Information pertaining to Electrostatic Loudspeakers

This is just a beginning of an accumulation of information. Please, feel free to add to this or ask questions in the forums.

What is an electrostatic loudpspeaker?
Electrostatic speakers work on the principle of creating sound the same way a conventional speaker does, by creating high and low air pressures which is sound. The way in which it moves it's diaphragm is different however. Most conventional speakers use electromagnetic energy to move a voicecoil back and forth, with this motive force transmitted more or less well to the rest of the diaphgram, which in turn pressurizes the air. An electrostatic loudspeaker uses an electrostatic field which acts on the entire area of the diaphgram, to make it move.
For more basic information, refer to [HowStuffWorks??.com].

Things that an ESL DIY-selfer will eventually need to have

Step-up audio transformers >40:1 ratio (unless using a Directly Coupled Amplifier)
Stators made of perforated steel, aluminum or any other conductive material. 60%+ open area, with holes no larger than 5-6mm is a general rule of thumb (perforated metal stators are actually quite troublesome w.r.t. arcing due to the sharp edges they provide in such abundance. smoothly rounded conductors are much better in this respect)
Spacer/insulative material (dimensions depend on design, see Sanders' book below)
Mylar or other thin strong material for diaphram
A very low current, high voltage power supply (2 - 6kV depending on design)
Insulative coating for stators when high bias voltages are being used (here again, perforated sheet stators are sub optimal. the coating will almost certainly be thinnest right where it is most needed - at the edges of the perforations!)
An amp that will be able to drive the capacitive load of the ESL
Other odds and ends such as interconnects
Time
Some experience with construction

Books to read

"There is one book that's relatively cheap, but still provides a very good resource for electrostatic loudspeakers. Roger Sanders' 'Electrostatic Loudspeaker Design Cookbook' turned out to be a pretty good read. Focuses on construction, but gives a bit about design as well. It sells in the 35 dollar range, I know amazon carries it. " - G-Daddy [Electrostatic Loudspeaker Design Cookbook by Roger Sanders on Amazon.com]
[Electrostatic Loudspeaker: Design & Construction by Ronald Wagner on Amazon.com]
Sander and Wagner's books are fine, but they tend to be more cookbooks than really helping to teach fundamental theory (although Wagner does try). For that, I recommend "Electroacoustics, The Analysis of Transduction and Its Historical Background" by Frederick V. Hunt; originally published in 1954, reprinted in 1981. Check Google for sources. If you truly digest Prof. Hunt's chapter on electrostatic speakers, you are on your way to being an expert!

Helpful URLs

[Mark Rehorst's ESL Page, with an excellent construction plan and an alternative and safer bias power supply]
Do a patent search for "electrostatic loudspeakers" at www.pto.gov. Easy to do, and you can download image files for any patent. I've got a 3" stack on ESLs alone! You will learn a lot about theory and techniques by reading patents (on any topic, for that matter). I don't know why more people don't use this on-line resource.
There's a whitepaper by Jim Strickland that explains a lot (though not at length) of the pros and cons of perforated metal stators and some of the alternatives. [must find URL of this]

Sources

Perforated metal: [McMasterCarr??] or other bulk material distributors (checky locally).
Transformers: [Antique Electronic Supply] A tube tranny hooked up in reverse will work, look for a high impedance (>8K) with a center tap. Of course, there are more professional (thus expensive) sources out there.
Mylar: Try talking to [DuPont??] directly to find local distributors of what you need.
High Voltage Bias: A simple voltage multiplier can easily be built with common parts. Just be carefull! Also check out Mark Rehorst's design on his website (above).

Good Luck!