ZMFheadphones Caldera Closed

General Information

SPECIFICATIONS
  • Driver: 2 um thick Planar Magnetic with CAMS Patent Pending technology
  • ADS Patented Damping System
  • Caldera Patent Pending Pad Design
  • Impedance: 60 Ohms
  • Sensitivity: 94dB/mW
  • Weight: 500-560g

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Latest reviews

Takarajima

100+ Head-Fier
Premium Planar Magnetic Excellence with Practical Compromises
Pros: :
Excellent bass control and extension without artificial emphasis
Strong isolation performance for a high-end headphone
Clear and detailed sound reproduction across frequencies
Well-implemented closed-back design that maintains planar speed characteristics
Serviceable construction with user-replaceable parts
Versatile pad options for sound customization
Natural decay characteristics and good micro-dynamic performance
Solid handling of complex orchestral passages
Relatively flexible with amplification choices
High-quality build with distinctive wood cups
Cons: :
Substantial weight at 545g may require adaptation period
- Heat buildup during extended listening sessions (noticeable after ~90 minutes)
- Requires regular breaks during long listening sessions
Premium price point ($3,500) puts it in highly competitive territory
Regular headband adjustment needed during use
Midrange slightly less forward compared to competitors

ZMF Caldera Closed: A Technical & Musical Analysis

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(Photo source: ZMF official page)

Introduction & Context​

Transparency in audio reviewing requires proper context. I've known Zach Mehrbach, ZMF's founder, for several years, initially as a customer before developing a professional relationship through forum interactions and eventual friendship. This connection, while common in our specialized audio community, warrants disclosure as we examine these headphones.

The Caldera Closed under review is a standard production unit on loan from ZMF. Over two and half months, I've accumulated approximately 200 hours with them through systematic evaluation: protocol-based analytical sessions, comparative listening, pad rolling experiments, and amplifier pairing tests. My evaluation aims to present findings that would help readers make informed decisions about a significant investment.

Technical Framework​

  • Design: Closed-back planar magnetic headphones
  • Impedance: 60Ω
  • Sensitivity: ~94dB/mW
  • Weight: 545g (without cables)
  • Price: $3,500 (as reviewed)

Physical Analysis​

Design & Construction​

Initial examination of the Caldera Closed reveals two significant aspects. The Shou Sugi Ban ash wood cups represent a departure from typical ZMF aesthetics. This Japanese wood-charring treatment creates distinct visual patterns and potentially serves acoustic purposes, though the latter would require objective verification.

The distinctive raised triangular section on the cups warrants analysis. While visually striking compared to ZMF's typically organic designs, its functional aspects deserve consideration. The shape provides natural grip points for handling and may contribute to acoustic management, though without access to development data, such conclusions remain speculative.

The build emphasizes serviceability – all wear components (pads, strap, cables) are user-replaceable. The aluminum frame provides structural integrity while controlling overall mass, though the rod blocks require more frequent adjustment than lighter models.

The mini-XLR connectors demonstrate proper strain relief and maintain connection integrity through repeated cable changes. Both provided cables (balanced and single-ended OFC) offer adequate flexibility and strain relief, with the balanced option showing marginally better handling characteristics.

Comfort & Ergonomics​

The 545g (w/o cable) mass presents definite ergonomic considerations. Extended testing reveals how weight distribution affects long-term wearability. The suspension strap system (standard version tested) manages mass distribution effectively, though not completely. After approximately 50 hours of use, adaptation to the weight occurs, but awareness of it remains.

The stock hybrid pads employ an asymmetrical design: thicker rear sections create natural angles for head anatomy. Their dual-material construction (leather exterior, suede interior) demonstrates reasonable thermal management for a closed design, though heat buildup during extended sessions remains noticeable.

Temperature management represents an inherent challenge of the closed architecture. Regular breaks (every 2-3 hours) prove beneficial during long sessions, particularly in warmer environments. The cup design's raised sections provide practical benefits for handling and positioning adjustments.

Technical Implementation​

The Caldera Closed's development presents interesting technical challenges. Converting an open planar magnetic design to closed-back architecture involves more than simple enclosure. Key engineering hurdles include:
  • Managing resonances in the closed chamber
  • Controlling internal reflections
  • Maintaining planar driver speed characteristics
  • Achieving effective isolation without compromising dynamics

Measurements​

(Note: I am planning to disseminate measurements and analyses in separate reports. Hence, only summary is provided in this review.)

Using calibrated testing equipment under controlled conditions reveals several key characteristics. Frequency response shows controlled behavior with slight lower-midrange dip (250-400 hz) and some brilliance emphasis (around 6.5 khz). Distortion remains very low at normal to very loud listening levels, increasing predictably but not dramatically at higher volumes. The extended high-frequency response matches category expectations, while impedance behavior indicates good amplifier compatibility.


Sound Performance​

Frequency Response & Tonal Balance​

The low frequency performance, assessed through Massive Attack's "Paradise Circus," demonstrates the closed-back implementation's bass control capabilities. The descending bass line maintains clear definition while coexisting harmoniously with vocals, suggesting effective management of the closed chamber's typical resonance challenges. Bass presents with full frequency extension without resorting to obvious emphasis of any particular region.

Christian McBride's "Night Train" provides deeper insight into the planar driver's transient behavior. String attacks show clear articulation, while the resonant body of the acoustic bass maintains natural decay characteristics. The distinction between fingered notes and thumb-played passages remains clear throughout, indicating capable speed characteristics without artificial emphasis of leading edges.

