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published: Jun-25-2013

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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.

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.

Frequency response (tonal balance) is the most sound-determining aspect of headphones. A horizontal line shows audible neutral response in the plots on this website. Deviations in different severities at different frequency bands have an effect on the sound character.
The bigger the deviation the stronger the effect.

Below an aid to help determining the sound character of headphones with relation to the frequency response.


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Stax SR-5 with SRD-6 energizer


Stax SR-5 white with converted SRD6-SB energizer. The original energizer is of the so called Self-Bias type which means the bias voltage is generated by the audio-signal. a disadvantage of this is that you need to play it loud before you can start listening so the bias voltage is high enough. When playing soft for a while the bias voltage drops and so does the SQ. I converted the SRD-6 energiser so it is powered directly from mains. For an oldie (manufactured somewhere between 1970 and 1980) it doesn’t sound that bad and if it weren’t for the lack of bass extension it would give most headphones a run for their money.

sr5 + srd-6

Frequency response is fairly flat and well extended in the highs it only really lacks in the sub-lows.  Bass response isn’t even that bad but a drop-off below 60Hz is a bit meagre. When it is NOT played loud and the lows are compensated by a little boost it sounds quite full and well behaved.  When playing louder it starts to distort in the bass though (as expected) as the membrane is tensioned pretty well, even after all these years. dropping the 10kHz slider on the EQ makes it sound even better !

sr5 + srd-6 csdCSD is remarkably clean with no obvious ringing anywhere.  Even at 500Hz it behaves extremely well. Impressed with what Stax could make already 40 years ago and still works well till today !

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