ZMF Caldera Closed Review

X axis is frequency, Y axes are dB SPL (on the left) & Ohms impedance (on the right).

The tan curve is impedance vs frequency of the Caldera Closed (from @purr1n 's measurement); the other curves are the SPL vs frequency changes, relative to 90 dB SPL from a nominal zero-impedance amp, that are predicted from voltage division out of amplifiers with the specified output Zs.

My simple voltage-division calculator is based entirely on resistances. I do now wonder though whether any capacitor in the filter needs to be further accounted for (ie beyond its implicit effect on the impedance/frequency curve). @zach915m , I'd be happy to be corrected here if necessary.

 

For the impedance plot, gotcha (sorry I’m looking on my phone, in the sun and I am “color impaired” ).

This electrical dampener is actually a bummer for current mode amplifiers like the Bakoon/Enleum HPA-2x . You’d lose 6dB by 10kHz and 8dB by 15kHz :/

 

Didn't realize how many headphones Zach has now until your trying to discern 8 different colored lines in a chart. Converted to a table for those with trouble seeing the color changes.

 

Ok, I admit this is silly; and am weak too willed to avoid this

AO = 41.5
AC = 40.5
Auteur Classic = 39.5
Bokeh = 35.5
CO = 39.5
CC = 41
VO = 43
VC = 43

 

Time to revive this thread! I finally completed my full writeup about the Caldera Closed. Huge shoutout to @zach915m !!

Tl;dr. They're great. I like them.

But why and how? Well, let me elaborate.

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Initial Impressions, Build, Design & Comfort

Had the Caldera Closed for about 2 months now (review unit, going back to ZMF soon). Put in roughly 200 hours between critical listening and daily use. As usual with my reviews here, full disclosure: I know Zach, owned several ZMF cans before, etc. You all know the drill.

First thing that caught my eye was the ash cups (Shou Sugi Ban). Slightly atypical ZMF aesthetic - there's this raised triangular section that initially seemed like a bold design choice. After living with it, I'm starting to think it's more than just looks. Reminds me a bit of how the R10's cups were designed with specific acoustic properties in mind. Whether it's some computational modeling or empirical testing (probably both), it seems to play a role in managing internal reflections.

Build quality is... well, it's ZMF. We all know what that means by now. Same robust construction, same serviceable parts philosophy. What's new here is how they've adapted the design for a planar closed-back. The weight comes in at 545g (1.2 lbs) - not light, but the distribution is done well enough that it doesn't become a deal-breaker.

Comfort is interesting. Coming from someone who regularly does 4-5 hour sessions with Susvara and Stealth (both significantly lighter), I was concerned. The first day was an adjustment period for sure. By the 50-hour mark, something clicked - the weight distribution just works. Using the standard headband here, though curious about the BBB option. The clamp force is slightly firmer than usual ZMF offerings, but it actually helps with weight distribution.

The stock hybrid pads (leather outer, suede inner) deserve their own mention. The asymmetrical design creates this natural angle that works with head anatomy. Did some pad rolling with protein and suede options - more on that later, but the hybrids hit a sweet spot for comfort vs. seal.

Heat buildup is present but managed better than expected for closed-backs. Still, on warmer days, you'll want short breaks every couple hours. That's just physics - no getting around it with closed planars.

One practical note: that triangular design element actually makes handling easier. Gives you a natural grip point away from the pads. Small detail, but appreciated during daily use.

 

Sound Analysis

Time to dive into how these actually sound. Rather than breaking it down into discrete categories, let me share how these aspects come together in actual listening.

The overall character strikes me as less colored than typical ZMF offerings, though that organic quality they're known for remains present. The planar implementation achieves impressive technical performance without veering into analytical territory. It reminds me of how the original Caldera balanced technical capability with musicality, though here we're hearing it through the lens of a closed-back design.

Starting with the low end, the bass extension and control immediately stand out. Listening to Massive Attack's "Paradise Circus," that descending bass line maintains clear definition without bleeding into the vocals - something many closed backs struggle with. Moving to James Blake's "Limit to Your Love," the sub-bass presence is substantial but never overwhelming, with clean leading edges and natural decay characteristics. When I put on Christian McBride's "Night Train," the speed of the driver becomes apparent in how clearly it differentiates fingered notes from thumb-played passages.

