[100VoltTube]

Try Licron
 
Have any of you tried making a quadraphonic headphone?

 

[chinsettawong]

Hi Julez,

Why do you dilute the antistatic solution down? Try applying it without dilution.

 

[Julez]

Because than it has too low resistance. I checked the pure fluid before applying on the drivers by applying on a strechtched piece of mylar. Best is to have 1-2 gigaohm per cm. Without dilluting it is around 100 megaohm per cm (mesured with resistance meter and two coins one cm away from each other). Unfortunatly it is also a spray and I can't really apply a spray evenly. So I have to get it out of the can before applying it. Next is that I allways get dust onto the membrane when applying coating with a sponge or similar method. I apply the coating mix by filtering the mix through a dustfilter onto the membrane so that all surface is covered and then I tilting the driver so most of the liquid drops back into the bottle. I do this in a selve made dustfree box (here in Germany in the bigger citys I have a lot of dust). It did work before.
 
Thanks for the hint with the licron crystal spray. I will see if I can get it for a reasonable price in Germany. I read it seems to work fine with speakers (with insulated stators). I have not found a good insulating material yet to insulate my holesheets. Perhaps someone has a good idea. It seems that the sharp edges of the holesheet are a problem to properly insulate.

 

[chinsettawong]

Please try my method. Here in Bangkok, the air quality isn't very good either. I put a small drop of antistatic on the diaphragm and wipe it on the diaphragm using a lint free cloth. It's also called microfiber cloth. It's the cloth you use to clean TV or computer monitor. A good lint free cloth doesn't leave much dust on. After the coating is dry, you clean your diaphragm again using a piece of dry lint free cloth. This time you get a good light source and look at the diaphragm on its side against the light. If there is any dust, you will see it quite clearly. Clean it until you can't see any dust. Please don't dilute the antistatic solution. Once you wipe it nice and even, you'll see that the resistance isn't that low. The resistance of over 100 mega ohms is fine too.
The resistance of over 1 gigaohms is too much, IMO.

 

[Julez]

Thanks Wachara, I will try your method soon.
 
I measured a Stax 507 driver and the result was around 2-3 giga ohm (I had to measure less than a cm to get a reading with my 2gigohm meter). Higher resistance means that the charge can't reload too fast and therefore burning the membrane should be no problem with dustinduced arcing anymore. The headphones allways worked with about 1,5 gigaohm resistance per cm. Also it should help to protect against moving charge on the membrane (my own headphone has far less flatter stators). I ordered the Licron crystal spray now. I hope this will solve the problem.
 
BTW has anyone got a good idea how to insulate stators properly?

 

[Julez]

100VoltTube
 
Thanks for the tip with Licron crystal!
 
What do you exactly mean by quadrafonic headphone? A headphone with four drivers? Why would you do that? 

 

[chinsettawong]

Licron crystal won't give you so high resistance value either. Please don't be too serious about trying to get so high resistance. I have made and fixed so many electrostatic headphones, and I never bother to get the resistance so high. I know that high resistance on the diaphragm is good for preventing the charge migration, but on the other hand, it also makes the diaphragm difficult to fully charge. That's why you have the problem of the sound getting soft overtime.

In the bias circuit, there is another 5 mega ohm of resister protecting the charging current. So don't worry too much about it.

Wachara C.

 

[100VoltTube]

  100VoltTube
 
Thanks for the tip with Licron crystal!
 
What do you exactly mean by quadrafonic headphone? A headphone with four drivers? Why would you do that? 

No problem! just repeating what I've heard elsewere.
 
A quadraphonic headphone headphone is exactly that: a 4 driver headphone. 2 in the front, and 2 in the back. It's like having a 5.1 system on your head, only without the center channel and the subwoofer. It only really has advantages when you are listening to things with surround channels, unless you have more driver area, in which case it would probably have a bigger soundstage.
 
In theory, you could have a driver with one diaphragm, but multiple regions on the stator, allowing you to move some regions of the diaphragm differently from others, giving you a surround effect without a loss in bass extension as you would have if you just had two equally sized drivers. It's very likely that having a driver like that would have some pretty bad problems, like breakup and added distortion. It would also require more amp channels, which could make it fairly expensive.

 

[dude5OO]

Did you fold Stax' membrane on itself (however many times necessary) and caliper to see how thick it was (in applied-coating aggregate)? 

 

[Congo5]

  BTW has anyone got a good idea how to insulate stators properly?

not sure what you mean but
at first I used nylon screws but they are a pain.....
then started using Polyphenylene Sulfide (PPS) washers, very high voltage, for transistors.
example: SW-125-150
Avid makes them as well just pick the diameter and length you need to get through your stators.
in this pic you can see two on the Float clone. then you can use metal screws.
also that green is an insulating varnish from Grangers supply 2800v per mil. seemed to help....
Insulating Varnish

 

[chinsettawong]

Hi Congo5,
 
Nice to see those headphones.  How do you like the sound?  Which ones do you like the best?

 

[Congo5]

those are two year old pic's I mostly listen to ortho's and build amps.
but they sound just fine and  use them  to test  new amps
so far have not burnt any but that would be fixable
 
I found that other than diaphragm tension and coating the rest is not that important.
OK active area greater than 80mm...
 
but shape and hole size, placement hard to hear.
its close but like the 007 pattern best, lower front
 
  at some point I do plan to make some new ones..
Thanks

 

[chinsettawong]

Yes, I agree with you that diaphragm tension and coating are among the most important things.  
 
Please keep us update with your progress.
 
Wachara C. 

 

[-JFK-]

Hi all,

What is the rotation speed (RPM) and feed speed (mm/min) that you use to drill your FR4 PCB stators?
I continuously broke my carbide drill before the end...
I'm currently using for 1.6mm FR4 PCB:
12000 RPM (the maximum of my motor)
200 mm/min

Thank you for your help!

 

[-JFK-]

No one?
Wachara?
Or maybe this questions have been asked many times.
If yes, sorry, I fail to find it...