In this feature, we review the ZMF Headphones Caldera which is a new proprietary 80mm planar magnetic driver flagship open-back headphone. It is priced at $3499.
Disclaimer: This sample was sent to us in exchange for our honest opinion. Headfonics is an independent website with no affiliate links or status. We thank ZMF headphones for this opportunity.
You can click here to learn more about the ZMF Headphones products we have previously featured on Headfonics.
Note, that this article follows our latest scoring guidelines which you can read up on here.
If it wasn’t for the US student loan system ZMF Headphones might not have been a thing. A gentle push into a hobbyist sideline that has now turned into a lucrative business, ZMF has built and released a wide range of popular headphones over the last decade or more.
Our last foray was the excellent high-end dynamic driver Atrium back in the middle of this year. Right at the end of this review, Zach commented to stay sharp as he had a planar headphone in the works that might be right up my alley.
He wasn’t joking either with the launch of what could be loosely considered their flagship planar headphone, called the Caldera.
Certainly, one of their most ambitious projects to date it has all the hallmarks of a ZMF Headphone both in looks and its timbral bias. Critically, it has the technical chops to merit being a TOTL headphone, at least for my tastes.
Tech Highlights
The Caldera is a high-end circumaural open-back planar magnetic headphone but unlike the modded projects ZMF Headphones started on, this one is designed from the ground up. That means a unique and freshly designed driver and magnet array as well as drawing from the Atrium damping system.
Driver
The driver inside the Caldera is a new 80mm planar driver with a 61mm active moving surface area, all encased in a carbon fiber baffle to keep the weight from the coil and magnet array down to a fairly comfortable level.
This is not an off-the-shelf driver so the Caldera driver materials and design are quite new. The 4 traces and 8 pathway patterns are gold-plated copper rather than aluminum and might go some way to explaining the 60Ω impedance rating.
The Caldera diaphragm has a special silver coating to maximize excursion along the traces. ZMF does not reveal the Caldera diaphragm’s thickness so you won’t hear terms such as nano-grade thickness being bandied about.
However, I do know it is not as thin as a HIFIMAN design but enough for a deep excursion and get the bass filled out as well as retain the trademark expansive staging quality of a typical ZMF Headphone.
CAMS
An evenly pressured diaphragm with good soundwave management is what makes a good planar driver tick and every company has its unique approach to this. ZMF Headphones and the Caldera are no exceptions to this norm.
There are several solutions applied to the Caldera but the most salient point to make out of all of them is that they cannot be treated in isolation. Each has an effect on the other with particular reference to airflow.
The first key innovation is the Caldera Asymmetrical Magnet Structure or CAMS. This is a dual-sided trapezoidal-shaped N52 (Neodymium) magnet array designed to create a very even magnetic tension on the diaphragm from a minimized magnet footprint.
The specific magnet shaping also lessens any potential blocking of the Caldera diaphragm surface area, allowing the coil traces to be less obstructed and more evenly dispersed over the diaphragm.
Damping System
However, this in itself is not the full solution, and much like, for example, Audeze and Abyss, the Caldera soundwave and airflow management extends beyond and into acoustical space outside and towards the ear itself using an adaptation of the Atrium damping system, (ADS), and custom design earpads.
Damping as a selling point seems to have become a big thing with DCA Stealth’s AMTS waveguide control as a prime example. ZMF has also taken a similar route by placing damping front and center though through a different methodology.
For your reference, ADS is the spongy-looking construction on top of the driver in the picture above.
The Atrium Damping System primarily focuses on reducing back-wave cancellation with a more uniform application of pressure exerted via a controlled angle or radius of the damping material.
Because it is also customizable it is not a simple lift from the Atrium and placed inside the Caldera cups. It has been modified specifically for this headphone.
Caldera Pads
Like CAMs, the Caldera ADS system should not be treated in isolation. ZMF has one more trick up its sleeve with a freshly designed earpad called the Caldera pads.
These are specially fluted design pads with a semi-vented airflow system. They are physically different from the Atrium version with a wider internal dimension and a wall that eased out in size the further away it gets from the driver.
This wider path manages the continual airflow from the driver, through the CAMS and ADS to your ear which results in a change in the ‘perceived size’ of the driver performance. In short, a much bigger sound than otherwise possible with a regular pad.
Design
White Oak
If you are familiar with ZMF Headphones you will be familiar with the Caldera form factor with that striking wood cup design forming the heart of the visual experience.
There are a few variations in the rollout of the Caldera with a darker-grained Kingwood Edition costing you a little bit more. You can also get the Caldera in a Coffee Gold finish.
The sample we have here is the stock American White Oak version with a hard wax finish which is a slightly darker and grittier grain than the Cherry wood from the Atrium.
White oak has a low stiffness and a high level of strength. It holds up extremely well over time and can also be machined extremely easily which makes it a prime candidate for headphone cups.
It does have a less polished look compared to the Atrium wood finish and feels rawer to the touch, or just perhaps woodier. Because it is real wood every Caldera cup finish is unique to the buyer’s headphones, no two headphones will be alike.
