FX25

The FiiO FX25 is a tribrid in-ear monitor with seven drivers per side, housed in hand-laminated carbon-fibre shells. It borrows the electrostatic tweeters from FiiO’s flagship FX17 and pairs them with a dynamic driver and two Knowles armatures. For anyone who wants an open, airy top end without giving up weight and warmth lower down, it’s a very interesting proposition.

Seven drivers, each with a job

A 10mm dynamic driver with a light, rigid lithium-magnesium diaphragm handles the bass, with a flexible surround for low distortion and natural-sounding voices and instruments. Two custom Knowles balanced armatures cover the mids: one tuned for clear upper mids that blend smoothly into the treble, the other with a vented back chamber for fuller lower mids, which suits pop vocals in particular.

The top end comes from four Sonion EST65QB02 electrostatic drivers, the same type used in the FX17, for an open, airy treble. FiiO has added a second-order filter to tame resonance peaks from the drivers and shell, so the treble stays easy to listen to rather than bright.

That’s a lot of engineering to describe. What matters is how it suits your music and your ears, and that’s always where I’d start the conversation.

Tuned shells in carbon fibre

FiiO’s patented S.Turbo sound tube in the front chamber adds bass weight and punch while filtering excess upper frequencies from the dynamic driver. Micro vents in the rear chamber balance the pressure for deeper bass and clearer vocals. The shells themselves are hand-laminated carbon fibre, light and rigid at around 7g per earpiece, and every pair has its own grain.

Ready for any source

The silver-plated 6N single-crystal copper cable uses twist-lock plugs, so you can swap between 3.5mm, 4.4mm balanced and a USB-C DAC plug for your phone. At 20Ω and 106dB/mW, the FX25 is easy to drive from a phone with that USB-C plug, and it scales up nicely with a good player or amplifier. The standard 0.78mm 2-pin connectors also take upgrade cables if you want to explore later.

Want to go wireless? The FiiO LINK TWS turns the FX25 into true wireless earphones. At the other end of the scale, the FiiO Class A desktop amplifier is a lovely match at home.

Plenty in the box

FiiO includes 22 pairs of eartips, from SpinFit and FiiO HS18 to memory foam and double-flange, so finding a good fit and seal should be straightforward. You also get an aluminium and leather NEST CUBE case, a magnetic cable clip and a cleaning brush.

FiiO FX25 at a glance

• Type: tribrid in-ear monitors
• Drivers per side: 1 × 10mm lithium-magnesium dynamic, 2 × custom Knowles balanced armature, 4 × Sonion EST65QB02 electrostatic
• Frequency response: 10Hz to 40kHz
• Impedance: 20Ω at 1kHz
• Sensitivity: 106dB/mW at 1kHz
• Shells: hand-laminated carbon fibre, Dusk Brown (every pattern is unique)
• Weight: approx. 7g per earpiece, excluding cable
• Cable: 6N single-crystal copper, silver-plated, cryo-treated, approx. 1.2m, 0.78mm 2-pin
• Plugs: swappable 3.5mm, 4.4mm balanced and USB-C DAC
• Hi-Res Audio certified
• In the box: cable with three plugs, NEST CUBE case, 22 pairs of eartips, magnetic cable clip, cleaning brush

Talk to Audio Concierge

If you’re weighing up the FX25 against the IEMs you already know, or you’d like to know how it will fit with the rest of your system, get in touch. Tell me what you listen to and what you listen with. No jargon. Just good advice.