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Headphone Pad Thickness Effect

solderdude

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There has been some discussions about pad thickness.
Mostly about the DT990.

I took some headphones I have lying around (all with lots of hours on it already) and put these on my flatplate. Measured the pad thickness on the outside and then pressed them onto the rig using velcroband around the rig/headphone and compress the pads.
This is not a scientific study nor is this done on a HATS and the measurements are done without a pinna.

This makes a different situation from reality where your pinna is inside changing the air volume and masking of rear sound.
It should be noted that when the pads are completely compressed (in most cases) the pinnae are bent so this too will have a different effect than what is shown here.
Especially in the region above 5kHz.

Anyway enjoy these utterly crappy and flawed measurements.

Lets start with the DT880 Black Edition but this one has the grey pads on them as these are less 'mid-bassy'.
These are the exact same pads as would be used on DT990 and already are softer than new pads.
It is interesting to note that the grey pads actually take a lot less pressure to compress than the black DT880 pads.
DT880.png

What can be seen above is that when the pads are compressed (green is normal pressure) that the amplitude of frequencies below 4kHz increase while above it they don't. Effectively, seen from the area between 100Hz and 1kHz, where we base our perceived loudness on, not only the amplitude changes but compared to the not changing treble that treble is seemingly lower. The efficiency increases effectively for the lows and the mids.
It should be noted that any normal user would not use this fully compressed as your pinnae would be crushed and is uncomfortable as hell. One would probably start to replace already at the 'blue' stage. Your pinnae would already be touching the foam on the drivers.
A similar effect will be seen on the DT990.

Interestingly enough, because the pads are compressed the foam becomes 'stiffer', which would not necessarily be the case when foam decays, you also see the 'pad bounce' frequency go up. Above nearly 200Hz (red), near 100Hz (Blue) and near 60Hz (green).
Yes... ignore the 50Hz wiggles.. it's mains leaking in the mic capsule.

Below the DT1990 with original A pads (the Analytical/flat sounding ones)
DT1990.png

Here the same effect is seen. Hardly any changes in the area above 4Hz but much more below 600Hz. These pads are firmer (less soft) than the grey ones and takes more pressure to compress. I reckon they will stay in shape much longer than the grey ones. Relatively the treble becomes lower while in reality the efficiency for lower frequencies becomes 10dB higher and between 1kHz and 4kHz 5dB higher.
Here too we see pad bounce shifting in frequency.

Below the HD560S.
HD560S.png

Upto 4khz the tonality not change much but for higher frequencies there are some changes especially in the 6khz range. When the pads (who are quite firm and take a lot of force to compress) are compressed and the drivers are angled the effects above 5kHz will differ depending on your pinnae.
Overall the tonality changes are smaller than those of the Beyers. Pad bounce also shifts frequency here.

Below the HD650 (black screen with old pads). As these are older pads (more comfy than newer pads) the green line is not present. That is reserved for newer pads.
The used pads here are already 20 years old and are very easy to compress.
HD650.png

A tonal balance change is observed when the pads are compressed even more. The change with the HD650 however is more of a tonality 'tilt' change.
Yes, it gets 'darker' sounding over time but not as extreme as the Beyers.

Below the X2HR. It should be noted that this headphone is modified. It has the bass boost lowered and the treble peak lowered using a filter.
These pads are quite thick and take a lot of force to compress them about 7mm.
X2HR.png

The tonal balance also changes but more similar in effect than the Beyers (below 1kHz). Overtime the headphone thus becomes a but less 'clear' sounding. Pad bounce hardly changes (190Hz) with these stiff pads.


below the K702. I tried to maintain the angling of the pads (relatively) but of course the angle gets smaller when the depth changes. These pads are thick and firm so take a lot of force to compress. Didn't test the memory foam pads (should have in hindsight) which compress much easier.
K702.png

There is something interesting going on. The efficiency above does not change much. Not more lows when compressing but instead lows get relatively softer.
The resonances I see clearly shift due to the changes in driver distance. These peaks will thus be lower when measured with a HATS as the reflection surface isn't flat in reality.


