ZMFheadphones Caldera Closed

Disclaimer and intro

Zach Mehrbach, the founder and designer of ZMF has kindly lent me this Caldera Closed in exchange of my honest opinion.
Last year I reviewed the Caldera open and compared them to my Meze Elite. After spending months with both headphones, I fell in love with the Caldera open's rich, organic texture and dynamic, lively sound: I had to order my own pair.
Fast forward to May 2024, the closed version of the Caldera has just been released. I was really intrigued to hear and discover the differences. The question arose: would I like the closed version even more?


Burnt Ash (Shou Sugi Ban), one of the current stock woods.

Closed-back headphones in general and thoughts on other ZMF models

I will be upfront; in general, I really dislike closed-back headphones. I see them as a necessary compromise, in case someone does not have access to the 'full package' of open-back headphones and needs isolation. My experience is when we close the back of the headphones, we lose a serious amount of airiness, space and naturalness. Furthermore, designers face an awful lot of challenges to direct airflow, reverb and cup reflections versus the natural airflow open cups offer by nature. This often results in odd sounding headphones: claustrophobic soundstage, poor instrument separation, boxy treble, hollow midrange, over-damped or too bright sound. Even headphones like the Denon D9200, Audeze, HiFiMan, Focal or Sennheiser closed-backs are not free form some of these problems.
I admit, I am more sensitive to their shortcomings and more critical with closed-back headphones than the average consumer: for me closed-back headphones have always been the 'necessary bad'.



Zach has developed a unique and original, patented airflow and damping system. Here you can read about it in more details, but to sum-up the result: ZMF closed-back headphones sound the most natural to me out of all closed-backs I have heard. When listening to ZMF closed-backs, I do not feel I have to make terrible compromises or that, there is something really off with the sound. ZMF is the only brand whose closed-backs I am actually able to enjoy. That said, I still prefer the open counterparts of all ZMF models, but the difference between them is not as enormous as it is with other brands.

As many of you already know, Zach started out with Fostex T50RP modifications, which are planar headphones. Then he went on a different journey and developed several models with dynamic drivers. Since the very beginnings, he had a 'super planar' in mind which manifested in the Caldera open in late 2022. This is a completely in-house design from scratch, even the transducers are designed and developed, built by ZMF. (They have patent pending on their magnet structure.)


While I tried all ZMF models at different auditions and shows, the first pair I bought was the Caldera open.

Dynamic driver ZMF headphones almost have a cult-like following, and I am saying this the kindest possible way. Many people religiously love the synergy of high impedance ZMF dynamic headphones and OTL tube amps and I can clearly see why. There is some organic, thick, warm, lifelike and musical, engaging, euphonic magic going on between tubes and dynamic ZMF headphones.

I come from the planar world, mostly owned Audeze, Final and Meze headphones before the Caldera. To me personally the Caldera open is the best ZMF. They are special in the sense that the advantages of dynamic headphones and planar transducers somehow meet in one chassis. The Calderas (both of them) have a natural, organic tonality and thickness, richness that is often associated with dynamic drivers, yet they have the technical edge of planar transducers: enhanced speed, extension, clarity, detail retrieval, resolution. To my ears the Calderas offer the best of both worlds.

Some say, the Caldera deviates the most from the original ZMF house sound. I tend to agree, if under deviation we mean improved clarity, relative neutrality and higher level of technicalities. Still, the organic ZMF signature sound is absolutely there, and that is why I fell in love with my Caldera open.



User-tuneable headphones

ZMF is also famous for its highly user-tuneable headphones. You can tune the sound to your liking with several ear-pad options and damping meshes. It is not uncommon to have 8-12 different tuning options with certain models. These meshes and ear-pads can truly change the sound, so experimenting is highly recommended if you feel the headphones are good, just 'not quite there'. I am almost certain, that with some patience you will be able to find your 'yes, that is it!' combination.
The Caldera closed comes with a thick mesh and hybrid pads as stock. The tuning kit I have here includes another, thinner felt mesh and three more ear-pads; full leather (protein), full suede and thick leather.


Caldera closed with the thinner black felt and Caldera open without any mesh or felt. They both have carbon fibre rings.

On my open Caldera I tried five different ear-pads and settled down with the thick leather pads with no mesh. These pads tame the upper-mid/lower-treble forwardness just enough for long-term listening and slightly emphasise bass, plus smooth out treble a bit. Thick pads on the Caldera open are ever so slightly warmer to the more neutral stock option, but to my ears it is a welcome adjustment to the energetic and dynamic, yet most organic sounding king of planars.

