[charlo89]

Hi,
I just stumbled on this wonderful thread. I would like to know what tricks work well.
For the stator: What materials to use? What coating used?
For the spacer, what materials to use? What thickness is favorable for a 580V bias ?
For the diaphragm,How to measure the pressure to apply?
Thank you 

 

 

[chinsettawong]

  Hi Wachara,
That really goes a long way back.  There wasn't a lot to it.  I machined an aluminum cup about an inch in diameter outside, and 3/4" inside.  A short distance down from the rim of the cup there was a small flange. Next I made a ring which fit over the cup and was screwed down with nylon screws  to the flange.  The  aluminized mylar film was held over the top of the cup and the ring was bolted down to the flange tensioning it somewhat. with everything properly insulated I connected a 300VDC power supply between the cup and the conducting side of the mylar. The capsule cup and mylar then went into a household baking oven, power was applied, the oven raised to some 350 degrees F.for about an hour.  Then the power supply was turned off and the oven left to cool slowly.  The mylar was charged and the assembly converted for use as a microphone.  It worked as a microphone into a high impedance vacuum tube amplifier (hi gain stage). and was still working more than a year later.  Sorry, but that is all I can tell you about it. 
 
You might want to try that procedure with one of your Jacklin Float capsules.  I have no idea how much if any volume you could get with it.  Let me know if you have any success at all. Regards,
BillG.

 
Hi BillG,
 
So you basically just charged the diaphragm while baking it?  It's interesting to hear that you're using aluminized Mylar film.
 
Thanks for sharing. 
 
Wachara C.

 

[chinsettawong]

  Hi,
I just stumbled on this wonderful thread. I would like to know what tricks work well.
For the stator: What materials to use? What coating used?
For the spacer, what materials to use? What thickness is favorable for a 580V bias ?
For the diaphragm,How to measure the pressure to apply?
Thank you 

 

 
Hi Charlo89,
 
Everything you need to know has already been posted here many times. 
 
For stators and spacers, I use FR4 copper clad PCB.  The thickness I use is 1 mm for stators and 0.5 mm for spacers.
 
For tensioning the diaphragm, unfortunately I haven't come up with a good and reliable way to measure its tension.  The tension is done based upon my experience and trials and errors.
 
Wachara C.

 

[BillG]

   
Hi Charlo89,
 
Everything you need to know has already been posted here many times. 
 
For stators and spacers, I use FR4 copper clad PCB.  The thickness I use is 1 mm for stators and 0.5 mm for spacers.
 
For tensioning the diaphragm, unfortunately I haven't come up with a good and reliable way to measure its tension.  The tension is done based upon my experience and trials and errors.
 
Wachara C.

Hi Wachara,    
 
I wonder if you could bounce a laser pointer beam off a tensioned diaphragm onto a wall and then drop a small ball bearing ball onto the diaphragm and observe/measure the deflection.of the beam. the ball would have to drop a specified distance each time it dropped.  So far easy.  now the hard part, how to calibrate the bounce. I don't know!  Rather than dropping a ball, perhaps one could use a calibrated puff of air in the manner the eye doctors do for measuring pressure in the eyeball. If we research that procedure we may learn something more.
BillG

 

[chinsettawong]

Quote:

  Hi Wachara,    
 
I wonder if you could bounce a laser pointer beam off a tensioned diaphragm onto a wall and then drop a small ball bearing ball onto the diaphragm and observe/measure the deflection.of the beam. the ball would have to drop a specified distance each time it dropped.  So far easy.  now the hard part, how to calibrate the bounce. I don't know!  Rather than dropping a ball, perhaps one could use a calibrated puff of air in the manner the eye doctors do for measuring pressure in the eyeball. If we research that procedure we may learn something more.
BillG

That sounds too complicated. 

 

 

[schorsch]

Hello,

Learned some new things in the last Weeks. I have my Stax f81 speakers for repair at a well known German manufacturer.
He Told me that Stax does no coating.
They produce mylar with the necessary ingredients to make them electrostatic.

All other Makers coat the mylar.

Regards Georg

 

[n3rdling]

One kind of simple way to measure the tension is to run the driver open air with a FR plotting software/mic and check the resonant frequency.
 
Georg, that's interesting but how is he so sure?  I think Sennheiser used gold vapor deposition to lightly coat their diaphragm.  A sputtering gun can be built for pretty cheap if you have machining capabilities, most expensive part would probably be the lab vacuum.

 

[phauszzie]

Thats when you borrow the local university's lab

 

[Tachikoma]

Hello,

Learned some new things in the last Weeks. I have my Stax f81 speakers for repair at a well known German manufacturer.
He Told me that Stax does no coating.
They produce mylar with the necessary ingredients to make them electrostatic.

All other Makers coat the mylar.

Regards Georg

Maybe what they mean is that the F81 uses electret film?

 

[Tachikoma]

  Hi Wachara,
 
I've made further investigations :
- spacer rings on my SR-5/NB look like PCB, where those from my SR-X are stainless steel / aluminum
- I've tried more agressive coating with my SR-X right channel (still crackling) : lots of coating with a very light brush, especially around the inner circle edge, then slightly wiping coating marks / residues with microfiber tissue. Mint looking when finished (no holes, no black points)
The result : almost no more sound on this unit ! 
 
