Custom One Pro

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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.
The 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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Beyerdynamic Custom One Pro


The Beyerdynamic Custom One Pro is a closed over-ear (circumaural) dynamic headphone.
The COP (Custom One Pro) retails for around € 150.-. but got this one for half the price second hand.
This headphone is now called the Custom One Pro Plus(COPP). It is available in white as well. There is also a gaming version and a studio version. The studio version has different drivers (80Ω) and different pads (velour) as well as a coiled cable. The gaming version has a microphone connected to the plug with a mute button and volume control in the cable. The headphone part is the same.
The ‘Plus’ part is the fact that it comes with 16 different ‘shields’ which can be replaced using the supplied allen wrench.

Besides the ‘custom’ shield replacement trick this headphone has another trick on its sleeve. You can ‘customize’ the amount of bass in 4 steps. In practice those that are looking for balanced sound with a bit of bass boost there are only 2 ‘steps’  available.
The first position could be interesting in a studio when monitoring. The last step… well maybe usable for monitoring too. Monitoring… not mixing.
That’s why there is a ‘studio version’ I reckon. Strangely enough there are reasons why I don’t find it a studio headphone at all. Its build quality is certainly useful but the power rating is what makes it not that suited.

The headphone itself is comfortable but the pleather pads can get a bit sweaty and sticky. They are soft and feel pleasant. The headband and gimbals construction is the same as the DT770-990 series and works well. Enough adjustment possibilities. Excellent clamping force and sits on the head quite well even when moving around.
Very Beyerdynamic as it were. Both the pads and headband padding are (easily) replaceable.

The cable is replaceable and has a thick 3.5mm TRS plug with a little ‘slot’ in it on the headphone side. This ensures the cable sort-of clicks and doesn’t rotate in the cup.
The cable feels ‘cheap’. It isn’t thin nor rediculously thick. It is a bit long for portable duties and a bit short for ‘sitting at home in the relaxed chair a few meters away from the stereo’ duties. It is somewhat microphonic though so you can hear the cable rubbing on clothes and when touching it. The cable connects to the left cup. Signals to the right cup go through a small cable running through the headband.

The COP has a rather low impedance so this kind of rules out it being used with transformer less tube gear. But in all honestly, those buying that expensive kind of gear won’t be interested in the COP anyway.
A low impedance means it is well suited for portable duties. Together with the low power rating (100mW) makes it look like the driver was designed for this goal.
This makes it less suited for studio usage where higher impedances are more common and higher power ratings are more practical. Some musicians have the habit of using headphones as small ‘monitors’ hanging around the neck or have them lying on the desk and play them like small ‘monitors’. This will most likely destroy the drivers.


Type: Over ear, closed
Usage: Home, Studio, Portable
Isolation: decent, 18dBA
Driver type: dynamic
Pads: replaceable, pleather (faux leather)
Inner Pad dimensions: depth = 23mm, ∅ 55mm (22mm, ∅ 58mm velour)
Collapsible: No
Headphone connector: 3.5mm TRS socket with a small slot.
Cable entry: single sided (left)
Cable: 1.5m terminated in 3.5mm TRS with screw-able 6.3mm adapter + 1.3m headset cable with microphone and 1-button remote with a 3.5mm TRRS plug (CTIA compliant).
Driver size: ø 40mm
Nom. power rating: 0.1W (100mW)
Max. voltage: 1.3V
Max. current: 70mA
Max. S.P.L.: 116dB
Impedance: 16 Ω
Efficiency: 96dB/1mW (114dB/1V)
Weight: 290 g.
Colour options: black, white
Clamping force: low-medium
Accessories: 1.5m terminated in 3.5mm TRS with screw-able 6.3mm adapter + 1.3m headset cable with microphone and 1-button remote with a 3.5mm TRRS plug (CTIA compliant), 16 custom ‘shields’, allen wrench.

