Stax SR-009 and SR-007 Mk1 earpad DIY mods
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zolkis

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After the discussion has started on
http://www.head-fi.org/t/677809/the-stax-thread-iii/4425#post_11309570
it seemed appropriate to start a separate thread on these reversible mods, in order to have things in one place.
Copying here the post, and adding some pictures.
 
  I have joined the club of SR-009 + SR-007 Mk1 owners.
 
Guess what, I tried to improve the 009...
You may remember that I use custom pads with the 007 Mk1's, using a 009 ear pad and some custom stuffing.
The standard 009 and 007 earpad stuffing is made of normal foam, plus a 3 mm thick base, from a denser, rubbery foam.
I have figured out 2 optimum configurations for the 007:
 
Pad1. full carbon foam pads, 105/73 mm diameters, about 15mm high in the back and about 10 mm high in the front
Origin: 
http://www.amazon.co.uk/gp/product/B007NYQDMK/ref=ox_sc_sfl_title_1?ie=UTF8&psc=1&smid=AV0WDM2FFQCUE
http://www.amazon.co.uk/gp/product/B005AK9FQ0/ref=ox_sc_sfl_title_2?ie=UTF8&psc=1&smid=AV0WDM2FFQCUE
 
Pad2. wool felt ring replacing the 3mm thick base foam ring. That means I have separated the base from the foam part with the help of a sharp cutter and a lot of care. I have tried many kinds of felt, and this one sounded the best:
https://www.etsy.com/listing/127274609/3mm-100-merino-wool-felt-7-x-11-20x30cm?ref=shop_home_active_1
(note the colour, other colours sounded more muffled, this was quite clear).
 

On the left, the original 009 earpad stuffing. The lower white ring will be replaced with the grey felt ring on the right. The two parts are glued together using a thin adhesive layer. It almost comes apart by pulling. With a sharp cutter and a lot of care, make an incision between the two foams, then make it deeper, pulling them apart gently, until cut through the width; then advance slowly on the circumference. Then put together the upper part of stuffing from the left, and the felt ring. Do not glue them together. That would block air flow between them and will affect the sound.
 
Since I anyway had the modded 009 ear pads, I tried Pad1 on the 009. Not much change, I actually I preferred the original ones.
Then I tried Pad2, and behold, the 009 has transformed:
- much deeper bass with great clarity and slam
- larger and better sound stage
- no noticeable treble "haze", highs sounded very clear this time.
If you thought the 009 is lacking some bass, now it has it in spades, with excellent control and resolution.
I also have a Fostex TH900 - which I very successfully modded to sound way much better than the stock one - and actually the modded 009 gets quite close to the slam, without the slight overhang. Not bad from a 'stat, huh?
 
I figured out the 007 and 009 pad optima are different. It was the turn for the 007. I ended up with:
Pad3. 3mm wool felt ring base and a carbon foam pad with similar diameters as in Pad1, but reduced thickness: at the back around 10mm, and in the front about 7mm.
When assembled, the pad doesn't feel too thin, it worked for me, but there may be people for whom this would be too shallow.
 
    
 
That worked like a charm. Now the 007 sounded very close to the 009, embarrassingly close, with the following differences:
- more bass slam, about the same extension, but the 009 has a bit better mid-bass and better bass control; however, with instruments, the 007 sounded better in the bass
- more euphonic midrange, some people would prefer it over the 009, some would not
- slightly better defined treble, with cymbals having more attack and decay, the 009 was somehow flatter, but feels more airy and extended
- sound stage is deeper, a tiny bit wider, but less high; also, a tiny bit less focused; however, quite minor difference. Depending on different music I preferred the sound stage of one or the other, but more times the 007.
 
[Added on 20. Feb. 2015]
Pad4, for the 007
Since I have found the neutrality of the 009 preferable for long term, especially with piano timbres, I have experimented with more pads for the 007. With Pad2, the 007 and 007 sound with similar piano timbre, but since the 007 is doing its own thing very well, I was seeking a middle path. That is how Pad4 was born, which is in essence similar to Pad2, by using the same felt ring, and the upper foam part of the original 007 pads, made circular in the interior, and trimmed to 10 mm thickness at the back, and 6 mm thickness at the front. The resulting sound is very open, warm, and midway neutral to the 009, with such a wonderful sound stage that it makes music listening a pleasure.
 
Pad5, for the 007.
For the folks who don't want to ruin an original 007 pad, much of the benefits can be obtained if you replace the lower 3 mm thick white 'urethane part of the original 007 pad filling with the wool felt ring described and shown at Pad2.
 
