Fostex TH818 is an open-back over-ear headphone with a solid acacia wood housing, positioned as the new standard model in Fostex's premium line — one step below the TH919 flagship with its Japanese-lacquered maple housing. Every component except the housing is identical to the TH919: the 50mm BioDyna driver with an updated voice coil and reinforced diaphragm surround, magnesium alloy chassis, dual-density urethane foam earpads covered in silk protein synthetic leather, and a natural sheepskin headband. The open-back design delivers a wide soundstage and natural timbre at the expense of isolation — TH818 is aimed at reference listening in quiet studio or home environments.
Updated BioDyna driver: lower bass distortion with TH919-level resolution
The 50mm BioDyna transducer in the TH818 is a revised version of the TH919's unit — differentiated by a new voice coil and a reinforced diaphragm surround, which Fostex states reduces distortion and muddiness in the bass range while fully preserving the flagship's resolution and character. The diaphragm combines bio-cellulose fiber with other fibers at optimal ratios for simultaneous low specific gravity, high Young's modulus, and high internal damping — resulting in fast transient response and an extended frequency range. The 12.5 Hz to 40,000 Hz reproduction range reaches well into the ultrasonic region, ensuring harmonics far beyond the audible band are accurately reproduced. At 25 Ω impedance and 100 dB/mW sensitivity, the TH818 will run from a portable headphone amplifier, but maximum power handling of 1,800 mW means the transducer is engineered for high-output desktop amps where its full dynamic range becomes accessible. The solid acacia wood housing — a material used in guitars and ukuleles for its resonant properties — shows natural variation in grain, texture, and color between individual units, with no effect on acoustic performance.
Materials and ergonomics: magnesium alloy, sheepskin and dual-density foam
The headband and yoke assembly are constructed from magnesium alloy, reducing weight by approximately 20% compared to previous models in this class — TH818 weighs 385 g. The headband pad is covered in natural sheepskin leather. Earpads are built from dual-density urethane foam covered in silk protein synthetic leather — a material softer and more peel-resistant than standard PU, with a more natural feel against skin during extended sessions. Included: 3.5mm detachable cable with 7N oxygen-free copper conductors and a 6.3mm adapter. Balanced operation requires the separately available XLR cable (ET-H3.0N7BL). The detachable cable connector uses rhodium-plated contacts.
KEY FEATURES
- Open-back over-ear design — wide soundstage, natural timbre, no environmental isolation
- 50mm BioDyna driver: bio-cellulose diaphragm, updated voice coil, reinforced surround, 1.5 T magnetic flux density
- All components except housing identical to flagship TH919
- Solid acacia wood housing — natural grain variation between individual units
- Magnesium alloy headband and yoke: approx. 20% weight reduction vs. previous generation
- Earpads: dual-density urethane foam + silk protein synthetic leather
- Headband pad: natural sheepskin leather
- Detachable cable: 3.5mm / 7N OFC + 6.3mm adapter included
- Balanced XLR connection supported via ET-H3.0N7BL cable (sold separately)
- Detachable connector with rhodium-plated contacts
- Manufactured in Japan
TECHNICAL SPECIFICATIONS
- Type: open-back, over-ear
- Driver: 50mm BioDyna (bio-cellulose + composite fibers), 1.5 T magnetic flux density
- Frequency response: 12.5 Hz – 40,000 Hz
- Impedance: 25 Ω
- Sensitivity: 100 dB/mW
- Maximum input power: 1,800 mW
- Weight: 385 g (without cable)
- Housing: solid acacia wood
- Headband / yoke: magnesium alloy
- Earpads: dual-density urethane foam + silk protein synthetic leather
- Headband pad: natural sheepskin leather
- Included cable: 3.5mm, 7N OFC + 6.3mm adapter
- Balanced cable: XLR ET-H3.0N7BL (sold separately)
- Cable connector: detachable, rhodium-plated contacts
- Availability: from late April 2026
