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Old 22nd March 2011, 08:54 PM   #1
sdad is offline sdad  United States
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Location: Grand Ledge, MI
Default criterion 85-es

Just came up with a set of 85-es speakers. Apparently the tweeters are not working. Anyone with a schematic for this speaker? Physical evidence points to the ps, but would be handy to have schematic. The supply is simple enough to reverse, but looks like some pieces are removed ?????, so again a schematic would be handy

Never done anything with electrostatics, so this is just to get boxes running, not to bash the quality or lack thereof.
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Old 24th March 2011, 03:17 PM   #2
sdad is offline sdad  United States
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I have reversed the pc board and have come up with a schematic. The ps is directly coupled to line voltage (120vac) and a doubler gives me 275 VDC out. The audio signal is transformer coupled to modulate the dc output voltage. The tweeters are single ended, a metal perfed grid with a plastic film over the top. Contacts for the grid and the film are good, no shorts between film and grid. I have 2 supplies and 8 tweeters.

I do get output from each tweeter and each ps. Audio levels are pretty much the same for all combinations. I am witnessing very low audio levels, however. Not knowing what to expect, the fact that both ps's and all tweeters work pretty much the same, I'm tending to think that this is normal. Would anyone care to speculate? (maybe a good 20db below a direct radiator connected to same port, I mean, it's quiet)

Being that these tweeters are single ended, much of the low distortion of the more typical electrostatic speaker has been design out. Since I have very little invested, any suggestions as to how I might go about (1) converting to a push-pull arrangement (2) improving on the efficiency.
Never once have I done a thing with electrostatics, so not sure what I might consider, if anything at all. Again, little invested, so let the good times roll.
I can supply photos and a drawing of schematic if that would be of productive benefit

Last edited by sdad; 24th March 2011 at 03:20 PM.
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Old 24th March 2011, 04:11 PM   #3
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The only thing I could find is that they were made by ESS for lafeyette.
It sounds like it could be a fun project.
Drawings and photo's would be great.
However the time spent trying to convert the esl drivers one could build a complete new driver very easily.
My method uses plastic lighting grid and window screen coated with spray paint (clear acrylic).

here are just a few examples
Material for ESL

How to construct a cube louver (Acoustat)

How to construct a cube louver (Acoustat)

Acoustat panel angles? 8" vs 9" panels?


Last edited by geraldfryjr; 24th March 2011 at 04:31 PM.
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Old 24th March 2011, 04:49 PM   #4
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And one more,but not the picture I was looking for. jer

ESL Diaphragm coating

Found it.

are ESL's, planars etc for me?

Anyway if you posts some pics it may be very possible to acomplish your goals easily aswell by using some pcb material like my micro driver.
It was tested with only a 500v supply applied and worked rather well. jer

Last edited by geraldfryjr; 24th March 2011 at 05:13 PM.
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Old 24th March 2011, 07:08 PM   #5
sdad is offline sdad  United States
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Thanks, Jackson. Grand Ledge appreciates! Allow me to read over all you sent. At the diaphragms I have 280V. The output transformer is about 1:14. Built in crossover is about 5K. With no ac applied I get the same amount of volume as when there is power, both low. As there isn't any amplification, not surprising. I'm not detecting any difference in distortion however, and this is surprising, but with the low level and my nasty signal source (don't ask, please) not sure this means much. So who needs bias anyway (snicker, jeer).
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Old 24th March 2011, 07:58 PM   #6
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yeah,unfortunately they don't work so good without it. jer
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Old 24th March 2011, 08:00 PM   #7
sdad is offline sdad  United States
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OK, I'm back. First thing I noticed is the use of a couple of Radio Shack copper clad boards for the +/-stators. I have several 1.75 x 2.5 China perf boards. Too small for a first pass? Window screen should work, also. I have seen screen up to about a 1/2" grid. Would this been too far apart?

You mentioned a 500v bias, how about the 280v that I have? Too low? Caps that I have are 400v, so a tripler is out.

The diaphragm mat'l from my existing spkrs should be large enough, perhaps a recoating?

