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Overview
Styled in black, the T50RPmk4 from Fostex is the latest iteration of the company's highly regarded Regular Phase (RP) series of headphones, now equipped with a completely redesigned RP planar magnetic driver. The headphones utilize proprietary technology in order to ensure an accurate reproduction of sonic material, thereby rendering these semi-open headphones suitable for monitoring in studio situations. To ensure a full representation of the sonic spectrum, these headphones have a frequency response of 10 Hz to 40 kHz.
The RP technology planar magnetic driver, first developed over 50 years ago and refined continuously throughout the years, has now hit its 4th generation. A new printed coil pattern shape has been employed to expand and equalize the vibration area of the flat diaphragm. Additionally, the number of magnets that sandwich the diaphragm has been increased substantially. Furthermore, the components of the magnetic circuit have been redesigned to optimize their magnetic flux distribution, suppressing unnecessary resonance and achieving even better transient response. This 4th generation driver, developed by fully incorporating various technologies cultivated over the years, simultaneously achieves improved sensitivity, smooth frequency response, and superb transient characteristics. By accurately and delicately reproducing elements all across the frequency spectrum, the soundstage and localization have also been improved. The new driver is also more efficient, requiring less power from the headphone amplifier to achieve peak performance.
Both the left and right housings are equipped with connectors for the supplied cable, so that the cable can be connected to either the left or right depending on the usage environment. In addition, by making the left and right housings symmetrical, the difference in sound characteristics, usually caused by differing internal structures between sides, has been eliminated. The connector is equipped with a 4-pole 3.5mm connector, which supports balanced connections, increasing ease of use and versatility. The cable uses high-quality OFC conductors.
Features
• Refined Fostex proprietary Regular Phase (RP) diaphragm driver using copper foil etched polyimide film and powerful neodymium magnet
• The maximum input level of 3000mW to comply with various professional uses
• Newly developed low repulsion ear pad and head pad for maximum comfort
• Comes with 3m 1/4” plug detachable cable for best serviceability and 1.2m mini plug cable for portable audio use
Generating expert take…
Fostex emerged in 1973 as the branded consumer and professional division of Foster Electric Co., Ltd., a Japanese loudspeaker manufacturer founded in 1949. Established to bring Foster's high-quality speaker components directly to dealers and customers, Fostex quickly gained international recognition through innovative products like the T20RP headphones and 6301 studio monitors. The brand's foundation rests on Foster's position as one of the world's largest OEM loudspeaker developers, employing tens of thousands across multiple countries and manufacturing millions of speaker units monthly.
The company built its reputation across three interconnected product categories: professional studio equipment, consumer headphones, and powered monitor speakers. Fostex became particularly renowned for pioneering RP (Regular Phase) technology, which delivers clear sound with high sensitivity and wide dynamic range—a signature that defines their headphones, microphones, and speaker designs. Beginning in 1978, the brand expanded into professional speaker development, eventually introducing the PM series of powered monitors and establishing itself as a trusted choice for recording studios, broadcast facilities, and serious home listeners.
Fostex occupies a distinctive middle ground in the audio market: neither ultra-premium boutique nor mass-market consumer, but rather a respected specialist brand with deep professional credentials. Their products appeal to recording engineers, studio owners, and discerning hi-fi enthusiasts who prioritize accuracy and reliability over luxury positioning. The 6301B monitor remains an industry standard after decades in production, while the T20RP headphones maintain popularity among studio professionals—testament to Fostex's enduring reputation for sonic integrity and engineering excellence.
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