Single Stator Electrostatic Headphone - issues?

[gentlevoice]

Oh - aaarghhh!! - had just replied to you and then it all disappears because the system timed out

.... anyway ... thank you all for replying and not least outlining the force, Q & V relationships in an electrostatic speaker. I now find that I - hopefully - know what I need to know to progress with my design.

@calvin:

Jesper, I wouldn´t cast the stator in metal, but just metallize the stator surface toward the membrane side.

It's a very attractive idea which I've actually had myself. Unfortunately, the plastic of the 3D print I ordered from Shapeways is not firm enough so I doubt it would sound well. Also, I don't know what the dielectric coefficient of the plastic is so attaching conductors to the surface probably will influence the sound.

I've also decided to not cast the stators - it'll either be too expensive for me or challenging with the rods being so thin. Instead I will draw circular or oval copper rods and mount them on a similar outer frame.

@godfrey:

If the membrane is centered between the plates, it will be equally strongly attracted to both of them, so the forces cancel.

Interestingly, if it's not centered then the forces don't balance and the membrane is pulled more strongly towards whichever plate it's closer to. So the electrostatic forces act as a kind of anti-spring, partly counteracting the stiffness due to the membrane tension.

Hmmm... so I guess some experimenting with tensioning relative to low frequency response & voltage is necessary. Thanks for mentioning this

Now off to working on the headphone ...

'Best for your day,

Jesper

[Calvin]

Hi,

Also, I don't know what the dielectric coefficient of the plastic is so attaching conductors to the surface probably will influence the sound.

The dielectric constant of the stator wouldn´t be of much interest here, since the metallization would face towards the membrane. It´s the insulation layer on the metallization (between the metallization and membrane, as in the sketch) that would influence on sound and this could be a PU-laquer or similar. The cast or printed frame has to fulfill mechanical requirements in first place and to insure electrical safety by sufficiently large dimensions.

jauu
Calvin

ps. Jesper, a very danish name Btw. How´s the weather on Helgenaes?

[gentlevoice]

jauu Calvin,

So you know of Helgenæs Actually, today the weather is mostly overcast & right now it's raining, temperatures are about 18 degrees. Although I'm not on Helgenæs I'm only a few kilometers from there so probably more or less the same weather there ...

To me it's a suitable day for "projects" ...

Regarding insulation on cables or other items my experiences are that most all materials laid outside a conductor influences the sound. I used to work with TARA Labs cables here in Denmark and was fortunate enough to own a couple of their The One cable sets. Those were good, however, the cables I mostly liked were uninsulated ones, akin to Tara Labs' The Zero. See e.g. here (at the bottom there's a description of their vacuum design):

TARA Labs The Zero interconnect | Stereophile.com

So, without entering into a discussion on the sound of cables (one of audio's many never-ending discussions in my experience...) I tend to be very cautious of putting materials close to the conductors - with or without an electric field across the material (if that is what you were thinking about?).

This also means that although I'd really like to make these stators in a firmer plastic - my aesthetic sense really likes them - I hesitate to do so because I reckon that the metallization onto the plastic may influence the sound....

To that end: Any of you know of a zero-dielectric coefficient plastic to metal glue that's absolutely enviromentally sound as well

Greetings &

Jesper

[geraldfryjr]

You could cover your frames with aluminium duct taped and form it through slots as I have done here,

Material for ESL

and then coat it with some clear spray acrylic.

I used a bath of sodium hydroxide to etch away the unwanted left over edges in the holes after masking the top surface.

I used a bias of +500v on these.

jer

[Calvin]

Hi,

I´m not sure if You understood correctly what I meant with metallization and insulation. The optics of the stator frame wouldn´t change at all, but safety issues would be greatly reduced against a fullmetal stator. Its just so that the ´function-side´of the stator towards the mebrane would need metallization. The bulk plastik would face towards the head/ear and functions as safety insulation. The metallization would in theory not even need an insulation, if the membrane coating would be of very high resistivity and if the ESL capsule were symmetric. In this case the voltage differential between membrane and stator reduces the closer both approach each other. At distance 0 (contact) the voltage differential would become 0 also, hence no flashover.
Still though a stator insulation towards the membrane is fully recommended. With a SE-ESL, featuring a highly conductive membrane, insulation is not an option but an obligation.
There´s a chance that the stator plastic influences on the electrostatic field and as such influences on sonics, because it functions similar to a ´conductor´ for the electrostatic field. But for a) the dielectric constant is low (bad ´conductor´) and b) is it orientated away from the sound-generating field. The influence is therefore very small, insignificant.
The effects on sonics that follow the decision of using a single stator design, are much greater and they are generally negative effects.
I´d suggest that You get a working -and I mean safe working- symmetrical ESL capsule going and get some basic experience before thinking of certain details which may even seem plausible at first glance, but aren´t.

jauu
Calvin

Yeah, I know Helgenaes. Made holidays there a couple of years as a youngster. Saw my first Rega planar 3 in a shop in Aarhus.

[oshifis]

Here is another interesting thread on this topic with a lot of useful construction details:

Has anybody made an ELS headphone?

[chinsettawong]

Hello!

I haven't been back here for a while. It's always nice to see somebody interested in making electrostatic headphones.

@ Calvin: Have you any progress with those headphone parts I sent you years ago?

@ Gentlevoice: The best and economical material for making stators and spacers, IMO, is PCB. They come in many thicknesses, and can be cut and drilled easily.

Wachara C.

[gentlevoice]

Hey all,

Pleased to read your writings & suggestions And good to see you come around Wachara - I've been reading the thread you started some time ago on EL headphones quite some - very interesting indeed It had/has many sources of inspiration - to me not least your Orpheus shape stators and Phil47's ideas and suggestions.

@calvin:

The metallization would in theory not even need an insulation, if the membrane coating would be of very high resistivity and if the ESL capsule were symmetric. In this case the voltage differential between membrane and stator reduces the closer both approach each other. At distance 0 (contact) the voltage differential would become 0 also, hence no flashover.

Hi Calvin, I'm not quite sure I understand what you mean in the above sentences. How can the differential be zero with the membrane polarized to maybe 500 volts? Wouldn't there be the risk of an accidental blow of wind making the membrane touch the stator(s)?

Regarding my comments in the previous post I (hope) I understood what you meant. On the other hand my point was that everything close to a conductor "sounds" - more or less and even if there's no electric field to make the electrons go in the direction of the insulation - so not having anything other than the stator/conductor is preferred to me. And, yes, I'll do a first version which I can learn from.

@geraldfryjr: Hey jer. Thank you also for suggesting & linking. I've taken a look at your link & it looks interesting - yet my approach is somewhat different - but thanks again for posting

@Wachara: Hi Wachara. Appreciate your input, yet in the first round I'd like to more or less go with what Philippe Hiraga suggested in the posts he made in the thread you started. Round or oval wires and a design that makes the air flow "smooth". But I'll keep your suggestion in mind

Greetings to you all,

Jesper

[Calvin]

Hi,

@Wachara: get out the baseball bat...I deserve it

jauu
Calvin

[gentlevoice]

Hi again,

Still in the process of doing the headphones as a question came up which I hope one of you may just know about:

Suppose I design the electrostatic headphone to have spacers of 0.6 mm between the membrane and the stators and a membrane area of about 50 cm2 do you know what the current requirements for the headphone amp will be (I don't play loud and aim at a 50 Vpp maximum output level)?

Regards from autumn Denmark,

Jesper