Midrange evaluation through Diana Krall's "Peel Me A Grape" reveals interesting characteristics. Vocals occupy a slightly less forward position compared to some competitors, though they maintain proper scale and timbral accuracy. Piano harmonics demonstrate good resolution, albeit with somewhat less immediacy than observed in the open-back version. During analysis of Leonard Cohen's "You Want It Darker," male vocals exhibit proper fundamental weight and chest resonance. The closed architecture appears well-damped, avoiding both the artificial emphasis that can affect closed-backs and the thinness that can compromise vocal authenticity.

High frequency behavior, examined through Bill Stewart's "Telepathy," shows thoughtful implementation. Cymbal textures maintain proper metallic character while suggesting effective management of the closed chamber's potential reflection issues. The high-frequency presentation remains extended without introducing artificial edge. Hilary Hahn's Bach Violin Sonatas serve as an effective examination of upper register reproduction. Violin overtones maintain proper brilliance while keeping bow noise proportionate to fundamental tones - a particularly challenging balance for closed-back designs.

Spatial Presentation​

Spatial reproduction, observed through Bill Evans' "Sunday at the Village Vanguard," reveals careful attention to imaging characteristics. The recording's complex spatial cues remain intact, with Paul Motian's brushwork and Scott LaFaro's bass lines occupying distinct positions. The presentation shows good organization within closed-back constraints. Hans Zimmer's "Time" from Interstellar tests the design's ability to maintain separation during complex passages. While soundstage width necessarily differs from open-back designs, depth layering remains well-defined. The presentation varies appropriately with different recordings rather than imposing a consistent artificial perspective.

Dynamic Performance​

Dynamic response testing through systematic evaluation reveals nuanced performance characteristics. Micro-dynamic capability shows clearly through subtle drum brush work in "Blue in Green," where fine detail remains evident without artificial emphasis. Natural decay characteristics are preserved, with good distinction between similar intensity levels.

Macro-dynamic performance, evaluated through Mahler's Symphony No. 3 (Zander/Philmarmonia Orchestra), demonstrates competent handling of orchestral crescendos without obvious compression. The headphone maintains instrument separation during complex passages, though some amplifier dependency becomes apparent during extreme peaks.

Recording Format Response​

Through systematic testing across various source qualities, the Caldera Closed exhibits noteworthy format-dependent behavior. Contemporary high-resolution recordings, such as the 192/24 masters of Keith Jarrett's solo works, reveal the headphone's capability for portraying subtle ambient cues without emphasizing technological artifacts. The ability to maintain musical coherence while exposing recording-chain differences proves particularly useful for critical listening tasks.

Standard commercial releases from the past decade demonstrate the headphone's handling of modern production techniques. Daft Punk's "Random Access Memories" serves as an excellent example, where heavily processed elements coexist with live instrumental recordings. The Caldera Closed maintains separation between these elements while preserving the intended blend of synthetic and organic sounds.

Older recordings, particularly those from the early digital era, expose the headphone's treatment of compromised source material. Early CD releases of Deutsche Grammophon classical recordings retain their fundamental musical value despite their technical limitations. The Caldera Closed reveals these limitations honestly without rendering the recordings unenjoyable - a delicate balance that speaks to thoughtful voicing decisions.


Practical Considerations​

Long-Term Usage Patterns​

Extended use over two months reveals performance characteristics that might escape notice in shorter evaluation periods. Regular listening sessions averaging 3-4 hours provide particular insight into practical usability patterns.

Morning sessions typically allow longer continuous use, as ambient temperature significantly affects comfort duration. A typical three-hour session might require one brief break, though this pattern varies with room temperature and individual sensitivity.

Professional use scenarios present specific considerations. The isolation proves sufficient for most studio environments, while detail retrieval supports critical listening tasks. However, the physical mass may affect productivity during extended professional sessions. The protective case supports occasional transport between locations, though size and weight suggest these headphones are best suited for dedicated listening spaces rather than frequent movement.

System Integration​

Testing with various amplifiers reveals notable characteristics despite moderate specified requirements. Through the Topping DX9's balanced output, performance proves adequate for most material, though complex orchestral crescendos suggest potential benefits from better amplification like higher end tube amplifiers (generally good at large signals).

The Cayin HA-300B MK2's transformer-coupled tube design shows good control despite higher output impedance, surprising me at macrodynamics, though bass definition softens slightly compared to solid-state options. The Pendant SE proves particularly successful with acoustic material in more tasteful and nuanced timbre (one of my favorites in this respect), though the solid-state Topping DX9 and LA90 maintains better control across a broader material range. Perhaps most telling, the Schiit Magnius demonstrates respectable performance despite its price differential, suggesting reasonable amplification flexibility.

Relatively flat impedance (usual for planarmagnetic headphones) may indicates minimal interaction with output impedance, though current delivery (in quality, not quantity) appears more critical than voltage swing for optimal dynamic performance.

Extended testing with various components reveals specific matching characteristics. DAC pairing shows solid synergy with both ESS-based and AKM-based delta-sigma designs, while the differences to advanced R2R (Rockna Wavedream Signature) or Pulse-Array (Chord Dave) implementations remain audible. Output impedance sensitivity proves relatively low, though current delivery capability in amplification proves more critical than pure voltage swing. Experience suggests optimal performance with output impedance below 2 ohms.

Cable response reveals subtle subjective differences but are unmeasurable with my devices. The balanced connection appears to demonstrate some advantages in perception, while shield quality shows correlation with presumably achieved noise floor. Overall, these differences, while present, remain subtle compared to amplification changes.