Also, the 007 sounds quite much better (especially resolution, and I mean not only the treble) without the black dust grill cloth, similar to the older round Stax models, e.g. SR-5 Gold. The slight treble peak at 10-12 kHz is tamed with the felt ring in the pad. The result is really good sounding. Try it out.
[end of addition 20.2.2015]
 
My personal subjective ranking is the following (last updated on 22.2.2015):
stock 007 Mk1 << stock 009 <= 007+Pad1 << 007+Pad5 < 007+Pad3 < 007+Pad2 <= 009+Pad2 ~= 007+Pad4
Details:
- the 009+Pad2 is the reference for neutrality and overall sound quality
- the stock 007 Mk1 sounds rather dark (but not Audeze-dark) compared to the rest, and there is a rather big quality difference to the stock 009
- the stock 009 sounded more open, but sometimes a bit artificial in comparison; there was some musicality in the 007 sound that went dry with the 009;
- the 007 with Pad1 (the carbon foam pad) was a bit more musical/euphonic than the stock 009, and sounded more natural with string instruments and percussion, but wind instruments were more preferable with the 009
- (a big jump here)
- the 007 with Pad5 is the obvious mod for 007 people wanting much of the benefits without any risk
- the modified 009 with Pad2 was so much better then the stock 009 (I played them many times back and forth), there is no way back. I'd say this mod is absolutely recommended to try for 009 owners and it's entirely reversible.
- the modified 007 with Pad3 again sounded a bit more musical, in the way described above, but this is matter of taste. I am sure many people would prefer the 009 + Pad2, which is also easier to drive, and about 3 dB's (a lot) louder, which makes comparisons very difficult. I tried to tell if the modded 009 is also more resolving (in bass, mids and highs), but I concluded they are pretty much similar in resolution. Perhaps I could give the nod to the 009, but mainly out of politeness. Because the more perceived "air", many people would prefer the modded 009.
- the 007+Pad2 is the poor man's 009 headphone, with very similar timbre, a tiny bit more warm, with a bit bigger bass
- the 007 with Pad4 is definitely the high end "fun" headphone, being more neutral than most other TOTL headphones, but warmer and more 'musical' than the modded 009. Purists will still prefer the 009+Pad2 or the 007+Pad2, but I guess most would be fine with the 007+Pad4. 
 
Just for fun, I tried using a parametric equalizer to see if I could "simulate" the sound of one with the other.
The 009+Pad2 sounded like the 007+Pad3 if I bumped +3 dB at 30 Hz, and notched down -3dB at 16 kHz.
The 007 needed a small bump of 2 dB at 8 kHz and 3-4 dB at 16 kHz to sound like the modded 009, but with better bass slam and more velvety mids.
 
An important note here.
The sound quality of the 007 is so much dependent on the shape and fitting of the head band, that it's nearly impossible to get consistent results from people to people. What works for me, doesn't necessarily work for others: it depends on head shape, ear shape etc. The sound described here was obtained with 007 head bands adjusted wide/flat and turning in like the 009 headband does. Moreover, I didn't use the circular spring for the 009 earpad mounted on the 007. 
Removing and assembling the 009 pads on the 007 takes only seconds. By rotating the pads on the 007, the sound changes. I use the front part turned upwards a bit (about 10 degrees), this provides the most open sound and best sound stage.
The best ear pads for the 007 are a bit more shallow than the stock pads, so it won't fit everyone.
There are none of these problems with the 009, they are consistent sounding and more comfortable. 
 
Note #2. If you have never taken off a 009 ear pad, don't try it yourself unless you know what you are doing. I will post pictures later, but it goes like this: 
1. remove the inner dust grill through the ear pad opening (by gently bending inwards and pulling out)
2. by pushing the ear cushions aside with a precision Phillips screwdriver, gently open 4 turns on each of the 6 screws, going round and in diagonal like with car wheel change
3. pull the internal metal ring outwards a bit, and gently take off the pad.
Assembly is in reverse order. 
 
Note #3. All of these pads sound quite flat with a frequency sweep, but I cannot do proper measurements. To my ears it's very clear which sound better, but I oubt the waterfall would measure fundamentally different.
 
Since the modded 009 are still more neutral, more comfortable, and easier to adjust, they are likely the better choice to keep.
Also, the 009 mod is very straightforward, and will give consistent results, whereas the 007 can be set in so many ways that it's easy to get it suboptimal.
However, it is absolutely worth doing it.
 
