dan Claek Audio Ether 2’s. The majority of my headphones are closed back so I have little frame of reference when it comes to open back units.

Finally, the sound. The ZMF Calderas are the best sounding headphones I have ever had the pleasure of listening to for an extended period of time. Their defining characteristic is how utterly engaging they are. The sound is full, lush and fast. Whether connected to a tube or solid state amp, the Calderas just make me want to close my eyes, smile, and enjoy my music. The sound is relaxed without being muffled in any way. On Stevie Ray Vaughn’s Mary Had A Little Lamb (Live Alive, 1986), Stevie Ray’s frenetic guitar playing floats seamlessly above Reese Wynans’ keyboard riffs. Both easily distinguishable from one another without losing any of their individual power.

Again, instrument placement and definition is excellent, to whit, Miles Davis’ Duran (Take 4) (The Complete Jack Johnson Sessions, 2005). The interplay between Davis and John McLaughlin and their relative placement in the virtual space really give the impression of two wily fighters sizing each other up. The instrument clarity is sublime while both the lows of McLaughlin’s guitar and the high’s of Davis’ horn manage to stretch the soundstage to it’s breaking point.

Female vocals are also handled with aplomb. Natalie Merchant’s San Andreas Fault (Tigerlily, 1985) is rendered silkily. Her voice, strong and smooth is conveyed flawlessly above the delicate keyboard backing track. No sibilance whatsoever.

Lastly, a bit of Electronic to round out the listening impressions and see how the Calderas convey bass. AtomHD’s I Love U (Like I Love My Drum Machine) (HD, 2013) brings the low end forcefully, making you feel like your eardrums are the synthesized drum skins.

All of this is to say that the ZMF Caldera is an exceptionally well rounded headphone. Base, mids, and treble are all handled masterfully and the overall experience is one of complete immersion in the music, regardless of genre. These are the most engaging and enjoyable headphones I have ever heard and I heartily recommend them to anyone looking for an end game headphone that will last for years and never lose it’s charm.

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 😊