Single stator design

[yrmeli]

There has been practically no information about single stator panels.
I found one reference in www.audiocircuits.com as ESL-WL-1
That is with center stator and membranes on both side.
Also is seem that aluminized mylar was used as diaphgram.
Is the any experience other than this.
Cheers.

[SY]

Originally posted by yrmeli
There has been practically no information about single stator panels.

There's a reason for that: intrinsically high distortion.

[yrmeli]

Oh well, the article did not mention anything about distortion.
The fellow seemed rather happy about them.
OTOH, He put them to his wifes room, maybe that explains it.

BTW, Which is considered better, wire or perfplate stator ?
Why ?

Cheers.

[Calvin]

Hi,

could You post a more concrete link? The above one was totally useless to me.

After Your description, I admit to SY´s opinion, that the thing will work, but will function badly. Apart from the quadratical term in the Force-formula with asymmetrical ESLs -hence distortion- this is a non constant charge design -hence another distortion mechanism.

jauu
Calvin

[frank ziel]

Hi,
http://www.audiocircuit.com/index.php#
select "Electrostatic Speakers"
and than "Projects"
final ESL-WL-1

If the stator is highly resistive, I think constant charge
is given too. And the different force to the two diaphragm is
almost equalised, because of the embedded air.

So long

[yrmeli]

Sorry, there was a typo, this link should work
http://www.audiocircuit.com/A-HTML/A...____-O-A01.htm

This is not asymmetrical, as there is membrane on both sides of the
stator.

Cheers.

[Calvin]

Hi,

the constant charge principle as I understand does not only lead to a constant charge amount, but also to a ´fixed´ charge over the area. In a classical symmetrical ESL the stators build up a homogenous field that acts on a constant and fixed charge, which leads to equal forces on the charge at any point within the field (regardless of diaphragm bowing). Applying the law of actio=reactio leads to the assumption that the charge on the highly conductive stator plates -although varying in volume- will too be equally distributed over the stators area. Because of the absence of a homogenous field the described ESL won´t show a fixed charge behaviour on the membrane but one with great variations of charge density over the membrane area -even with a constant and fixed charge on the stator. To me this design is no constant charge design, but I´d like to read comments on this, because I´m not shure wether the thoughts about equal charge distribution with classical symmetric designs is correct either.

The described ESL looks symmetrical with regard to construction, but isn´t symmetrical in terms of electrical driving forces. It´s really clever to cancel at least a part of the inherent unlinear drive with the second membrane -i.e mechanical forces. Too there should be a rise in SPL of max. 6dB over a certain frequency range (depending on the membranes distance and thus on their phase relationship, because the coupling of the membranes through the air shows frequency dependancy and is not constant). But the driving forces are lower than with a symmetrical stator design, so with regard to SPL nothing is gained.

The disadvantages of this design are many.
- two coupled membranes with varying coupling factor
- inherent nonlinear drive
- building tolerances, e.g different membrane tensions
- additional protective covers needed for the membranes
- highly conductive membranes are prone to destruction by high energy sparks
- using a highly insulating gas inside the ESL can push the limits farther, but may give new problems and different behaviour with varying atmospheric pressure.

I wouldn´t leave the ESL open, because of the destruction thread to the membranes. But when protective measurements have to be taken anyway, why not add two stators on the outside and have a really symmetrical, constant charge ESL with protected membranes and the benefit of risened SPL?

jauu
Calvin