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Review: Campfire Audio Supermoon

Review: Campfire Audio Supermoon

This article follows on from my previous article, My first custom in-ear monitor: a personal journey. If you want the story of how I ‘discovered’ Supermoon, that’ll give you some context.


Campfire Audio is a name that needs no introduction, but here’s one anyway. In 2009, Ken Ball started a small boutique audio cable company in the green city of Portland, Oregon, called Audio Line Out, better known today as ALO Audio. From those humble beginnings the company evolved, and then split in two, with Ken’s sister company, Campfire Audio, introducing handcrafted in-ear monitors to the product line.

Over the years, Campfire gained a reputation for its unique IEM designs with an excitable, sometimes bold tuning, definitely not the play-it-safe variety. Indeed, with the release of the iconic green Andromeda in 2016, Campfire created one of the ‘gateway drug’ IEMs for many higher-end audio enthusiasts, and ushered in a flood of new designs that challenged what was then possible in and around the kilobuck ($1,000) price bracket. 

Fast-forward six years and 45 new or derivative designs, and Campfire is once again looking to disrupt a now mature IEM market. Supermoon, the company’s third custom IEM, is not only the world’s first custom planar magnetic IEM, but also the first high-end sealed planar monitor. Featuring a custom-developed 14mm planar driver and Campfire’s unique solid body sound chamber, the $1,500 Supermoon is already changing the price-performance equation of single driver IEMs at the highest echelons of the hobby. 

Planar technology explained

You may be new to planar magnetic technology, especially in IEMs, but know that planar technology itself is not new. Planar magnetic designs have been around for years in full-size headphones, and even longer in speakers. What’s new here is the miniaturisation of the technology without sacrificing the inherent properties that make these drivers so effective in larger formats. 

Unlike dynamic drivers which use a cone-shaped diaphragm, planar magnetic drivers use an ultrathin flat diaphragm and an array of magnets that push and pull the surface of the diaphragm to create sound waves. Compared to their headphone-size counterparts, there’s a limit to how large the diaphragm can be inside an IEM, and also how many magnets are used to energise the diaphragm. 

According to Ken Ball, the planar magnetic driver inside the Supermoon is the first such design he considered suitable for customising and using inside a Campfire IEM. 

I have been sent many small IEM-size planar drivers in the past and never used them because the drivers were not suitable for an IEM and did not meet the high sonic bar for a Campfire product. The issues have always been that the transducer was not sensitive enough, or the frequency response was not to my level of performance,” he says. 

This [Supermoon] driver was in my opinion more advanced as it uses a very thin 1 uM diaphragm, is sensitive enough [for use with portable sources], and while the frequency response was not what I would call perfect, it was good enough for me and my team to make spatial acoustic tuning improvements.” 

Indeed the reason Ken and his team were even interested in the technology in the first place was, in his words, “to be able to use the wonderful inherent sonic qualities that a planar system can provide in a IEM.” 

These inherent sonic qualities include the ability to extend the frequency range in both directions, particularly bass, down to 20Hz and beyond 20,000kHz, while maintaining better linearity, a faster transient response, and lower distortion than even the most advanced dynamic drivers. The downside is that despite their exceptional extension, planar drivers tend to lack the dynamic contrast of the best dynamic drivers, even though they produce a ‘cleaner’ sound overall.

Whether or not Supermoon inherits some or all of these characteristics is something I’ll explore in greater depth in this review.

Speaking specifically about the Supermoon driver, Ken says: “I received the raw driver and worked with the manufacturer to make minor changes. There was some back and forth, then when we were closer to being able to use it, me and my team made a series of spatial acoustic tuning improvements to the front and back load of the planar [array] to fine-tune the performance of the frequency response.” 

I also asked Ken how planar technology is different to other driver designs, like the balanced armature (BA) and dynamic drivers that Campfire continues to use for other IEMs:

“Each driver technology has its own signature ‘sound’ and its own strengths and weaknesses based on the raw design. A BA excels at clarity, detail and speed [but] has mechanical resonance problems. A dynamic driver is warm and lush but can be soft in detail. A planar has a flat diaphragm, so right away there are advantages of propagation of electroacoustic energy from a flat surface versus a cone. 

“It is my job to minimise the weaknesses and accentuate the inherent strengths of a driver. We do this with a number of [techniques] we have built in our experience in tuning over the years. As the technology advances in miniature planar designs, we hope to stay at the leading edge of this technology.” 

Two of the techniques that Ken infers above are Campfire’s solid body design and 3D-printed interior. According to Campfire, solid body design ‘uses a single housing with specially designed ports…allowing [the] driver to be routed to the nozzle of the earphone’. The body-and-driver assembly is then ‘inserted into the housing much like an engine being lowered into a car’. This makes assembling the IEMs easier, and reduces sample variance by ensuring the design of each 3D printed earpiece is accurate and precise. 

Supermoon also features a 3D printed interior, individually modelled to optimise acoustics relative to each user’s ear anatomy. In theory this lets Campfire design a unique acoustic chamber that helps shape the sound of each driver for a specific target, eliminating any variance in frequency response for consistent sound quality between units.

Continue to packaging and accessories



Picture of Guy Lerner

Guy Lerner

An avid photographer and writer 'in real life', Guy's passion for music and technology created the perfect storm for his love of portable audio. When he's not playing with the latest and greatest head-fi gear, he prefers to spend time away from the hobby with his two (almost) grown kids and wife in the breathtaking city of Cape Town, and traveling around his native South Africa.


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