Sound description:

Setting 1 (all ports closed):
Bass sounds ‘anemic’ and lacks deep rumbles. It sounds ‘pinched off’ in the lows. Mids sound clear ,’open’ and quite dynamic but also a bit ‘hollow’. I see no reason why someone would ever want to use this setting for hifi usage. For monitoring this setting could be usable.
Upper treble lacks nuances. Treble is present though somewhat subdued and completely lacking the ‘beyer peak’ in the treble.

Setting 2:
Bass sounds present and has deep rumbles as well. All bass notes are there and bass sounds ‘full’ but the quality is not the best and lacks ‘definition’. Those that are looking for excellent bass won’t find it in this headphone.
Mids sound clear ,’open’ and quite dynamic, but like the bass, are also lacking in ‘definition’ and ‘finesse’. The mids are lacking in ‘clarity/presence’ and sound a little too ‘laid back’ for me.
The treble quality is a bit on the ‘coarse’ side and lacks finesse and refinement. Treble is not sibilant nor sharp but on the correct level. The infamous ‘beyer peak’ is not present. Alas ‘air’ is also missing.
Excellent qualities for monitoring but less suited for ‘Hi-Fi’ sound enjoyment.
It’s not that the sound quality is poor. The sound is very balanced with deep lows and no annoying peaks or dips. Very dynamic and ‘open’. It just does not excel in the typical audiophile qualities.
This setting is the most ‘neutral’ setting it hass.

Setting 3:
Bass sounds a bit ‘fat’ and ‘uncontroled’. Mids are ‘warmer’ than neutral. Guitars sound a bit ‘resonating’. Aside from the bass and lower mids the sound is still ‘open’ but a bit less dynamic than in the ‘2’ setting. Like the bass the mids are also is lacking in ‘definition’ and finesse’.
The treble quality is the same as on setting ‘2’.
This setting is usable on music that lacks bass and ‘warmth’.

Setting 4 (all ports open):
Bass sounds ‘fat’ and ‘wooly’ and is disattached from the mids and ‘hollow’. Just like setting 1 I see no reason to use this setting for ‘Hi-Fi’ sound reproduction.
Mids sound hollow and have a an overly ‘warm’ character to it. Treble sounds a bit more subdued because the upper bass/lower mids peak ‘mask’ the upper mids and treble somewhat.

This basically leaves 2 usable settings for music lovers. The first and last setting may be usable for monitoring purposes only.


Below the frequency response of the COP in setting ‘2’ (Left, Right)FR (2)Channel matching is good above 300Hz. Below 300Hz there are some differences which could be caused by one of the sliders not sealing properly (one is a bit ‘loose’) or could be because of some ‘leakage’ around the 3.5mm TRS jack in the left cup. When the small hole in setting ‘2’ is observed and seeing the impact that makes on the sound it is easy to conclude that a small leakage somewhere in the cup can have a noticeable influence on the sound.
Bass is well extended and flat to 20Hz. A small (5dB) bump around 100Hz is most likely responsible for the bass quality. Mids are neutral (flat) between 150Hz and 2kHz.
The dip between 2kHz and 7kHz could be slightly less in reality (just a few dB) because of so called Concha gain. As the drivers are not angled the effect is very small at the most. This means that a ‘dip’ is audible in the upper mids/lower treble. This is responsible for the lack of ‘details’ in the mids. The lack of ‘presence’ and ‘clarity’ thus.
This makes instruments less ‘detailed’ and less ‘refined’.
The COP does not have the infamous ‘treble spike’ so there is no sibilance nor any sharpness at all. In fact the treble is bordering on being somewhat sudued. The treble lacks ‘air’ and ‘finesse’.
ports COP
Below the frequency response of the COP in all 4 settings.
1 (all ports  closed as shown on the left in the picture), 2 (most neutral setting), 3 (more bassy) and 4 (all ports open as shown on the right  in the picture)4 pos FR (Left)Setting 1 is bass shy and hass a ‘warmish’ character to the mids. Setting 2 is the most ‘neutral’ one. It has good bass extension and a small boost (+3dB) around 90Hz. Setting 3 has a noticeable bass boost (+6dB) which works well with recordings that lack ‘body’. Setting 4 has too much mid bass boost (+9dB) which bleeds into the mids making the sound ‘fat’.

