T40RP mk3
headphones
$120
Used market: $95*
Specifications
3 of 7 values have a recorded sourceExpert Audio Engineering Commentary
Tonal Profile
The sealed RP, and the least sensitive headphone in this batch at 91 dB/mW — 100 dB needs 7.9 mW, about 0.63 V into 50 Ohms. That is the whole argument for pairing these with an interface rather than a phone: not that the phone cannot reach the level, but that it reaches it with nothing left for peaks.
What the datasheet actually says
Quoted verbatim from the manufacturer’s own page, with the date we checked it. We state what is printed, not what anyone intended by it.
«model (e.g. of a vehicle) Sealed RP Dynamic / driver (of a vehicle) RP diaphragm»
Fostex labels the RP series 'dynamic', and in the loose sense of an electrodynamic transducer that is true. But the RP diaphragm is a printed conductor on a thin polymer film suspended in a planar magnetic field — an orthodynamic design, not a moving coil in a gap. The distinction is not academic for choosing a source: a moving-coil driver has a resonant impedance peak in the bass that a high output impedance turns into a tonal shift, while a planar diaphragm presents an essentially flat 50 Ohms across the band, so a high-output-impedance source costs level but not tonal balance. We classify these as planar magnetic for that reason and note the manufacturer's own wording here.
checked 8/5/2026* Estimated with the depreciation fallback (~79% retained value). · checked on 8/5/2026