The midrange presentation takes an interesting approach. It's somewhat less forward than you might expect from ZMF, but this serves the overall coherence well. Leonard Cohen's "You Want It Darker" demonstrates proper male vocal scale without artificial chest resonance. Switching to Diana Krall's "Peel Me A Grape," the piano harmonics are well-served, though slightly less immediate than what I recall from the open Caldera. Bill Evans' "Sunday at the Village Vanguard" reveals how well these preserve complex spatial cues for a closed-back design - Paul Motian's brushwork remains distinctly separated from LaFaro's bass lines.

In the upper frequencies, we get well-extended treble without unnecessary emphasis. Bill Stewart's "Telepathy" shows how cymbals maintain proper metallic character without becoming splashy. This becomes even more evident with Hilary Hahn's Bach Violin Sonatas, where upper registers maintain proper brilliance without developing an artificial edge. The bow noise remains present but proportionate - exactly as it should be.

The technical performance deserves special attention. Resolution sits comfortably at the level you'd expect at this price point. Listening to the Koln Concert, mechanical noises and audience sounds come through clearly without being artificially spotlighted. The spatial presentation, while different from open-backs (as physics demands), shows impressive organization. Yosi Horikawa's "Bubbles" maintains stable positioning that feels natural rather than forced. Dynamic contrast really shines in pieces like Tool's "Fear Inoculum," handling transitions from subtle percussion to full band without compression, though I noticed very complex passages can show slight congestion at high volumes.

 

Comparisons

Having spent considerable time with most of ZMF's lineup and several competing flagships, I think it's worth putting the Caldera Closed in context.

The comparison with the open Caldera (which I had on hand during the review period) proves particularly enlightening. As expected, the open version demonstrates advantages in stage width and immediacy. The closed version trades some of this spatial openness for better bass control and more liquid mids. This becomes especially apparent with something like Patricia Barber's "Modern Cool" - the open version better reveals room ambience, while the closed version provides more focus with bass lines and percussion. Neither version claims absolute superiority; they're different tools for different needs.

Against the DCA Stealth, we're seeing two serious attempts at TOTL closed planars taking somewhat different approaches. The Stealth edges out slightly in pure detail retrieval, while the Caldera Closed presents a more organic character with certain material. The Stealth demands more from amplification, but both demonstrate impressive technical performance. The choice really comes down to tonal preference rather than any objective superiority.

Comparing against the Atrium Closed and Verite Closed reveals a fundamentally different approach to closed-back design. The dynamic drivers in AC/VC excel at tonal richness, especially in the midrange. The Caldera Closed's planar implementation prioritizes speed and control - particularly noticeable with complex electronic music where faster decay characteristics become advantageous.

While perhaps not entirely fair given the design differences, I can't help but compare to my daily driver Susvara. The Susvara maintains its leadership in "air" and absolute spatial presentation - no surprise given its open design. What impresses me is how well the Caldera Closed maintains planar speed while adding isolation. It's a different tool for different needs, but the technical accomplishment here shouldn't be understated.

 

System Matching & Pad Rolling

System matching with the Caldera Closed reveals some interesting characteristics. On paper, the 60Ω impedance and ~94dB/mW sensitivity don't suggest particularly demanding requirements. However, actual use reveals these benefit more from current delivery than voltage swing.

My primary testing ran through the DX9's balanced output. While adequate, this pairing leaves something on the table with dynamic expression. Brief time with the Cayin HA-300B MK2 proved engaging but revealed some output impedance sensitivity. The ZMF Pendant SE showed particular promise with acoustic material. Perhaps surprisingly, even the Schiit Magnius proved a capable basic pairing. Throughout testing, the balanced connection consistently provided better control and scale.

The pad options deserve careful consideration, as they each bring distinct characteristics to the presentation. The stock hybrid pads (leather outer, suede inner) deliver the most balanced presentation and the best isolation-to-comfort ratio. This became my default choice through most testing. The protein pads increase impact and bring slightly forward upper mids, running warmer but working particularly well with electronic music. The suede pads offer a slightly relaxed upper midrange presentation, though they prove trickier to maintain a consistent seal. They run cooler, making them appealing for longer sessions with brighter recordings.

