Custom Art's big idea turned up by accident. In early 2016 the Warsaw company was working on new in-ear designs when, in founder Piotr Granicki's words, it "stumbled across an interesting occurrence." Most in-ear monitors sound a little different depending on what you plug them into, and Marcus of Headfonics explains that the headphone jack itself shapes an earphone's tone to some extent, so the same pair can sound different from a phone and from a dedicated player. Custom Art found a way to build its drivers so they behave the same whatever drives them, and named the result FIBAE. Pinky Powers of The Headphone List writes: "Its frequency curve remains constant." TechPowerUp's reviewer heard a FIBAE 5 keep the same overall sound from a laptop and from an expensive DAC/amp. Custom Art says its house sound is often described as balanced, slightly warm and natural. The brand suits listeners who move between sources and want one tuning.

All three current models come as custom-molded or universal fits, so the choice is mostly about bass. The FIBAE 5 is the one Custom Art aims at listeners who like more bass, and Suman Sourav Meher of The Headphone List still found it "exceptionally balanced." The Hybrid 3 Pro is the other hybrid, and Meher called its bass "Sheer perfection." Both hybrids take swappable filters that change the sound, and Meher likes the Hybrid 3 Pro's brown filter for detail and the yellow for a juicier sound. The flagship is the FIBAE 7 Unlimited, and Audio Rabbit Hole's reviewer calls it "easily the most comfortable CIEM I own." The hybrids want current more than voltage, so TechPowerUp suggests a good portable DAC/amp. For a custom fit, Marcus advises fresh ear scans every two to three years, and he asked for a long stem for a deeper fit.

Piotr Granicki founded Custom Art in Warsaw in May 2012. He had spent years reviewing portable audio and building his own gear, and Berkhan of Headfonia writes that this experience convinced him he could make great-sounding monitors. In his account the company was first known mostly for its Harmony 8.2 flagship. Custom Art filed for an international patent in mid-2016, and by 2018 the FIBAE line ran from the single-driver FIBAE 1 to the three-driver FIBAE 3. A six-driver collaboration with Massdrop, the FIBAE ME, helped the brand grow popular quickly in Headfonia's account, and it later joined Custom Art's own range as the FIBAE 6. The FIBAE Black was the first Custom Art model to use 3D printing, and Prime Audio's reviewer collected one from Granicki in person at CanJam Singapore in 2019. Every Custom Art IEM is still made in Poland, 3D printed and finished by hand. Marcus notes that the FIBAE 5 was the company's first hybrid developed wholly in-house.