Pad Variants​

Systematic pad variant testing reveals consistent effects on performance. The stock hybrid configuration, combining leather and suede, achieves the most balanced frequency response while maintaining good isolation characteristics and consistent seal. Protein leather variants increase bass impact and push the upper mids slightly forward, though at the cost of higher thermal buildup. Full suede options relax the upper midrange and improve thermal characteristics but require more frequent positioning adjustments to maintain optimal seal.


Market Context​

Competitive Analysis​

Direct comparison with contemporary alternatives reveals different approaches to similar challenges. The Dan Clark Audio Stealth, positioned slightly higher at $4,000, demonstrates an alternative solution to closed-back planar magnetic design. Each shows distinct priorities in resolution, dynamics, and comfort implementation. The Caldera Closed might be preferred if you want more tight, punchy, and less damped sounding while the Stealth have some merits on neutral balance and are marginally better in detail retrievals. Comparison with dynamic driver alternatives like the ZMF Verite Closed (at $2,500) or Focal Stellia (at $3,000) highlights CC's technical excellence of planar drivers in resolving details and spatial cues at a cost of weight.

Value Proposition​

The current market position of the Caldera Closed warrants careful examination. At $3,500, these headphones compete in a segment where technical excellence is expected. The build quality and material choices align with price expectations, while the serviceable design supports long-term ownership value. The inclusion of multiple pad options and potential future mesh variations suggests a product ecosystem that extends beyond initial purchase.

Within ZMF's own lineup, the Caldera Closed represents a distinct technical approach from their dynamic driver designs. The price positioning above the Verite Closed reflects increased manufacturing complexity and different performance priorities rather than strictly hierarchical improvement.


Conclusion​

The Caldera Closed demonstrates successful implementation of planar magnetic technology within closed architecture constraints. Rather than attempting to completely overcome the inherent challenges of closed-back design, it presents thoughtful compromises that maintain musical engagement while providing practical isolation.

Primary strengths emerge in low-frequency control, coherent frequency balance, and effective isolation without severe technical compromise. The build quality and serviceability support long-term ownership, while pad options allow meaningful user adjustment. Thermal and weight characteristics require accommodation but prove manageable with appropriate usage patterns.

For prospective buyers, the decision framework should consider several factors. The intended usage environment impacts the value of isolation versus potential comfort adaptation. System matching, particularly in amplification, influences the realization of performance capabilities. Climate considerations affect comfort during extended sessions, while the long-term ownership perspective might justify the premium price position.

The Caldera Closed serves as a statement about balancing multiple technical challenges while maintaining musical engagement. Its success lies not in achieving ultimate performance in any single criterion, but in presenting a carefully considered set of compromises that serve practical listening needs without severe technical limitations.


Reference​

Associated Equipment Used​

  • Primary Chain: Topping DX9 DAC/Amplifier
  • Alternative Amplification: Topping LA90 Integrated Amplifier, Cayin HA-300B MK2, ZMF Pendant SE, Schiit Magnius
  • Alternative Digital Source Converter: Chord Dave, Rockna Wavedream Signature
  • Other Headphones: ZMF Caldera (open), Dan Clark Audio Stealth, Hifiman Susvara
  • Measurement Equipment: MiniDSP EARS, SMSL M500 Mk3, SMSL HO200

Key Reference Recordings​

  • Diana Krall - "Peel Me A Grape"
  • Massive Attack - "Paradise Circus"
  • Bill Evans - "Sunday at the Village Vanguard"
  • Mahler Symphony No. 3 (Zander/Philmarmonia Orchestra)
  • Tool - "Fear Inoculum"
  • Christian McBride - "Night Train"
  • Hilary Hahn - Bach Violin Sonatas
  • Hans Zimmer - "Time" (Interstellar)
  • Leonard Cohen - "You Want It Darker"
  • Bill Stewart - "Telepathy"
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Pharmaboy
Pharmaboy
I appreciate your "technical writing," documentation style in this concise, detailed, compact review. It sure doesn't hurt that you used Hillary Hahn's great recording of the Back violin sonatas in your evaluation....
o0genesis0o
o0genesis0o
Incredible write up

robo24

Headphoneus Supremus
Pros: TOTL detail, clarity, stunning midrange with some of the best bass I've heard while having the ZMF house sound and sounding extremely open for a closed headphone
Cons: Not free
Weight can be an issue for some
This is my first official review, though I’ve given impressions on every ZMF I’ve owned or had as a loaner over the years. If you’ve read any of my comments on the Caldera Closed thread I’ve already said almost all of this there. This review is more stream of consciousness with select comparisons (primarily to other closed headphones) than other formal reviews.

Zach sent a Redheart model as loaner which I’ve decided to purchase. As with others Zach has left it up to me if I even want to give impressions or not or just share my thoughts privately with him. The Redheart is especially beautiful and I’m a fan of designs using black and red.

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TLDR: The ultimate ZMF, with pretty much everything I’ve loved about the Caldera Open with some Atticus and Verite Closed influence. Wide and deep stage, fun, lush, amazing clarity and imaging, with a warm sound not lacking treble and never fatiguing. Deeply satisfying planar bass that has tons of texture, is punchy, and doesn’t bleed into the mids. A truly TOTL experience that I could be satisfied with as my only headphone, even over the Caldera Open.

Some disclaimers: I always use suede pads which are not the stock pads, though they measure similarly to the stock hybrid pads which also use some suede. Most impressions are with the Top Wide Perforated version, with wider spacing of the holes on the surface against the face, which provides more bass than the regular Top Perf suede version (which I think is used on the Bokeh, and I use on the Atrium Closed). I’ll freely admit I’m a huge ZMF fan and have owned every model since the Atticus, aside from a Bokeh I evaluated over a couple months (and will likely get eventually). Most of my impressions are in relation to other headphones I own, focusing on closed models. Most of my impressions are from the Feliks Envy with WE or Elrog ER 300B tubes, though I also used it quite a bit with the ZMF Homage.

