Fit and Comfort

Seen above are the three types of ear tips that come with the Campfire Audio Holocene, in size M, installed on the right ear bud and inserted into an artificial ear mold. 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, although I would in this case rate the best fit in terms of isolation and comfort with the memory foam tips followed by the final Type-E tips, and then the more generic Campfire Audio silicone tips. The flanges on the latter set are simply too soft to work with the slightly larger form factor compared to the CFA Honeydew/Satsuma, where it was a better fit owing to more room for the flanges to grasp on to. These relatively average IEMs in terms of size have at least 2 to 3 points of contact with the tragus and anti-tragus when in the ear. There is not much outward pressure to worry about, especially with a good self-supporting seal from the memory foam tips. Each ear bud also weighs ~7 g, which is about average, so the only thing to consider is the MMCX connector with its 360° rotation wherein you may have to fiddle around slightly to make sure the cable is oriented to go over the back of the ear.

Audio Performance

Audio Hardware

Given the release timing and some of the marketing talk from the company, there was many a comment on whether the Campfire Audio Holocene used the Satsuma as a base. Looking just at the driver configuration, I can potentially see that train of thought. After all, the Satsuma went with a single balanced armature driver and the Holocene goes with three custom balanced armature drivers. The difference lies in the details, however, with the Satsuma using a full-range ported balanced armature driver for its entire 5–18 kHz frequency range, while the Mammoth goes with two balanced armatures for the mids/lows and the third for just the highs. There is not much more information on the material and construction of said diaphragm or the magnets driving it, however. All these are fed to the acoustic chamber that gets the 3D print custom treatment, which ultimately means it is designed with the intention to deliver optimal sound output from the drivers to your ears.

There is also a massive difference in the impedance of the Holocene relative to the Satsuma, with the former rated for all of 5.4 Ω only (at 1 kHz) compared to the relatively massive 46.4 Ω for the CFA Satsuma. Driving the hardware should be very easy thus, no aftermarket amps are required here. DACs will always go a decent way in the audio experience, however, and a portable DAC/amp might well be part of your collection if you are considering IEMs and other audio solutions in the $150+ price range. Also, the lack of a 3.5 mm audio jack for most phones these days is another reason to consider a DAC/amp that takes digital input and provides a 3.5 mm jack since you will otherwise have to use an adapter anyway, or even a dedicated DAP. If not on the go, space is less of an issue, but the shorter cable typically included with IEMs might be a potential handicap if connecting to a PC as the audio source. Campfire Audio also rates the signal sensitivity at 94 dB and a long frequency response of 5 Hz to 20 kHz, but good luck making use of that range!

Frequency Measurement and Listening

I will mention that I have a general preference for a warm neutral signature, emphasizing a slightly elevated bass and smooth treble range with 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 IEM buds can feed into enough for decent isolation similar to real ears. 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 the sound card. 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 1/6th 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 ear mold that fits to the audio coupler for a separate test to compare how the IEMs fare when installed in a pinna geometry and not just the audio coupler by itself. 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 Campfire Audio Holocene, or at least the useful part of it. 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 nearly identical through the bass and mids, and within +/- 1 dB throughout the measured 20 Hz to 20 kHz range. There wasn't any burn-in effect either with pretty much what you get unboxed being it even after 50 hours of having music and a mix of white/pink noise going through the Holocene. The response with the artificial pinna in place is also quite impressive in how similar it is to the coupler itself, but that in itself does not mean it is better than others to actually listen to. I will also mention here that the IEMs had consistent hissing with nothing playing—something I expected from a more sensitive set. As with the Mammoth, I am left wondering whether it was the ultra-low impedance causing it. Any music, or just audio in general, played out of these IEMs gets rid of the hiss, and unlike the Mammoth, there isn't any underlying haze on the sound signature this time around.

