Fit and Comfort

Seen above is the right channel of the Campfire Audio Solaris Stellar Horizon placed into an artificial ear mold with the included size M silicone ear tip installed. I have average-sized ears, and the ear mold above represents my own experiences well enough as a proxy. Size M silicone tips are my go-to for testing, since foam tips are not included by some brands, but note that Campfire Audio has its foam tips pre-installed on the Solaris Stellar Horizon so you may want to try it out first. The new Solaris is a medium-sized set that fits in the ears comfortably owing to the relatively taller profile which also happens to be more ergonomic than the image above makes it seem. Indeed, the takeaway is the wider bottom section of the shells sits comfortable in the concha and the gently curved thin nozzle is long enough to easily be inserted into the ear canals too. I ended up with a secure and comfortable seal in my ears, and those with smaller ear canals need not worry either. The shells weigh ~7.5 g each owing to the all-metal construction and that ends up feeling solid in the ears as opposed to being physically fatiguing if heavier or giving you a sense of being loose if lighter. The MMCX connectors are naturally angled upward to make the pre-formed ear hooks in the cable also naturally go over and around the back of the ears for further support as needed, with the freely rotating connection aiding this. I don't have any complaints on the fit and comfort of the IEMs themselves but would have still appreciated a cable that is easier to handle as pointed out on the previous page.

Audio Performance

Audio Hardware

I was hoping Campfire Audio would share one of its neat 3D renders of its IEMs showing off the internals clearly but it appears we'll have to make do with words this time round. In a nutshell, the Solaris Stellar Horizon uses a quad driver configuration using a custom 10 mm dynamic driver for the lows. It uses an ADLC (amorphous diamond-like carbon) coating for increased stiffness and responsiveness of the driver to the magnetic flux generated by the associated magnets. We do not get any further information about the magnets or the voice coil used here, although the radial vents used mean that the diaphragm has full access along its diameter to push air back and forth rather than on IEMs with a vent on the front or back where a fraction of the available area is taken up that way. Likewise, there isn't much info provided on the custom dual diaphragm balanced armature drivers used thereafter, except that they are new drivers, with one of these handling the mids and two more for the higher frequencies incorporating Campfire Audio's T.A.E.C. (Tuned Acoustic Expansion Chamber) technology that "expresses high frequencies without fatigue or sibilance." These all come together to make for a set of IEMs that is extremely efficient and, in typical Campfire Audio style, has an ultra-low specification of just 4.4 Ω rated impedance (at 1 kHz) and a sensitivity of 94 dB @1 Hz 9.145 Vrms which isn't trivial to compare against pretty much everyone else who reports values in dB/mW—why can't you do this too, Campfire Audio? The bottom line is that, if anything, you need to be concerned more about a dark background with your source rather than worrying about whether it has enough power to drive the Solaris Stellar Horizon. I ended up pairing it with the aforementioned Questyle M15 for most of my listening needs although the Cayin RU6 presented a nice warm sound that worked well with some music genres. I also made sure to test all three provided cables to confirm there is no discernible difference in the audio signature from them outside of the balanced connections making for a louder output.

Frequency Measurement and Listening

I will mention that I have a general preference for a warm-neutral signature with a slightly elevated bass, smooth treble range, detailed mids, and good tonal separation. I also generally prefer instrumental music over vocals, with favored genres including jazz and classical music.


Our reproducible testing methodology begins with a calibrated IEC711 audio coupler/artificial ear that IEMs can feed into enough for decent isolation. The audio coupler feeds into a USB sound card, which in turn goes to a laptop that has ARTA and REW running and the earphones connected to the laptop through a capable and transparent DAC/amp—I used the Questyle M15 here. I begin with an impulse measurement to test for signal fidelity, calibrate the sound card and channel output, account for floor noise, and finally test the frequency response of each channel separately. Octave smoothing is at the 1/12th setting, which nets a good balance of detail and noise not being identified as useful data. Also, the default tuning was used for testing, and no app-based settings were chosen unless specifically mentioned. Each sample of interest is tested thrice with separate mounts to account for any fit issues, and an average is taken of the three individual measurements for statistical accuracy. For IEMs, I am also using the appropriate ear mold fitted to the audio coupler for a separate test to compare how the IEMs fare when installed in a pinna geometry instead of just the audio coupler. The raw data is then exported from REW and plotted in OriginPro for easier comparison.


The IEC711 is such that you can't really compare these results with most other test setups, especially those using a head and torso simulator (HATS). The raw dB numbers are also quite contingent on the set volume, gain levels, and sensitivity of the system. What is more useful information is how the left and right channels work across the rated frequency response in the Solaris Stellar Horizon. The left channel was separately tested from the right one, and colored differently for contrast. I did my best to ensure an identical fit for both inside the IEC711 orifice, so note how the two channels are pretty much identical to each other—well within 1 dB as it is and honestly the slight offset may well be from my matching the coupler resonance point at 8 kHz. Suffice to say then that I never noticed any channel imbalance before or even after measurements, including when I was deliberately looking for it with sine sweeps. This is good because my expectatations are higher for a more expensive set and Campfire Audio has met my standards accordingly. Measurements taken after 50 hours of testing, which included these playing a mix of various songs as well as white or pink noise and sine sweeps, showed no difference. There was no perceived burn-in effect thus, and none was measurable, either. The response with the anthropomorphic pinna in place matched the ideal scenario in the coupler quite well and this is an indicator of how good the fit and seal was when installed in the artificial ear. Please note that measurements taken after the coupler resonance matched here at 8 kHz are best taken with a grain of salt.