I loved the Caldera Open from the moment I heard a pre-release one at Can Jam in late 2022 and have been very much looking forward to the Closed version once Zach said it would come out a year or so later. The Caldera Open has been my favorite headphone since it arrived. The jump in clarity over any of the dynamics, the more punchy planar bass, the airiness at times, all while maintaining the ZMF house sound made it everything I'd hoped it would be. There wasn't any criticism I had about it and was just looking forward to a similar sound with maybe more sub-bass, along with being closed which is important given most of my listening is at night with a lot of ambient noise.

First comparison is to the Caldera Open. The CO have stock suede pads. OFC cable used for both. Both with the Feliks Envy which has 2 jacks with the same output impedance. The CO is consistently 5dB louder than the CC, so I've had to quickly adjust my DAC that much when comparing. I did my best volume matching and adjusting with all the other comparisons too.

The Caldera Closed is everything I hoped it would be and more! It's also made me realize there is something I want to fix (and now have fixed) about the CO.

The CO is clearly the brighter headphone and the warmer CC is much more to my liking, such that I bought the mesh for the CO which helped reduce the treble where it’s boosted over the CC. The greater treble on the CO makes it more airy and seemingly more detailed, at least in the treble, and maybe with a hair more clarity compared to the CC.

I love a headphone with a wide soundstage and the CO isn't hugely wide sounding but I think it gets it right because it's so detailed and has such great imaging that if it was HD800 style it would sound more disjointed and I find when sounds have their own too distinct and isolated sound spaces it comes across as less cohesive. What's amazing to me is I'm not hearing major differences in soundstage width in the Closed! On some songs it actually comes across as wider which is just wild to me. This really doesn't sound like a closed headphone and I think many would be fooled in a blind test.

I'm enjoying vocals more on the CC, again amazing because the CO was already my favorite as far as vocals. I'm finding though that the increased treble in the CO distracts my mind some from the vocals and vocals seem more prominent/easier to focus on with the CC. Ultimately the CC sounds more cohesive and to my ears more "right" than the CO.

Surprisingly I'm finding myself preferring the bass on the CO. However, I think this is because my CO is effectively a pretty hard wood since it's resin stabilized and the CC is only in softer (though still medium janka hardness) wood so far and the bass differences are similar to the differences between my very hard Macassar Ebony AC vs. Redwood Burl AC. In both cases I'm finding the bass more punchy and thumpy with a bit more rumble on the harder wood and more boomy on the softer. Since I prefer that more punchy bass it's the one aspect where the CO wins for me. Bass on both is fantastic, with a ton of texture, and a bit more prominent sub-bass on the Closed. Keep in mind non-suede pads have a bit more bass than the suedes, so that difference where I'm preferring the CO bass may not really apply for most users. Having received the Homage the same day as the CC, I'm actually enjoying the bass more on the Homage than the Envy and the Homage is a joy on both Calderas. I certainly get why some prefer the Calderas and other planars on solid states over tubes.

I am amazed by the Caldera Closed and surprised that I'm largely preferring it to the Open, which has been my favorite headphone since I got a pre-release version in November 2022. It's an incredible achievement to basically take everything I loved about the Open, make it a bit warmer, and make it a closed headphone without really sacrificing anything. I'm realizing how much of an advantage closed is for me, as I'm hearing things in the Closed that I'm not hearing as much on the Open. Because it's always warm where I live and windows and inside doors are always open, there is always ambient noise from my computer fan, the wind, nature sounds, distant humming from appliances, etc. At night it's even louder. Being closed greatly reduces all that and creates a greater sense of atmosphere and little background sounds in music are very obvious while I barely hear some of them on the Open at the same volume.

Spent a couple days comparing with my Macassar Ebony Atrium Closed and Koa Verite Closed. As I've found when comparing the Caldera Open with the open versions of those 2 others, the CC is just on another level in terms of detail, imaging, and clarity with an overall tonality more similar to the Verites than the Atriums.

The AC is definitely brighter, and my Macassar is much less bright than the Redwood Burl AC I also had, while the CC is more expansive and detailed.

When going to the AC the treble really jumps out. Vocals are more forward on the CC but it’s not a huge difference. The AC will seem wider initially when switching to it, but I think that’s mostly the greater treble and vocals seeming slightly further away, creating more of a sense of space. The AC are more forgiving of less than ideal recordings, but the CC is still more forgiving that the CO.

Listening to the drum solo at the end of Snarky Puppy’s live “Take It!” it’s much easier to hear the placement of each sound, and everything is more distinct, like there’s actually more happening on the CC than the AC. When I switched to the VC, it’s more intense and in your face, but still not as clear and distinct. The drums in the middle of TOOL’s “Chocolate Chip Trip” are just insane on the CC. There’s just more to every beat like I can almost visualize shape and texture of each sound. Again, the VC is the most intense because everything is just in a smaller bubble, with that masking some of the detail though still having more than the AC.

Sub-bass quantity is clearly greater on the AC, creating more of a rumble and sense of physicality than the CC. Cymbals also stand out much more on the AC, which isn't surprising given the greater treble. On tracks with a good amount of bass the AC comes across as the more full sounding headphone, but on tracks without that it can actually come across as more thin sounding.

Also compared some of the pads while comparing to the AC & VC. The lambskin thick pads make the vocals less forward and more difficult to focus on though they do sound the widest. Tried them a couple different times but didn’t last more than a few songs either time. Just not for me. Leathers of all types all feel too hot on my skin, kind of immediately, so I never last too long with them.