I will come back to the tuning options of the Caldera closed a little later.

A few words on comfort, weight and build

ZMF headphones are a feast for the ears and for the eyes. The individually crafted wooden cups are simply gorgeous; like a musical instrument made for order. Weight can vary a lot depending on the wood type, but Calderas tend to hover between 470g-600g. To my surprise, there is no difference between the weight of open and closed Calderas. I would have thought the full wood cups of the closed version weigh more, but the stock Ash closed Caldera I have is 510g which is significantly lighter than my open-back black&white ebony Caldera with its 560g. Open-back Calderas can go down to 470g with redwood cups and magnesium chassis, and on the other end of the spectrum you have the stabilised and hard-wood versions around 600g.



The weight alone should not scare away any customers, as weight distribution and comfort are top notch. There are plenty of options to add more padding to the headband and buy the lighter magnesium chassis. My open Caldera has the 'BBB strap' which is the simplest and most subtle headband upgrade: a wider leather strap under the headband improving weight distribution. The demo Caldera closed does not have the BBB strap, it came with the basic stock headband. I have to say, thanks to this $59 addition, my 50g heavier open Caldera feels significantly more comfortable than the stock closed pair. After a while I feel the weight of the closed Caldera more, than I do with my own open Calderas. Clamping force is also stronger on the closed version, I am not sure if this is to balance the effects of the simpler headband or these headphones are just less worn in.

My point is, I would highly recommend the BBB straps to anyone who considers a purchase. My previous daily drivers before the Caldera were the Meze Elites, which are true comfort kings. Even after the Elites (430g) I have no weight or comfort issues at all with my 560g ebony Calderas.



I cannot miss mentioning the unique shape of the ear-cups. These asymmetrical dips and dives are not only aesthetic design elements, but they also serve a sonic purpose inside the cups and contribute to achieving a relatively lighter physical weight.
I applause, when a manufacturer dares to be different, and for me this unique design is an absolute hit; I love it. I read different opinions from people who cannot get their head around not having the same round cups like on any other headphones, but hey, more talk means more marketing.

Where is the Caldera positioned on the market from a sonic perspective

Since I have a Caldera open as my daily driver, I am clearly biased, but will try to bring in some objective insights. These observations are true for both the open and closed models, I will go into the differences between them a little later.
I owned many nice headphones and extensively auditioned flagships I did not own.
I usually gravitate towards planar headphones, as I really enjoy their speed, clarity, linear bass that effortlessly extends down to 20Hz and so on. At the same time, I prefer a thicker, slightly warmer, more euphonic and natural sound as opposed to neutral and analytical perfection. For these reasons I picked Audeze, Final and Meze planars as opposed to the thinner and more diffuse sounding but arguably more 'technical' offerings from HiFiMan for example.

In my opinion the Caldera is the most organic and natural sounding planar with the best timbre, texture and bass slam I have heard so far. They are not as detailed as a well-driven Susvara can be, but they are not far off and sound meatier. The soundstage is not as big as it is on the Meze Elite, but the ZMF flagships separate even better. Bass can be pretty much equally good as it is on the Abyss 1266, but with ZMF's more organic flavour and more alive midrange. The Final D8000 series are also wonderful headphones, but for me the Caldera once again has better dynamic range and a uniquely appealing, organic aliveness.



Caldera closed versus Caldera open sound

After discussing open versus closed design in general and where I think the Calderas stand on today's market, let's look into comparing these two models directly.

At my very first listen of the Caldera closed I was more surprised about the differences than struck by the similarities. Of course, the same Caldera sound is preserved in the closed cups, but to me these headphones feel more like cousins and not siblings. As mentioned earlier, I do not feel the serious compromises with ZMF closed-backs that I feel with other closed-back headphones; the sound is still natural, not congested or limited in any sense. Yet, in direct comparison the end of the soundstage bubble on the closed Caldera is palpable, while the open model sounds, well, more open and airier without the sense of a finite background. When listening to the closed version only, this space limitation is not bothering at all, yet in direct comparison to the Caldera open, becomes apparent.

Another thing that was instantly obvious is the warmer and softer tuning of the closed version versus the more neutral/slightly brighter and more dynamic sounding open-back wooden beauty. There is no better or worse here, just different which I think will divide the audience more or less equally.