Here is the average frequency response for both channels of the Campfire Audio Solaris Stellar Horizon plotted against my personal target taken from VSG.squig.link, which also gives you an idea of my personal preferences to better correlate any possible biases. The tuning of a set of headphones or earphones does not have to match my target as long as it is tuned with some direction, makes sense, and is executed well. After all, no one set will appeal to everyone, and having different options is what makes this hobby so interesting and hard to quantify. With Campfire Audio, it's even more relevant since the brand does seem to go for a variety of different sound signatures with its IEMs rather than something safe. I can get behind this approach as long as it makes sense. I was not convinced this was the case with a few CFA IEMs reviewed in the past but the Solaris Stellar Horizon is easily the best set from Campfire Audio I've listened to so far. It makes for a warm, mid-forward tonality that almost comes off W-shaped and may look like there are strengths and weaknesses if you are purely basing on the graphs above, but actually ends up also being one of the best flagship-class IEMs I've heard too.

Given the 3-way crossover of drivers used here, you'd expect to see the dynamic driver typically cover the lower frequencies. The Solaris Stellar Horizon uses a really good driver here that makes for good bass reproduction. We see extension all the way down to 20 Hz and the bass slope begins earnestly from 600 Hz itself to where it's not like a subwoofer and yet works fine for EDM and synth music. The set has low enough distortion to also take a deliberate EQ filter for those wanting even more bass, although I will note that this can disrupt the tonal balance for vocals. The Solaris Stellar Horizon is also quite resolving and I grew some appreciation for indie/progressive rock titles with it. Bass guitars hit hard and I could tell right away there's good dynamics at play. Metal music is also a strength for the set with excellent instrument separation and layering allowing you to appreciate both leading and trailing ends of tones.

The transition over to the lower mids can be divisive though. I personally prefer a cleaner separation at ~250-350 Hz allowing for minimal boomy/muddy playback whereas the Solaris Stellar Horizon cuts it close owing to the bass slope employed here. Others may instead prefer the warmth and emphasis provided to vocals, especially male vocals for baritones and country music alike. Imaging felt accurate albeit mostly centered around the front, and soundstage was slightly wider than usual—could be from the mid-forward presentation. Timbre did feel on the plasticky side for me though, especially with cymbal strikes and snares. Female vocals can be... interesting. While it's not as roller-coastery as the graph suggests, artists like Beyonce can sound fine whereas ABBA's female singers can sound hollow courtesy the recessed upper mids. This is the only point where I encourage people to play around with EQ, even if I think the current tuning keeps things interesting and can help those who prefer less ear gain. A simple filter at ~3 kHz can potentially add in more body for vocals and can make for a more accurate set capable of music monitoring across the board. It can also help address the otherwise smooth and extended treble response which might come off slightly hot in the stock tonality. I do appreciate the lack of sibilance and fatigue otherwise though, this is one of the better controlled Campfire Audio sets that makes the Solaris Stellar Horizon work nicely for jazz, blues, even classical music. No need for ESTs here, the extension does not feel forced and remains detailed.


The first time I heard the Campfire Solaris Stellar Horizon, I immediately thought of 64 Audio. This is a similar presentation going warm and then with the earlier ear gain followed by smooth extension thereafter. The U12t in particular felt like a natural comparison, especially with the new m12 module that launched with the U4s. The modules do allow for different sound signatures on the U12t but overall I'd say the technicalities are quite different. The Solaris Stellar Horizon has much better bass quality where you can clearly listen to the increased dynamics and resolution thanks to the dynamic driver used rather than smaller BA woofer drivers. I'd say the Solaris Stellar Horizon is more detailed whereas the U12t ends up more of an all-rounder with a smoother sound. The Solaris Stellar Horizon does give you way better accessories though and both are equally comfortable for me.

Among the multi-kilobuck sets I've listened to critically, the recently released LETSHUOER Cadenza 12 (review coming soon) might be the closest competitor to the Campfire Solaris Stellar Horizon. It's a 1 DD/11 BA set that goes for a similar bass slope approach with slightly more sub-bass, a more full sound in the upper mids, and comes off very resolving too except for perhaps too much energy in the upper mids/lower treble that can make it slightly fatiguing and prone to sibilance. If you are sensitive to the 5 kHz region, for example, the Cadenza 12 will necessitate some EQ fixing. LETSHUOER may not have the brand heritage that Campfire Audio has but it does pack in an excellent set of accessories too although the titanium shells used on the Cadenza 12 feel like they won't last the test of time. It's also larger in form factor to where the new Solaris is more likely to be comfortable than the Cadenza 12.

There are plenty of other sets which cost less than the Solaris Stellar Horizon and many others which cost more. I was thinking of pulling up the Astell&Kern x Campfire Audio PATHFINDER here but I am convinced the new Solaris outperforms it every which way to where I'd rather save more and get this instead. I'll say the same for the Lime Ears Pneuma too, and the 64 Audio U18t is more or less covered already with the U12t comparison above—it's more resolving than the U12t and is even smoother on the ears, but the Solaris Stellar Horizon still ends up with better bass and detail retrieval. I do think the U4s is worth considering though if you want to try out this sound signature, it also uses a hybrid driver configuration with DD bass and is more versatile with the apex modules. As for even more expensive sets, those tend to be highly esoteric to where they usually do some things exceptionally well rather than be jacks of all trades. There are exceptions such as the Subtonic Storm that I think is excellent, but it does cost significantly more than the Solaris Stellar Horizon. The likes of the Noble Audio Viking Ragnar go the other way by being technically great but very much suited for only some music genres. I just could not get past that treble harshness ultimately. I'd also say the Viking Ragnar is less comfortable for those with smaller ears/ear canals, so the Solaris Stellar Horizon wins there too.