Use of pre-metalized mylar

[willyCJ]

So I've decided to stop reading and start working on building something. I'm not going to pursue all my crazy ideas at this time and instead work on building a traditional diy ESL speaker.

As I go looking at films there are plenty of vendors who sell clear mylar film. However I've also found silvered and metallized films. These guys do silvered film
http://www.mirrorsheeting.com/ and state that the film should not be used in proximity to electricity, however it seems like a thin paint layer would provide enough insulation. Plus if the silvered surface was visible, it would be fun to 'watch' the sound based on the deformation of the film.

Alternatively, these guys only have thicker films, but seemingly the metal coating would also work http://www.rplastics.com/metallized-mylar.html

So my question is: is this a good idea? I'm aware of ER Audio and the fact that I can order film identical to what most other people are using, however doing something unique sounds quite a bit like fun.

Also, what is the best source for reasonably priced transformers? For a first try at building speakers I would prefer a low cost prototype and then do the job perfectly the second time once I've learned most of the tricks.

Thanks for the info!

Bill

[SY]

In a standard ESL design, the metalization has much too low resistivity to operate in constant charge mode- you want the charges to stay put as the diaphragm moves. There are some special designs that do use a metalized diaphragm and high resistance stators (notably Beveridge), but those are unusual, difficult to build, and the diaphragms tend to catch fire when overdriven.

[stokessd]

I've been told that low resistance diaphragms can actually be dangerous. There's a significant amount of energy stored on that diaphragm, if you do get an arc from the diaphragm to the stator, the entire charge can migrate through the arc and the arc can have enough energy to actually catch the diaphragm on fire.

I've never seen it happen personally, but I can see that it could happen.


Sheldon

[Geoff H]

I have thought of cutting up antistatic bags from PC mainboards.

Geoff.

[MJ Dijkstra]

Hi,

If you want to use metalized stuff just to get something unique, that's fine of course. Just take care to put a high value resisitor between the high voltage supply and the mylar (100 to 500 Mohms will do). Just take around 10 to 20 resistors in series to handle the large voltage. Normal resistors can handle a few 100 volts max!, so that's why.
The high value resistor will keep the total charge constant. It will not prevent charge-migration, but you probably already knew that.

Regards, MartinJan