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published: Sept-16-2021, updated: Feb-20-2022

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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.

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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audio-technica ATH-M50X (Limited Edition)

M50X kl

The popular audio-technica ATH-M50X is a well known headphone that often gets recommended. It is the successor of the ATH-M50(S). From 2012 limited editions were made in a few color combinations. Inside they are no different from the regular black (or white) ATH-M50X. The one above is from 2014. Below the different LE models (picture source: audio-technica)
It comes with a soft pouch (same color and material as pads/headband). Also 3 different cables are included. A 1.2m straight cable with 3.5mm plug, a 3 meter straight cable with 3.5mm plug that can take the also supplied 6.3mm screw-on adapter and a 1.2-3m coiled cable with 3.5mm plug that can take the also supplied 6.3mm screw-on adapter. The cable is in the same color as the cups.
They terminate in a 2.5mm locking TRS connector in the left cup.

The headphone is closed which means people around you don’t hear what you are listening to and outside noise are attenuated. Attenuation of outside noises is decent.

The cable is just very slightly microphonic so in quiet passages and silences the cable rubbing against clothes are barely audible in the left cup.

The cups are collapsible and can fold flat. The pads are pleather. Pleather is made of cloth covered with a very thin layer of leather look vinyl. Alas, after a few years the vinyl starts to break and flake off. The black pads are easily replaced but the other colors not. Some color pads can be found after market but these will sound different.


Room for the ears is not plentiful. The depth is just under 20mm.
The pads are easily replaced and can be found in many colors including the original. The headband, however, also flakes after a few years and these are not available as spare parts. There are some foam-like things one can wrap around the headband but these don’t look nearly as good.

For this headphone I replaced the headband cover with some tech-flex tubing. Looks good and won’t fall apart. The result of the new pads and Tech-flex headband is shown below.

With a sensitivity of 116dB/V (101dB/mW) and an impedance of 38Ω this headphone can be used from phones as well. The high power rating means the M50X can reach 130dB SPL and will be hard to destroy.


Type: Over ear, closed
Usage: Home, studio, portable
Driver type: dynamic
Pads: replaceable, pleather
Collapsible: yes and can be folded flat
Headphone cup connector: 2.5mm locking TRS
Cable entry: single sided (left).
Cable: 1.2m with 3.5mm TRS jack, 3mwith 3.5mm TRS jack + 6.3 screw on, and 3m coiled cable.
Inner Pad dimensions: depth = 18mm, Width = 35mm, height = 52mm, oval shaped
Driver size: 40mm (angled 9 °)
Max. power rating: 1.6W
Max. voltage: 7.8Vrms (22Vpp)
Max. current: 200mA
Max. S.P.L.: 133 dB
Impedance: 38 Ω (measured)
Efficiency: 101dB @ 1mW
Sensitivity: 116dB @ 1V
Weight: 285 g.
Clamping force: medium
Accessories: 3 cables, 6.3mm screw on adapter, soft pouch.

Subjective sound description:

The bass is somewhat elevated and a bit on the ‘woolly’ side as in ‘not tight’. Mids have a warmish / full character. Clarity is good. Treble is on the correct level and not shrill/harsh in any way.


Below the frequency response of the ATH-M50X (Left, Right)


The channel matching is not perfect but the pads were not in the same condition either.
Bass extends well down to 20Hz. Slightly elevated between 80Hz to 200Hz which is the reason it sounds a bit woolly when a perfect seal is obtained. It improves a bit when wearing glasses.
From 200Hz to 3kHz the response is sloping downwards a bit which explains the ‘warmish’ mids.
From 4kHz to 9kHz the response is not elevated so no sibilance nor sharpness. From 10kHz to 20kHz the level is slightly elevated but a bit wiggly. Above 20kHz the response drops off fast.


Below a comparative measurement of the ATH-M40X and the ATH-M50Xbrown = M40X, teal = M50X
The ATH-M40X and M50X have a similar bass response and in the treble they also do not differ very much. The treble quality of the M40X is slightly less in quality. The biggest difference is how the mids are perceived.
The M40X has more forward mids (more clarity) where the M50X is a bit warmer sounding.

Phase response

Below the phase response of the THH-M50X (Left, Right)

phase M50X
Gentle sloping phase is not audible. Above 3kHz the phase changing within a narrow frequency band which is potentially more audible but aside from the 10kHz bit the phase variance is not problematic.

output resistance / damping-factor

As this is a dynamic headphone the frequency response can be amplifier output resistance dependent when certain higher output resistance amplifiers are used.
Instead of showing impedance plots, which are hard to ‘read’ when it comes to assessing the tonal balance change in the real world, the ATH-M50X is measured via a
few different resistance outputs (0.2Ω, 10Ω, 32Ω and 120Ω). On a higher output resistance amplifier the output level will be lower of course due to voltage division. To compensate for this the amplifier is cranked up to the same level (14.5dB for 120Ω at 1kHz in this case). This way the plots are overlaid and it is easier to see how the tonal balance changes. Output resistances between the mentioned resistance values will result in tonal changes between those traces.120 ohm -14-5dB

The tonal balance hardly changes when a higher output resistance amplifier is used. Up to 32Ω output Resistance makes very little difference. At 120Ω the pad bounce frequency (the dip around 60Hz) is slightly affected but the amount of lows does not change.


