Fostex TH900 mods

stjj89 said:

Replacing a th900 driver with another th900 driver.

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Hum, how much did you pay for the driver ? Where can you buy it please

So I found a new mod to make angled pads on stock pad by inserting the cut to shape 2.5 mm non-open cell foam. But then I realized if the ports on the plastic plate got blocked...the bass and the trebles will lose it details and energy. I never thought that these ports affected it by this much. The sound leakage is less pronounced as well. Now what if I apply some acoustic filtering material on these ports ? Would the trebles spikes be less pronounced and preserve the bass ? Hang on

So...today I took the filter on top of Shure 840 pads, and slot into the stock pads . I think I tamed the vocal sibilants+trebles spikes, and doesn't lose much details at all...just as suspected. The 4 ports on the chassis+plastic disc (holder the pads) are ports that control airs into the drivers, which then being controlled further by the foam disc inside around the drivers. Shure840 pads took up 2/3 do these ports priorily. Then the filter ontop of the pads, hence many details were being filtered out....bass lost it punches and impacts due to these ports being restricted.

This explains so much why pads roll effect Fostex sound quality in a way and not just comfort alone.

Shure840 pads had 3 different differences from stock pads.

1/ no hard plate underneath and around the pad rings, just plain leather on foam ring (This created pressure against on top of these ports upon wear), hence it effectively blocking air being vented
2/ thicker acoustic filter on the surface (which attenuates trebles)
3/ thicker leather on the back edges which cover and hug the plastic white rings which effectively taking up 2/3 of the spaces on these vents

So all of these 3 above explained why such nuances details were lost with Shure 840 pads. Now, if you want to effectively filter and attenuates these spikes and sibilants...well, I cut and ruin my shure840 pads, but that is the best filters I have had on these

Final pic

Stock pads filter

Shure 840 pad with thicker foam filters

Stock pad with the cut-out shure840 filters side by side

Stock pad with shure840 filter installed (slotted inside)


Simple, and yet yield a good result as sibilants and harsh trebles extensions get filtered a bit further, the details stand out more, bass is not effected, and it cleaned up the rest of the air-spaces needed to observe and even deeper soundstage

whitigir said:

Hum, how much did you pay for the driver ? Where can you buy it please

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I have a spare TH900 driver.

where you guys get the spare th900 driver?

Question for @zolkis and @playitloud: What did the two of you find when you reduced the inner diameter of the carbon foam pad from 73mm to something between 65mm-70mm? I imagine the sound gets less open, but does it also become warmer and bassier? I'm looking at tweaking my mods to make my TH900 a little bassier and "fun" (rather than neutral like it is now), and I was wondering if the pad inner dimension would be the key to achieving this sound.

stjj89 said:

  Question for @zolkis and @playitloud: What did the two of you find when you reduced the inner diameter of the carbon foam pad from 73mm to something between 65mm-70mm? I imagine the sound gets less open, but does it also become warmer and bassier? I'm looking at tweaking my mods to make my TH900 a little bassier and "fun" (rather than neutral like it is now), and I was wondering if the pad inner dimension would be the key to achieving this sound.

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IIRC the inner diameter was tricky and better to be left alone. If you open it too much, the sound becomes hollow. If you close it too much, you lose on sound stage. I suggest if you want bassier, make the pads higher, eventually add a thin layer of more dense foam than the carbon pads. You can also play with the damper thickness and diameters (much bigger effect per change). 

zolkis said:

   
IIRC the inner diameter was tricky and better to be left alone. If you open it too much, the sound becomes hollow. If you close it too much, you lose on sound stage. I suggest if you want bassier, make the pads higher, eventually add a thin layer of more dense foam than the carbon pads. You can also play with the damper thickness and diameters (much bigger effect per change). 

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Thanks for the advice! May I ask what damper thickness/diameter configurations have yielded more bass in your experimentation? Thicker / Smaller inner diameter = more bass?

Hello STJJ89. I think I have send you some extra material to experiment with. Did I also include the ECRU colored dampers? If I did, you can try those, they are definitely thicker than the white dampers.  You can also try to include the 2mm felt rings in the ear pads. From the perspective of your ear, this is how you position them in the ear pad: ear- leather- carbon foam-felt ring- thin plastic ring- thicker white ring-headphone. That will give you a different kind of sound, more bass if I remember correctly.
If the ECRU dampers give too much bass, you can trim them a bit to get them how you want them. Good luck

playitloud said:

  Hello STJJ89. I think I have send you some extra material to experiment with. Did I also include the ECRU colored dampers? If I did, you can try those, they are definitely thicker than the white dampers.  You can also try to include the 2mm felt rings in the ear pads. From the perspective of your ear, this is how you position them in the ear pad: ear- leather- carbon foam-felt ring- thin plastic ring- thicker white ring-headphone. That will give you a different kind of sound, more bass if I remember correctly.
If the ECRU dampers give too much bass, you can trim them a bit to get them how you want them. Good luck

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Awesome. I'll play around with the Ecru dampers first then. Thanks!

These are new mods, and very EZly effective.

http://www.head-fi.org/t/802704/th-900-fostex-ez-simple-mods-and-other-fostex-dynamic-variants-x00-denon-more-bass-mid-soundstage-smooth-trebles#post_12447388

A few pads measurements, and subjective listening.
 