Natural imperfections often enhance beauty.

Zach said, he tunes the closed-back versions of his headphones a little warmer on purpose: closed-backs tend to sound brighter and sharper, therefore more damping needs to be applied. This results in a warmer (and apparently softer) sound versus the open versions. There are many people, who absolutely love this warmer and softer approach: after all most ZMF headphones are tuned like this to smaller or larger extent. For example, fans of the Atrium, who found the Caldera open too bright and energetic, will most likely welcome the more familiar tuning of the Caldera closed with its softer treble and warmer overall tone.
On the other side of the coin, those who love the Caldera open for its supreme dynamics, detail retrieval, energy and impact might find it slightly disappointing that the closed Caldera will not offer the familiar, punchy fun to the same extent. Do not get me wrong, the Caldera closed still retains the fabulous tonality of the well-known ZMF Caldera sound, but inevitably it is wrapped into some damping material which will round off those dynamic edges and tame the overall energy of the open version.

To me, as someone who generally dislikes closed headphones, this is still an acceptable compromise which says a lot about Zach's patented air flow/damping system. I could live with the Caldera closed, but to me it is still a 'B variant' of the original which I would only use if I needed isolation.
The sound is wonderful, just not as open, not as airy as the first iteration. With this necessary damping we also seem to lose a few percentages of details and clarity compared to the open version: not much, but a noticeable amount.

This is a common theme throughout the frequency spectrum, so I won't go into too many details regarding bass, mids and treble. The closed version of the Caldera is smoother, warmer, slightly darker, less dynamic and a little less detailed than its open counterpart. Bass is still fabulous, just not as snappy and punchy. In stock form you get more mid-bass quantity, but clarity, precision, speed and impact are superior on the open version. Vocals are more forward on the open Caldera, a little further away in the closed model. Mids in general are more pronounced on the open, and slightly more recessed on the closed pair. This gives a modest sense of V-shape curve versus the opens. I would not call the Caldera closed V-shaped in general, but in direct comparison to some extent they appear to be.
Those, who found the Caldera open treble too bright or too energetic, will love the softer and easier treble tuning of the closed version. Those, who love the open version, might miss the bite, dynamics and energy that they are used to.

I personally miss the outstanding dynamics, clarity, slightly better technicalities and liveliness of my open Caldera. This is why I was trying to tune the closed-back version closer to my open pair, using the available ear-pads and meshes.



Earpads and meshes

As of now, the Caldera closed comes with the thick mesh installed and the hybrid pads on. I think, the hybrid pads are a good choice for stock pads, as they are the most balanced out of the four. The hybrids have relatively good bass focus, but also sound airy and natural in the upper-mids/treble. The leather (protein) pads improve bass focus, speed up transients, give more energy to the attack. In other words, you get a more focused and punchier bass, but at the small price of a slightly less open upper frequency range.
The suede pads are great choice for mid-centric music, vocals are the nicest and most natural on these pads. Bass and treble however become too soft and loose to my liking, lacking dynamics to make EDM enjoyable.
Hybrids are the 'in-between' solutions, but I personally love the attack and punchiness of the protein pads, so I am willing to make the compromise of a slightly less airy treble.
With the thick pads I liked the bass and treble response, but for me they suck out mids too much. Vocals are not just more distant, but also become a little bit hollow to my liking.



I personally found the stock felt mesh a little too much as front damping. To me these make the sound slightly too thick and warm. I prefer the thinner mesh, as they add a bit of brightness to the treble.
Not using a mesh at all just makes the sound too bright, falling out of balance: a mesh is necessary, but for me the thinner one is enough.
With the thin mesh and leather pads I was able to bring out the best slam, most focused bass and quickest attack from the Caldera closed. This is the closest I was able get to the open Caldera's dynamics.
The open version still sounds more natural, airier, quicker, more detailed and more energetic, but with the above-described tuning combination I felt I am not losing out too much on dynamics.

Other enthusiasts will love the increased warmth and smoothness of the closed Caldera with stock thick mesh and different ear-pads. Diversity makes the world a beautiful place and the huge variety of ZMF tuning options really widen the potential audience of these wonderful headphones.

Gear used

EverSolo DMP-A6 (streamer only), Holo Cyan 2 R2R DAC, Flux Mentor, Schiit Mjolnir 3, Cayin HA-3A (Bendix 6V6, E80CC).

