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Just listened to some Fostex T50RPs today... WOW!
May 14, 2012 at 7:27 AM Post #8,206 of 11,346
Quote:
Originally Posted by micmacmo /img/forum/go_quote.gif
 
The thin microfiber with the rock wool gave the flattest frequency response and, to my ears, the most pleasing sound. 
 

 
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Quick! ninja-edit your post and ask $400 to mod phones with it ^^
Nice find and thanks for sharing, I'll look into it
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May 14, 2012 at 7:55 AM Post #8,207 of 11,346
Thanks for this new stuff to try!  I found a local supplier 2 miles from my house. I'll pick up some after work.
 
Did you keep or remove the acoustic foam in the cup floor "wells?"
 
 
Quote:
micmacmo said:
One isotope of Unobtainium I've wanted to get my hands on for awhile is rock wool. Joelpearce mentioned it many months ago as a cup dampener and said he had it leftover from a construction project. It turns out that it's not just sold in bulk for construction but also commonly used in the plant nursery and hydroponics industry as an artificial "soil" for germinating seeds. 
 
I went to a hydroponics shop in town (I now know where marijuana grow-ops get their equipment) and picked up some 3-inch and 4-inch cubes of rock wool. Cheap. It's made by Grodan with a 70 kg/m^3 density (vs the Roxul Safe'n'Sound fiber Joel used with its 40 kg/m^3).
 

 
 
I cut 1-cm-thick slabs and cut them to fit into the bottom of the cups and around the hanger "hump," thusly:
 

 
I tried the rock wool with various materials on the back of the driver (on top of the stock white material). The only effect of these over-the-driver materials was to enhance or decrease the mids and treble, from about 1 kHz up (no effect on lower mids or bass). Plush microfiber (from a dusting cloth) gave the brightest sound, then, in descending order, thin/smooth microfiber (from a lens cleaner), dense cotton (from a nursing pad) and stock material alone.
 
The thin microfiber with the rock wool gave the flattest frequency response and, to my ears, the most pleasing sound. 
 

 

 
(Note the apparent "ridge" at 60 Hz in the heat graph. I'm not sure what that is but it's consistent across all my mods involving rock wool. I can't hear it, though. Maybe that's why Purrin truncates his amazing waterfall charts to ignore the lower end of the spectrum?)
 
This mod measures similarly to my mods involving absorbent cotton in the cup and plush microfiber over the stock white driver material. However, I think this sounds a little more open (although I'm not sure what I'd need to measure to convince myself that it is truly so! 
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 )   I'll stick with this mod until I find some fault with its sound and start mod'ing again. 
 
 
 
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May 14, 2012 at 10:20 AM Post #8,209 of 11,346
BMF, I have AcoustiPack on the bottom of the cups with 1-cm-wide Paxmate strips on the vertical walls.

The rock wool is rigid enough that it is easy to cut with a serated blade or razor. (Personally, I worked it using bare hands and only got one sliver. It's easier to handle than fiberglass.) The AcoustiPack is just thick enough so that the bottom of the wells becomes flush with the central ridge (I think the Paxmate would do the same.) So the only feature within the cup you need to "project" into the rock wool is the hanger hump. I traced the outline of the hump on the rock wool and cut it out from the full thickness. I cut the resulting plug to a half thickness and reinstalled it in the hole. The hanger hump fits perfectly in the remaining half-thickness hole. (I still have the four posts in the cups, the ones with the x-shaped cross section and the rubber plugs on top. I removed the rubber and pushed the posts through the rock wool.)

Otherwise, my t50s include tungsten putty in the baffles (Plasticine or Newplast would be equivalent), stock felt over the cup vents, stock white material over the back of the driver, one baffle hole open, B-Quiet (Dynamat equivalent) around the driver on the earside with adhesive felt over top. O2 pads.
 
May 14, 2012 at 10:43 AM Post #8,210 of 11,346
Quote:
micmacmo said:
BMF, I have AcoustiPack on the bottom of the cups with 1-cm-wide Paxmate strips on the vertical walls.
The rock wool is rigid enough that it is easy to cut with a serated blade or razor. (Personally, I worked it using bare hands and only got one sliver. It's easier to handle than fiberglass.) The AcoustiPack is just thick enough so that the bottom of the wells becomes flush with the central ridge (I think the Paxmate would do the same.) So the only feature within the cup you need to "project" into the rock wool is the hanger hump. I traced the outline of the hump on the rock wool and cut it out from the full thickness. I cut the resulting plug to a half thickness and reinstalled it in the hole. The hanger hump fits perfectly in the remaining half-thickness hole. (I still have the four posts in the cups, the ones with the x-shaped cross section and the rubber plugs on top. I removed the rubber and pushed the posts through the rock wool.)
Otherwise, my t50s include tungsten putty in the baffles (Plasticine or Newplast would be equivalent), stock felt over the cup vents, stock white material over the back of the driver, one baffle hole open, B-Quiet (Dynamat equivalent) around the driver on the earside with adhesive felt over top. O2 pads.
Click to expand...