What's noteworthy is how each pad maintains the core technical performance while modifying specific aspects of the presentation. The stock hybrid seems most carefully tuned for all-round use, suggesting it represents the intended tuning target.

Caldera hybrid pads:


Caldera protein thin pads:


Caldera suede pads:

 

Measurements & Objective Analysis

Been spending time with various measurement configurations trying to understand what's actually happening with the Caldera Closed. My setup (MiniDSP EARS) shows some interesting results, but what's more fascinating is comparing these across different measurement systems.



Looking at frequency response first: There's a generally neutral-warm tilt with a moderate lift in the lower midrange around 200-500Hz. This explains that subtle fullness I'm hearing with acoustic instruments. The upper midrange shows good presence without the typical 3kHz emphasis many modern headphones exhibit. Treble extends well past 10kHz with good linearity, though there's some expected roll-off above 15kHz.

The measurements I'm seeing with protein pads show an interesting shift in upper bass/lower mids that correlates well with listening impressions.

The bass response is particularly interesting. My measurements show a gentle rise below 200Hz that maintains good linearity down to about 30Hz. This matches what I'm hearing - substantial bass presence without obvious bloat. However, this is where measurement methodology becomes crucial.

When comparing across different measurement systems, I'm seeing some notable but interesting variations. See the 3 normalized graphs below. The Techpowerup measurements using their GT-01 show stronger bass response, likely due to their methodology of applying significant inward pressure for a perfect seal. Meanwhile, GadgetryTech's IEC711-based measurements show slightly different treble characteristics.





(Note: to control measurement system effects, I tried to get the frequency response normalized to Caldera Open. All with stock pads. This enables double difference aka difference-in-difference comparison)

For reference, here are more detailed specifications of the listed measurement rigs (as per disclosure):

• Mine: MiniDSP EARS w/ stock dummy ears
• Techpowerup: Partclelab GT01 binaural microphone (presumably claimed as IEC711-compatible) w/ stock dummy ears
• Gadgetrytech: Clone IEC-711 compliant coupler (possibly purchased on Aliexpress) + Gras KB0060 pinna simulator

What's intriguing is how these variations align with real-world listening experiences. The Caldera Closed seems quite sensitive to positioning and seal - not unusual for closed-backs, but worth noting. My approach of averaging multiple positions without excessive inward pressure might better represent my typical listening conditions, though it potentially understates the maximum bass capability.

The variance between measurement systems raises some important points about closed-back planar measurements in general. Beyond just methodology differences, we're dealing with:

• Product to product variability
• Seal consistency - Leakage or pad compression can notably affect bass response. This also reflects real-world use.
• Placement variation - small changes in position may change internal directivity and different interactions with dummy ears, affecting upper frequency response. I believe the raised triangular cup design might actually help standardize placement somewhat, but it's still a factor.

Looking at the aggregated data, a few technical achievements stand out. The bass extension maintains linearity without the typical closed-back resonance issues. The midrange shows good coherence without sharp peaks or dips that would color timbre. The treble manages to extend well while avoiding the brittle character some planar implementations exhibit.

Some may raise concerns regarding the variations between systems. But having spent significant time with these headphones, I'd argue these variations actually explain us certain aspects of perceptional difference across listeners. Usual take-home message is not to overtrust measurements at face value. I personally take any measurements (mine included) as a sampled datapoint from much wider objective space.

Overall, from what I'm seeing in the data, these measurements support what I'm hearing - a technically accomplished closed-back that manages the usual challenges of the format well. The variations between measurement systems actually help explain some of the subjective impressions I've seen posted here and elsewhere.

 

Additional data points to compare CC to DCA Stealth. Deviation plots from mine, TechPowerUp, and Super* Review.

 

@Vtory Excellent review of the CC! Thanks for sharing. I hope there’s a SBAF loaner soon, so more of us can give these a listen.

One quick note, from the picture it looks like the wrong Caldera Suede pads were sent with your review unit. The CC is supposed to use the Caldera pads that are “top perforation only”, and the Suede pads you photographed have side perforations as well. I use those “top and side perforation” Caldera Suedes on my Atrium Closed, but they aren’t recommended for the CC.