Out of these three wonderful amplifiers I personally prefer the Cayin. The Mjolnir 3 brings out the most outstanding bass slam, but it lacks resolution and refinement in the upper frequencies compared to the other two amplifiers. The Mentor is refined and highly detailed, but for my personal taste lacks the life that tubes breath into vocals and acoustic instruments. The Calderas are happy on both solid state and transformer coupled tube amps; you just have to pick the correct tubes for a smashing bass experience. (OTL tube amps need to be avoided with low impedance planars.)



Finishing thoughts

The Caldera closed did not change my perception of closed versus open headphones. Still, I think currently these headphones are amongst the best three closed backs on Earth. Which are the other two? In my opinion they are the Verité closed, and Atrium closed. The ranking between these three will be completely subjective. For me personally, the Caldera closed are the best closed-back headphones I have heard to date.
If I needed sound isolation, ZMF would be my go-to brand, but luckily, I am able to use open headphones all the time; therefore, I will stick with my beautiful open Calderas for now. My choice does not change the fact that Zach has just put down yet another masterpiece on the lavish table of the world's audiophiles.

The Caldera Closed = Emotive Clarity!



Caldera Closed in Shedua Wood!

The Lineage:

The Caldera Closed (CC) has the Caldera Open (CO) lineage and the ZMF overall house sound. That is a good thing in my opinion. But the CC has its own magic that I sure enjoy.

Along with Planar clarity. the emotions are visceral with the CC. The ZMF emotions of the notes comes first and foremost before the clarity with the Caldera Closed.



From memory the Caldera Closed and the Caldera Open:

From memory the CC is darker than the CO. I spent many hours with my CO but had to sell my CO, Susvara and Utopia OG because I was barely getting any open back listening time due to when I listen and the need to not bleed sound or there was too much ambient noise. Even the air conditioner going on and off bothered me with open back HPs.

Burn In:

I am not sure if it is burn in or brain burn but it took about 60 hours of burn in and 10 hours of listening for me to become buddy buddy with the CO. I am hearing it as balanced in signature. Neither the bass (Atrium Closed for example) nor the treble (CO for example) are the stars. They play a great role along with the mids. I cannot handle V shaped IEMs nor HPs. I am not hearing a V shape. The vocals are present and accounted for in a great way.

This is the first time that I have recommended burning a HP or IEM in before making judgement.

Amps:

I do hear an obvious difference when running the CC with Holo Bliss versus with Ferrum Oor/Hypsos stack. Oor is using Holo May L2 with a Khozmo Passive Pre and Bliss is using May KTE with Serene. Oor gives the CC more clarity and intensity. Too much intensity at first but now with burn in/brain burn it is just right. Bliss provides CC with more warmth and texture (darkness).




ZMF Camps of sound:

I did an Atticus/Eikon Review awhile back. The Caldera Closed is bringing back memories of that review. I have owned every ZMF headphone except for the Bokeh.

I find that the ZMF house sound is all the way through all HPs. I also would like to amuse myself and overgeneralize and say that the ZMF HPs fall into two camps: There is the first camp of increased detail, clarity and a slight sub bass bump of the Eikon/Auteur and Atrium Closed and Open. The second camp is made up of higher resolution and fun with darkness and a slight mid bass bump. Camp two is made up of the Atticus/Aeolus and Verite Closed and Open.

The open and closed of each version stay within one of those camps which makes sense. The closed and open versions have the same exact driver.

For me the Caldera Open and Closed are the first ZMF headphones that do not stay within the same camp. From memory for me the Caldera Open was about the clarity and detail. Very quick. I also had the Audeze LCD 5 at the same time as the Caldera Open and the Caldera did lean (not all the way thankfully) in the direction of the LCD 5 intenseness and clarity of notes.

For me on the other hand the Caldera Closed is in the resolution/darkness and fun camp. That said of course the CC being a Planar driver has for sure a good amount of clarity and detail. What is unique with the CC is that it really has a wonderful “fun” sound for being planar.

I am guessing that ZMF played around with the tuning of the CC to be able to add some fun darkness which the CO has less of.




The Caldera Closed and the Dan Clark Audio Expanse:

I mentioned before that the CC gives off a Verite Closed vibe which I will write about later in the review. The CC also gives off some DCA Expanse vibe. The Expanse is considered an open back HP but I would call it a semi open back HP. It attenuates about 1/2 to 2/3 of the background noise most likely due to its tuning system (AMTS). The same goes for how much noise bleeds out of the Expanse. So, I treat it more like a closed back HP.