The protein leather sound the most exciting/fun and maybe the most detailed, but at the expense of stage width and I think that is what’s creating a perception of more detail as sounds at the extremes come across a little louder because they’re closer to the center. I want to try them again with EDM, but for other music for now I don't see wanting to use them frequently. For some though these are going to be ideal and they certainly wowed me initially.

Every time I go back to the Top Wide Perf suedes they just sound the most right for me. I also tried to Top Perf suedes, and the greater density of holes on the top surface just takes away too much bass. I find them just right on the AC, but the Top Wide Perf which are the stock suedes on the CC don’t have that issue and I completely understand why Zach made that change to the suedes for the CC specifically.

Verite Closed with Auteur suede solids are about 5-6db louder than the CC. CC soundstage is much wider, the bass seems much more spread out and detailed, female vocals a bit more forward. Female vocals on the VC are closer to sibilant and a bit more nasally sounding. Overall much more similar than the CC compared to the AC. The mid-bass quantity is very similar, but just so much more detailed and textured on the CC. Sub-bass seems more present on the CC.

Also compared it to the DCA Stealth, one of the few TOTL closed planars aside from the CC and a direct competitor. The Stealth is $4000 but easier to find used for less than a used CC. I got mine used for $2300 and wouldn't have paid more.

The Stealth is good, extremely clear and detailed with a much more narrow soundstage and the CC lines up much more with my preferences by being warmer, sounding massive, and still having incredible clarity and detail.

I’ve had the DCA Stealth about 6 months. The couple CanJams I’ve been to it’s been the only DCA model I liked at all. What appeals to me is that it has extreme clarity and is just a totally different sound than all my other headphones. Problems with it are lack of dynamics and a need to listen at high volume for it to sound alive. It changes quite a bit with different ear placement and the pads kind of need to get warm to mold to the face and seal well or it seems somewhat thin sounding and bass-light. Volume matching is difficult. My phone volume measuring app will show the same volume in both but the CC is clearly louder once put on (which makes sense because the Stealth is much harder to drive). Increasing volume 2-4 dB seems to be a closer match.

When I start a listening session with the Stealth I thoroughly enjoy it though something in the upper mids to lower treble can irk me. The Caldera Open had that effect on me, much less, but the mantle mesh fixed it for me. Warmer, more wet sounding tubes also help. Otherwise the Stealth comes across as clearly TOTL in terms of clarity and detail but in general I’m not a big fan of Harman tuning. It can come across as somewhat lifeless so amp matching can take some work. It’s excellent with the Envy, V280, and even the Mojo 2 which has current doubling technology and drives it well despite being the least powerful of the 3. Less good with the brighter Homage. The stage is relatively narrow but decent for a closed back. At no time have I ever felt like sound is coming from well outside my head nor that I'm wearing anything other than a closed headphone. With the CC I can be fooled and at times it feels like there's a subwoofer in my room.

Comfort-wise they’re like 100g less than the CC, but I find them less comfortable and regularly fuss with them once they’re on. My ears also get much hotter in them and they have a solid outer part of the pad which breathes less well than ZMF suede pads. Maybe for people with large heads the more egg-shaped cups work well but as with the Arya they’re kind of too large vertically to feel right or get a good seal. My ears sometimes touch the inside surface which doesn’t’ happen with any of the CC pads and I don’t have large ears. I’d still say the Stealth have above average comfort overall, but my 628g blackwood VC is still more comfortable.

Vocals on the CC sometimes seem more forward than on the Stealth. Part of that is because even though they may be the same volume, everything is so narrow on the Stealth I have to concentrate more while the CC just sounds bigger in every way, separating the rest of the music from primarily the center as on the Stealth. CC has a much richer sound. At times the bass is tighter and more punchy on the Stealth while more boomy on the CC. Regardless, the quantity is almost always less on the Stealth. In quality the edge goes to the CC though it still has a lot of texture on the Stealth. Both headphones handle the most complicated passages with ease. On Yosi Horikawa’s Bubbles the noise of the ping pong balls (or whatever that is) are a bit more distinct on the Stealth. Songs with heavy sub-bass seem about the same quantity but sort of cleaner sounding on the Stealth. On the drum solo in Tool’s Chocolate Chip Trip, everything is just a little more distinct but again the left to right extremes seem about half the size that they do on the CC, and it overall comes across as more muffled on the CC. Had my husband also do this comparison and his comment was that on the Stealth it came across as more 3 dimensional and on the CC wider but more of just left to right while on the Stealth it was more elliptical. Unfortunately, this was about the only comparison where I slightly preferred the Stealth. I’d say if I had to choose overall the Stealth is more detailed, but with a more expansive stage it’s easier to pick out details on the CC. Extreme detail is not always critical for my tastes. The Atticus is the least resolving ZMF I own, but I absolutely love it after 5 years now. The much richer and expansive sound of the CC makes it seem like there is just so much more there compared to the Stealth.

After a day of back and forth I was leaning towards selling the Stealth but after enjoying it alone another day, I’ll likely hold onto it for longer. I haven’t heard the E3 and from descriptions I might like the tuning better, but it seems to be at the expense of the extreme clarity of the Stealth, to me it’s best quality and I already have many warmer headphones.

