Campfire Audio Astrolith: Pinnacle Planar

Special thanks to Ken Ball and Chris Halasz for entrusting me with one of the first production units of Astrolith in exchange for my honest and open review. Your continued support is greatly appreciated.

It wasn’t until I got a chance to experience two firsts with Campfire Audio – my first custom IEM and my first planar IEM, in the form of Supermoon – that I finally clicked with what Ken Ball and his passionate team were all about. 

This is a company determined to not just “follow along” with what everyone else is doing, or what’s popular right now. Instead, Ken has a keen sense of tuning that conforms to his own ideals of how sound should be presented, knowing full well it won’t find favour with everyone. 

You only need look at the hoo-ha surrounding Trifecta, the current flagship, to see how liberating – and divisive – this approach can be. Which is why, when Ken and Chris first approached me with news about a ‘very special’ IEM they were about to reveal, my heart started racing at the thought of the drama that was surely about to follow. 

Except now, having spent these past weeks getting intimately familiar with Astrolith – Campfire’s all-new $2,199 custom dual planar IEM – I’m not sure there’s going to be any ‘fallout’ at all. To my ears and, this is quite simply the best-tuned, most technically-capable IEM Campfire has produced to date, at least of the ones that I’ve personally heard and enjoyed. 

Supermoon introduced us to the technical potential of micro-planar drivers, albeit with their numerous tonal quirks. Trifecta came as close to an unapologetically ‘take-it-or-leave-it’ design that you can get, sacrificing puritan performance for raw emotion, uncontrolled as that could sometimes be. 

Astrolith, for me, cherry-picks the best of both. It improves on the technical excellence of Supermoon but leans closer to Trifecta’s warmer, bass-first tonal character. The result is a distinctly Campfire IEM that showcases how far planar technology has come in a short time, but also course-corrects some of the tonal and technical shortcomings of its predecessors. 

That’s not to say Astrolith is going to be Campfire’s goldilocks, because that’s just not how Ken rolls, which in his own words:

“Takes what’s possible with planar magnetic tech and accentuates the things it does best, maximising dynamic range by pushing sub low to the extreme, while not having roll off on the high end at all. It is again Campfire going out on a limb to try and achieve something different. I think it hits the mark, and is something I plan to continue to pursue.”          

Whether or not Astrolith hits the mark for your own preferences is something else entirely, but in the course of this review I’ll at least try to paint the most vivid picture possible of how it sounds to me, what it does well (and maybe not-so-well), and who I think it might ultimately delight. 

Introducing Astrolith 

Astrolith ushers in several ‘firsts’ for Campfire. It’s the first Campfire IEM to feature dual planar magnetic drivers: an all-new, Campfire-customised 14.2mm planar magnetic driver for sub-low to midrange frequencies, and a 6mm planar tweeter for highs. 

It’s also the first Campfire IEM with a Particle Phase Resonator (PPR), an acoustic system developed to phase and frequency-correct the 6mm tweeter. Without the PPR, it would not have been possible to use the 6mm tweeter in a crossover-less design. 

The 14.2mm sub-low/low/mid driver is set inside another first, Campfire’s newly-developed Additive Acoustic Optical Inclusion (AAOI) housing. This precision-shaped chamber uses front and back-end acoustic load engineering to both shape and refine the target output of the driver. 

Also new is Astrolith’s 3D-printed acrylic shell, which features optically-inclusive internal chambers within a transparent exterior. This creates a gem-like effect, with internal visibility from various angles. 

At first glance the shell appears sleek and black, but look closer and turn it into the light to get glimpses of the various chambers inside. The shell is capped with a high-grade, mirror-finish, stainless steel lid, with a sleek new ‘terraced’ design. This piece is made from a full CNC billet process and polished by hand. 

According to Ken, Astrolith is “technically the best IEM we have ever made, demonstrating superior performance in measurable electro acoustic parameters.” He backs this claim with some impressive numbers:

Total Harmonic Distortion (THD): Astrolith boasts ultra-low THD, less than 0.3%, one of the key advantages of using planar magnetic drivers. Campfire’s custom drivers already feature very low distortion levels, and the company claims the new planar drivers cut this number in half. 

Rapid Impulse Response (IR): Belying the drivers’ rapid, accurate movement is their outstanding impulse response, the ability of the driver to respond to signal and stop resulting movement quickly. This allows the driver to move from note to succeeding note without overlap or ‘smearing.’

Below is a comparison between the impulse response of Astrolith’s new 14.2mm planar and one of Campfire’s most advanced dynamic drivers. Highlighted in blue, Astrolith’s rapid impulse response demonstrates its ability to quickly bring the large diaphragm to a complete stop. 

Even Diaphragm Movement: Astrolith’s planar drivers’ serpentine voice coil is distributed evenly over the entire surface of the diaphragm, preventing the drivers from warping or bending as they move. This contributes to the accuracy and rapid impulse response, tightening each note and avoiding the type of ‘smearing’ typical in large dynamic drivers.

Planar Wavefront: A defining feature of Astrolith’s planar performance is the propagation of a flat planar wavefront, contrasting with the conical wavefront created by standard cone speakers. The shape of any given wavefront changes the acoustic interaction with the ear canal, creating reflections and altering our perception of sound. Astrolith’s flat wavefront contributes to its unique timbre and sonic character. 

Impedance Magnitude: Astrolith’s impedance measures almost completely flat, from 5Hz to 25KHz, producing accurate and balanced sound throughout the frequency spectrum with minimal deviation.

Packaging and accessories

Presented in a colourfully-themed recycled cardboard box, Astrolith’s packaging is not quite at the same intricate level as Trifecta’s somewhat OTT wooden box contraption, but the high-quality accessory list remains the same. 

This includes a black leather folding wallet, handmade in Portugal, two TimeStream cables (terminated in 3.5mm and 4.4mm connectors), Campfire’s ‘Breezy Bag Micro’ two-pocket mesh pouch, a selection of silicone and foam tips in three sizes each, an IEM cleaning tool and a bonus Campfire Audio lapel pin. 

It’s the same accessory pack that ships with Trifecta and also the Deluxe Editions of Campfire’s Chromatic Series IEMs, minus the now-redundant 2.5mm cable. 

Design and fit

The two-toned acrylic resin and stainless steel housings are exceptionally well-made. If you were underwhelmed by Trifecta’s nylon shells or the rounded resin housings of the Chromatic IEMs, I think you’ll be pleasantly surprised by how premium Astrolith’s shells look and feel. 

Comfort, always a potential dealbreaker with universal IEMs, is thankfully superb. The stainless steel nozzles are similar in shape and size to other Campfire IEMs like Andromeda and Solaris, which is to say fairly girthy but thankfully not too long. With small tips they slide easily into my narrow ear canals, with the smooth acrylic fascias sitting flush against my ears. 

To date I’ve had zero discomfort, even after long listening sessions, and have even managed to get a reasonably deep fit without inward pressure building up after hours of continuous use. I still think the Chromatic Series universals pip Astrolith in absolute flush-fitting comfort, though I find Astrolith superior to Trifecta’s angular and somewhat awkward fit.  

As with all of Campfire’s IEMs, Astrolith features beryllium and copper MMCX connectors claimed to be some of the most robust on the market. 

Continue to sound impressions…