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ZMF Caldera Headphone Review

Rate this headphone:

  • 1. Poor (headless panther)

    Votes: 48 27.6%
  • 2. Not terrible (postman panther)

    Votes: 84 48.3%
  • 3. Fine (happy panther)

    Votes: 30 17.2%
  • 4. Great (golfing panther)

    Votes: 12 6.9%

  • Total voters
    174

amirm

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This is a review, listening tests, equalization and detailed measurements of the ZMF Caldera planar magnetic headphone. It is on kind loan from a member and costs US $3,500.
ZMF Caldera Planar Magnetic Headphone open back review.jpg

The Caldera is absolutely gorgeous to look at. It is lightweight and with its large cup, very comfortable to wear. Will have to find out from the owner which set of pads it came with.
EDIT: owner let me know that it has stock lambskin perforated pads.

The large cups allowed almost instant fit on my GRAS 45CA headphone measurement rig. I am always happy when that happens. :)

ZMF Caldera Headphone Measurement
As usual we start with the headphone frequency response measurement and comparison with our target:
ZMF Caldera Planar Magnetic Headphone Frequency Response Measurements.png

OK, I get the flattish bass response but what is up with the three troughs above 1 kHz? Watching company video, they talk about their house sound but one has to be quite daring to choose a response like this. Fortunately the big areas should be relatively easy to fill in with EQ:
ZMF Caldera Planar Magnetic Headphone relative Frequency Response Measurements.png


The large drivers produce very little distortion even at highly elevated levels:
ZMF Caldera Planar Magnetic Headphone THD Distortion Response Measurements.png


There are some narrow band errors though which would have bee nice to iron out:
ZMF Caldera Planar Magnetic Headphone Absolute THD Distortion Response Measurements.png


I forgot to mention the messiness above 10 kHz which we also see in Group Delay:
ZMF Caldera Planar Magnetic Headphone Group Delay Response Measurements.png


As expected from planar magnetic drivers, impedance is essentially flat:
ZMF Caldera Planar Magnetic Headphone relative Impedance Measurements.png

Combine that with average sensitivity and you have a headphone that is pretty easy to drive compared to a lot of its competition:
Easiest headphone to drive review.png


ZMF Caldera Listening Tests and Equalization
First impression out of the box was inoffensive but pretty boring sound. There was almost no deep/sub-bass response so that was the first low hanging fruit to fix with equalization:

ZMF Caldera Planar Magnetic Headphone Equalization EQ Parametric Target Curve Measurements.png

That alone made a remarkable difference. But the job needed to be completed with the three other filters to fill those holes. Once there, I liked the effect very much but thought the sound was a big bright so took down the peaks a bit. With the complete package, the transformation was dramatic as you can imagine. There was impressive bass and excellent detail and quite good spatial effects.

This testing was more exacting than usual in that I had listened to the same test tracks last night with my Revel Salon 2 speakers as part of an amplifier review. Without EQ, the experience with Caldera was simply not there. Tracks that made me drool last night were "meh" without EQ. Turn on the EQ and you get the bass response I heard last night (and a bit deeper actually). The rest did not mimic the speaker response but at least was another high-fi experience. People who like the stock sound of the Caldera really need to do this comparison of an excellent speaker against what this headphone is producing. I am confident they would re-think their idea of "house sound" as we have measured above.

I also compared to my headphones that match the target and they too had superb bass that again, Caldera without EQ lacked.

Conclusions
Objectively it is clear that Caldera deviates significantly from what research tells us is highly preferred frequency response. That is fine but company needs to conduct its own research to see if their target is more performant. In my subjective and objective testing, I find that to not be the case, wasting what seems to be beautiful physical design. Fortunately we have EQ and fix its errors since its distortion is very low. And once there, have an excellent sounding headphone that looks great and is comfortable to wear.

I can't recommend the ZMF Caldera without equalization. With EQ, it sounds excellent but whether it is worth $3,500, you have to decide.

Manufacturer SPECIFICATIONS:
  • Impedance: 60 Ohms
  • Driver: 80mm with CAMS Patent Pending technology
  • Weight: 490 - 550 (weight varies depending on Chassis)
  • Sensitivity: ~95dB/mW


------------
As always, questions, comments, recommendations, etc. are welcome.

Any donations are much appreciated using: https://www.audiosciencereview.com/forum/index.php?threads/how-to-support-audio-science-review.8150/
 

Attachments

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thewas

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First impression out of the box was inoffensive but pretty boring sound. There was almost no deep/sub-bass response so that was the first low hanging fruit to fix with equalization:

ZMF Caldera Planar Magnetic Headphone Equalization EQ Parametric Target Curve Measurements.png
Personally I wouldn't want to have a transducer which needs such narrow positive peaking filters (which actually are resonators from system theory point of view) for correction. Yes, probably such might be not really an audible problem but knowing it I wouldn't enjoy it especially for that price.
 

solderdude

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All ZMF headphones look gorgeous but none of them seem any good sadly.

This one as well as the Auteur (1.5k$) and Verite Closed (2.5k$) do not seem to be poor sounding (not Harman target in the bass)

These headphones are about the wood and craftsmanship and their 'tuning' and are not intended for the general public but people with disposable income that appreciate it for what it is.
EQ can get them where you want them if needed.
You will end up with a gorgeous looking and sounding (with EQ) conversation piece.
 
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sai

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Finally we have measurements of the Caldera from a GRAS system!