The basic configuration is this:
- Cups lightly filled with Twaron Angelhair
- Fostex original damper in position #2, or the wool felt damper earlier described in this topic
- Pads: stock Fostex, trimmed Fostex, carbon foam, Brainwavz flat leather, Brainwavz hybrid (also flat, not angled), Stax 007 pads (modded).
 
The stock TH900 pads are measuring so close to the trimmed Fostex pads that I left it out.
 
First, the stock TH900 pads (blue) vs the Brainwavz hybrid (violet) vs the Brainwavz flat (dark green). The foam damper is used in all these.
 

 
Subjective evaluations with a range of instrumental (piano, wind instruments, violin, cello), jazz, and pop/electronica.
The stock pads on the given basic mods described above make a balanced, clean sound at first impression.
 
Compared to the stock, the leather Brainwavz pads are a bit darker sounding (notice the recess at 7 kHz), but with more body and slightly bigger stage. Slightly more ringing with bright piano. The CSD confirms that: very slight resonances (short gentle ridges) at 9 and 15 kHz, and a shorter one at 3.5 kHz. More damping in the cups cures the 3.5 kHz ridge and takes most of the treble ridges as well.
 
The hybrid Brainwavz pads have the same 9 kHz ridge on the CSD, but no ridges at 3.5 kHz and 15 kHz. It sound between the two others, a bit better with electronica than the stock pads, but worse with instrumental.
 
The stock pads have lowest distortion, followed by the hybrid Brainwavz, followed by the leather Brainwavz.
 
I recommend buying the stock Fostex pads, since they are a good start, and can be transformed into something much better, with the carbon foam inserts. Also, one can try the hybrid Brainwavz pads, they actually sound very good, and are more comfortable and have better seal than the stock pads.
 
Based on how the leather Brainwavz pads fared, the angled leather pads will likely have bigger bass (good) and better mids and treble (shallower in the front).
TODO: I need to order them and insert the measurements and evaluation here.
 
Next up, the Stax 007 black angled pads vs the stock pads. Note that these are not the stock 007 pads. I have taken out the filling (it folds out easily) and removed the lower 4 mm thick styrol white base from the foam pad.
After the Brainwavz, the Stax pads sound like fresh air with jazz and instrumental. More body and nicer tones than with the stock pads. Also, much better with the electronic, rock, metal than the stock pads. It sounds like a great improvement, also in build quality and comfort and sealing - a class above the rest so far (also price). They are real lambskin leather, and will last several times longer than the pleather pads. My Fostex TH900 pads were worn out in 2 years.
Let's see how do they measure... the Stax in green, the stock in blue.
 

 
The Stax pads have a slight 3 kHz ridge on the CSD, but otherwise the FR and THD is better than the stock. I definitely recommend these pads, in stock form or modified.
 
Next, the stock pads vs the EZ (Easy, by Whitigir) mods vs the PZ (by Playitloud and Zolkis) mods used with the original Fostex foam damper (i.e. the same damper is used, in position #2).
 

 
The EZ mods are audible, but the measurements don't show much difference. However, the sound stage and the harmonic structure are positively affected.
The carbon pads from the PZ mod bring a noticeable improvement in all areas: sound stage, bass, clarity, apparent resolution, midrange body, etc.
 
Next up, the stock pads vs the PZ mods with the foam damper vs the wool felt damper.
 

 
The stock pads sound as everyone knows.
The PZ mods with the Fostex foam dampers are described above.
The PZ mods with the wool felt damper have less bass than the foam dampers, but sound more open, more clear, midrange much more filled up with life and light, and microdynamics are better.
The foam damper is very good with electronica, metal, rock, pop.
The felt damper is clearly much better with instrumental, symphonic/classical, small chamber, and jazz, and it's also wonderful with other types of music.
If I have to choose one of them to be the default, it is the felt damper. It also sounds closer to my Stax 007.
 
Next, the PZ mods + wool felt dampers vs the Stax 007 with the foam dampers. Let's see if the Stax pads get close to the wool felt - that would be nice.
 

 
And voila... the Stax pads measure more balanced than either PZ mods.
The CSD for the felt damper and the Stax are quite close. The CSD for the PZ + stock foam damper is cleaner.
The THD of the Stax pads and the foam dampers is similar, the wool felt damper are very slightly higher, mostly even harmonics, resulting in more apparent bloom.
 
On subjective listening, the carbon pads still sound better, especially with the wool felt dampers, but the modded Stax 007 pads are close.
 
I will skip listening with the Stax 009 pads on the TH900, since they are next to unobtanium these days and the price is prohibitive.
 
In summary, I do recommend both the carbon foam mod on the TH900 pads, and the wool felt dampers. If you don't go there, get the Stax 007 pads (optionally mod them as desribed above), and enjoy your TH900 transformed (if you also do the EZ cup mods, and use position #2 of the foam dampers -- thanks to Whitigir for developing those mods!).
 
However, as I am ending this listening with the carbon foam pads and the wool felt dampers, there is a big jump even from the Stax 007 pads, and will only cost you a small amount of money.

Where do you buy the wool for damper rings ?

That is the very good question. All my wool felt was sourced by Playitloud from Netherlands (except my first versions). The one I am using now is a 5 mm black wool felt, need to look up from which batch. Since all felt sounds different, you'd need to order a few types of 5 mm wool felt, make a lot of rings and listen which sounds best.

Food for thought on further mods...
 
http://www.head-fi.org/t/806714/2016-tokyo-spring-fujiya-avic-headphone-festival-impressions#post_12545888