Campfire Audio describes the Holocene as a new Epoch in Hi-Fi, which we saw used as a reference point before. The company goes further to describe these with a "remarkably even and balanced frequency response curve" with a sound that is "fast and layered with rich, inviting detail, channeling that spirit of explosive expansion." There is certainly some marketing freedom being taken since the Holocene is currently middle of the pack in even Campfire Audio's own lineup when it comes to what it does, but it is certainly much closer in meeting expectations set forth by these very marketing claims than the Mammoth or even Satsuma. The Holocene is also closer to the warm neutral signature I personally prefer, but the review itself will work based on intended goals and how well it meets them.

Unlike the Honeydew and Mammoth, the CFA Holocene is not going to provide much bass response. In fact, sub-bass is practically non-existent, so most things I described from the previous two Campfire Audio IEM reviews when it comes to the lows will not even apply here. Yes, there is tonal resolution and detail, but it is more in the sense of accuracy for the bass notes in music than to provide impact for the likes of electric guitars in metal music or the anticipated drop in EDM music. This made the Holocene quite a decent pairing to the Mammoth in having two sets that are clearly focusing on different things. The bass response also decays quicker than I anticipated going in. For example, bass notes in jazz music and drums don't get time to breathe before the next set of tones come in. This can be irksome if you are of the type to like music notes to resonate and sing to you.

Range is certainly the name of the game when it comes to the mids proper, with plenty of room to allow vocals and instruments to shine together. There is consistent warmth across the region, with a flat line that will be a love or hate affair. There is detail and resolution, but there is also frustration for those used to the commonly seen V-shaped tuning. This is not fully neutral either, which I appreciate since it allows for the IEMs to be the first Holocene rather than, say, a second or third Etymotic ER4SR. As long as you are aware of it, the added warmth still can help make these alright for monitoring, but these really are better-suited for listening to band music. I know we have not got to the pricing yet, but I will say that the balance of imaging and soundstage on the Campfire Audio Holocene is one of the better ones I have heard from IEMs, rivaling even many headphones around the price range. These go a long way in explaining why IEMs can be the end game for closed-back headphone lovers in allowing a sufficiently wide and deep soundstage without coming off empty or inflated as with the CFA Mammoth.

If I had an issue with the Holocene as it pertains to its own intentions, it would be in the upper mids. There is a weird lack of compensation for in-ear resonances, so much so that if some IEMs tend to overcompensate and get shouty here, the Holocene feels anemic instead. Female vocals, pop music, and percussions in particular come off lacking, and I ended up with a small EQ boost at around 2 kHz it took to fairly well. Just be careful if doing so since some vocals can get tinny with the artificial boost. There is enough room to instead tone down the area around as well if you have these paired with a decent source—almost a must with these ultra-low impedance IEMs and EQ. The treble response is quite decent, and I can't say I have any strong feelings either way here. The small bump at 4 kHz adds some presence to the audio output, but it is accentuated more by the dip, where you expect a faster transient response. When in the ears, this is certainly as fast as CFA claims it to be without any perceived fatigue before things get dark and dip past ~12 kHz.

Comparison to other IEMs

Here too I decided to have two sets of comparisons, with the former at least more relevant than with the Mammoth. I will compare two other IEMs from other brands to the Holocene first, both of which are tuned with similar enough intentions even if the pricing isn't necessarily in the same ball park. This is especially true of the Audeze Euclid, which I personally think sounds better most of the way and takes EQ very well in all but the ultra highs, where there isn't much to save. The Etymotic EVO is intended to be more neutral, but has more of a bass presence than either of the other two. The Holocene slots between both in price and balance from the mids and higher. Compared to two other CFA IEMs released recently, the Mammoth really is a whole other beast that complements the Holocene as a two-pair set for different music genres—it is not a replacement for the Holocene. The Satsuma, on the other hand, gets quite shouty in the upper mids and just lacks resolution and soundstage to where I can certainly see the Holocene as a (much) better Satsuma for those wanting a reference point from Campfire Audio. I am sure there are other alternatives, especially in the price range of the Holocene, but I don't have more comparisons to make at this point in time, unfortunately.