Fit and Comfort

Seen above is the right channel of the Custom Art FIBAE 5 placed into an artificial ear mold with the included size M single flange 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, as was the case here. The FIBAE 5 is about average in physical size, which also makes it among the smaller of the tribrid IEMs I've tested to date. Helping further is the relatively compact shell design without any ridges and a more angled and longer nozzle allowing for a deeper fit in the ear canals. The nozzle is also plenty manageable for most people I dare say, so there is a higher likelihood of the FIBAE 5 being a comfortable fit for you. The shells weigh ~5.5 g each to make for a low density and minimize any potential of being physically fatiguing. The pre-formed ear hooks combined with the relatively supple cable also makes for an additional point of contact and support for the IEMs, although once again you can see where having flush-mount connectors or even an angled housing would have been better. Note that the filter, or lack thereof, is also the vent here to the dynamic driver. So you effectively dampen the bass response that way while also controlling any pressure build-up in the ear canals depending on what you decide for the filter and also whether you opt for different ones entirely. I was fine in both cases for longer periods of time (~1.5 hour listening sessions on average).

Audio Performance

Audio Hardware

The Custom Art FIBAE 5 employs a tribrid driver configuration in that there are three different driver types here for a total of five drivers per side. We don't get a lot of information about the actual drivers used unfortunately, just that the lower frequencies are handled by a 10 mm dynamic driver followed by dual BA drivers for the mids and then two planar magnetic drivers for the higher frequencies (one for highs and the other for super highs) to where the latter two are analogous to tweeters in functionality. This seems to be a 4-way crossover design then, and the photos I've seen of the CIEM models where some people have opted for clear shells don't help easily pick up the internals either. Custom Art claims a 10 Hz - 21 kHz frequency response range here, although the 20 Hz to 20 kHz range is mostly of interest to humans. The shells also accommodate a 3D-printed wave guide and further electronic circuitry to make for the FIBAE technology I mentioned earlier. This helps give the FIBAE 5 a flat impedance and phase curve across the entire frequency range, to where the output impedance of your source won't affect the tonality of the set. So you can drive it off your laptop or a much more expensive dedicated DAC/amp and the overall sound signature will be the same. Driving the set can take slightly more power than the typical set of IEMs owing to the lower sensitivity of 109 dB/0.1 Vrms and the 10 Ω impedance to make it more current-demanding than voltage. Any decent portable DAC/amp will be fine though, and I mentioned before how I mostly paired this with the Questyle M15 which does make for a great sounding, highly portable combination to show simply getting loud isn't always enough!

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 such as the Questyle M15 used 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 Custom Art FIBAE 5. 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 practically identical across the entire useful 20 Hz to 20 kHz range! The peak amplitudes being slightly off in the higher frequencies feel more like measurement artifacts given the nature of this coupler and I certainly could not discern any channel imbalance in my ears even when deliberately listening for them. Given the price range the FIBAE 5 operates in, I expect to see driver matching with decent quality control and, at least when it comes to this review unit which happens to be a randomly chosen retail unit, things are more than satisfactory. 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 anthropometric pinna in place matched the ideal scenario in the coupler very well too and this is an indicator of how good the seal was when installed in the artificial ear.


Here is the average frequency response for both channels of the Custom Art FIBAE 5 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. You will also note how there are two different tuning signatures here based on whether or not you choose to use the filter provided. Given the discussions on it earlier, you can effectively control the bass shelf between these two points, or go even lower, by opting for any of the other Knowles dampers sold by many retailers online for a reasonable price. It's not a lot of change but still enough to provide a neat fine-tuning aspect that is a bonus here with the FIBAE 5.