Below the most interesting one. The Hifiman Edition XX. I have nor reason to believe other similar looking models will behave much differently.
Edition XX.png

No tonality increase in efficiency nor tonality changes. Well.. in the clarity range (1-3kHz) the tonality changes very little. It becomes a bit clearer sounding as pads compress. 12mm compression is a LOT though. The same thing as with the K702 happens in the upper treble range. The resonance shifts a bit upwards because of the driver distance and air volume changing. This peak will also be pinna dependent.

Contemplating adding these tests to my regular measurements.
 
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samwell7

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Great work, thanks for this!

Might be worth adding to regular suite of tests (if it isn't too time intensive, that is) as it shows the real-world effects of wear-in or 'burn-in'.
 

Feelas

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Impressive and very informative! Also, @solderdude, I wonder whether there would be dependence between compressing the pads and THD dropping - since there's less air to move, correct?

A few years ago, there were two ... well, maybe not really popular, but at least discussed on Polish forums, mods for HD-681 and for Creative Aurvana Live! - both were the same: just push something undeneath the pads to extend them as far upwards as possible; back in the day I can remember there were some esoteric descriptions on what's happening, and yet now it makes sense that it could really work.

It'd also be interesting to see how decreasing the clamping force (e.g. by stretching the headband) but not as much as to cause leakage to happen, changes the response. So, in essence just doing the same but backwards.
 

amirm

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Anyway enjoy these utterly crappy and flawed measurements.
Actually it is exactly the opposite and highly useful research and data. Promoting to home page.

Edit: took the liberty of making the title more descriptive. Hope you did not mind. :)
 

cursive

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Thanks for the work, another excellent post!

@solderdude May I ask what rig you use to do these measurements? And is it the same rig from diyaudioheaven?

So interesting to see yet another variable of headphone listening that often gets overlooked. Between pad thickness, head size, clamp pressure, ear shape/size, I'm convinced no headphone could possibly sound exactly the same to two different people lol.
 
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solderdude

solderdude

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It'd also be interesting to see how decreasing the clamping force (e.g. by stretching the headband) but not as much as to cause leakage to happen, changes the response. So, in essence just doing the same but backwards.

All pads (except for the old HD650 pads used here) hardly compressed so the green lines are about the minimum needed for a good seal on a FP.
Lowering the clamping force will most likely lead to seal loss. Not a really big problem for open headphones but it will be for closed ones.
Of course on human heads (which vary is size and shape substantially) all bets are off when it comes to seal.
Seal loss usually shows itself by loss of the lowest frequencies and sometimes a boost in the 200-400Hz range.
In a lot of my recent reviews seal loss is shown. That's as close as you can get to the reverse of the above.

There are headphones that hardly react to seal loss. For instance the D8000 (shown below)
seal-loss2.png

proper seal, substantial seal loss

Also the HD560S retained tonality even when lifting the pads slightly which surprised me.
seal.png

full seal, thick armed glasses.

There were also popular mods where paracord rope was stuffed under pads and made measurements of that too.
Below the SRH1440 where the owner had included the paracord and was interested to see what that did.
paracord.jpg

You can see the paracord under the pads which pushes the pads outward (but doesn't absorb low frequencies which pads do)
paracord-mod-1.png

without rope, with rope

@solderdude May I ask what rig you use to do these measurements? And is it the same rig from diyaudioheaven?

Yes its that rig.
 

ishouldbeking

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Something interesting to consider is how two different users might get an objectively different response from a particularly clampy headphone depending on the respective size of their heads and the headband design. Not hard to imagine pads compressing more for some users than others.
 

HereYaGo

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D8000
seal-loss2.png


hd800s
fr-hd800s.png


One day there will not be treble peaks and things will sound clear and natural and not mangled.
 

respice finem

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I still remember my first headphones, 45-ish years ago. These look identical: https://www.springair.de/en/mb-quart-k-600-headphones/h52946
Its liquid-filled pads had perfect fit (for me) and did not change at all for about 15 years, then the plastic around the liquid became brittle. I wonder why nobody seems to be making liquid-filled pads nowadays, after all today's plastic varieties are way better (or maybe their longevity is the very reason for "extinction"). :cool:
Today, we have elastomere-like stuff or memory foam, but with daily use, don't expect pads to last >2-3 years (own experience), and as they age (as has been shown here) the acoustical properties of the headphones are changing.
 
