FiiO FD15 Magnalium Dynamic Driver IEMs

The FiiO FD15 is a single dynamic driver in-ear monitor and the successor to the much-loved FD5. Its large 13.8mm driver combines a magnalium (magnesium-aluminium) diaphragm with a W-shaped DLC surround, a long voice coil and a 1.5T external magnet, for a spacious, relaxed and natural sound with new levels of detail. FiiO’s patented “Tesla valve” design deepens the bass, a frontal acoustic prism keeps the FD5’s celebrated vocals, and the 316L stainless steel shells are polished to a mirror finish. Two pairs of sound nozzles and a 480-wire Furukawa copper cable with 3.5mm and 4.4mm plugs are included. It is Hi-Res Audio certified and won VGP awards in 2024 (Gold) and 2025.

In the engineer’s words: “grand”

One of FiiO’s engineers calls the FD15 one of FiiO’s most balanced in-ear monitors for vocals: dense and lush, capturing both mid and low voices and their emotion without losing resolution. The large driver and its structure give deep, cohesive bass, so drums sound solid and powerful. It may not match the very best multi-armature earphones for ultra-high-frequency detail, they say, but in dynamic, complex passages the treble stays clear, and it shows the large soundstage expected of a magnesium-aluminium driver. If they had to choose one word: “grand”, for its solidity, dynamics and soundstage.

Magnalium diaphragm, DLC surround

The FD15 brings a truly high-end driver design to the line. The magnalium diaphragm, a scientifically calculated blend of magnesium and aluminium, is hard and moves with low distortion for clear, detailed treble. The DLC (diamond-like carbon) surround is both rigid and flexible, so there is less break-up and higher-quality sound.

FiiO also brings a high-end headphone principle to an earphone: a W-shaped surround, which increases the effective vibrating area by 30% compared with a conventional diaphragm of the same size. With more area and greater movement, the driver delivers a denser, more solid sound.

A bigger driver, a longer coil, a stronger magnet

“Tesla valve” bass

FiiO’s patented F.T.B.S. “Tesla valve” design uses channels in the shell, made possible by high-precision powder metallurgy, whose length, angle and number are precisely calculated. As FiiO explains, when air flows out of the cavity the channels make it behave viscously, lowering the cavity’s resonance for deep, impactful bass; when air flows back in, nothing hinders it, so the pressure balances quickly and the driver can work at its best.

A frontal acoustic prism

An acoustic filter in front of the driver keeps the FD5’s acclaimed vocals while adapting to the new driver and spreading the treble. It corrects the tiny delays caused by sound waves taking different paths, for consistent phase and precise control.

Built for comfort

• Nozzle angle: based on user feedback, the nozzle is raised 6.7° along the Y-axis (same length), so it fits the ear canal better and sits more securely.
• Curved MMCX connectors: instead of a rigid right angle, a curve that suits more ear sizes and doesn’t press behind the ear.
• Front contact surface: narrowed for a better fit, less movement and less friction.

316L stainless steel, mirror finished

The closed-back shells are 316L medical-grade stainless steel, made by powder metallurgy sintering at 1,400°C in ten composite processes for durability, then hand-polished and PVD-plated for a mirror finish, with surfaces that play with light and shadow. Choose obsidian black or racing silver.

Two sound nozzles

A Furukawa cable, without the mark-up

Cables made from Furukawa’s high-purity monocrystalline copper have been sought after since FiiO used them with the FT3. The FD15’s cable (identical to FiiO’s LC-RC 2024) is coaxially braided from four large strands, each of 100 Furukawa monocrystalline copper wires (0.05mm) and 20 Furukawa silver-plated copper wires (0.08mm): 480 wires in all, 22AWG, after secondary refining at 1,050°C and 744 hours of isothermal sintering. Expanded MMCX connectors give a more stable connection, and twist-lock 3.5mm and 4.4mm plugs (a design licensed from FABRILOUS) let you match your source.

Good to know

• FiiO ships either the new or the older design of interchangeable plug; both are genuine and the cable is the same.
• In the box: FD15, cable with 3.5mm and 4.4mm plugs, red and black sound nozzles, balanced (M fitted), vocal, bass and HS18 ear tips (S, M, L), two pairs of foam tips, HB11 case, MMCX quick-release tool, cleaning brush and quick start guide.