My coating is crap indeed, I've to test anything else. Anyone did test rinse aid ?
 
Ali

The crackling might be caused by tiny fibers left behind by the brush or microfiber. I would use a sponge, or if you are really lazy like me, a finger.
 
You probably need more coating, don't be shy with it, just spray it all over the diaphragms and rub it till its even. That's how much I needed to get comparable volumes to a fully working drive.

 

[davidsh]

Bump!
Quote:

So you tried the rinse aid for repairing your bugged out sr-5? Glad to hear it works!
I've got a question about the general principles of electrostats. Basically, we are talking a charged film suspended in a varying electric field. Anyway, the charge on the film is one variable that is correlated to the efficiency of the 'stat. The charge depends on the capacitance of the film and the voltage, no?
What determines the capacitance of the film, though? Can you somehow alter it?

Does anyone know an analysis on the electrostatic speaker principle perhaps? I have read the cookbook...
 
Or perhaps another way for me to find out?

 

[ondesx]

Hello,
 
I somehow redefined the specifications of the tension jig as follows : 
 
- easy installation of the film, 
- allow to choose any face of it and, why not, each side, if one wishes to "treat" equally both sides, 
- the best balanced tension all around the film, 
- very good retention of the latter to the masses used, even heavy,
- knowledge of "the tension mass" for a given type of film, 
- achieve several membranes at once, which in principle should lead to constant membrane tensioning.
 
As my stators are 10.5 cm of diameter, I achieved a system that takes at least two diameters of the stators, which leads to 4 equally "tensioned" membranes, obtained simultaneously.
 
I opted for a ring system in MDF, closed with 8 bolts and butterflies, a 6 mm nitrile joint (a silicone one might as well do the job ...). Here are pictures of this "revisited" stretching jig:
 
External face :
 

 
Internal face :
 

 
With the bolts in place - please notice the groove where the nitrile joint will be inserted in order to clamp the Mylar:
 

 
With the nitrile joint inserted:
 

 
Mylar in place in between the rings :
 

 
Jig in action with the masses - Here, near to 14 kg of charge on a 12µ test film !...
 

 
The central cylinder receiving the whole system ! 
 

 
This jig can be "reversed" in some sense... Instead of "press" around the ring, it's possible to maintain the rings solidly around a central hole in which the cylinder may be "pushed up", but in this case, again, a surface tensiometer is needed, in order to know the submitted tension !
 
My jig has several advantages, aside a very good distributed tension of the film and the possibility to flip over easily the rings to access equally to both sides for whatever treatment, one can obtain 4 diaphragms of same tension in one shot, know the value of this tension for a given plastic film, save some Mylar since only a small surface is not used !...
 
Hope this helps !
 
OndesX

 

[charlo89]

Thank you for your answer
I'm currently reading the topic, there are many pages but it is very interesting.
I wondered if it was possible to design stators with the "fazor" system of audeze, it would require a precise cnc machine to adapt the "fazor" to the tiny holes of an electrostatic stator, but is it worth it?
 
Edit: I made some research, the problem is the large size of magnet. it's not important on electrostatic structure.

 

[chinsettawong]

  Hello,
 
I somehow redefined the specifications of the tension jig as follows : 
 
- easy installation of the film, 
- allow to choose any face of it and, why not, each side, if one wishes to "treat" equally both sides, 
- the best balanced tension all around the film, 
- very good retention of the latter to the masses used, even heavy,
- knowledge of "the tension mass" for a given type of film, 
- achieve several membranes at once, which in principle should lead to constant membrane tensioning.
 
As my stators are 10.5 cm of diameter, I achieved a system that takes at least two diameters of the stators, which leads to 4 equally "tensioned" membranes, obtained simultaneously.
 
I opted for a ring system in MDF, closed with 8 bolts and butterflies, a 6 mm nitrile joint (a silicone one might as well do the job ...). Here are pictures of this "revisited" tension jig:
 
External face :
 

 
Internal face :
 

 
With the bolts in place - please notice the groove where the nitrile joint will be inserted in order to clamp the Mylar:
 

 
With the nitrile joint inserted:
 

 
Mylar in place in between the rings :
 

 
Jig in action with the masses - Here, near to 14 kg of charge on a 12µ test film !...
 

 
The central cylinder receiving the whole system ! 
 

 
This jig can be "reversed" in some sense... Instead of "press" around the ring, it's possible to maintain the rings solidly around a central hole in which the cylinder may be "pushed up", but in this case, again, a surface tensiometer is needed, in order to know the submitted tension !
 
My jig has several advantages, aside a very good distributed tension of the film and the possibility to flip over easily the rings to access equally to both sides for whatever treatment, one can obtain 4 diaphragms of same tension in one shot, know the value of this tension for a given plastic film, save some Mylar since only a small surface is not used !...
 
Hope this helps !
 
OndesX

 
Hi OndesX,
 
Your diaphragm stretcher looks interesting.  Have you tried it with 2 or 3 microns Mylar yet?
 
Wachara C.

 

[ondesx]

Hello Wachara,
 
Not yet, but I suppose it'll work in the same way. The unknown for me is the resistance of such a thin film...
 
A friend of mine told me that it's a delicate material and it'll easily rip. 
 
What is your opinion ?
 
OndesX
 
PS : Though this method has not yet solved the problem of the correct tension value !