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solderdude

solderdude

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How long pads last will depend on:

Clamping force
Humidity
hours of usage
proper cleaning
used foam type (or gel or whatever is in there)
used cover material (thickness and type of material) in case the pads are not all foam.
body fluids reacting with the pad material
start 'thickness' of the pad material
temperature
How far ears stick outwards and one finds touching the pinna a nuisance.
How the headphones are stored (fuming of plastics or hardboard etc)
smoking or non smoking environment

there are probably more reasons.

Needless to say pads are consumables.
Aftermarket pads mostly change the sound signature often even more than just pad degeneration. This also depends on the used headphone (type). Here is something I wrote 5 years ago about how different pads measure differently on different drivers. It clearly isn't just pad thickness.
Pads are one of the tools that can be used to 'tune' a headphone. Even when on the outside they appear very similar they can vary substantially in acoustic properties. The Beyer DT770 pads and DT880/990 pads are difficult to tell apart just looking at the velours but differ substantially.
So are DT1990 and DT1770 pads in the same way.
Below the DT1990 that comes with 2 different pads. The Analytical and Balanced pads. The A pads turn the DT1990 more into a DT880 and the B pads turn it more into a DT990 alike signature.
DT1990 pads.png


Likewise the DT1770 sounds very different when slapping on different pads.
DT1770 pads.png

Those differences can be up to an extremely audible 10 to 15dB.

For HD800 for instance (not so for HD820) the pad thickness won't really matter as the driver-ear distance hardly changes because the pads are very thin to begin with. It will more be a comfort issue for these phones.

So you can use different pads (that mechanically fit) to change the sound of a headphone. This can be anything ranging from a total disaster through hardly any changes to a complete success. In general the choices made by reputable manufacturers are what the manufacturer was aiming for.
Not all headphones are intended for music enjoyment. Using those not meant for this may not always work out well. Might be solved with different pads.. might not be.
 

JohnYang1997

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Great information.
However I think all headphones change sound when the earpad is compressed because it will eventually compress the pinna hence changing the sound that way. And the actual change in frequency response would be different than here in the higher frequencies.
Great effort nonetheless.
 

JohnYang1997

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How do you control the compression? I would like to try this but seems difficult to do.
 
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solderdude

solderdude

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Great information.
However I think all headphones change sound when the earpad is compressed because it will eventually compress the pinna hence changing the sound that way. And the actual change in frequency response would be different than here in the higher frequencies.
Great effort nonetheless.

Yes, that's why I mentioned that factor is not calculated in there. To test this one has to use really soft and compliant fake pinnae and even then these might not bend like mine or yours.

How do you control the compression? I would like to try this but seems difficult to do.

I use velcro band (about 1m) and pull this around the headphone. I can tighten that band to specific pad depths by inserting something between that 'belt' and the rig and measure pad depth when tightening that 'belt'.

Have been using this method for quite a while because the FP doesn't always achieve a perfect seal with face contour shaped pads (think Ananda for instance) and then I lightly compress till I get a proper seal to measure.
 

LearningToSmile

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Very interesting data.

One thing that I've also noticed with some pads(ok, just with my Elear pads)is that when they were new the pad softness changed when they were warmed up - so if I put them on cold they were pretty stiff, and once I wore them for a bit and they were warmed by my body temperature they got more pliable. I noticed the slight sound difference but assumed I just got a better seal, but maybe the compression also played a role. This could affect measurements on artificial heads slightly, but I don't think it's common, no other headphone I own behaved this way.

However now that they're worn in somewhat, they don't really get the stiff anymore.
 
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solderdude

solderdude

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Memory foam pads are temperature dependent and soften (take on the shape of the skull) when warmed up.
I haven't seen this with normal foam.

To check whether pads are memory foam or not just push the pad all the way in with your finger. When you release it and pops back immediately it is regular foam. When it comes up a bit slow then it's memory foam.
 

aldarrin

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Do you have any planars and/or estats on hand to try this with? Could be useful next time we have a "but did you get a good seal" thread war...
 
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solderdude

solderdude

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Not supposed to but some become really grudge and the stuff you use to clean them cab have an influence on the foam/cover material.
 
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