They both are planar so the amount of detail retrieval with both is excellent. They are both fast. They both have the darkness and the fun factor and mid bass vs. sub bass focus. The resolution of both come to the forefront. The notes of both linger a little bit to help feel the emotions of the notes.

CC is easier to drive. Expanse needs a really strong system to shine. The DCA Stealth and Expanse, just like the Hifiman Susvara really need good systems to shine. They can sound very lifeless otherwise. With Caldera Closed I think it does not need a system built around it to show what it is made of.

Caldera Closed notes are closer to you in your head. The Expanse notes are a little further out there in space. CC is less dark sounding due to being closer in your head.

The Caldera Closed wins out in the “it makes my toes tap when I put them on” category.







Caldera Closed and Atrium Closed:

Song: Dreams by Fleetwood Mac (2002 Remaster). The very first thing that jumps out to me is that the sub bass of the Atrium Closed (AC) is more pronounced. The CC is more mid bass focused but the bass blends in super well with everything else. The treble is a little more pronounced on the CC. By a little and of no concern of being too much at any point like some feel with the Caldera Open.

The CC needed the volume turned up a little bit compared to the AC. The CC preferred being on Lo Impedance and AC Hi impedance when using the Holo Bliss. That is to be expected due to their driver make up. With Low impedance the AC bass became a little less clean and the treble became a little too much. With High impedance the CC bass became a little dead and the treble less clean.

I really am not hearing a difference in the mids other than basic Planar versus DD sound. Thank you ZMF for keeping the ZMF mids on both extremely special.

Miles Davis, My Funny Valentine (Live Version 1964): The is where the Planar of the CC shows its stuff. Picking up minute details of each instrument. Rather impressive. With AC I am listening to the whole song as one. With CC, I am picking up the details in space.

With CC leaning in the direction of a DD in resolution and musicality, the differences between the two are not massive. The gestalt of the AC shows its stuff though. The big picture of the music. The CC also does that but has the Planar ability of increased clarity and detail. The rumble down under with the AC is very apparent. Not annoyingly but in a good way. That brings the center point for me with the AC in the mid to lower mid-section.

With the mid bass and Treble being prevalent with the CC, the center point for me is the mid to upper mid-section. Hence, most likely the reason I am not able to point out massive differences with the mids of the two. Both mids are excellent. I am not able to tolerate a V shape for very long. I am not hearing a V shape with either of these HPs.

I am guessing over time; I would reach for the CC for either super-fast stuff like Metallica or for slower music with fewer instruments like Modal Jazz or Trio Jazz or simple Folk music. I would reach for AC for all music in-between. Your standard rock bands like Tom Petty for example. Both HPs of course could easily overlap in both directions.

For me the AC has a more intimate soundstage. The venue is a little smaller and I am closer to the stage. The CC has a little bigger stage and I am a few rows back. For closed back HPs, I find no issue with the staging. I do not find either closed in which is an impressive feat by ZMF.

I do not think you could go wrong with either the Caldera Closed or Atrium Closed. Nor could you go wrong with both.




Caldera Closed and Verite Closed

In general, the Caldera Closed comes across as more balanced. Everything is equal. Smooth and fast. With a tinge of darkness.

The Verity Closed (VC) on the other hand has the midbass bump and a treble bump. Mids are not recessed but bass and treble are a tiny bit more elevated. There is a darker fun going on with VC. CC has a dark fast fun.

It is like ZMF wanted a fast dark DD with great resolution with the VC. And with the CC they wanted a fast dark Planar with great resolution. The only difference in those superlatives are “DD” and “Planar.”

The stage of the CC is wider than VC in my opinion. VC is closer to the stage. The notes are closer with the VC but there is still this 3D thing going on. CC is more left to right and wider and sitting further back from the stage. And of course, the notes are faster with CC as to be expected.

VC likes to get right to the point. Minimal foreplay. With CC the foreplay is a little longer. Both are a joy. There is just a different way of getting to the apex with each.


Pad Rolling:

Comparing 3 pads:
Caldera hybrid pads which will be the stock pads.
Caldera all leather thick pads
Bokeh protein thin bads
I first went from the Caldera stock hybrid pad to the Caldera all leather thick pad. What I noticed is an overall increase in the thickness of the notes with the thick pads. From low frequency to the mids to the high frequency range. It is not better or worse but is for sure discernably different. This increase in thickness could most likely be called an increase in resolution. The drawback would be a decrease in clarity and speed.

