FiiO FP3 In Ear Monitors

The FiiO FP3 is a “mini planar”: a planar magnetic in-ear monitor built around FiiO’s own second-generation 14.5mm planar driver. Its 1µm diaphragm, the thinnest among its peers, carries FiiO’s patented titanium and aluminium dual coating, applied twice with a 28nm-grade process; 0.055mm traces and 14 N52 magnets drive it, and FiiO’s patented “Tesla valve” design deepens the bass. Inspired by a “mini wooden bowl”, each earpiece has a solid rosewood or black walnut faceplate and weighs about 6.5g. It is Hi-Res Audio certified and won a VGP 2025 Summer award.

Planar sound, in-ear size

FiiO began developing “mini planar” IEMs in the third quarter of 2022. Unlike over-ear headphones with large planar drivers, an in-ear planar has to keep the high resolution and wide frequency response of planar drivers in a tiny space while still delivering good bass and a full sound. After two years, and by breaking with industry norms, FiiO created the FP3.

FiiO’s own 14.5mm planar driver

FiiO designed the second-generation driver from the ground up: the diaphragm, the patented dual coating, the width of the traces, the tuning of the magnetic circuit and even the standardised bracket fixings. Unlike an off-the-shelf driver, it lets FiiO build a complete acoustic system around it, for a large, almost limitless soundstage that FiiO says is rare among its peers, deep bass and detailed treble up to 40kHz.

A 1µm diaphragm with a patented dual coating

After two years of research, FiiO created a class-leading 1µm diaphragm on a high-performance PET substrate. Even the step from 2µm to 1µm makes a noticeable difference when the film vibrates at high speed: it responds with lightning speed, reproduces subtle ultra-high frequencies and gives exceptional dynamic range. FiiO’s patented dual-coating system adds aluminium first, light and conductive, to improve the traces’ conductivity and lower the impedance and power needed, then titanium, very hard, to stiffen the diaphragm and improve treble resolution and transparency. As the chief engineer of FiiO’s IEM R&D centre puts it, each material has its own natural frequency and timbre, and pairing them opens up a rich variety of sound.

Made with a 28nm-grade process

A driver this intricate needs nanometre-level precision that traditional coating can’t reach. Borrowing from semiconductor manufacturing, the trace material is ionised in a vacuum of 6.6 × 10⁻³ Pa at 120°C and built up on the 1µm film to exactly the right thickness, which also makes the traces far more durable. The FP3 runs this process twice on every diaphragm, once for each coating. (The FT5’s traces, made the same way, passed more than six months of ageing tests at FiiO without detachment or breakage.)

0.055mm traces, 14 N52 magnets

Following F = BIL, FiiO made each trace just 0.055mm wide, as fine as a hair, so more of them fit densely in the magnetic field: 486.5mm in total, for more driving force and a high sensitivity of 105dB/mW. Seven N52 magnets on each side of the driver, 14 in a 7 × 2 matrix, place the traces evenly in the field so the diaphragm is pushed equally on both sides and moves without irregularity, for low distortion.

“Tesla valve” bass

Like the FD15, the FP3 uses FiiO’s patented F.T.B.S. (FiiO Tesla Bass Sound) design (patent ZL2024203547620): the length, angle and number of channels inside the shell are calculated to form a Tesla-valve structure, for deeply extended, textured bass.

Rosewood or black walnut

Comfortable for a planar

• 3D-printed front shell: shaped freely for comfort, then hand-polished and UV-coated for a luxurious feel.
• Less pressure: a smaller contact area with your ear breaks the idea that planar IEMs are bulky.
• Secure fit: a support shape in the hollow of the ear keeps it stable.
• Light: about 6.5g per earpiece, so you can listen for hours without fatigue.

392-wire silver-plated cable

Fourteen wires twist into a small strand, seven small strands into a main strand, and four main strands give 392 silver-plated copper wires, each enamel-insulated and Litz-braided for a larger conductive area and better treble resolution. The angled 0.78mm 2-pin connectors curve gently around your ears, and because the cable detaches you can upgrade it later.

Good to know

• This is the 3.5mm FP3; the 0.78mm 2-pin connectors let you add a 4.4mm balanced cable.
• Natural wood: every faceplate’s grain is slightly different.
• In the box: FP3, 0.78mm 2-pin silver-plated copper cable, HB11 storage case, three pairs each of treble (M fitted) and balanced ear tips (S, M, L) and quick start guide.
• Prefer a single dynamic driver? See the FiiO FD15.