Fostex T50RP Incremental Mods and Measurements

[Thujone]

Bottom of post #1 has nick n's mod which involves plastidip IIRC.

 

[Armaegis]

I have one mod where I sprayed a tar sealant into the cups...
 

 
It improves the seal between the cups and baffle, maybe helps damp out a tiny bit of vibration, but ugh for the effort required and the mess it creates... very diminishing returns on this one.

 

[MuZo2]

Working late on damping.Looks like I am done for a while.

 

 

[c61746961]

Nice!, are those microphones placed in your ears or in a coupler?

 

[MuZo2]

There is no one material to damp all frequencies. So have to work with 3 different materials to get this result. 

Similar to acoustic filters on BA drivers. Using some filter on the front of driver smooths the FR (Bumps & cavities).

 

[MuZo2]

Nice!, are those microphones placed in your ears or in a coupler?

Its in a DIY coupler.
http://www.johncon.com/john/wm61a/

 

[bluemonkeyflyer]

  Working late on damping.Looks like I am done for a while.

 

 
Very nice work, MuZo2. I'm happy to see you and others are using measurements to help dial-in modifications.
 
Are you planning on sharing any of the details about your measurement kit (phantom power circuit, type of mic, sound card) and damping scheme? Many people will be interested...including me.
 
Thanks!

 

[bluemonkeyflyer]

  Does your tuning work for all sources ?

To my "ears and gears" yes.
 

 
Any more findings with this mod? Did you measure them ?

I made this mod to see if I could do it without destroying the diaphragm and snap tabs = Success.
 
I have been busy with many other projects and put damping/measurements on the back burner. I will eventually get back to it and share what I learn.
 
Thanks for the interest.

 

[MuZo2]

   
Are you planning on sharing any of the details about your measurement kit (phantom power circuit, type of mic, sound card) and damping scheme? Many people will be interested...including me.

Sure will do. 
Mic is wm61a with 9v phantom powersupply. I think I used same circuit like you.

 

[c61746961]

Its in a DIY coupler.
http://www.johncon.com/john/wm61a/

Nice resource!
So, you're also using plastic tubing to simulate an ear canal?, you tweaked your mods for flat response at the eardrum, is that right?

 

[bluemonkeyflyer]

Nice resource!
So, you're also using plastic tubing to simulate an ear canal?, you tweaked your mods for flat response at the eardrum, is that right?

 

I tried John Conover's tube-to-baffle with rubber bands setup. It works but I prefer the "In my own ear" (IMOE) method. Here's why:

 

1. I made all FIMMs with this method.

 

2. I have made well over 1000 measurements with this setup, in addition to FIMM, so IMOE works best for me.

 

3. Standardization is paramount for "within measures" comparisons...i.e. comparing measurements of headphone "A" to headphone "B"; comparing tweak 1 with tweak 2, etc. To optimize standardization, the following variables must be controlled and replicated each time a measurement is made:

   a. the same mic placement ---> depth and angle

   b. the same placement/position of the headphones on a dummy head (Mine!)

   c. the same clamping pressure ---> rubber bands are difficult to match and they become weak as they stretch with use. Over time and after making many measurements, rubber bands will        likely lose their elasticity, resulting in less clamping pressure and unwanted error variance.

   d. ensuring a good seal all the way around the headphone pads to head

 

4. The IMOE method provides "biomarker feedback" not offered by other methods, including:

   a. Tactile, proprioceptive, and kinesthetic feedback 

   b. The "feel" of my preferred headphone placement on my head helps me obtain the same position from one measurement to the next.

   c. The "feel" of the mic inserted into my ear tells me if I have the same depth and angle used in previous measurements.

   d. The pressure of the headphones on my head tells me that I have a good seal around the pads and the same clamping force as previous measurements.

 

5. Whatever method a person may chose, try to standardize it as much as possible. With repeated measures comes experience. With experience comes more accurate measurements and a finer understanding of how your kit and software works. This knowledge is necessary for meaningful interpretation of your measurements.

 

6. Remember that "one guy's" measurements cannot be directly compared to "another guy's" measurements.

 

7. A measurement kit is only a tool.

 

8. Measurements do not necessarily equate with SQ due to a boat load of objective and subjective variables, including:

   a. individual hearing acuity

   b. personal preferences

   c. music file type

   d. source

   e. both positive and negative expectation bias

   f. hearing fatigue

   g. mood

   h. your energy level

   i.  your "ears and gears"

 

Cheers

 

[zkkzkk32312]

Holly......
 
So amazing that somewhere between the test you managed to almost completely flattened the frequency responds.
 
respect.

 

[MuZo2]

What do you guys think about wm61a inside this ?

 
 
 

 

[Armaegis]

What... is...
 
 
 
 
... oh... OH... that's an ear...
 
 
 
 
 
 
 
nevermind. carry on.

 

[Hutnicks]

  What... is...
 
 
 
 
... oh... OH... that's an ear...
 
 
 
 
 
 
 
nevermind. carry on.

It's the new Philips glass ear challenge first prize!