Fostex TH909 is Fostex's flagship open-back dynamic headphone — the successor to the closed-back TH900mk2, expanding its platform with an open acoustic chamber, double-layer etched metal grille, and a redesigned acoustic path. The 50mm BioDyna driver with 1.5 Tesla neodymium repulsion magnet circuit is carried over from the TH900mk2; the open architecture widens the soundstage and improves stereo image separation at the cost of passive isolation. The Japanese ornamental cherry birch housing is finished in bordeaux Urushi lacquer by the Sakamoto factory. A headphone stand is included in the full accessory package — the key differentiator from the TH909LE. Hand-assembled in Japan.
Open chamber with double-layer grille and 1.5 T repulsion driver: full dynamics without closed-back loading
The 50mm BioDyna driver with repulsion magnet circuit at 1.5 Tesla magnetic flux density operates in an open acoustic chamber — eliminating the acoustic pressure that builds on the inner side of the earcup in closed designs and allowing the diaphragm to work under minimal additional acoustic loading. The result is a wide, spacious soundstage with precise instrument localization and depth of field. The double-layer etched metal grille diversifies the resonance points of the housing, preventing energy concentration at specific frequencies — while also providing the housing's characteristic visual depth. The BioDyna diaphragm in bio-cellulose and composite fibers delivers low specific gravity, high Young's modulus, high internal loss, and a free-edge design. Frequency response: 5–45,000 Hz, impedance: 25 Ω, sensitivity: 100 dB/mW, maximum input: 1,800 mW. The TH909 rewards careful amplifier matching — its 25 Ω impedance and high sensitivity allow portable source driving, but full resolution potential emerges with higher-quality headphone amplifiers.
Sakamoto bordeaux Urushi lacquer, included headphone stand and complete flagship package
The Japanese ornamental cherry birch housing is finished in bordeaux Urushi lacquer — handcrafted by artisans at the Sakamoto Otosho Shoten factory, established in 1900. The technique involves applying a base black lacquer and an adhesive layer, over which several types of sulfur-smoked silver foil are applied in a torn-paper manner — creating a depth and layering effect unique to each individual unit. Japanese ornamental cherry birch used in the housing has acoustic properties comparable to lutherie tonewoods. Low-resilience urethane earpads covered in high-grade synthetic leather. Included cable: 3 m, 7N OFC, 6.3mm plug, 2-pin connector with rhodium-plated contacts. Balanced connection via the optional XLR cable (ET-H3.0N7BL). The full accessory set includes a headphone stand — the element distinguishing the TH909 from the TH909LE — and a synthetic leather carrying bag. Manufactured and hand-assembled in Japan.
KEY FEATURES
- Open-back dynamic design — Fostex flagship headphone, successor to TH900mk2
- 50mm BioDyna driver: bio-cellulose diaphragm, neodymium repulsion magnet circuit, 1.5 Tesla magnetic flux density
- Open acoustic chamber — expanded soundstage, precise localization, no closed-back pressure loading
- Double-layer etched metal grille — resonance point diversification
- Japanese ornamental cherry birch housing with bordeaux Urushi lacquer (Sakamoto factory, est. 1900) — each unit unique
- Low-resilience urethane earpads + high-grade synthetic leather
- Included cable: 3 m, 7N OFC, 6.3mm plug
- 2-pin connector with rhodium-plated contacts
- Balanced XLR connection via ET-H3.0N7BL (sold separately)
- Included accessories: headphone stand + synthetic leather carrying bag
- Hand-assembled, manufactured in Japan
TECHNICAL SPECIFICATIONS
- Type: open-back, over-ear, dynamic
- Driver: 50mm BioDyna (bio-cellulose + composite fibers), neodymium repulsion magnet circuit, 1.5 T
- Frequency response: 5 Hz – 45,000 Hz
- Impedance: 25 Ω
- Sensitivity: 100 dB/mW
- Maximum input power: 1,800 mW
- Weight: approx. 385 g (without cable)
- Housing: Japanese ornamental cherry birch + bordeaux Urushi lacquer (Sakamoto), double-layer etched metal grille
- Earpads: low-resilience urethane foam + high-grade synthetic leather
- Included cable: 3 m, 7N OFC, 6.3mm plug
- Cable connector: 2-pin, rhodium-plated
- Balanced cable: XLR ET-H3.0N7BL (sold separately)
- Accessories: headphone stand, synthetic leather carrying bag
- Manufacturing: hand-assembled in Japan
