High-Sensitivity Planar Headphones

The FIIO FT15 is a full-size open-back planar magnetic headphone built around a 101mm driver, an 800nm ultra-thin diaphragm, a full-surface diamond coating, and a patented uniform magnetic field design. Its 95dB/mW sensitivity makes the 24Ω FT15 suitable for portable audio sources, while a 425g chassis, North American black walnut construction, and a liquid-nitrogen-treated 6N monocrystalline copper cable round out a carefully engineered design.

800nm ultra-thin diaphragm

The FT15 reduces diaphragm thickness from the previous-generation FT5's 6 microns to just 800 nanometers, an 86.7% reduction. The lower moving mass allows the diaphragm to respond quickly to small signal changes, supporting precise transient reproduction and improved retrieval of high-frequency detail. Greater diaphragm compliance also helps reduce distortion and contributes to smooth treble during extended listening.

Full-surface diamond coating

FIIO applies its patented multi-layer coating technology to the FT15, combining a silver-aluminum alloy voice-coil coating with a full-surface diamond coating on the diaphragm. Diamond's high hardness and structural stability reinforce the ultra-thin diaphragm, helping control high-frequency breakup while improving response speed. Frequency response extends to 40kHz, while high-temperature vacuum treatment lowers the substrate's resonance point to support deeper bass extension.

Proprietary planar technology

The FT15 develops FIIO's planar magnetic platform with a thinner diaphragm, diamond coating, and a refined magnetic circuit. Force is distributed more consistently across the diaphragm to reduce unwanted vibration and distortion. This engineering supports solid bass, smooth midrange and treble, and a warm, natural tonal balance.

101mm planar driver

A 101mm full-size planar driver provides an effective vibrating area of 6,443.5 mm², approximately 35% greater than the FT5. The larger radiating surface gives the FT15 greater capacity for low-frequency output and dynamic changes while contributing to a broad, naturally proportioned soundstage.

Uniform magnetic field design

FIIO's patented magnetic circuit uses custom-shaped high-strength magnets and optimized positioning to distribute magnetic flux more evenly across the diaphragm. A wider effective magnetic field increases the usable voice-coil area and keeps driving force consistent as the diaphragm moves. This helps suppress nonlinear breakup and reduce harmonic distortion while preserving fine signal detail.

28nm manufacturing process

The FT15 voice coil is formed on the diaphragm using a 28nm chip-grade vacuum electroplating process. This strengthens the bond between the conductive layer and diaphragm substrate, helping the assembly remain stable through prolonged vibration. The process also improves consistency in diaphragm movement and reduces the likelihood of vibration-related coil damage.

High-sensitivity planar design

With a sensitivity of 95dB/mW at 1kHz and an impedance of 24Ω, the FT15 is designed to work with a wider range of sources than many traditional planar headphones. A dual-sided heterogeneous magnet array keeps the voice coil within a strong portion of the magnetic field, providing the driving force needed for use with portable players and dongle DACs.

425g lightweight construction

The FT15 weighs approximately 15.0 oz (425g) without its cable. FIIO reduces weight through a carbon-fiber headband, a specialty modified-plastic magnet bracket, and an optimized dual-sided magnetic circuit. The bracket provides rigidity comparable to aluminum alloy at roughly two-thirds of its density, while the revised magnetic circuit cuts magnet weight without giving up required driving force.

North American walnut ear cups

The center frame uses FAS-grade North American black walnut selected for consistent grain and limited natural imperfections. Each piece is finished and polished to retain the wood's natural pattern, giving every FT15 a distinctive appearance while maintaining the structural requirements of the open-back enclosure.

Cryogenically treated copper cable

The supplied cable uses 6N OCC monocrystalline copper with a stated purity of up to 99.99998%. Its conductors undergo more than 100 hours of cryogenic treatment at -313.6°F (-192°C), a process intended to release internal metal stress and refine the conductor's microscopic structure. FPA insulation is also used around the conductors. The cable terminates in a 4.4mm fully-balanced plug and connects to the headphones through dual 3.5mm TS connectors.

Two tuning ear pad options

Two sets of ear pads allow the FT15's tonal balance to be adjusted without changing hardware. The suede pads emphasize bass warmth and smoother treble, making them suitable for pop and vocal-focused listening. The protein leather pads place greater emphasis on high-frequency definition and vocal clarity, with tuning suited to classical instruments and higher-register vocals.

Flexible connection options

The supplied 4.4mm fully-balanced cable is joined by two adapters. A 4.4mm-to-6.35mm adapter supports conventional full-size headphone outputs, while a 4.4mm-to-XLR-4 adapter provides compatibility with four-pin balanced headphone connections.

Custom storage case

FIIO includes a custom Yaoli linen storage case sized for the FT15 and its accessories. The fabric construction provides a dedicated place to store and protect the headphones between listening sessions or during transport.

Hi-Res Audio certification

The FT15 carries Hi-Res Audio certification from the Japan Audio Society. Its specified frequency response spans 7Hz to 40kHz.

Product highlights

• 800nm ultra-thin planar diaphragm
  
• Full-surface diamond diaphragm coating
  
• 101mm proprietary planar magnetic driver
  
• 6,443.5 mm² effective vibrating area
  
• Patented uniform magnetic field design
  
• 28nm chip-grade voice-coil manufacturing process
  
• 95dB/mW sensitivity for use with portable sources
  
• Approximately 15.0 oz (425g) without cable
  
• FAS-grade North American black walnut construction
  
• Carbon-fiber headband
  
• Liquid-nitrogen-treated 6N monocrystalline copper cable
  
• Two included tuning ear pad sets
  
• Hi-Res Audio certified

Specs

• Headphone type: Full-size open-back planar headphones
  
• Driver type: 101mm proprietary planar driver
  
• Frequency response: 7Hz–40kHz
  
• Impedance: 24Ω at 1kHz
  
• Sensitivity: 95dB/mW at 1kHz
  
• Sensitivity: 111dB/Vrms at 1kHz
  
• Weight: Approximately 15.0 oz (425g), excluding cable
  
• Clamping force: 3.8N ±0.3N
  
• Cable material: Liquid-nitrogen-treated 6N monocrystalline copper
  
• Cable length: Approximately 4.9 ft (1.5m)
  
• Headphone connectors: Dual 3.5mm TS
  
• Audio plug: 4.4mm fully-balanced

What’s included

• FIIO FT15 headphones
  
• Fabric storage case
  
• 4.4mm headphone cable
  
• XLR-4 male to 4.4mm female fully-balanced adapter
  
• 4.4mm female to 6.35mm male adapter
  
• Suede ear pads, pre-installed
  
• Protein leather ear pads
  
• FT15 packaging box
  
• Quick start guide