Just looked at the Caldera Closed page on the ZMF site, and the stock Suede option to have installed on the headphones when they ship is actually the Caldera Suede “top wide perforation”. The perforations on these pads are only on the top but are spaced farther apart, making them more like a solid pad, increasing the bass quantity over the “Caldera Suede TP” and its more closely spaced perforations.

 

Good catch. I was indeed a bit confused!

Like you said, on the web page, it seems top-wide perforation (TWP) suede is recommended to use with CC.

CC's pads slection (installation):



Secondary choice:



And the separate pads section also recommends TWP over TP for CC:
(TP is compatible but TWP is recommended)





I am still not sure if there are 2 different versions of TWP suede though.

 

It’s my understanding that there is only one Caldera Suede TWP and one Caldera Suede TP, and both of these are in the standard Caldera pad thickness. Neither “thin” nor “thick” suede Caldera pads seem to be available.

I bought Bokeh Suede pads for my Atrium Closed at Zach’s recommendation back when I ordered the headphones. With the current naming scheme, they would now be called Caldera Suede Thin TP pads. I don’t think these are sold anymore. The Suede option for the Bokeh Closed is now the regular thickness Caldera Suede TP instead of the “thin”.

Long story short, you need to get some Caldera Suede TWP pads to try on your demo CC if possible. Pads can make such a difference on ZMF headphones that you want to be sure you’ve tried all the recommended options.

 

When ZMF announced the Caldera Closed, Zach wrote at quite some length about the ZMF Ori's and how these were kind of the spiritual successor to those -- at least that was my interpretation of his remarks.

This was definitively boner-inducing for me. I've gone on record as saying that the Oris (with oval pads) are likely my favorite-balanced headphones of all time. (The VCs beat them for romantic presentation and smoother rendering; the HD800s w/ ZMF Leather pads for sense of soundstage and clarity; the Atrium Opens for sense of space and production nuance dissection; but the Oris, to my ear, still trump all of these in terms of timbral accuracy, and a bass production that feels like a live musical performance, especially with rock music.) The open Calderas were excellent headphones, rather neutral and almost reference-like in their presentation -- the Closeds, surely, would ratchet up the bass to those Ori levels, right? Was there finally a grand usurper to take the throne from the wizened modded Fostii of old?

Not really.

That's fine though! The CC's strengths are uniquely its own, even among the stable of new ZMF Closedbacks.

To my surprise, the Caldera Closed (to my ear) are tuned moreso towards naturalistic, open-like presentation, despite their being closed. They achieve this with gusto -- these are the most open-sounding closed-backs I've ever heard. It's really quite the magic trick. What they share with the opens is a flatter timbral presentation, where the soundstage is presented in a rather 2D (not pejoratively) way. There is a great sense of balance and detail, and the soundscape is all fairly well represented -- at least with (what I believe are) the thin cowhide pads. As with the Opens I most enjoy the characteristics the thin cowhides imbue the Closeds -- they bump up the bass a bit and soften the treble ever-so-slightly, and it makes for a more impactful listen. With the other pads included (which I believe are lambskin thin pads, and leather of some kind with suede ear cavities) I found the Closed to be just a bit tizzy in the top-end, to the extent that on certain heavy rock songs the top-end-through-upper-mids didn't really coalesce the way I really like such tracks to. But jazz and softer tracks are very enjoyable, as the Caldera Closeds -- while not sleepy by any means -- are a bit reserved or relaxed, while still being very revealing; in my opinion it's fair to say they are very "reference". I think these would be really effective studio headphones for mixing or mastering as they don't exactly 'envelop' so much as 'show' or reveal, in my opinion. I notice the layering of reverb and delay effects, especially on vocals, really pop out at me with these. They give bass justice (including mid-bass 'slap', from bass drum mallets), but unlike a lot of headphones don't really derive their sense of energy or engagement from the bass -- they engage moreso in the upper mids. Which, again, I find kind of surprising and uncommon for closedbacks.

