Electrostatic Speakers - made today in 4 hours from mostly junk

I had today off so I decided to see if I could make some electrostatic speakers. I'd been thinking of doing so for about a week - just for grins.

I didn't want to spend any money and even less time.

So - I scrounged together a few parts and in about four hours it was done and pumping out the tunes - sounds good, too.

Here's what I used:

A an old 5 1/4" floppy disk (just the magnetic media)
An old CFL power supply (from a broken LCD monitor backlight).
A universal 110V/220V/5V power transformer.
A few disc caps, rectifiers and resistors
Some paper clamps (not paper clips)
Some old metal computer slot covers (like what's probably on the back of your computer to fill up its unused openings)
Some old PC board material I had sitting around (for the two outside stators).

I cut open the floppy disk envelope and sliced a couple of rectangles out of the inside disk to use for the diaphragm. I reasoned that the magnetic oxide coating might make a perfect high resistance, relatively thin, conductor.

Cut a couple matching, but slightly smaller rectangles out of two equal sized PC boards with a Dremel.

Sandwiched the two diaphragm pieces between the two pieces of holed PC boards (copper side in and touching the edges of the two cut up floppy media).

Squeezed the two diaphragms between the two PC boards using paper clamps.

Made the outside stators using four metal computer slot covers - two on each side - one pair under one end set of clamps and the other under the other. The PC slot covers should not touch the opposite set of clamps.

Put together a simple 1/2 wave voltage tripler and attached it to the output of the CFL driver. Then, attached it to the wire I had soldered to the inside of one of the PC boards which was pressing against the floppy disk media. That made my high voltage bias supply for the diaphragm (around 1500 VDC). You can buy those CFL high voltage things for about $4.00 each.

Oh - I also added a 40 Meg resistor to protect the diaphragm in case of arcing - I actually had to buy that from a TV supply place today. That was about an hour of the four hour job.

Added a 3 Ohm, 10 W resistor to the 5V primary of the power transformer (so that the amp has a load about 4 Ohms). Wired the two primaries in series to get a step-up ratio of about 1:50. That was (barely) enough to energize the stators with a 25 W amp (about 500V = 10v x 50).

Put it all together using alligator clipped jumper wires on top of a piece of insulating styrofoam.

Checked the wiring.

Tried out the high voltage supply - check
Tried out the stator supply using a variac - check

Hooked it to a Kenwood 6600 I was working on, turned everything on, cranked up the volume and it made nice noise. The bass was distorting (no surprise there) - so I added a 2 uF cap in series with the input as a cheesy crossover and turned the bass down. Now - it sounded good.

I'm going to try using some static protective bag material next as the diaphragm. I think the static dissipative type (resistivity about 10 to the 12 power) will work best - but the anti-static type would probably be OK, too.

I've also thought about making some from old VCR tape strips.

I've attached some photos of my hi-tech system. Anyone want to buy it?? You can use whatever grill cloth you'd like.

DH

Interesting project!

Whoa!!! Now this is serious stuff!

:thmbsp:

I want to see homemade plasma speakers. Hehehehe.

When I was living in Quebec and still in my 20s I bumped into some guys who were building electrostatics (until some company jumped on them for some patent infringement). They coated 12" x 24" masonite sheets, the ones with the 1/4" holes (Pegboard) with conductive paint, then put insulating strips around the edges. Then they glued conductive plastic, stretched tightly, between two of these boards withe the conductive paint facing the plastic. When the two boards were connected directly to the plates of a PP amp and the plastic was connected to the B+ center tap - music! About 12 of these panels in an array gave an open and spacious sound even down to about 35 -40 Hz.

I imagine that they had to do some experimentation to determine the thickness of the insulating strips so that there would be no chance of arcing as the plastic contacted the paint, but with the right materials it should not be too hard to duplicate. As long as you did not sell them you would be safe from legal hassles.

WHSH93--if i'm ever lashed to a chair in a secret underground bunker, and there's a bomb with a red digital timer counting down the seconds attached to it, and the situation looks utterly hopeless for my imminent destruction, you would be the guy i hope was lashed to the other chair

Several sites on the web, and an audioXpress article, on building your own plasma driver. It's actually reasonably straightforward -- all's you need is an RF oscillator.
Here's an example: http://www.plasmatweeter.de/eng_plasma.htm

A love of high voltage is required for DIY electrostatics or plasma drivers.


(gotta love that inductive coupling)


Note, I think that the DIY electrostatic tweeter project that is the subject of this thread is really cool, and I really appreciate the OP's sharing it with us... but I think I lack the cojones to have a go at it myself.