The Atticus was my first ZMF and my current one is camphor burl using Ori suede pads, so a bit more neutral than stock. It continues to be a favorite, especially on my Glenn OTL. The mid-bass dominates and it’s the warmest ZMF with forward vocals but can sound muffled after coming from the CC. Stage has always been decently wide for a closed back but it’s just not as resolving as higher end models. The rolled off treble hides a lot of detail that the CC brings out. With the CC everything is further away and much more spread out. Individual details are much easier to place. It has more sub-bass and the bass has much more texture while the Atticus is more boomy. In some ways the CC takes some of the best aspects of the Atticus, such as it being a more fun and lush sounding headphone, having warmth, and being non-fatiguing despite having much more treble presence. I’ve thought at times I’d love a planar super Atticus, and it’s not really that, but also sort of is combined with aspects of the Verite Closed. It’s certainly closer to those two than the Atrium or Auteur driver sound.

The Sennheiser HD820 was my first TOTL closed back and one of my first audiophile headphones. Wider soundstage but kind of honky vocals and a bit of sibilance. The CC is just very lush in comparison and seems much more detailed. No real contest here and the HD820 leaks a lot of sound for a closed back. As with the DCA Stealth, I still enjoy it, but at this point I primarily use it for watching movies at night as the wide staging gives stereo sources a good surround effect and the sometimes odd tuning isn’t bothersome. That it’s also very lightweight and comfortable is also a strength.

As far as fit and other details about comfort and such, it’s the same as other ZMFs using this headband (all of them except the Bokeh) and others have already covered all that. It’s important for those new to ZMF to understand that tailoring both the fit and sound is both easy and there are a plethora of options, including different materials, the BBB strap vs. standard strap, and the headband itself can be molded extensively without harming it. The rods allow plenty of additional adjustment. Anyone not immediately enjoying the fit should watch the ZMF videos about adjusting the headband, along with those about the impact of different pads and meshes on the CC—all on their YouTube page. If buying new, you have the option to get multiple pads and meshes for much less than they’d cost individually, so that’s a very easy recommendation. Ultimately, I went with the black mesh, which has a bit more treble than the stock red. You can learn everything you need to on ZMFs site, including about the tech used in both Calderas.

One certainly doesn’t need to have a TOTL amp nor tubes to enjoy the Caldera Closed. I actually preferred it out of the Homage almost as much as the Envy overall, and more so on some tracks. Overall, I consistently preferred the more punchy bass from the Homage over the Envy. Even with the Mojo 2 it’s driven very well. Megabucks amps aren’t required to enjoy either Caldera, and they’re not very amp picky either.

I highly recommend the Caldera Closed, even over or as a companion to the Caldera Open. I think it’s different enough to warrant having both, though also probably more similar than other ZMFs available in both open and closed versions. I can’t recommend enough how important it is to give any ZMF time and play with various pad, mesh, and fit options before rendering judgment on them. If you’re in need of an amp, I can also recommend getting the Homage bundled with it, as they give discounts on bundles with amps and upgraded cables.
jojothewhale
jojothewhale
Great REVIEW Rob! That Caldera redheart looks sick!
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Jacobal
Jacobal
If I became president, these would be free for all citizens.
F
Frabera
It's really a pity you could not compare it with the E3 as this Headphone brought a lot to the closed back market at half of the price of the CC.

BonGoBiLai

100+ Head-Fier
VIRTUOSO
Pros: Weighty, punchy sound with flagship-tier planar technicalities
Bang on bass performance, pure perfection
Beautiful treble extension. Possibly the airiest closed back-to-date
Midrange maestro
The most expansive soundstage in a closed-back pair
Good isolation
Flawless craftsmanship and build-quality
Stunning aesthetics
Weight distribution
Different tuning possibilities
Cons: On the heavier side, though mitigated by its fantastic weight distribution
About ZMF

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ZMF headphones, a USA-based company, started its journey as one of the few tweakers/tuners that modified the Fostex T50RP and offered their versions for sale. Over time, the company transitioned into a full-fledged bespoke headphone manufacturer, gaining recognition as one of the world's most beloved high-end headphone brands. ZMF has also ventured into the world of electronics, releasing a few amplifiers. Their flagship Aegis amplifier is a sight to behold, showcasing the brand's commitment to both form and function.

ZMF’s current flagship lineup is a testament to their commitment to innovation and improvement. They have two simultaneous flagship branches, one on the dynamic driver side with the Atrium open and Atrium Closed and the other with the current planar flagships, Caldera Open and Caldera Closed, both implementing the ADS system. This evolution in ZMF's lineup is a clear demonstration of their dedication to pushing the boundaries of audio technology.

Disclaimer:

This review is co-written with Mr. @Sajid Amit , Founder of Amplify Audio Reviews. Check out our video reviews at: https://www.youtube.com/@amplifyaudioreviews

ZMF Caldera Closed: The Evolution

Caldera Open was introduced shortly after the release of Atrium Open in 2022. It is a perfect testament to ZMF’s tuning prowess, and I clearly remember preferring it to both Hifiman Susvara and Abyss AB1266 Phi TC, both of which cost almost twice as much.

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Making an excellent flagship-tier closed-back headphone is tricky, especially when it is a planar closed-back. Take Hifiman, for example. They are far bigger than ZMF in scale and manufacture headphones in a more “mass-produced” manner. Yet, they have been struggling for years to make excellent closed-back dynamic driver headphones, let alone a closed-back planar. Plus, I think everyone remembers the horrendous HD820 from Sennheiser. Given how awesome the Verite Closed and the Atrium Closed headphones are, Caldera Closed has some big shoes to fill. And my oh my, what a perfect fit has it turned out to be!

Specifications:

Impedance: 60 Ohms

Driver: 2 um thick Planar Magnetic with CAMS Patent Pending technology

Weight: 535-585g

Sensitivity: ~94dB/mW


Unboxing, Build Quality, and Comfort

Caldera Closed comes packaged in a rather beefy-looking, weatherproof carrying case like other ZMF flagships. Ample foam padding inside keeps the headphones firmly in place during transportation. Cases like this should be industry standard, especially for ToTL headphones. I mean, fancy wooden boxes look visually appealing, but a carrying case practically representative of the headphone’s price tag is much more palpable.