I am so happy to see Custom Art offer a vastly different tuning with the FIBAE 5 compared to the rest of the market that is mostly content following either a warm-neutral or Harman tonality, if not V-shaped for more mainstream appeal. I'd go so far as to say the FIBAE 5 comes off as V-shaped for the audiophiles in that you have a bass shelf that extends up from the mids at ~800 Hz and then plenty of treble energy too courtesy that emphasized extension on either end. I am also thankful to Custom Art for its patience with how long this review took simply because I had not heard any other set that sounded like this at the time this arrived. It took a while to clear up any preconceived notions of how IEMs sound, especially given the FIBAE 7 Unlimited is a far more balanced and analytical set better suited for music monitoring. The FIBAE 5 is instead not going to be for everyone and that's a good thing, given it does a few things far better than others rather than trying to be yet another jack of all trades.

The FIBAE 5 is extremely bassy, although we've seen now how you can control the extent of this owing to the use of filters provided or purchased separately. Unfortunately, this mechanism does make for a less impactful bass to where it sounds more tame than the graphs suggest. There's plenty of detail and I personally went with the filter route for this reason as otherwise the extra loudness was threatening to take over, and I'll even go far enough to say there's plenty of dynamics and speed to where both leading and trailing ends of tones come off tight and controlled too. I just felt that there isn't a lot of slam and weight behind them though, and I especially felt this with kick drums and snares. There's not a lot to say about the mids here given they seem to just be there, nothing exactly was noteworthy unfortunately. Vocal rendition is fine albeit doesn't come off as natural as I'd have wanted to see—the faster overall pace makes for a less smooth and enjoyable rendition of baritones and imaging felt slightly hazy with string instruments in particular not easily discernible in a midst of other instruments. I would not say instrument separation is poor though, just not on par with where the FIBAE 5 should be at.

Soundstage is.. interesting, to say the least. There were multiple times where I felt the FIBAE 5 came off cramped with acoustic jazz and many other occasions wherein it felt plenty open even with orchestral music. I suspect it's the upper mids tuning that is making for this given the relatively lower pinna gain coupled with that 4-5 kHz peak resulting in an unnatural, less relatable sense of space created. Female vocals might sound hollow, especially with trailing ends and opera singers, but on the flip side this means very little to no sibilance. It also makes the rest of the frequency response more palatable and this is what eventually sways the FIBAE 5 to a more positive experience in my books. On its own, I'd have called the treble response here to be overly emphasized and even "spicy." Those who are treble-sensitive will probably still find this set fatiguing. On the other hand, the series of dips and peaks makes for a more controlled sound that is more sparkly and airy than shrieky and annoying. The bass shelf suddenly comes back in the picture to help balance this out, so I am glad Custom Art made it more customizable. I personally preferred the filter version for my tastes but your mileage may vary.


Another reason I took my time with this review is because I was waiting for the ThieAudio Prestige to come out. This is another tribrid set that released recently (review coming soon) which uses a 1DD+4BA+4EST driver configuration and a higher price point to put forth a similar sound, but falls short in going for a more analytical bass shelf and mids that makes for an overly emphasized treble response. The Prestige has different strengths and weaknesses compared to the FIBAE 5, yet ends up sounding more similar to other sets from many different manufacturers than something quite different that Custom Art did here. I'd personally go with the FIBAE 5 as an accompanying set to a more balanced pair of IEMs rather than get the Prestige to try and do it all, if that makes sense. Then there's the more famous ThieAudio Monarch MKII at the same price as the FIBAE 5 and this is a good example of that accompanying set I mentioned above. It is a good all-rounder and very well tuned for a multitude of different genres and yet the bass hits even weaker with less details than the FIBAE 5 and the treble response could be smoother too. It does have excellent vocals and instrument reproduction though! The real competiton to the FIBAE 5, in my opinion anyway, comes in the form of the Symphonium Helios with its four BA drivers! In one of the best examples of "it's not the driver type or count, but rather the execution that counts," the Symphonium Helios has excellent bass and one of the best treble responses of any IEMs at any price points. The FIBAE 5 offers me more mid-bass though for bass guitars, and I personally do like the bass shelf customization to help balance out the sparkly treble too. The FIBAE 5 also fits easier and better in my ears compared to the Helios, which also costs more, and yet I'd be more likely to recommend the Symphonium offering if I had to only pick one set.