EDIT: There is a book available (if still in print) on DIY electrostatic drivers. Check Antique Electronics Supply or Old Colony Sound Lab.
http://www.audioxpress.com/bksprods/products/bkaa20.htm

That's pretty cool. I'm assuming that the PP amp was a tube amp - otherwise the voltages involved would not be high enough to work (which is why mine needed a step-up transformer on the input).

I made my kludge just to get a feel for that type of speaker. I'm sort of toying with the idea of making a "good" set and installing them. I once listened to a pair of Infinity servo-Statics (in 1973, I think) and I was so impressed I swore I'd get a pair eventually.

Well, it still has not happened.

DH

merrylander said:

When I was living in Quebec and still in my 20s I bumped into some guys who were building electrostatics (until some company jumped on them for some patent infringement). They coated 12" x 24" masonite sheets, the ones with the 1/4" holes (Pegboard) with conductive paint, then put insulating strips around the edges. Then they glued conductive plastic, stretched tightly, between two of these boards withe the conductive paint facing the plastic. When the two boards were connected directly to the plates of a PP amp and the plastic was connected to the B+ center tap - music! About 12 of these panels in an array gave an open and spacious sound even down to about 35 -40 Hz.

I imagine that they had to do some experimentation to determine the thickness of the insulating strips so that there would be no chance of arcing as the plastic contacted the paint, but with the right materials it should not be too hard to duplicate. As long as you did not sell them you would be safe from legal hassles.

Click to expand...

MacGyver I'm not!

shrinkboy said:

WHSH93--if i'm ever lashed to a chair in a secret underground bunker, and there's a bomb with a red digital timer counting down the seconds attached to it, and the situation looks utterly hopeless for my imminent destruction, you would be the guy i hope was lashed to the other chair

Click to expand...

It was a simple PP 6V6-GT David Bogen DH-10

Now, build a second and fashon a headphone band. (no need for the 2uf)
Mount the thing in a pair of tin cans....

I don't think I'd want 1500 VDC too close to my ears, and, by extension, my brain

Yikes! Good ingenuity there...

btw - I've been lucky enough to hear the original Dukane Ionovac speakers with the Plasma tweeter. The best hi-freq duplication I have EVER heard... too bad the rest of the speaker couldn't keep up...!

Impressive!

Further experiments

I have now tried out a couple of other materials to use as the diaphragm:

The anti-static bag material worked OK - but it tends to stretch unevenly and that makes it harder to apply evenly.

The VCR tape worked great. Easy to stretch and attach. The fidelity was very good and it seemed to better able reproduce lower notes. It was also louder for some reason. I expected it to be lower volume since there was less total area.

The best, so far, of the three types I've tried is the VCR tape. I think a really good set of electrostatic tweeters/midranges can be had by using that stuff.

I'm considering making some long, narrow drivers that can then be arranged in sort of a half circle to help imaging and dispersion.

I'm a little stoked about this early success and just ordered a tube transformer to move the experiment along to "real" speakers.

DH

whsh93a said:

I have now tried out a couple of other materials to use as the diaphragm:

Pink anti-static bag material
VCR tape​

The anti-static bag material worked OK - but it tends to stretch unevenly and that makes it harder to apply evenly.

The VCR tape worked great. Easy to stretch and attach. The fidelity was very good and it seemed to better able reproduce lower notes. It was also louder for some reason. I expected it to be lower volume since there was less total area.

The best, so far, of the three types I've tried is the VCR tape. I think a really good set of electrostatic tweeters/midranges can be had by using that stuff.

I'm considering making some long, narrow drivers that can then be arranged in sort of a half circle to help imaging and dispersion.

I'm a little stoked about this early success and just ordered a tube transformer to move the experiment along to "real" speakers.

DH

Click to expand...

Pretty neat! .... What about 4 foot long strips of the VCR tape running vertical?

The anti-static bag material worked OK - but it tends to stretch unevenly and that makes it harder to apply evenly

Click to expand...

Wonder if a heat gun or hair dryer might help (or just make a mess)?

speakerlust said:

Pretty neat! .... What about 4 foot long strips of the VCR tape running vertical?

Click to expand...

Yes - in fact that's about what I thought. I may attach the tape at different length intervals just to reduce any standing waves an resonance peaks.

My plan now is to make a couple of driver arrays and mount them on the wall about head high. I'm thinking that I can use one sub-woofer shapped like a table or ottoman. This may result in a system that really sounds good and takes up much less space.

If I use a picture frame to mount the electrostatics, then it will blend in nicely with the room decor - especially if I put a photo on the grill cloth. Almost invisible.
DH

That may work - but I'm much more into the easier way (I'm pretty lazy) - that means the VCR tape. And I'd worry about the stretchy plastic sagging over time.

DH

mhardy6647 said:

Wonder if a heat gun or hair dryer might help (or just make a mess)?

Click to expand...