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Old 23rd April 2004, 04:19 AM   #11
Duo is offline Duo  Canada
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Yeah. I wondered about that too. What's supposed to be the best: Graphite on one side? or both sides.

If on one, which side?
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Old 23rd April 2004, 04:46 AM   #12
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Default graphite coating.

One side as far as I know.
What do you mean by which side ? It doesn't make a difference.
Your contact is from the coated side.

If it is the usual shiny film , any side is OK. If one side is duller , I guess that would hold the graphite better . I'm not sure.
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Old 23rd April 2004, 05:54 AM   #13
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I'm suprised Sheldon Stokes hasn't jumped all over this thread. His site has excellent info on ESL contruction. Quad ESL Pages

Sheldon recommended ER Audio as a good place for supplies like films and coatings.

For whatever reason Sheldon doesn't seem to have updated his site in a while regarding his ESL projects.
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Old 23rd April 2004, 09:40 PM   #14
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has anyone tried dish washing liquid? I think it was Wagners book that mentioned using dish washing liquid over graphite because it was easier to deal with. Has this been disproved?
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Old 23rd April 2004, 09:47 PM   #15
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Miscellany:

Dishwashing detergent is reputed to not be stable.

One side is sufficient. If you have surface-treated film (e.g., corona-treated, sometimes called "print-treated"), you want to coat on the side with the highest surface energy.

I've read about Nylon solutions being used as coatings- that might be interesting to pursue.

The best coatings are dispersions of colloidal carbon in a carrier polymer- stable as can be, very good control of resistivity, easy to apply. The downside is that the surfaces MUST be print-treated, and the colloids are solvent-based so must be handled with care and generally heat-cured.
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Old 24th April 2004, 04:20 AM   #16
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how about a thin, pliable, sprayable paint with graphite in it? like maybe a dusting of something that will stick without having to rub in.
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Old 24th April 2004, 04:34 AM   #17
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Quote:
Originally posted by johnkramer
how about a thin, pliable, sprayable paint with graphite in it? like maybe a dusting of something that will stick without having to rub in.
That's pretty close to optimum; you probably would want a high structure factor carbon black (like a channel black) rather than graphite, though, because the goal is a uniform HIGH resistivity. The main difficulty for the home constructor is getting it to stick well to diaphragm films. I home-brewed my own coating formula, but I have access to some pretty sophisticated blown plasma systems to permit proper adhesion of the coating to the film.
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Old 24th April 2004, 01:01 PM   #18
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Default Found a possible film,

Quote:
You don't want to use Teflon. It's impossible to get coatings to stick using commonly-available techniques, and it cannot be heat shrunk. Poor tensile strength, too. Also, 1 mil (0.001) is too thick- you want one-half to one-quarter that thickness.
How about either .00063 for one film I see, or .00015 for the other? Seems like the thinner one will work.

How about getting the tension correct? Making up a jig may work, but how important is getting the film stretched equally?

Many thanks all, for ideas in the forums,

GH

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Old 24th April 2004, 01:06 PM   #19
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I haven't seen free-standing film as thin as 0.00015- I can't see how you could handle it. What's the material?

0.00063 is a bit thicker than optimal but not outrageously so. Tension is your friend- you want lots of it for stability and to tame the fundamental resonance, which is why a heat-shrinkable material is desirable. It's pretty easy to get the tension reasonably even with a heat gun and some patience.
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Old 24th April 2004, 02:49 PM   #20
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one-quarter mil mylar is what sanders used, its not heat shrinkable, he used spring scales in a jig to tension the membrane.

One question I have about shrinkable plastics. How much tension do you apply in the initial stretch of the diaphragm, before you use a heat gun?

Of all the DIY speaker building projects one can take on, an ESL is probably the easiest for an apartment dweller like me to take on. I've been pondering a project that can be made in a small kitchen with basic hand tools. The only power tools needed is a soldering iron for the electronics and maybe a heat gun
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