Marv's review described the CCs as being 'low contrast' which I think is a great way to put it -- I think of how footage from cinema cameras is captured at low-contrast, with saturation and contrast added later, all to preserve detail -- somehow the CC's give me this impression, that I'm listening to a somewhat reserved representation of the music; the full scope of the music is held back, somewhat, but by din of that you notice things that otherwise would maybe get swept up and away. This to me is where the CC's are special and a unique offering; these are extremely 'mature' headphones, in my opinion best enjoyed while reading a book, or doing work, or if listening very critically to songwriting and production.

If I have to feel out why they leave me feeling comparatively a little unenthused, I feel they lack a certain depth or richness that I was, personally, really hoping to hear from the Closed variation of these new ZMF planars. There is an intimacy that I really love with the VCs and Oris, that I personally think of as a 'closed back' thing, but this is largely missing from the CC's. Not to beat a dead horse but my hunch is this was the intention of the Closed Calderas, and to be clear it is an impressive and remarkable achievement; but personally I actually like a closed-back that sounds, well, like a closed-back... like I'm in some little velvet-lined room, just me and the music. (In this vein, I found the isolation to be less effective than my Cocobolo Oris or VC Camphor Burls.) But there is obviously much value to be had from a closed-back that sounds very, very open.

I actually think these would pair really f'ing well with the Mjolnir 3 -- I think the MJ3 could inject just that little bit of extra oomph into the Calderas that might just tip them into f'ing Excellent territory. For my tastes, these would be great to have around for somewhat more-passive listening usage, but for my personal tastes I couldn't see myself specifically reaching for them to hear how they will render a certain track.

As always thank you @zach915m and the SBAF team for the loaner!

 

First of all, thanks @zach915m and @ChaChaRealSmooth for organizing the Caldera Closed loaner:


TLDR: I enjoyed my time with Caldera Closed and I think they’re probably the most balanced and organic sounding closed back planar I’ve ever heard



Intro/Background

Well, this is my first time participating in a loaner in this hobby and that also means it’s my first time writing a semi-formal review/impression of a headphone myself. Anyways, in terms of ZMF house sound, I’ve been sparingly introduced to their headphones and as such this is actually a firsthand extended listening to one of their headphones and the closest ZMF I’ve had most time is the ZMF Atrium Open so I’ll be describing these in relation to that as well as my daily driver Hifiman Susvara

Sound Impressions

The moment I put this on and started playing, I was struck with how similar it sounds to ZMF Atrium Open but a bit softer in attack and lower treble bite. Then a few minutes later I notice how well balanced the sonics are from bottom all the way to the upper treble. Tonality is generally downward sloping with a gentle rise to mid-treble which gives it enough sparkle as to not sound overly warm. Soundstage is also remarkable for a closed-back which gives an open-back presentation though not the most open one I’ve heard; that belongs to DCA Stealth. Coming from Hifiman Susvara, at first, I thought Caldera Closed is a bit “boxy” and too laid-back sounding, but that immediately fades away with brain adjustment. The notes are thicker than most planars I’ve heard except for maybe Meze Elite (TSAV demo) which made me realize this is what ZMF house sound is all about and to me Zach has done an amazing job with the intended tuning.

Sound Breakdown and Comparisons

Bass

I find Caldera Closed to have excellent bass extension with great sense of punch and physicality. Its bass quantity is tastefully elevated to give it heft but avoiding that soft/pillowy overall dynamic nature of lower end egg shaped Hifiman planars and DCA headphones. In contrast to ZMF Atrium Open, AO has better bass attack and slightly better plankton (inner detail combined with microdynamics) though bass doesn’t extend as low as the Caldera Closed. Against Hifiman Susvara, Caldera Closed has less subbass extension, inner detail and sense of physicality. Even though CC have more bass quantity, it doesn’t slam as hard as the Susvara and is less textured overall. The key thing though is that Susvara’s bass is vivacious just like Atrium Open while CC is all about warmth and density. Overall I actually have no qualms at all with Caldera Closed bass since the tuning and the balance of plankton and dynamics still makes me very engaged and lost in the music!

Keep in mind the following characteristics below don’t determine any preferences.