Judging from the looks and the measurement it might be the stock lambskin perforated pads (the cowhide variation is thinner) , but I could be wrong.
 

sai

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Yes, I just realised the pads seem too deep to be the cowhide version. That one is rather thin.

The stock pads seem to offer the result most compliant to Harman.
 

ObjectiveSubjectivist

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I used to have their Auteur - beautifully made, and sound was also very good reminded me HD600/650.
Zack is really a guy who cares, I'm sure at some point I'll be back to one of his headphones.
 

Jimster480

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Auteur Classic is their flattest response, I believe.
I believe it is. My friend had one.

They are alright sounding but I'm just not their target audience with the price tag. I didn't have any specific complaints about the sound though in the sense that it didn't sound bad the way some expensive stuff I have listened to has.
 

taotone

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Nice review.

I much prefer your new style for IEMs and headphones. "Doesn't match Harman - I don't like it but you may.", instead of "Doesn't match Harman - it's junk."

I think this better matches the real world of enthusiast/audiophile listeners. I'm with you on the bass, I like the Harman bass shelf, for the mids I prefer a bit of a 3KHz dip as I do with speakers.

We can each take responsibility for knowing our own personal preference curve.

In this case however $3,500 for a very quirky FR seems like too much of a gamble to me.
 

phoenixdogfan

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I am sending my 2015 version of the LCD-X back to Audeze to update to the 2021 version. When I get it back, I sincerely doubt that the Caldera will be any more performant than them. So, no. Definitely not worth $3500. Especially considering the 2021 LCD-X has a similar performance in distortion, efficiency, and FR and sells at a street price of around $1k. And they both still need EQ. So absolutely not!

Moreover, I've always also thought that the ZMF phones looked like the heating/air conditioning vent in the panelled library of some British men's club. You know the kind where a butler delivers you a message on a silver tray while you're sipping your brandy from a snifter while reading the Times and harrumphing at the way the PM has 'bollixed everything up." If this design were any more dated, we'd have pictures of HG Wells wearing them.
 

Seta Seta Pop

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I am sending my 2015 version of the LCD-X back to Audeze to update to the 2021 version. When I get it back, I sincerely doubt that the Caldera will be any more performant than them. So, no. Definitely not worth $3500. Especially considering the 2021 LCD-X has a similar performance in distortion, efficiency, and FR and sells at a street price of around $1k. And they both still need EQ. So absolutely not!

Moreover, I've always also thought that the ZMF phones looked like the heating/air conditioning vent in the panelled library of some British men's club. You know the kind where a butler delivers you a message on a silver tray while you're sipping your brandy from a snifter while reading the Times and harrumphing at the way the PM has 'bollixed everything up." If this design were any more dated, we'd have pictures of HG Wells wearing them.
Jajajajajajajajajajajajajajajaja (Spanish laughter)
 

Maiky76

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Here are some thoughts about the EQ.

Please report your findings, positive or negative!

Notes about the EQ design:
  • The average L/R is used to calculate the score.
  • The resolution is 12 points per octave interpolated from the raw data (provided by @amirm)
  • A Genetic Algorithm is used to optimize the EQ.
  • The EQ Score is designed to MAXIMIZE the Score WHILE fitting the Harman target curve (and other constrains) with a fixed complexity.
    This will avoid weird results if one only optimizes for the Score.
    It will probably flatten the Error regression doing so, the tonal balance should be therefore more neutral.
  • The EQs are starting point and may require tuning (certainly at LF and maybe at HF).
  • The range around and above 10kHz is usually not EQed unless smooth enough to do so.
  • I am using PEQ (PK) as from my experience the definition is more consistent across different DSP/platform implementations than shelves.
  • With some HP/amp combo, the boosts and preamp gain (loss of Dynamic range) need to be carefully considered to avoid issues with, amongst other things, too low a Max SPL or damaging your device. You have beed warned.
  • Not all units of the same product are made equal. The EQ is based on the measurements of a single unit. YMMV with regards to the very unit you are trying this EQ on.
  • I sometimes use variations of the Harman curve for some reasons. See rational here: https://www.audiosciencereview.com/...pro-review-headphone.28244/page-5#post-989169
  • https://www.audiosciencereview.com/...pro-review-headphone.28244/page-6#post-992119
  • NOTE: the score then calculated is not comparable to the scores derived from the default Harman target curve if not otherwise noted.
Good L/R match.

I have generated one EQ, the APO config file is attached.

Score no EQ: 66.2
Score Amirm: 57.0 (documented Amirm's preferences towards more LF and less HF make the error regression have a steeper slope)
Score with EQ: 85.2

Code:
ZMF Caldera APO Score EQ Flat@HF 96000Hz
November302023-204241

Preamp: -8.9 dB

Filter 1: ON PK Fc 22.72 Hz Gain 5.98 dB Q 0.28
Filter 2: ON PK Fc 223.52 Hz Gain -2.31 dB Q 0.81
Filter 3: ON PK Fc 1453.31 Hz Gain 6.27 dB Q 2.24
Filter 4: ON PK Fc 2505.62 Hz Gain -2.24 dB Q 5.51
Filter 5: ON PK Fc 3703.41 Hz Gain 8.67 dB Q 3.23
Filter 6: ON PK Fc 6284.36 Hz Gain 4.02 dB Q 6.00

ZMF Caldera APO Score EQ Flat@HF 96000Hz.png
 

Attachments

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