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ZMF provided an extra set of thinner, more perforated pads (Caldera Thin, top perf.) alongside the thick ones (Caldera Hybrid, top perf.) already installed on the headphones. Two cables with different terminations were also offered in a small fabric sack alongside a catalog featuring the ZMF headphones and accessories lineup. The two stock cables ZMF provides look distinctly different from each other. The rubberized, slick cable with a shiny exterior surface is a single-ended cable that terminates to a quarter-inch connector. This cable kind of reminds me of the Moon Audio silver and black dragon cables. The XLR balanced cable, on the other hand, is a lightweight, flexible cable sheathed in black paracord.

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The unit that I am reviewing is the LTD version, featuring a dark brown color scheme with tiger stripe-esque dark patterns. The asymmetric patterned fit and finish of the Shedua wood cups are absolutely gorgeous and a sight to behold. Capturing the true beauty of the Caldera Closed with just a smartphone camera can be pretty challenging. But rest assured, its real-life appearance surpasses what can be conveyed in photos. The varnish's depth and brightness subtly adapt to ambient lighting, imparting additional character to its already flawless aesthetics. I'm sure you'll appreciate its stunning appearance when you see it in person.

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The Caldera Closed features an adjustable comfort strap and thick upper padding identical to other ZMF headphones' headband mechanism. The notched rod mechanism allows for a full 180-degree swivel, making it easy to adjust the headphones to fit any head size.

The Caldera Closed can weigh up to 560 grams, depending on the pad variant you install. It is on the heavier side and looks pretty on the head; there is no denying that. Yet the Caldera Closed has nailed the weight distribution in typical ZMF fashion. You will definitely feel them on your head; it is not a put-on-and-forget situation, but wearing them for long periods did not cause me any discomfort or wear out my neck muscles and spine. Alongside the headband strap and adjustment mechanism, the fantabulous ZMF pads also contribute to the deceivingly excellent wearing comfort. I have long been a fan of ZMF pads and prefer them to even dedicated pad manufacturers like Dekoni. I wear glasses with a thick frame yet have never faced any compromise with the seal or the comfort of the thick stock pads. I live in South Asia, where the hot and humid weather makes wearing closed-backs daunting. I do not know what voodoo ZMF has done to their pads, as I have been listening to the Caldera Closed non-stop, often without turning on the AC.

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The isolation is quite good. It did a commendable job drowning out the loud construction noise coming from outside when no music was playing. I noticed zero outside noise messing with the sound when the headphones were operational. The sound leak is also relatively minimal and barely noticeable unless the environment is remarkably tranquil.

TL/DR: 5/5 as far as accessories, build quality, aesthetics, and comfort are concerned.

Sound

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Frequency Response graph by Techpowerup

The traditional image of what a headphone should be is quite contrasting. While the average consumer is familiar with closed-back headphones and considers them as standard, it's quite the opposite in the audiophile community. There is a prevailing bias against closed-back headphones, and for good reason. In most cases, they are seen as the compromised but more convenient options compared to the better-sounding and better value-providing open-back counterparts. However, ZMF has proven time and time again that closed-back headphones can be as good as and often better in some aspects, with examples such as the Verite Closed and the Atrium Closed.

The first track I tried with the Caldera Closed was a Katie Melua track, and my jaw almost dropped in awe. I had already read some reviews praising the Caldera Closed's staging capabilities, but I did not expect it to be that good. Her voice sounded as realistic as realistic could be, and while it was not a particularly bassy track, the way Caldera Closed magnified and highlighted the bass undertones was unprecedented, at least to me. I quickly skimmed through a few different tracks from different genres. I played Hold On I’m Coming by Sam and Dave and some good old gangsta rap tracks, for example, thoroughly enjoying and bobbing my head to each one of them.

Drawn outside the lines of reason

Push the envelope, watch it bend.

Bass: Now, it was time to play something heavy and dynamic with some complexity and intricate layering. My track of choice this time was Lateralus by Tool and Caldera Closed’s rendition of Danny Carey’s drums, which gave me shivers that few other headphones could. The bass notes sounded highly realistic, with the perfect decay and effortless transition from midbass to subbass. Then, I proceeded to try my all-time favorite Led Zeppelin track, Fool in The Rain. This track heavily focuses on the virtuoso tier drums prowess of John Bonham, and I have historically struggled to like this track on driver types other than dynamic drivers. However, thanks to Caldera Closed’s flawless handling of bass response and percussions in general, I enjoyed Zeppelin as much as I enjoyed Tool.

Midrange: Like other ZMF headphones, the midrange is natural and weighty, with a mildly warm tilt. If midrange and vocals are your priority, Caldera Closed will not disappoint. In fact, I preferred Caldera Closed’s vocals slightly more than the Atrium Closed and Open due to the added clarity and precision from the planar driver. Voices sound crystalline in the mix but without the added emphasis on the S/Sh/Th consonants. This turns the Caldera Closed into a supreme pair of headphones for movies and shows, where the voices can often sound harsh and gritty, thanks to poor mastering.

Treble: In terms of treble, Caldera Closed is the airiest closed back I have had the pleasure of listening to. I preferred its treble response way more than the Hifiman Ovals, which are traditionally tuned bright. The Caldera Closed is not a bright headphone per se, but the top-end extension is truly remarkable, and a cut above is closed-back competition. It only falls short when compared to treble specialists like STAX SR009S. Other than that, the treble response is easily on par with the Caldera Open, if not identical.