Seal can be an issue especially with closed-back headphones. Breaking the seal (improper fit on the head) usually means a loss of (sub)bass. Perfect sealthin armed glasses, thick armed glasses and seal broken by a 6.3mm plug.seal
Bass extension is affected as soon as the seal is broken. Still 30Hz is still very low in frequency. The elevated bass area is at the correct level with a bit of seal breach. The elevated area around 500Hz can give the sound a slightly ‘honky’ character when the seal is broken a bit.

Below the distortion measurements of the ATH-M50X (Right channel).Dist R M50X
The plot above shows the level differences between the signal (upper trace around 90dB SPL) and the harmonics. Most people prefer to see percentages instead of level differences so below the exact same plot except ‘normalised’ to the actual signal and level differences given in percentages.dist R percent M50X

Distortion in the bass below 80Hz is predominantly 3rd harmonic which points to linearity issues. 3rd harm. at 90dB SPL is already 2%.  At 97dB SPL it almost reached 5% which is less than 1mW.
Above 200Hz distortion is low enough.
The actual 2nd harmonic distortion above 1kHz may well be lower than 0.2% . A shortcoming of my measurement rig.


Because of the relatively high 3rd harmonic distortion linearity may not be that great. The ATH-M50x is measured 4 times at different levels. Once at 70dB, 80dB, 90dB and 97dB SPL. To make the plot below the 70dB sweep is amplified 20dB, the 80dB sweep by 10dB and the 97dB sweep by -7dB. When the traces are the same shape then there is no compression. .compression M50X
Above 80dB SPL the 3rd. harm. distortion rises and linearity suffer as well. The issue is only there below 70Hz where the biggest excursions are needed.

Below the CSD (waterfall) plot of the ATH-M50X . (Left and Right are overlaid)CSD M50X
Aside from the short lingering around below  1.2k, the small resonance at 4kHz the CSD looks very well behaved and well damped. Above 10kHz the response consists mostly of a few resonances.

Below the Group Delay plot for the ATH-M50X (Left, Right)GD M50X

There is some  pad bounce around 60Hz and small one at 100hz. Otherwise there are no timing issues.

A different plot is the spectrum plot. This basically is a CSD (Waterfall) plot but viewed from above where the level differences are colour coded instead of being in the vertical axis. Also the frequency range of the spectrum plot is wider (from 100Hz instead of 500Hz). The time span is also bigger in the spectrum plots and expired time is shown from below to top where in the CSD the time is shown from rear to front.

Below the spectrum plot of the ATH-M50X (Left channel)Spectr L
Below 300Hz there is some lingering present. Bass notes thus do not stop on a dime. Otherwise no alarming resonances.

Step response

Below the step response plot which, when the sound is balanced and well extended should show a fast rise to around 0dB, (indicating fast driver response) and then should be slightly sloping downwards indicating bass extension. (Left, Right)
step M50X
Bass extension is excellent. The horizontal trace hardly sags the first 2.5ms. The warmer response is also seen in this plot as the initial rise doesn’t reach the 0dB line. Because of this the headphone lacks some sparkle and ‘air’ despite the elevated response above 10kHz.

square-wave and impulse response

Below 40Hz and 440Hz square-waves and 100μs impulse response, stimulus (and target) and measured response.
SQ ATH-M50XThe 40Hz square-wave shows good bass extension with a boost in the upper bass.
The 440Hz square-wave shows an emphasis and ringing at higher frequencies but does follow the target.
The needle pulse shows overshoot and some high frequency ringing which after 0.5ms rings on at a lower frequency.


The audio-technica ATH-M50X is a well known and often used closed headphone. It can be found in many studios as well as homes. There also is a BlueTooth version of it.
This headphone can be driven from many different sources including phones and most audio interfaces.
There are also limited editions but alas there are no spare parts for these models. After a few years the pleather starts to fall apart and become ugly. Only black and white pads are available as spare parts so the limited editions are also limited in time of usage.
The sound is a warmish neutral. Bass response is a bit on the woolly/mushy side (as in not tight/punchy) and it lacks a bit in sparkle and ‘air’ yet is well extended in the lows and highs.
For an affordable closed headphone this is one of the headphones that sounds quite decent to good but is not top level material.

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