Fostex T50RPmk4CL is the first closed-back variant of the T50RPmk4 platform — the fourth-generation RP driver in an enclosure sharing the same internal geometry as the T50RPmk4, with ventilation ports sealed and a separate acoustic calibration applied for the closed-back loading condition. The primary use case is studio tracking — vocal and instrument recording sessions requiring isolation — and dense monitoring environments where the semi-open T50RPmk4 bleeds too much ambient sound. The symmetrical housing with bilateral 4-pole 3.5 mm sockets is carried over unchanged from the T50RPmk4.
Unified housing geometry — the deliberate engineering decision
Fostex built the T50RPmk4CL by taking the T50RPmk4 housing, sealing the ventilation points, and re-tuning the acoustic balance for the sealed chamber rather than designing a new enclosure from scratch. The practical consequence is significant: an engineer alternating between the T50RPmk4 for mixing and the T50RPmk4CL for tracking does not need to compensate for tonal differences caused by divergent housing geometries — both pairs share the same mechanical platform and the same fourth-generation driver. The redesigned printed coil, increased magnet count, and optimized flux distribution of the fourth-generation driver maintain fast attack and decay regardless of enclosure type, making the T50RPmk4CL a reliable tracking tool for acoustic instruments and vocals where transient accuracy directly affects punch-in decisions.Connector system and cable flexibility
Both earcups carry 4-pole 3.5 mm sockets supporting balanced connections. The included OFC cable is unbalanced (4-pole to 3-pole), but the headphone itself is balanced-ready without modification. The optional ET-RP4.4BL balanced cable (4.4 mm Pentaconn) connects directly. Symmetrical housing eliminates the internal acoustic asymmetry between left and right earcups that affects many headphones with single-sided cable routing — a meaningful advantage for critical monitoring where channel matching matters. Angled low-rebound ear pads are included as standard; optional Ultrasuede EX-EP-RP-SUEDE pads are available separately.KEY FEATURES
- 4th-generation RP planar driver — unified with T50RPmk4, fast transients, smooth monitoring frequency response
- Closed-back housing derived from T50RPmk4 — same internal geometry, separate acoustic calibration
- Full ambient isolation — vocal and instrument tracking, monitoring in loud studio environments
- Symmetrical housing with bilateral 4-pole 3.5 mm sockets — no L/R acoustic asymmetry
- OFC cable 2 m + 6.3 mm adapter included; optional ET-RP4.4BL balanced cable (4.4 mm) available separately
- Angled low-rebound circumaural ear pads — comfort over extended sessions
- Optional Ultrasuede EX-EP-RP-SUEDE ear pads available separately
TECHNICAL SPECIFICATIONS
- Model: T50RPmk4CL
- Driver type: Planar magnetic RP (Regular Phase), 4th generation
- Design: Closed-back
- Impedance: 28 Ω
- Sensitivity: 97 dB/mW
- Frequency response: 10 Hz – 40,000 Hz
- Maximum input power: 3,000 mW
- Earcup connectors: 2x 4-pole 3.5 mm (symmetrical bilateral)
- Weight: approx. 330 g (without cable)
- Included accessories: OFC cable 3.5 mm (4-pole to 3-pole, 2 m), 3.5 mm to 6.3 mm adapter
