Some interesting findings about Stax electrostatic stators

[210]

Hallo Wachara! If the spikes are conductive and work as controlled dischargers, you would need such material (maybe conductive plastic?). Maybe the powder coating will already make them conductive. Could you lend a multimeter from your friends (maybe one with 20megaohm range ore more) and measure the resistance (with cleaned measure pins) between the soldering point of the stator and some spike peaks ?

[chinsettawong]

I really don't think that they are conductive.

I'll try to see if I can measure anything with my multimeter.

Wachara C.

[210]

Probably the stator spikes just keep distance to prevent arcing/sparks and/or to prevent sticking of the diaphragm to the stators. But you, Wachara, can check for conductance to ensure.

[bear]

Can't really see what is there...

Take a magnifying glass, stick it flush to the lens on ur digital camera, put the camera in the closeup mode, hold the shutter halfway down to focus, then move the camera towards the object to focus - press shutter all the way... voila! Closeup really close!!



_-_-bear

[chinsettawong]

Originally Posted by 210

Probably the stator spikes just keep distance to prevent arcing/sparks and/or to prevent sticking of the diaphragm to the stators. But you, Wachara, can check for conductance to ensure.

I've just checked the conductivity and it certainly is higher than my meter can measure. I confirm that there is a layer of powder coating on the stator.

[chinsettawong]

Originally Posted by bear

Can't really see what is there...

Take a magnifying glass, stick it flush to the lens on ur digital camera, put the camera in the closeup mode, hold the shutter halfway down to focus, then move the camera towards the object to focus - press shutter all the way... voila! Closeup really close!!



_-_-bear

I'll try to take a better picture to show you.

[210]

Originally Posted by chinsettawong

I've just checked the conductivity and it certainly is higher than my meter can measure.

Well, then you can try them at your speakers without this uncertanty. Btw. you forget to write till how many MHz you measured. Regards!

[arend-jan]

Originally Posted by 210

Btw. you forget to write till how many MHz you measured.

Why would that be relevant?

[bobnick]

I just don't see Stax using the spikes to bleed away the diaphragm charge at high deflection. I think it would be a clumsy way of limiting the displacement of the membrane under high drive and would give some peculiar audible effects - a long time constant on the diaphragm charging system would produce soft pauses in the music. In any case, even if it worked, I think the problems of reliable manufacture would outweigh any possible benefits.

I also do not believe that the spikes are there to prevent arcing. The stators are coated, probably with a high dielectric breakdown coating which would effectively prevent arcing. Also, Stax knows the absolute maximum drive voltages for all their amplifiers and has designed all their previous headphones without the need for such a system.

I also do not understand how a diaphragm could electrically 'stick' to a stator under any circumstances using the normal bias voltage, the negative compliance generated by the diaphragm charge would seem far too small to allow this. Can anyone explain a mechanism where this could happen?

I also have not been able to determine that squeeze damping of the fluid between the diaphragm and the stator would cause any sticking of the diaphragm to the stator given the size and shape of the perforations. In any case the hard limiting of the diaphragm deflection would already be causing very audible distortion.

Again, I still think that the spikes will introduce a form of soft limiting at high deflection. But, I also have no idea if this is the purpose of the spikes, I just think it a consequence.

Regards,
Bob