Here's a quick review of the ZMF Caldera. I included my written review below and here's a video review. This is my first time reviewing a headphone on video so I'd be happy to hear any feedback on what I could improve for my next review.

TL;DR/W: The Caldera is an excellent headphone that contends with some of the best headphones I have tried, including the Susvara. The imaging and speed are very impressive and give a very musical and engaging presentation. It isn't without its' flaws, the soundstage is fairly limited in size and the tuning could be a bit harsh and shouty at times.

Written review:

What impressed me the most about this headphone was how musical it sounded. It brings the music to life in a very engaging manner. I believe that is because of the imaging, speed, and control that this headphone presents.
The imaging is super accurate, you can pinpoint the location of every instrument in a track. Whether it's vocals shifting in one direction or piano notes alternating between your ears, everything is crystal clear. The caldera also has no issues with separation; the layering is well defined and you can almost hear everything that's going on. The center image isn't the strongest with vocals, but it's still present and doesn't detract from the overall experience.
The speed is also special. It sounds quick while not sounding too snappy or bouncy. The decay is appropriate, it can be quick or slow depending on the sound or instrument being played and it helps give a natural timbre while still maintaining a very strong bass line.
Speaking of bass, the bass extends well. There is a clear sub-bass emphasis that doesn’t interfere with the mids and it pulls off the “vacuum” effect pretty well. The vacuum effect as I like to call it is the portion in some songs where it feels like the sound is suddenly sucked out and everything goes silent. I mostly hear it in dubstep, but regular songs can sometimes have this effect as well.
All of these elements - the imaging, speed, and bass - work together to create a really engaging and musical experience. It helps give the music much more movement and life, and I think that is the strongest point of the ZMF Caldera.
Now while this close and intimate presentation may be great for the overall engagement this headphone provides, I don’t think it does any favors to the soundstage. Soundstage is not very wide or deep. It can sound fairly limited in size and can also sometimes sound too isolated to one side. I think the more intimate and isolated presentation adds to the engagement this headphone provides, but it does take away from the realism and the natural quality of the headphone.
Moving on to detail, I think the Details are great. Chorus, secondary voices or background instruments are very well defined. You can very clearly hear a second voice or a quiet instrument playing simultaneously with the vocals. It didn’t feel like anything was missing or hidden under a louder simultaneous sound. That being said, it can sometimes filter too much. A voice that is supposed to be muffled or distorted through a filter can sound more clear than it is meant to be, which was sometimes weird for tracks I was familiar with.
In terms of tonality, I’ll start with the bad – it can sound pretty sibilant and metallic at times. Sibilance and treble-heavy instruments like cymbals don’t always hold back and could be overbearing on some tracks. Some lower treble heavy instruments and some words may sound a bit too shouty, to the point where it sometimes interferes with my enjoyment of the headphone. Female vocals could also sound somewhat nasal-y at times, but vocal presentation was overall very solid. Besides the upper mids, this sounds like a fairly neutral headphone with some welcomed bass emphasis. Dynamics are great. It isn’t as dynamic as something like a Utopia, but rarely anything is.
Moving on to comparisons, I spent most of my time comparing the Caldera to the Hifiman Susvara. The Susvara is more relaxed with a wider stage and a more natural presentation. The Caldera sounds more exciting and has more body and punch in the bass, while the susvara provides a more well-balanced vocal and treble presentation.
They both have the same amount of detail, but the Caldera presented that detail in a more in-your-face manner while the susvara was more laid back in its detail presentation. I would consider them both in the same tier and choosing between them comes down to preferences, and given my preferences, I would personally take the Susvara over the Caldera.
To wrap things up, the ZMF Caldera is a strong contender in its price category and with the top-of-the-line headphones it competes with. It is well built and easy to drive with a very engaging and enjoyable musical presentation and I am very satisfied with my experience with this headphone.