Below the frequency response of the current Custom One Pro Plus. Settings 1, 2, 3 and 4

4 x FRThere seem to be some differences.
Didn’t check, but these differences may come from the pads. The COP had worn and flaking pads (second hand) and the COPP had new pads (and had many hours on it already). Below the measured response overlayed with the drawing on the box of the COP. The drawing has some resemblance … just not very much and certainly not as described on the box.

beyer COP overlay
Below the differences between the COP and newer COP-Plus in ‘2’  setting.COP-GD - COPP-TL


Getting a good seal is important for closed headphones. The soft leather earpads (cushions) help with getting a good seal. However, wearing glasses or hair between pads the head or bone structurede may affect bass response.
Below the Right channel is shown (setting 2).
Perfect seal
, wearing glasses with ‘thin’ arms, wearing glasses with ‘thick’ arms, bottom part of the pad slightly lifted so loss of seal. seal (2) RThe COP is suprisingly insensitive to seal loss for a closed headphone.  There is little to no audible differences when using thin armed glassed. It even get’s slightly more neutral even. Thick armed glasses leads to an audible loss of lows (5dB lower) but still sounds full and fairly extended. A complete loss of seal (lifted pads) leads to a more ‘cuppy’ sound and loss of body and bass.

output resistance / damping-factor

As this is a dynamic headphone the frequency response might be amplifier output resistance dependent when certain higher output resistance amplifiers are used.
To test this the headphone is measured via a low impedance amplifier (0.2Ω) and a high impedance amplifier (120Ω).
On a higher output resistance amplifier the output level will be considerably lower. To compensate for this the amplifier is cranked up to the same level (17dB at 1kHz) as the low impedance amplifier. This way the plots are overlay-ed and it is easier to show the tonal balance differences.R120 (2) 17dBAs can be seen the tonal balance of the does change tonal balance when driven from higher output resistance (desktop) ampifiers. About 5dB more (lower) bass is very audible. I don’t recommend using this headphone from devices with an output resistance above 10Ω.

Below the distortion measurements of the COP in ‘2’ position (Left channel)DIST (2)

Below the same distortion plot but with the vertical scale in percentages instead of level differences. Dist (2) L percent

The distortion in the bass is very high. The fact that the 3rd harmonics are high is pointing towards clipping alike non linear behaviour. 10% is audible but one has to remember this is measured at 90dB SPL so will be lower at more normal levels.
On top of that one has to remember that higher distortion levels below 100Hz are not really audible as distortion but rather as ‘coloration’ of the sound.
The 2nd harmonic distortion drops below 1% at 70Hz but remains kind of high till 2kHz and still above the limit of my measurement rig.

Below the CSD of the COP (setting 2). (Left and Right are superimposed)CSD COP (2)The CSD is actually quite impressive. There are no resonances that are problematic. Above 4kHz the plot shows there are several (very short lived) resonances but this is well audible levels.

Below the spectrum plot of the COP, setting 2 (Left channel) which doesn’t show any alarming issues at all.Spectr Cop 2 L

The step response plot below shows very little and short lived ringing. The initial rise does not reach the 0dB line and is indicative of the lack of ‘detailing’ and ‘attack’.
(Sub)bass extension and overall tonality is great given the horizontal trace on droops slowly and does not show much dips or peaks.
step (2) L


The main reason the COP lacks clarity and resolution is caused by the pads. Fortunately these can be exchanged for other pads.
The pads this second hand COP came with were already flaking.COP pad

I have no idea how old this headphone already is but has only minor scuffs so seems to have been handled carefully.
Most pleather pads start to flake after a while.
The leather look is made with a thin layer of PVC which covers cloth. Temperture, sweat, becoming ‘sticky’ and compression etc. wear out the very thin (and thus soft) PVC layer.
Of course these can be replaced and may well be available for some time as well.
Personally I like the comfort and feel of Beyerdynamic velour pads. As it turns out the DT770 pads fit well on these headphones. They are harder to get on there as the original pads but once on there fit like a glove. DON’T use the DT990 pads as the sound will be bassless even on setting 4. So only the Beyerdynamic EDT 770 V pads (for the DT770) can be used. When these pads are fitted the FR response and sound quality changes for the better. The ‘beyer treble peak’ appears as well though. To address this some additional damping (1 ply of  2ply toilet paper) is needed.
There also is a black velour version called the EDT 770 VB which looks nicer.