I have always preferred the stock pads on all the ZMF HPs versus other options I have tried with each HP. But with the Caldera Closed my personal preference are the thick pads. It is wonderful to have choices.

Protein Bokeh thin pads: The protein pads sure brought the planar into the planar. The increase in clarity and quickness is very apparent. And an increase in sub bass. Very interesting. I am getting more of a Caldera Closed vibe with the thin Protein pads and less of the Verite Closed vibe as with the all leather thick pads. The stock hybrid pads are right in-between those two in sound.



Conclusion:

I am extremely impressed with the ZMF lineup. Each of these high end ZMF headphones compete with other top tier HPs. None of the ZMF top tier HPs is an improvement over the other. Each offers a quality good time with many climaxes in store.

The Caldera Closed sound is an amalgamation of the emotive qualities of a dynamic driver headphone and the clarity of a planar magnetic headphone. That is what makes the Caldera Closed special and very unique.

This review is a special one for me. Not only is it my first review ever, but I get to review a pair of headphones from my favorite company. I’ve been a fan of Zach’s headphones since the first time I saw them a few years ago – leather, wood, metal, and sonic bliss all in one package? I knew I needed a pair. It was a little over a year ago that I was fortunate enough to get my hands on my first ZMF, a Verite Open Purple Heart. Since then…well just check my Head-Fi signature and you can see what happened! I really went down the rabbit hole.

After experiencing the Caldera Closed at CanJam NY, I reached out to Zach, and he was generous enough to loan a unit for me to try my hand at reviewing.

Being my first review, this was a very fun challenge! I hope you all enjoy reading my thoughts.

Tech Specs:
Wood: Shou-sugi ban Ash
Chassis Material: Aluminum
Weight: 541 grams
Pads used: Caldera Thick

Audio chain for this review:
My desktop setup is Spotify > USB > Schiit Gungnir Multibit A2 Unison > Schiit Mjolnir 3. I did all my testing on the Mjolnir 3.

Tracks used:

• Homemade Dynamite – Lorde
• Tennis Court - Lorde
• Black Mambo – Glass Animals
• Gooey – Glass Animals
• Heat Waves – Glass Animals
• Billie Jean – Michael Jackson
• Reckoner – Radiohead
• Interstellar Medley – Hans Zimmer Live in Prague 2017
• Inception Medley – Hans Zimmer Live in Prague 2017
• Pachelbel: Canon and Gigue for Three Violins and Continuo in D Major: Canon (Jean—Francois Paillard)
• Riders on The Storm – The Doors
• Remembrance – Balmorhea
• Mine – Bazzi
• LEMON – N.E.R.D – bass
• Radio – Lana Del Rey
• Everywhere – Fleetwood Mac
• Hotel California Live MTV 1994
• Crystalize – Lindsey Stirling
• 24K Magic – Bruno Mars
• Disasterpiece – Slipknot
• Unsainted – Slipknot
• Nero Forte – Slipknot
• With You – Linkin Park
• Formula – Labrinth
• Let Her Go – Passenger
• Round Here – Counting Crows
• Beat Bizarre – Save the Cheerleader, Save The World
• Give Life Back to Music – Daft Punk
• Pink Floyd - Dark Side Of The Moon (full album)
• Nothing In My Way - Keane
• Riders On The Storm - The Doors
• Spanish Sahara - Foals
• Bubbles – Yosi Horikawa

Dynamics
In Riders On the Storm you can easily appreciate the rain sounds as a backdrop in the music, even while the drummer hammers away on the ride cymbal. The details are not lost or washed out by any individual instrument, whether it’s the piano, guitar, or drums. Reckoner is also a great example, with the drummer in your right ear, guitarist in your left, and a subtle tambourine slap and piano supporting in the background. It is stellar how well the details are preserved, despite the rapidly rising and falling instrumental sounds overlaid on subtle noises. Dynamics also are wonderful in orchestral music, such as the Hans Zimmer Live in Prague - Interstellar Medley. The track’s subtle background of violins, drums, horns, and piano are still crystal clear despite the prominent electric cello and horns. The listening experience is intense. While listening to some headphones can be like watching an LCD screen TV, the Caldera Closed is like watching an OLED TV- the intensity is simply greater, there is more depth and information for your ears to extract.