Thanks, micmacmo.  How does the sound compare with previous mods?
 
If you've tried this configuration with 003 and 840 pads, how do the graphs look?  
 
May 14, 2012 at 12:31 PM Post #8,211 of 11,346
Quote:
applepancakes said:
from bare drivers on both sides:
-glued coffee filter on the back, used a pin to make a hole through the coffee filter to get more bass
-sandwiched pink insulation between stiff felt on the earside (to get rid of excessive 2.5k+)
(also recabled, plasticine flush, hm5pads)
 
sounds decent now. some channel imbalance. were i to do it again, i'd leave the stock felt and work from that.
 
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Genius - I was wondering how best to replace the material on the back of my drivers with something as close as possible to the stock material (I have tried transpore and its not that close) thanks so much.
 
One of the screw sockets which holds the baffle to the cup seems to have gone - I might need to find a better option for holding the baffles on between mods, but I think it might be too late for this pair.
 
@micmaco that FR plot looks incredible - is that paxmate under the rockwool?  I have fastidiously lined my cup with paxmate and really don't care to remove it for thisT50.
 
May 14, 2012 at 2:54 PM Post #8,213 of 11,346

Quote:
bluemonkeyflyer said:
Thanks, micmacmo.  How does the sound compare with previous mods?
 
If you've tried this configuration with 003 and 840 pads, how do the graphs look?  
Click to expand...

Hey, BMF, this mod compares favourably to my favourite previous mod. Without the benefit of a blind A/B, though, I'm reluctant to say that it's better.  (Specifically, I'm using the mod involving plush microfiber over the driver back and 2-cm thick absorbent cotton to fill the cup as a reference.) A nice balance across the spectrum. No obvious ringing. The sound of most instruments seems "realistic" and the music, from instrument to instrument, blends nicely into a cohesive whole. On the other hand, I've never gotten a great soundstage from T50s and this mod is no different.
 
Here's a comparison of the 003 pads and the 840 pads. Bear in mind that I never got terrific bass with the 840 pads (presumably because I never got a good seal with them.) Whlie the bass of the 840 pads is diminished, I get a flatter response through the mids and into the lower trebles (up until that peak around 5-6 kHz). Listening to Bill Evans right now, I think I prefer the sound with the 840 pads. The piano has more presence. But Bill LaFaro's bass is further in the background. 
 

 
This seems to contradict my assumption that the bass is louder the closer my ear gets to the driver. The 840 definitely puts my ear close to the driver, but I don't get a corresponding lift in bass. Volume effect? The effect of a poor seal? Or maybe I've just been wrong all this time.
 
May 14, 2012 at 3:37 PM Post #8,214 of 11,346
The 003 pad dimensions are tighter around the ear and the foam compresses more than the 840. On my mods the 003 produces a lift in bass with the new stock that I dont like so much. The 003 pads were better for me on the old stock. As always Ymmv depending on the mods you make.
 
Dan Clark Audio Make every day a fun day filled with music and friendship! Stay updated on Dan Clark Audio at their sponsor profile on Head-Fi.
 
@funCANS MrSpeakers https://danclarkaudio.com info@danclarkaudio.com
May 14, 2012 at 6:36 PM Post #8,215 of 11,346
​
drez said:
@micmaco that FR plot looks incredible - is that paxmate under the rockwool?  I have fastidiously lined my cup with paxmate and really don't care to remove it for thisT50.
Click to expand...


It's actually Paxmate around the walls of the cup and AcoustiPack lite lining the bottom of both sides of the cup. I think all Paxmate will work fine, though.
 
May 14, 2012 at 8:16 PM Post #8,218 of 11,346
Quote:
jgray91 said:
It is true, IME, although I don't know the science behind it. Someone else is better to explain it.
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It's pretty simple.  The more stuff you put in the way of the moving air the more power driver needs to push it around.
 
May 14, 2012 at 8:34 PM Post #8,220 of 11,346
Quote:
jgray91 said:
It is true, IME, although I don't know the science behind it. Someone else is better to explain it.
Click to expand...

 
Essentially the biggest problems these have out of the box is energy bouncing around inside the cup and getting "re-transmitted" through the transducer.  By absorbing the highs and mids that otherwise would have been hitting the diaphragm it you're reducing the effective efficiency. 
 
Dan Clark Audio Make every day a fun day filled with music and friendship! Stay updated on Dan Clark Audio at their sponsor profile on Head-Fi.
 
@funCANS MrSpeakers https://danclarkaudio.com info@danclarkaudio.com
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