Bass quantity: Caldera Closed (more lower bass) > ZMF Atrium (more midbass) > Hifiman Susvara

Bass macrodynamics: Hifiman Susvara >= ZMF Atrium > Caldera Closed

Bass microdynamics and bass plankton: Hifiman Susvara > ZMF Atrium > Caldera Closed

Midrange and Treble

Caldera Closed defines the line for me between laid back and polite. The way it presents the mids is just balanced throughout, making it sometimes sound ever so slightly restrained in the way it presents the inflections but not to the point of sounding polite since the upper mids rises slowly after the downward slope warmth from the bass region. Compared to ZMF Atrium Open and Hifiman Susvara, CC remains flatter sounding dynamically speaking with lower range for quiet to loud macro and micro dynamics. This is to me is where it can lack “richness or character” of both Susvara and Atrium Open.

Moving over to technicalities, I perceive the macrodetail retrieval and microdetail retrieval being better than ZMF Atrium hence more layered and resolved presentation on some tracks but loses though on Atrium Open’s vocal timbre and percussion plankton due to the flatter dynamics. Also, CC is a step below Susvara in every technical aspect yet tonally it’s a lot more tastefully sounding and at times even “correct” rather than just brutally revealing. Nevertheless, the tuning is so balanced that I can easily forget analyzing the track and just get lost in the music.

When it comes to treble, I find the Caldera Closed to have a slight lower treble emphasis that adds body to the shimmer and find it pleasing to me. Once again, even at the treble region, it retains the balance along with mids and bass. Likewise with the mids, I also feel that it has a slight reserved manner in the note attack and has good sustain and decent roll-off which makes for a very easy listening presentation. With ZMF Atrium and Susvara, the initial attack is more apparent, and the extension and air are a lot more present with Susvara but are completely absent with Atrium. All in all, Caldera Closed treble is very likeable tonally and never strays to being recessed nor peaky.

Once again, keep in mind the following characteristics below don’t determine any preferences.

Macrodynamics: Susvara > ZMF Atrium Open > ZMF Caldera Closed

Microdynamics: Susvara >= ZMF Atrium Open > ZMF Caldera Closed

Macrodetail and Microdetail: Susvara > ZMF Caldera Closed > ZMF Atrium Open

Plankton: Susvara > ZMF Atrium Open = ZMF Caldera Closed

Treble extension: Susvara > ZMF Caldera Closed > ZMF Atrium Open

Soundstage

Caldera Closed has a typical planar staging where instruments are “more cylindrical on a 2D plane” presentation while Atrium provides a very intimate yet wrap-around spherical presentation. To me, depending on genre and tracks, I might prefer one or the other. When it comes to the “ortho-wall presentation” when tracks get extremely complex, I don’t find the Caldera Closed to exhibit this phenomenon as much as lower end egg shaped Hifiman planars which to me is a great accomplishment by Zach’s ADS and treble tuning wizardry!

Amplification

Caldera Closed is probably the least amp dependent headphone I’ve ever tried provided you are using sufficient current (not from a Macbook from Super*Review lol). It sounded great and nuanced with Schiit Midgard (Halo Output), ZMF Homage and DIY Aegis (on lowest transformer tap) where the balance of tonality and technicalities are scaled equally as you increase the amp’s resolving power

Conclusion

I absolutely liked the Caldera Closed! Other than being a bit laid back for my taste on some R&B and Soul tracks where Atrium Open clearly shines, it’s an absolute all-rounder headphone that one should consider owning.

 

Hey guys - you'll have to remind me - does this tour unit have the protein thin top perf only caldera pads with it? Or what pads are with it now?

The protein pads are a bit more aggressive sounding, and I can't help but wonder for you guys that find it too laid back, or lacking bite, if the protein pads with the lighter front mesh would skew it in the other direction.

As with any tour unit, I'm haply to send out the complete kit and refresh it mod tour as stuff gets used more and needs a spritz.

Anyways let me know!

 

There were 3 sets of pads that are included with the loaner:

When I received mine, it came with stock Caldera Hybrids (suede inside, lambskin perf top, lambskin outside), I tried the all-lambskin deep pads and that's even more laid-back than the stock hybrids. Lastly, there was the Bokeh closed pads (don't remember if it was the Caldera thin protein or Caldera Suede) on the bag that's also included with the package that I didn't try because I find the Caldera hybrid stock pads the most balanced sounding from bottom to top and used it for my impressions

 

Got it! Whomever has it next let me know if it's the protein pads or not and if not I'll get a set out?

Thanks!