Instrument Separation, Resolution, Detail retrieval, and layering
The instrument separation and layering on the Caldera Closed are impressive, rivaling the Caldera Open in my testing. For example, in Spanish Sahara - Foals, there is a buildup throughout the song, where it begins with drums, adds guitar, and keyboard, and all the components come to a head in an epic medley (around 4:15). Despite the depth and layers, you can still pick out each instrument, each level of detail, even as the music intensifies. Another great example is in Hotel California, Live On MTV, 1994, where each instrument adds to the medley, but can easily be followed throughout the track. In terms of vocals, in Round Here - Counting Crows, you can practically imagine the room that Adam Duritz is singing in - the size and mild echo - and can hear his breaths while he sings! In the Hans Zimmer Interstellar Medley, you can hear the instant the drummer’s sticks make contact with the cymbals. The Caldera Closed does a wonderful job of bringing out these small details in songs.

The resolution and detail retrieval on the Caldera Closed is similar, but slightly worse than the Caldera Open. I believe this is simply due to the closed back cups muddying some of the sound. One caveat - in a room with any significant noise, I noticed better detail retrieval than the Caldera Open, since any ambient noise was interfering with my listening. In a dead silent room, Caldera Open would win in terms of resolution.

Soundstage
This is one of the most impressive features of the Caldera Closed. To put a number to it, to my ears the soundstage is perhaps ~80-90% that of the Caldera Open. Normally a closed-back headphone makes me feel somewhat claustrophobic (which is why I shy away from them), but the experience on the CC was delightful. Occasionally, I would forget that I was using a closed back! In terms of soundstage, it is easily the most impressive closed back I have ever tried. One thing I did notice, perhaps thanks to the closed cups, is the music felt more intimate and engaging than the Caldera Open. Thus, although there is some loss of soundstage versus an open back, I think it is marginal, and absolutely worth the sacrifice for sound isolation.

Imaging
I love using Bubbles – Yosi Horikawa to test imaging. It’s a binaural recording which really tests a headphone’s imaging capabilities. With the Caldera Closed, you can pinpoint exactly where sounds are coming from and follow them as they move in space, much like the Caldera Open. In this recording for example, there is a bouncing ping-pong ball moving from in front to behind your ears, and it is so realistic that when I closed my eyes it was easy to imagine the ball bouncing along its trajectory! With regular tracks, the imaging is also stellar. In most music I found that I could pinpoint sound sources within a 5-10 degree angle. Interestingly, it was also easy to imagine in my mind the “size” of that point of sound in space, creating a 3D mental map where each sound was emitting from within the cup. In comparison to the Caldera open, I could not really appreciate a difference in the imaging capabilities; they are very similar to my ears.

Bass
I found the bass on the CC to be punchy and visceral yet refined. For example, the bass in Hotel California – Live on MTV, 1994, the kick-drum feels like a punch to the ears (in a good way!); you experience the heft of the sound. The CC bass frequency response is very slightly elevated versus Caldera Open, and not bass light or rolled off in the low end. Compared to the Caldera Open and Susvara, the Caldera Closed bass is more pronounced and stronger, especially against the Suvara whose bass is lighter and airier to my ears. The speed of the bass is also very good, indistinguishable from the Caldera Open to my ears. In heavy metal with rapid double-bass pedal work, you can clearly hear every single kick drum beat without any bleeding into the next (for example in Slipknot’s Disasterpiece). I would rank the Caldera Closed bass performance as better than the other headphones I compared it against (CO, VC, VO, AO, Susvara).

Sub-bass
The sub-bass of the Caldera closed is excellent. I found in tracks like LEMON – N.E.R.D, and in the Hans Zimmer Live in Prague Dark Knight Trilogy Medley the sub-bass really stood out. The texture is also excellent and superbly smooth. The sub-bass is not laid-back. It is quite in-your-face, but it is not overwhelming, and I love how it brings out subtle low-end details. It truly is impressive, to the point where it almost feels like I’m listening to my speaker system with a dedicated subwoofer with how far into the low-end it can reach. I had absolutely no need to apply EQ to sub-bass frequencies on the Caldera Closed. I find that the CC sub-bass outperformed that of all other headphones I compared against (CO, VC, VO, AO, Susvara).