Below the differences between the stock COP (not modified) just sporting the grey velours pads, the modfied COP (see description below) with grey EDT 770 V pads and the modified COP with black EDT 770 VB pads.COPP vel-PU modGY - mod-Bl

While opening up the cups I noticed the driver is quite open at the rear and the back of the cup is flat and can reflect higher frequencies back. So adding some felt inside the cup won’t hurt the sound.
So 3 simple modifications can (to my ears substantially) improve the performance of this headphone. EDT 770 V pads, toilet paper and some 1mm felt (crafts store) or washable kitchen wipe (used here) and some double sided tape is needed.

Remove the pads by simply pulling them off. You end up with the situation below.pad removedThe next step is to remove the inner ring that holds the foam in place. This too is not very hard to do but requires a small flat screwdriver. Simply stick the screwdriver between the ring and the cup. Look for a spot where there is some room to stick the screwdriver in. The spot indicated below works well. Gently pry the ring upwards till it pops out.
The ring and foam disc are removed creating the situation below.

COP driver front

When the cup is held upside down the baffle with driver simply drops out. Be sure the keep your hand below it as the driver is connected with wires which you don’t want to break off. Below the rear of the driver (right cup) and the cup.

COP driver rear

Cut a disc of felt somewhat larger in diameter as the actual driver and put some double sided tape on it. Cut out a small circle about the size of the tube in the middle of the cup.
damping COP

Stick the felt disc to the bottom and put the driver back in. Ensure the wires are ‘free’ and note the small tab on the baffle and ensure this fits in the notch in the cup.

Take a sheet of soft 2 (or 3 or even 4 ply) toilet paper and cut a disc of the same size as the foam disc. You can use the disc as a template.
Now the individual plies need to be pulled apart. This is illustrated in the picture below.


You will end up with 2 (or 3 or 4) individual plies of toilet paper. Put 1 ply on top of the driver as shown below.front damp COP

Put the foam disc back on there and push the ring back in place. Mind the orientation of the ring. The small ‘pins’ that hold the foam must be down. There is a small tab that must fit in the slot again. This is shown below in the red circle. Simply press the ring back in

When the DT770 pads are put on the headphone looks like this:

COP vel

Below the measurements of the differences between a stock COP with pleather pads versus the modified COP with 1 ply and DT770 pads (both in 2 setting). The plot below is smoothed (psychacoustic smoothing) which gives a better idea of how the tonal balance changes.COP stock 2 vs modif 2 smoothedBass levels around 100Hz are lower. Subbass is now boosted a little. The perceived dip around 7kHz is gone. A small (+3dB) peak is now in its place filling in much of the ‘void’ in the lower treble. Frequency extends slightly better and is on the proper level.
What remains is the very dynamic sound and the tonal accuracy of the mids. What improves is the bass quality and quantity and above all the resolution and clarity/presence is there. Everything now sounds detailed and has ‘nuances’ that lack using the original pleather pads.


Below the frequency response of the modified COP with DT770 pads in all 4 settings. (no smoothing) Setting 1, 2, 3 and 4 (all ports open)FR modif 4 pos

Setting 1 is unusable unless you really hate bass… Setting 2 sounds very balanced with deep bass, neutral, dynamic and detailed mids. The treble is sparkling but not sibilant and of better (more pleasant) quality and detailed. There is enough air but not the ‘ethreal’ kind.
Setting 3 is very similar to setting 2 but has more bass. This works well with recordings that aren’t ‘full’ sounding and adds a good ‘body’ to those recordings.
Setting 4 is too bassy but not really suited for bassheads as these seek much higher levels of subbass. Bass is a bit bloated and ‘fat’ in this position.

