T50RP (mk2)

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NO SMOOTHING is applied to the shown plots. Most measurement sites have some smoothing applied which ‘irons flat’ sharp peaks and ‘wiggles’. I do not use smoothing because some info about sound quality is lost when plots are smoothed.

Aside from a small correction of the microphone itself also some correction in the lowest frequencies is applied to the plots to compensate for the perceived loss of bass when using headphones. This is described HERE in more detail.
A ‘horizontal‘ frequency response curve on the shown frequency response plots on this website thus indicates a perceived ‘flat’ tonal signature.

ALL measurements are made with a good SEAL on a flatbed measurement rig.
shape of your head, bone structure, pad size, pad ‘softness,  (compliance), hair or no hair and or wearing glasses may (drastically) change the frequency response of some headphones, so… your personal experience may differ substantially from these plots.

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Fostex T50RP

T50-940 pad

Below the measurements of a stock T50RP, Left, Right.

stock T50RP

Below the FR of a modifiedFostex T50RP with Shure SRH 940 pads fitted versus the same modified T50RP playing from a Kameleon amplifier.
EXT T50RP Kam vs stock

As can be seen the Kameleon amplifier (with T50RP module) extends the lows, lowers the midrange just slightly, fills in the 3kHz dip just enough and extends the top end.

Below the distortion plots of the (modified) T50RP driver.

DIST stock T50RP

Below the distortion measurements of the same headphone but playing on the Kameleon amplifier.

DIST kam T50RP

Below the CSD of the (modified) T50RP. Note that the stock T50RP will look different because of the added damping materials in front and rear of the driver (as well as due to the pads).

CSD 30k stock

Below the CSD of the same headphone playing from the Kameleon amplifier.


A nice and clean CSD which also shows the improved frequency response and extension up to 20kHz.

Another clue for signal response is the squarewave and needle pulse response.
Shown below the plots for the modified T50RP on the left versus the same headphone playing via the Kameleon amplifier on the right.


Especially the impulse response shows a much improved transient response. Also visible in the 440Hz square-wave where the leading edge (where the ‘attack’ is shown) is higher.

Do note that the filter PCB mentioned in the modification article is no longer available, it has been replaced by the Kameleon amplifier.

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