Grill
Like the Atrium, there is a choice of grills for the Caldera with this stock edition sample using a black finished plate that is not quite as elaborate as the Atrium alternative but does offer a very intricate level of machining with a tight multi-lattice effect right across the surface.
You can also order the same design with a coffee gold finish on the same grill cut with matching colored adjustment rods. Personally, I quite like the black finish and it does mesh well with the heavier grain of the White Oak Natural option.
It is beautifully detailed and a little bit denser in terms of open spacing between the lattice-like flow of the material compared to the more open-looking Atrium grill design.
Everything Else
Aside from the cups, the Caldera is built pretty much in the same vein as the Atrium. That means a mix of anodized black aluminum for the pivot blocks, gimbals, adjusting rods, and spring steel for the headband, as well as leather for the pressure strap and headband outers.
You can also get the Caldera in a lighter magnesium build which will take off about 34g from the final weight. However, the magnesium version is not anodized but rather painted so it might show some additional wear and tear over a period of time compared to the aluminum version.
Overall, the feel of the Caldera in your hand is a familiar ZMF feeling. It’s sturdy, and very well built with nothing at all in the way of tension creaks or squeaky joints. Most importantly, its articulation for fitting is excellent.
Comfort
Because the Caldera is a planar magnetic headphone you would assume it should be a bit heavier than the dynamic driver Atrium.
However, it is not significantly heavier at all with both having a starting weight of around 490g suggesting the majority of the headphone weight lies in the framework and cup materials.
ZMF does state that depending on the material choices it can jump up as high as 550g and in the case of the Kingwood Edition you are dealing with 600g, (Magnesium), and 630g, (aluminum), which is fairly hefty. You will not find a current Atrium variant much higher than 520g no matter what finish you choose.
That being said, given the framework and significant work done on the new pads, the pressure balance of the Caldera is every bit as good as the Atrium both laterally and vertically. If there is a nuanced difference it is the vertical pressure increasing due to the additional weight from the magnets inside.
However, the crescent strap and notchy rod adjuster system will give you plenty of room for head height combined with an adjustable pressure strap system that tucks right into the very soft leather-wrapped memory foam on the headband.
It’s a far cry from the limpet-like clamping of the LCD-5 or the somewhat ‘draped’ style of the Susvara and I dare say the soft finish of the pads mitigates any effects of its lateral clamping. The net outcome is a very comfortable fit indeed.
Pads
Once again, ZMF has supplied the Caldera with not just a newly designed detachable pad as explained in our tech highlights section but the ability to buy a few alternatives that do have a noticeable effect on the presentation.
The stock pad is a lambskin leather variant and of the 3 versions we have here, it is the thickest cut pad. The other two that were sent to us include a slim cowhide version and a very soft and vegan suede version that is as tall as the stock and feels more like Alcantara.
All supplied pads are perforated with a wedge-cut profile which is a requirement for the Caldera airflow system to work optimally.
Each pad also seems to have a slightly different internal cavity design, probably due to the overall height of the internal wall. The Cowhide’s slimmer profile will give it a perceptibly wider-looking opening with the stock lambskin looking the narrowest and the suede somewhere in between.
Fitting them is dead easy as they follow a tried-and-true slip-on at the base of the pad. You simply slide a bit of the pad base leather flap into a small, recessed channel, at the base of the Caldera exposed baffle and work your way around the cup until the entire slip is in the groove.
The only precaution you need to take is to ensure that when fitting the wedged pads the taller side is aligned to fit behind your ear and not in front.
Stock Cable
For this Caldera sample I only received the balanced cable version but for the full retail package should be getting two 5.5ft cables: a balanced 4-pin XLR/mini-XLR option and the other being single-ended with a 6.35mm jack and mini-XLR connectors.
The balanced version is an insulated copper wire with a twisted nylon jacket finish and a black-finished aluminum funnel-type splitter. The mini-XLR pins are terminated ‘Audeze’ style so their polarization is fairly standard.
The SE alternative is a 24AWG 4-conductor OFC copper wire with aluminum and copper shielding housed in a rubbery external jacket with the same black branded splitter and mini-XLR connectors. The 6.35mm barrel and wrapped in heat shrink with strain relief internalized.
The supplied balanced cable has low microphonics and very little in the way of memory retention. It handles very smoothly and compared to the SE rubbery version it’s my preferred cable with slightly better flexibility.
ZMF also provides a number of cable upgrade options to go along with the stock should you wish to roll a bit when buying the Caldera. Their OFC cables come in either 6ft or 9.5ft lengths with alternative Letrik C and S options starting at 4.5ft with increased intervals up to 12ft and with different prices.
Packaging & Accessories
ZMF has a fairly set pattern for their headphone packaging and accessories so it is no surprise then that the Caldera comes with a similar presentation to our previously reviewed Atrium.
That means a very sturdy and large, black-colored, weather-sealed carry case with plenty of internal soft foam padding for both headphones, cables, and the rest of the accessories.
For accessories, you get the two cables in a nice little cloth sack as well as an array of paperwork in a small red envelope to indicate your Caldera build type and QC checks as well the pads used and a catalog of ZMF Headphone products and earpad options.