The mod steps:
1. [for the 007 mod only] Order a replacement 009 ear pad from Stax through your local Stax dealer. That costs 140 euros, quite steep. For the 009 mod, you can use the original pads. The mod is reversible.
2. Meanwhile order the wool felt, it's cheap. The colour matters :)
3. Take the stuffing out of the replacement 009 ear pads. Then, cutting off the foam base is quite easy. Start from outside, with a small, precise cut, gently pull apart, get deeper, then through the whole width, then advance slowly around the perimeter. In the end, if you don't like the mod, you can reverse this step by glueing again together the two parts, using a double sided adhesive film.
4. Cut 2 felt rings of 105 mm external, and 73 mm internal diameter, using an Olfa circular cutter or similar. This is a size optimum for both the 007 and 009 for the given felt type. I have tried a lot of other sizes, including the elliptical original form.
5. Put the foam ring from step 3 and the felt rings from step 4 together, and assemble into the ear pads. Take care of orientation of the thinner part to the front. The felt ring comes to bottom and the foam is closer to the ear.
6. Mount the ear pads, or if you just want to test, it is enough to hold it on the headphones without mounting them (sounds the same and saves from a lot of hassle, especially with the 009).
 
For the 007 with Pad3, in step2 order also the carbon foam, and in step3 cut a similar size ring: 105/73, then trim it by a slant plane thinning towards front, about 10 mm high in the back and 7 mm in the front. It has to be thin enough, otherwise will sound more muffled and dark.
For the 007 with Pad2, Pad4 or Pad5, in step2 prepare the corresponding upper foam part.
As a last step, for the 007 only: adjust the head band and ear pad orientation.
 
My wife solved the issue by liking the modded 007 more, perhaps sound-wise too, but mainly because of the price :).
I have preferred the modded 007 almost every time, but that's telling about my taste, not necessarily the sound quality. Also, it is a very personal headphone, adjusted to my own head...
Since I am primarily a speaker guy, I will be content with the modded 007 Mk1 (and modded TH900), hopefully for a long time.
I have a prospective local buyer for the 009 with either stock or modded ear pads, but if it doesn't go through, one of you may get world's allegedly best 009 soon :).
I will repeat the whole experiment with an incoming BHSE, in a couple of weeks.
 
I am thinking about making a separate thread about modding ear pads for different headphones, so far the 007, 009, TH900. They make a lot of difference. Now I wonder what could I make of an LCD-3, since they seem to have the darkest and worst sounding ear pads, but that's another story... The best stock pads I've seen on a headphone are with the HD800 and to somewhat lesser extent the K812. I wouldn't even try improving those.  Anyway the modded Stax sound way much better (IMHO and YMMV :).
 
For most people I would recommend the modded SR-009: it's easier to mod, with more consistent results, and has better comfort.
For dedicated 007 Mk1 lovers, the road will be worth exploring despite the difficulties, and anyway you're already used with it :).
 
See the follow-up post here:
http://www.head-fi.org/t/677809/the-stax-thread-iii/4440#post_11315101
Arnaud makes a couple of important observations:
Earpad is critical indeed but it's only one part of the equation. I certainly do not believe all the difference between the 007 and 009 is coming from the pad exclusively. The enclosure differs, the drivers size differs, the stators differ, the membrane material differs, the DS gap differs. Most of all, one is miles more resolving (007 treble is a 10kHz peak, 009 is more even there and doesn't rely on one resonance to resolve treble). Sounstage layering is so much more precise on the 009, a pad can't possibly be the only factor for this.

I am not saying pad doesn't matter, far from it. Heck, I even showed the hughe influence of pad design on stat phone tonal balance some time back in the diy thread. i also think zolkis work is fantastic / really worth exploring to fine tune the phone to ones taste.

The distance from the driver to the ear, the orientation, the amount of leakage through the pad, the volume of the earpad cavity, all these parameters have a huge influence on any headphone response, and stat phones in particular as they very much rely on this loading effect (more so than typical massive ortho or dynamic phones driver).
But saying all the 009 innovation lies in the pad is silly.

Arnaud
 

   
These are indeed valid factors. The 009 has better technology for sure. The increased efficiency alone may be enough reason to prefer it. Also, I noticed that the 009 is far less sensitive to ear pad changes than the 007 Mk1. And it's easier to adjust to head, and more comfortable. And the sound is more neutral (the modded 007 Mk1 is still warmer and more euphonic).
 
I think it is safer to say that it was the 007 Mk1 which was held back because the ear pad. Even with the stock 009 earpads it sounds much more open, but then the small change in stuffing elevated it to a new level. It became more open for sure. The felt ring helped the treble, midrange and bass resolution. The sound stage layering IMO is on par with the modded 009 and better than the stock 009. The 009 has all the reasons to sound better, and perhaps it needs a more educated ear and precise measurements to tell which is objectively better. However, based on my auditive perception and a wide range of music I listen to, both the 009 and 007 Mk1 sound much better now, and are on about the same level of "enjoyability". Yes, there are small differences here or there, mainly coming from the different optimal stuffing, and in rest, to smaller extent, from structural differences. And when it comes to the subjective terms of musicality, I slightly prefer the modded 007 Mk1 overall, albeit I like many things with the 009 more. I am sure there would be people to keep both, but I am fine with the modded 007 Mk1.
 