Below the frequency response with a single ply of toilet paper. Left and Right.
COP modif (2)

When both the COP and COPP have been modified they measure and sound identical.COPmod2 BU - COPPmod2-OR

This gives me reason to believe the drivers have not changed when the COP became the COP-Plus.

Below the distortion measurements of the modified COP with DT770 pads in ‘2’ position (Left channel) with the vertical scale in percentages instead of level differences. Dist (2) DT770 percent

The distortion is about the same as with the original pads. No improvement here as the distortion is caused by the driver itself and not the pads.

Below the CSD of the modified COP (setting 2). (Left and Right are superimposed)

CSD modifThe CSD of the original pads looks a bit ‘better’ below 2kHz but the treble response is a bit less ‘jagged’. Resonances appear ‘worse’ but is caused by the levels starting a bit higher in the plot.

Below the spectrum plot of the modified COP. There is a bit more lingering around 700Hz and in the bass but around 2kHz the response is improved.Spectr modif (2)

Below the step response of the modified COP.
step DT770 (2)
Bass extension and linearity as well as impulse response is improved. There is a small emphasis (the small second peak) in the 7kHz area but aside from that the response is pretty good with short lived resonances.

Squarewave and impulse response

Below the 40Hz, 440Hz and 100μs impulse response oscilloscope plots of the modified COP.


The 40Hz squarewave reproduction is close to ‘perfect’. The measured signal follows the applied signal almost perfectly.
The 440Hz square-wave also is quite good. It is just slightly ‘lacking’ in the inital rise which is slightly lower (-2dB) than the applied signal but does not overshoot.
The 100μs pulse almost reaches the applied signal and shows a fast response. There is a second peak that is a bit higher than desirable but is narrow and high in frequency. After that scond peak the membrane is well damped and the resonances following it are low in amplitude and short lived.

variable bass

The Custom One Pro is not the only headphone with a variable bass. The Sennheiser HD630VB also has a similar feature except this is doen electrically with one stepless control which controls both sides at the same time.
Below the response of the HD630VB in center position vs the COP (setting 2) vs the modified COP with DT770 pads (setting 2). ‘Acoustic smoothing’ is applied.RD=COP2 BU=COP7702 = TL=HD630-mid

Another tunable headphone is the Takstar Pro82 in both the ‘early‘ and ‘later‘ version.
The Pro82’s are in setting ‘1’ (least amount of bass) and the COP in setting 2.COP(2) vs 2x P82 (1)


The Beyerdynamic Custom One Pro (Plus) is a reasonable priced closed headphone with an ‘open’ sound. The custom shields are a nice addition for those that care for this.
The headphone is sturdy and well built. Comfort and adjustability is good.
The usability of the ‘tuning ports’ is rather limited to 2 settings basically. A disadvantage is that both cups need to be ‘switched’.
While close to being tonally balanced in setting ‘2’ the headphone lacks finer nuances and ‘details’ in the bass, mids and treble which is a bit disappointing for those looking for the sound of  the DT770/DT990 but adjustable.
Fortunately the DT770 pads fit (although fiddly to get on) which improves on the negatives of the stock COP.
With these pads the modified COP has a nice and deep bass, open, dynamic mids with good clarity/presence and detail. Treble is improved and more detailed and nuanced with more air. It does not have the more ‘ethereal’ treble of the DT990 and DT1990 but also not the sibilance and sharpness these headphones have (without toilet paper mods).

This headphone can be driven well from portable sources but is less suited for powerful or all tube desktop amplifiers. The rather low power rating and rather high distortion in the bass make this headphone well suited for lower (SPL) level listening.

The pads flake rather soon it seems. A good reason to replace them with DT770 pads.
Those pads will set you back another € 20.- to € 25.- though.

Once modified it has an addictive and dynamic full sound that does not appear to have many drawbacks.
For Hi-Fi afficianados there is only one setting usable which makes the variable bass setting not really valuable/usable for those looking for realistic sound.

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