Overall tuning
This is where Zach knocked it out of the park. The tuning of the Caldera Closed is spot-on. The overall tuning is well balanced, without any component of the frequency spectrum being overwhelming or too weak. Bass is beefy and strong, without muddying the overall sound profile. The treble peaks are not overwhelming, but do a great job of bringing clarity to the music. I would not change a thing with Caldera Closed’s tuning, and I didn’t feel the need to apply EQ at all. The stock tuning of the headphone is dang perfect in my opinion and addresses two shortcomings of the CO for me – the sharp treble peak/mild sibilance and need for a bass boost. With my Caldera Open, I find that in certain songs (ex. Disasterpiece, Nothing In My Way, Reckoner) , hi-hats and cymbals can be a bit sibilant. However, when testing those songs on the Caldera Closed the sibilance was absolutely tamed.

We discussed the pros, now for the cons…
No headphone is perfect for every listener, Caldera Closed included. To me, there are very few things wrong with it, and I really had to think and listen hard to find shortcomings. There are a couple I want to mention. 1) the resolution and clarity is slightly diminished compared to the Caldera Open, and 2) in certain songs, there is a bit of muddying of the sound. I think both are just due to the closed cups. Neither is a deal-breaker, and really only noticeable with direct comparison to the Caldera open.

Pad and mesh rolling the CC:
This review was performed with the Caldera Thick pads, and stock (red) mesh.
Due to work I did not have time to roll pads, but I will update this review with my impressions.



The most important thing I look for in headphones is immersion. I want a pair of headphones that does not just present music to me, but makes me experience and feel a song, no matter how many times I’ve heard it before. Did the Caldera Closed achieve this?

Before I answer that question, I want to say – from the get-go I could tell the Caldera Closed would be a good headphone. I loved listening to it over the past few weeks while writing my review. It is a great all-rounder. Classical music? Oh yes. Rock and metal? This is it, chief. EDM, pop, or rap? Pick up the dang Caldera Closed! Anything I threw at it just sounded good. It was clearly very capable, and it became my go-to headphone during the past few weeks, so much so that even my beloved Susvara has not been on my head in weeks. My appreciation for the Caldera Closed, and what a good closed-back headphone sounds like, has grown since Zach sent me the headphone.

But, back to the question above. Did it meet my ultimate test? I found out the answer just a few days ago. And the answer is a resounding yes.

A few nights before publishing this review, I had a truly magical experience listening to The Dark Side of the Moon on the Caldera Closed. I had a tremendous appreciation for the headphone before that, but that album just completely enthralled me on the CC. I don’t think I have ever heard this album sound so good! Maybe the mood was just right, or maybe my audio chain just struck a magical synergy that night; but most likely, it was just the Caldera Closed doing its magic. When Brain Damage and Eclipse came on, I was teleported back to 2017 when I went to see Roger Waters in concert with my father. I could imagine the concert so clearly – the prism of light, and the color spectrum being shined across the audience in a wave, the spotlights shining on the band as they played that epic song. That concert was incredible, and Caldera Closed brought that wonderful memory back to me in such vivid detail, it nearly brought a tear to my eye.

Is it the most “natural” or realistic presentation of music? No. Caldera Closed is a distinctly ZMF product – it focuses on musicality, rather than an ultra-realistic performance, and that classic ZMF house-sound has not been lost in this headphone. Like using the proper tool for the job, if you want to have a deep musical experience, the Caldera Closed provides that.

So, would I buy Caldera Closed for myself? Yes. Writing this review has changed my perspective on closed-back headphones, which I usually completely avoid in favor of open-backs. These headphones really do it all – the great detail retrieval and excellent imaging, dynamics, bass and sub-bass, all similar to the Caldera Open, but with sound isolation to boot. But, keep in mind, we cannot simply simply call this headphone a “closed-back” version of Caldera Open. It has a sound signature, tuning, and musical presentation unique and distinct enough from the Caldera Open, that it would beautifully complement, rather than outright replace, a Caldera Open in your collection.

For those of you who are looking for a closed-back planar, I highly recommend the Caldera Closed. Zach has produced another masterpiece, taking the best properties of the Caldera Open and putting them into a closed-back package, creating yet another unique headphone in the ZMF lineup.
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Thanks to Zach for giving me this opportunity, I had a ton of fun testing out the CC and writing this review. To all the readers, I hope this review was entertaining and enlightening. Happy listening everyone!

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