Fostex TH1100RPmk2 is Fostex's flagship open-back planar headphone — the mk2 revision of the TH1100RP, incorporating redesigned air damping control inside the transducer, new earpads, and a transition from aluminium to magnesium alloy for all mechanical components. The RP (Regular Phase) driver is a technology Fostex has been refining since 1974; in the TH1100RPmk2 it uses the largest fully driven planar diaphragm Fostex has ever produced in a headphone. The solid Japanese maple housing is dyed using Awa Aizome — traditional Japanese indigo dyeing with plant-based Hon-ai dye from Tokushima Prefecture, applied by hand over several days with curing intervals between coats. The open acoustic chamber of the TH1100RPmk2 features double-layered precision-machined aluminium apertures with a carefully calibrated opening ratio.
RP mk2 driver with air damping control for optimized diaphragm amplitude
The defining change between the TH1100RP and the mk2 is inside the transducer: air damping control has been optimized through revised airflow geometry using new damping materials, complemented by new earpads that alter the acoustic conditions directly in front of the diaphragm. The result is better control of diaphragm amplitude in the low-frequency range without compromising transient speed or resolution in the midrange and treble. The fully driven RP planar driver differs from conventional planar designs in that the magnetic field covers the entire diaphragm surface in uniform phase — eliminating localized diaphragm deformation and reducing non-stationary resonances. The TH1100RPmk2's magnetic circuit uses an increased number of magnets sandwiching the diaphragm, a newly designed printed coil pattern and shape, and redesigned magnetic flux distribution components. Frequency response: 5–40,000 Hz, impedance: 32 Ω.
Awa Aizome housing, double aluminium apertures and magnesium alloy 20% lighter than aluminium
The solid Japanese maple housing is dyed with Hon-ai — plant-based natural indigo historically used in Japan, including by Hokusai in the Thirty-six Views of Mount Fuji woodblock print series. The dyeing process takes several days with curing intervals; temperature and humidity affect the penetration of dye pigment into the wood grain, making every unit unique in depth and distribution of color. Dense Japanese maple does not introduce its own tonal coloration due to its material properties — delivering firm, deep bass and clear, resonant treble. The open chamber features double-layered precision-machined aluminium apertures with a calibrated opening ratio optimized for soundstage reproduction and minimal listening fatigue. Mechanical components including the housing base plate and yoke are machined from magnesium alloy, reducing overall weight by 20% compared to the aluminium used in the previous generation. Weight: approx. 420 g. Mk2 earpads: dual-layer foam with silk protein synthetic leather covered by natural sheepskin leather. Included cable: 2 m Y-type unbalanced, 7N OFC, 6.3mm plug with rhodium-plated contacts on gold-plated base. Optional cables: XLR ET-H3.0N7BL (balanced) and ET-TH4.4BL (4.4mm / 5-pin). Leather carrying pouch included.
KEY FEATURES
- Open-back planar design — Fostex flagship RP headphone
- RP mk2 driver: largest fully driven planar diaphragm in Fostex headphone history, Regular Phase technology since 1974
- Mk2 optimization: air damping control inside driver + revised damping materials + new earpads for optimized diaphragm amplitude in low frequencies
- Housing: solid Japanese maple dyed with Awa Aizome (Hon-ai, plant-based natural indigo, Tokushima) — hand-dyed over several days, each unit unique
- Open chamber: double-layered precision-machined aluminium apertures with calibrated opening ratio
- Mechanical components: magnesium alloy — 20% weight reduction vs. aluminium
- Mk2 earpads: dual-layer foam + silk protein synthetic leather + natural sheepskin leather
- Included cable: 2 m Y-type, 7N OFC, 6.3mm plug, detachable 2-pin rhodium-plated connector
- Optional cables: XLR ET-H3.0N7BL (balanced) and ET-TH4.4BL (4.4mm / 5-pin)
- Hand-assembled unit by unit, manufactured in Japan
TECHNICAL SPECIFICATIONS
- Type: open-back, over-ear, planar magnetic
- Driver: RP planar magnetic (fully driven, Regular Phase), largest RP diaphragm in Fostex history
- Frequency response: 5 Hz – 40,000 Hz
- Impedance: 32 Ω
- Sensitivity: 96 dB/mW
- Maximum input power: 3,000 mW
- Weight: approx. 420 g (without cable)
- Housing: solid Japanese maple + Awa Aizome (Hon-ai), double-layered aluminium apertures
- Mechanical components: magnesium alloy
- Earpads: dual-layer foam + silk protein synthetic leather + natural sheepskin leather
- Included cable: 2 m Y-type, 7N OFC, 6.3mm plug
- Cable connector: 2-pin, rhodium-plated on gold-plated base
- Optional balanced cables: XLR ET-H3.0N7BL, 4.4mm ET-TH4.4BL
- Accessories: leather carrying pouch
- Manufacturing: hand-assembled in Japan