Please note that I said that I have found the stock 007 Mk1 quite much inferior to the 009. But then the modded 009 is much better in my opinion than the stock one, especially in the bass (extension, resolution, resonance), in the deeper sound stage and in the clarity of tones.
 
I would advise adventurous 009 owners to try my mod, it will cost them about 5-6 euros for the wool felt pad, 15 euros for the Olfa circular cutter, and 10-30 minutes of work. It's hard for me to imagine someone won't like the results more than the original, but in that case the mod can be reversed. There is no better test than verifying the claims by independent parties.
 
For 007 Mk1 owners the situation is more complex, since a replacement 009 pad is needed, and even small changes in the carbon foam part have audible effects. I will start a thread with steps, exact dimensions, and pictures.
 
 
Finally, images of the modded headphones:
 

 
 
Edits:
- added a clarification that replacement pads are only needed for the 007 mod.
- note that Pad3 also applies to the Fostex TH900 with the exactly same dimensions (though the TH900 can accommodate slightly higher pads too)
- 22.2.2015. Pad3 replaced for Pad4 or Pad2 for the 007. This makes the use of carbon foam unnecessary for the Stax mods.
 
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edstrelow

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Thanks for the pix. I also keep tropical fish and wonder about the carbon foam you use.  The carbon material I use in fish tanksdrops bits of carbon and I generally wash it before using it  in a tank.  I am not familiar with this exact foam however.  Does this stuff need to be washed?
 
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Subscribed, it's so refreshing to read someone tinkling with stat phones! I'd be very tempted to give it a try, need to get the courage to pry the 009 open :-O
Arnaud
 
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Very nice. I will refer to this thread once I get electrostats!
 
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As I understand it you have removed the stuffing material in the earpads and replaced the foam with carbonized foam and used a different foam ring. Why is it necessary to buy new earpads to do this? Their price is pretty steep. Can't you just use the existing one and replace the original stuffing if you don't like the sound of the modded ones?
 
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  Thanks for the pix. I also keep tropical fish and wonder about the carbon foam you use.  The carbon material I use in fish tanksdrops bits of carbon and I generally wash it before using it  in a tank.  I am not familiar with this exact foam however.  Does this stuff need to be washed?
 
A brilliant question, you know your stuff :).
In order to avoid misunderstandings, the carbon foam only applies to the 007 MK1, although it could be used with the 009 as well - but I preferred the 009 with its own foam + the felt ring replacing the 'urethan' ring.
To answer the question: if you buy the carbon foam filter from the amazon link I included (which is meant for fish tanks), then yes, you need to wash it.
If you buy carbon foam filter made e.g. for kitchen ventilation, then you don't need to wash, albeit you're free to do it.
 
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As I understand it you have removed the stuffing material in the earpads and replaced the foam with carbonized foam and used a different foam ring. Why is it necessary to buy new earpads to do this? Their price is pretty steep. Can't you just use the existing one and replace the original stuffing if you don't like the sound of the modded ones?
 
If you are modding the 009, then you don't need to buy replacement pads. I will edit the post to make this clear.
The 009 mod is reversible, by glueing again the two parts together with the help of a double sided adhesive film.
 
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If you are modding the 009, then you don't need to buy replacement pads. I will edit the post to make this clear.
The 009 mod is reversible, by glueing again the two parts together with the help of a double sided adhesive film.
Is the 007 mod reversible too or do you need the replacement pad?
 
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  Is the 007 mod reversible too or do you need the replacement pad?
 
The 007 mod means getting a 009 pad, which is absolutely needed, and replace the original stuffing with Pad3, i.e. does not modify at all the original stuffing. And of course the original 007 Mk1 earpads do not need touching at all.
 
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Update: for the 007, Pad3 replaced for Pad4, or Pad2. That makes the use of carbon foam unnecessary for these mods. They made a good application for the Fostex TH900, though. I have updated the initial post.
 
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How does one remove the SR-009 earpads?
 
See Note2 in the first post, now also here.
 
1. Remove the inner dust grill through the ear pad opening (by gently bending it inwards and pulling out). This will leave the wire mesh visible, and the upper black metallic ring which is mounted with 6 screws. You will need to loosen the screws next.
2. By pushing the ear cushions aside, use a precision Phillips screwdriver and open 4 turns on each of the 6 screws, going round and in diagonal like with car wheel change. Calm, soft, careful movements.
3. Pull the internal black metallic ring outwards a bit, which will make space for getting the ear pads off, and by going around the edge with the finger, gently take off the pad.
Assembly is in reverse order. 
 
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Hello gents. Please bear with me , I'm a 'newbie' to the whole Stax arena, having just acquired a pair of the SR-007's. Question - there is some sort of 'spacer'? baffle-screen type thing that is behind the earpad grille. Any idea what it's purpose is??
 
Thanks to any & all who can clarify.
 
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