August and September are often quiet months in my calendar but this year is different. I’ve never known such a busy time for tech launches and so it’s taken me a few weeks to get around to my review of the latest earphones from Portland’s Campfire Audio.
These new and high-end IEMs have been designed by Campfire’s Ken Ball. To call Ken a sonic genius isn’t stretching things too far because the team at Campfire Audio has been making superb IEMs for more than a decade and the Astrolith are the brand’s latest model and, in my opinion, probably the best yet.
The new Astrolith IEMs have been designed to deliver “a refined and enhanced acoustic-experience.” That’s a bold claim backed up by something Campfire’s calls its Additive Acoustic Optical Inclusion housing (AAOI). The interior of the Astrolith’s earpieces have been sculpted to produce a specific acoustic signature.
The Astrolith’s earpieces are made from stainless steel and have been hand-polished to a mirror finish. The internal acoustic chambers are housed within a transparent exterior. Look carefully and you can see the internal components from various angles and yet, even from a short distance, the earpieces look like silver and black shells.
Inside each of the Astrolith’s earpieces is a large 14.2mm planar magnetic driver designed to provide sub-low, low and midrange frequencies. These drivers are the Astrolith’s woofer Ken Balls says the drivers he has chosen are the first planar-magnetic models that are good enough to be in a pair of Campfire Audio IEMs.
The 14.2mm driver is joined by a 6mm custom planar magnetic driver housed in a tiny Particle Phase Resonator tuning chamber. The 6mm drive functions like a tweeter playing the high frequencies. Normally, Campfire would have used a balanced armature driver from someone like Knowles for this, but the technology behind micro planar magnetic drivers has improved so much that Campfire finally felt able to go all planar magnetic.
Planar-magnetic drivers use a sheet of material that is vibrated to create sound waves. Unlike dynamic designs, planar magnetic drivers are stiffer and return to their shape more quickly. This produces a tighter sound with a shorter decay that delivers a precise response with a low latency. The result is a snappier response that just sounds more nimble and agile.
These IEMs have been precision engineered to reveal the tiniest of details in a recording. The frequencies are split between the two drivers without using the traditional electronic crossover. Instead, Ken Ball and his team developed internal chambers that that deliver precisely controlled acoustic volumes. There is a load more detailed engineering on the Campfire Audio website, so if the physics involved in these amazing IEMs interests you, then take a look.
Despite the relatively large size of the drivers, the earpieces don’t look at all large. I recently reviewed the Novus IEMs produced by Astell&Kern and Empire Ears. Those IEMs have 13 drivers in each earpiece which makes them feel quite bulky but they are still an incredible feat of engineering. And yet, somehow, I think Campfire Audio has managed to produce something as close and, in some ways, better than the $5,000 Novus. The result is a clean sound with so much depth and width to the soundstage. These are stunning IEMs and I’m finally a convert to planar-magnetic technology.
The Astrolith’s have an incredibly flat impedance and the result is a balanced and accurate sound that is then sculpted to perfection by those two acoustic chambers. I don’t know how the Campfire engineers managed to create such a big sound from so small a place, but it is truly a work of sonic genius.
Before I reviewed the Astroliths, I spoke with Ken Ball from Campfire Audio about his latest IEMs and he said: “I think this one is the best IEMs I have ever made. The new batch of planar magnetic drivers are the best ever. Planar transducers are, as you know, a very old design but have only very recently have been good enough for IEMs. For larger headphones they have been around for a long time, but for IEM sizes they have not been efficient enough. These new designs are far more efficient and just really well made.
“I also got lucky and struck up a good relationship with a couple of higher end speaker manufactures and they were kind enough to give me their newest most advanced designs. And while I have been doing off-the-grid acoustic designs for a while, I feel that I and the couple of engineers I work with are really hitting our stride at the craft. It’s one thing to just get a good driver and another to make them sound as good as they can and or blend multi driver systems together.
“I am a firm believer that we have entered almost a new level of what is possible for earphones because of these new planar magnetic drivers. I was really amazed at what I was hearing. But even still we kept pushing the effort to make the overall frequency response better and better via the acoustic spatial geometry in front of the driver in a purely analog domain instead of adding a bunch of passive components in the signal path.”
“But technically the planar is, in my humble opinion, superior to a balanced armature or dynamic driver as all the measurable metrics are right there plain as day. Super flat impedance plots, tight impulse response, super low THD etc.
“A few things of note, the Astrolith scale very well with using 4.4mm balanced cables as the extra voltage swing is really noticeable compared to single-ended 3.5mm. They like larger gauge IEM upgrade cables, setting your player to high gain. If available, set the amp’s voltage at the highest setting. They scale also well with more power or a headphone amp.
Finally, Ken added: “Ear tip selection is also a big influence so I suggest people experiment with as many different tips as they can. I’m trying to source a lot of new ear tips and include them in the future.
The Astrolith are superbly nimble in the way they reproduce music. For my testing period, I first turned to Malian musician Boubacar Traoré’s “Dounia Djanjo” from his 2015 album Mbalimmaou album. Go and look him up on Tidal or some other Hi-Res music streaming service. If ever there was a recording designed to test the ears of Ken Ball and his engineering team’s handiwork, this is it. The width of the soundstage is stunning while that magnetic-planar woofer almost rocks the earpiece with a subsonic rumble. This is where the Astrolith shows its mettle.
Next, I played “Jarabi” by AfroCubism. Once again, with its superbly low harmonic distortion, the music is allowed to flow and even at high volumes there isn’t a hint of distortion or the sound breaking up. These are superbly efficient IEMs with plenty of volume and headroom. The agnostic nature of the drivers mean they sound great with almost any genre of music and they have a rhythmicality that is infectious.
The great test of a pair of headphones or IEMs is can you forget about the technology and allow yourself to be absorbed and drawn into the music. With the Campfire Audio Astroliths that’s exactly what happens. There’s plenty of definition and detail all the way from that subsonic base to the tiniest treble details and yet the sound never strains or tires the listener’s ears because the planar magnetic drivers show almost no distortion thanks to a Total Harmonic Distortion of less than 0.3%.
The Astrolith IEMs includes a beautiful black folding wallet handmade from leather in Portugal. There are 3.5mm and 4.4mm detachable TimeStream cables for balanced and single ended sources, plus a Breezy Bag Micro two-pocket mesh pouch. Campfire Audio also includes a selection of silicone and foam ear tips in small, medium and large sizes, plus a cleaning tool to keep the IEMs clear.
Verdict: I’ll admit here that I am a massive fan of Campfire Audio. The company makes authentic IEMs that aim to deliver the best possible sound for the money and with the Astrolith, Campfire has knocked it out of the park. I was impressed by the Novus IEMs but I prefer the Astrolith at less than half the price. Ken Ball says he thinks the Astroliths are his best IEMs yet and possibly the peak of a lifetime’s work. I would have to agree. If you love music and simply want to hear as much of the original recording as possible without color or distortion, the Campfire Audio Astrolith IEMs are about as good as it gets. You’ll need a good source and preferably one with a 4.4mm balanced output and you will be rewarded with stunning sound that leaves nothing behind. These are Campfire Audio’s best IEMs yet, which is saying something.
Pricing & Availability: The Campfire Audio Astrolith IEMs are available now and priced at $2,199 / £2,199 / €2,399 from select retailers including Audiologica and Audio Sanctuary and Amazon via HEA Distribution.
Tech Specs:
- Frequency response: 5Hz – 25kHz.
- THD: < .3%.
- Impedance @1K: 8.2Ω.
- SPL: 94dB @ 1kHz: 44.90mVrms.