Need to go back and see what you use for coating, connectors, spacers and output transformer. The criterion xformer doesn't have a ct, so can't use it, unfortunately.

Hmmmm, just may be able to afford this. That'd be cool.
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Old 25th March 2011, 12:23 AM   #8
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1/2" screen is to large I have seen 1/4" but I have not tried it and 1/8" has to be special ordered.

I use use common 14 x 16 or whatever happens to be on the shelf.

Some like to use preforated metal,but it is rather costly.
Lincane would be good for small drivers if you have any laying arround.
I saw some at menards a few weeks ago but it was over $40 for a small piece of it.

400v caps will work in a tripler or multiplier if the proper circuit configuation is used.
But it takes at least 2kv to 3kv to get good output on an average.
I push mine to the limit with a variable 0v to 7kv supply that I designed.

I never got to properly test the micro driver but it worked good as a headphone unit as this was its intent.
So Idon't know its limitation's yet.

The stator of that driver is actualy aluminium duct tape smoothed to the flat side with all of the holes poked through with a toothpick and I used an etching method aswell.

I coated with clear acrylic and sanded it flat on a peice of glass and some 600 grit sand paper and coated it again until I got a perfectly flat finnish.
This was critical because daigphram to stator spacing ( d/s ) was in the order of .025" to .035" as I used some gift credit cards for the spacers.
Then the whole thing was assembled with scotch double sided transparent tape.

If you have a micrometer handy it is priceless tool to keep every thing symmetrical but if it isn't perfect it does not mean that it won't work.

The best diagphram material to use is mylar I have some .25mil but it is hard to find.
.5mil is common some have even used some types of food wrap and shrink wraps sucsessfuly.
The thinner the better but mylar is the best to use due to its mechanical stability.
I used monokote on my first build with great sucess.

The coatings I have used are licron and licron crystal.
Don't waste your time trying to rub in graphite.
Some use a diy formula that uses white glue thinned with water.
I have experiment with this method but never actualy used it on a diagphram since I have the licron.
However I have made a nice conductive paint using the same method and mixing in some powdered graphite .

The transformers you have could probably be made to work but performance would be marginal.
Alot of us have discoverd using toriod power transformers in reverse and I did a big write up on using this method.
I personaly (as others aswell) don't have any issues about sound quality using this method but a ground up build could yield far better result aswell for reasons explained in that thread.

I have spent around $200 in research of different materials and if your resourceful
you could do it for well under $100 or even $50.
The most costliest part is the bais supplies and transformers.
The drivers them selves are next to nothing (under $20).

This is the cheapest method I could devise and I get great results from the panels I have made so far.
I was so blown away with the sound of one panel that I didn't even take the time to hook two up in stereo yet.

This project doesn't cost hardly any thing if your resourceful enough.
I have gotten companies to send me free samples of stuff like glues ,plastic films and thats how I (and others) got the licron which cost $30 to $40 a can.

Somtimes you can find some busted up pieces plexiglass to cut into strips for spacers.
The mylar used to cover windows or frozen food trays could possibly be used aswell if it is thin enough. jer
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Old 25th March 2011, 01:28 AM   #9
sdad is offline sdad  United States
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OK, I trash what I have, build from scratch. While gathering mat'l for panels do I build up power supply, seems to me that the spacing between diaphragm and stator is determined by supply voltage, correct? If so I can build up a supply of 5-7kv and build panels to match.
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Old 25th March 2011, 06:48 AM   #10
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Yes this is correct.
The breakdown of air is in the order of 80v to 100v per mil.
Plus the insulating factor of the stator coating.
But keep it on the low side to prevent any arc over.
So a 4kv supply will be suffiecent For a 1/16" d/s.
Most only use about 2kv to 3kv.
Making a variable supply is a nice feature.
You can make it variable by selecting different taps along the mutiplier string.
Once you get a feel of the construction process and material characteristics you can start pushing the voltage limits to try to squeeze as much effeciency you can.
However ,there are limits where nothing more can be gained.
I pushed one too far and arc over caused the panel to catch fire, but this was not caused by the bias supply.
Luckly it did not destroy the panel and I was able to make simple repair. jer
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