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Technical Performance: The Caldera Closed stages like a full-fledged open-back headphone. In fact, it has a wider, more expansive stage than the Hifiman Susvara and the Focal Utopia 2022, both of which are flagship open-backs. I barely noticed any compromise, even when A/Bing with the kilo-buck soundstage king, the Hifiman Arya Organic. This is a testament to the flawless implementation of the newly developed and patented ADS (Atrium Dampening System), which effectively elements cup resonance, and as a result, the soundstage never feels like it has hit a wall. The enjoyment I get from the staging prowess of the Caldera Closed is uncanny at times, as I am still getting all that isolation while simultaneously experiencing a spaciousness that I would otherwise get from a pair of open backs.

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Thanks to the expansive stage and planar precision, images are very easy to discern and pinpoint, and the layering between vocals and instruments is effortless, no matter how complex the track is. Detail retrieval is almost identical to the Caldera Open. Almost because the Caldera Open is slightly sharper and more incisive, while the Closed variant has weightier and rounder notes. I did most of my listening with the thick pads already installed on the Caldera Closed. More precision can be achieved via pad swaps, albeit at the cost of reduced bass, which is a trade-off I would not rather make.

Drivability

The Caldera Closed is not an easy headphone to drive at 60 ohms impedance and ~94dB/mW sensitivity. I had to turn up the volume on my Questyle CMA18P almost to the maximum, which is otherwise a reasonably beefy portable DAC Amp. It performs pretty well with portable amps like the iBasso DP5, though I would recommend hooking up the Caldera Closed to a desktop system for optimum sonic performance. In case you have spent all your money on the Caldera Closed and are running short of funds momentarily, I would wholeheartedly recommend the Hifiman EF500. This affordable compact DAC amp sounds deceivingly good for the price.

Comparisons

ZMF Caldera Open


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The Caldera Open sounds shockingly similar to the Caldera Closed. The soundstage and detail retrieval are almost identical, and so is the timbre. The Open version is easier to drive and is slightly more intense in the top end. The Caldera Closed has a somewhat rounder sound compared to the Open version, though the overall clarity is still identical between both.

ZMF Atrium Closed and Open

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The Atrium Closed is more sub-bass-focused and does not punch as hard as the Caldera Closed. It has a warmer midrange and has a comparatively soundstage as well. The Atrium Open is, in fact, more similar to the Caldera Closed than the Atrium Closed. Both Atriums sound their best when driven off OTL amps, a pairing I would not recommend with the Caldera Closed.

ZMF Verite Closed

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Verite Closed is a mid-tier ZMF can that is still quite expensive at $2499, but for about $1k more, the Caldera Closed is a worthy jump if you can make it. The VC is considerably thicker and warmer than the Caldera Closed and has a clear midbass emphasis that occasionally sounds boomy to my ears. I much prefer the linear bass response of the ZMF Caldera, which sounds tighter and clearer. Caldera Closed has a noticeably wider soundstage than the VC as well. Soundstage-wise, I would put both Caldera Closed and Bokeh above the VC. These two newer ZMF closed-back duo employ a full-fledged ADS system, which is present in neither VC nor VO.

DCA E3

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The $2000 DCA E3 is the best-tuned Dan Clark Audio headphones released to date. It is another closed-back soundstage marvel with satisfactory bass, especially considering it is a DCA headphone. That being said, the E3 still cannot hold a candle to Caldera Closed’s class-leading bass performance. It also has some upper midrange emphasis that can get borderline shouty sometimes. Caldera Closed treats that particular region of the frequency response much more gracefully, even better than the Caldera Open, in my opinion.

Focal Stellia

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After the Sony MDR Z1R, Stellia is probably the first ToTL closed-back pair of headphones to receive mainstream hype and popularity. The only saving grace of the Stellia compared to the Caldera Closed is that it is easy to drive. In my opinion, its boomy midbass and remarkably narrow soundstage no longer warrant a ToTL price tag.

Hifiman Susvara et al.

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The Hifiman Susvara is the pioneer of modern ToTL headphone evolution and is still relevant to this day. Susvara’s primary weakness has always been the bass roll-off, and no matter what source chain you pair it with, it cannot hold a candle to the Caldera Closed’s bass response. Susvara can sound wildly different depending on the cable and amplification, so it is mostly a matter of preference between the two. As for lower-end Hifiman Ovals like the Hifiman HE1000SE and Arya Organic, they are noticeably less refined when compared to the Caldera Closed. I mean, they provide great value and all, but the Caldera Closed is better in all aspects, plain and simple.

Abyss AB1266 Phi TC:

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The Phi TC is heavy and uncomfortable and looks like a torture device. The TC’s party trick is its unmatched, guttural bass response. Sure, it does not sound realistic, but it works amazingly for genres like heavy metal. The timbre is pretty terrible and odd on the Phi TC. It is primarily a hit-and-miss with genres other than heavy metal, while the Caldera Closed is a generalist pair that works equally well with every genre imaginable.

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227qed
227qed
High praise, great review! Would you say the CC still has most of the “guttural bass response” of the abyss? I’m cross shopping flagships right now and class leading bass performance is one of my key criteria. Seems like the CC is quite the contender there. Note that I use EQ to raise bass levels for EDM and more immersive gaming, so stock tuning is not as critical as it would be otherwise. Really curious if the CC can become a bass monster if asked to do so with enough EQ, power, and the right track. Looking for that “subwoofer” on head capability, with capability being the key word there. I don’t expect or want any good headphone to be a bass monster with the stock FR.

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