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Old 23rd November 2007, 03:52 PM   #51
SY is offline SY  United States
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Daan, if I were to guess, I'd guess that Sound Lab's film supplier is using one of the fluorocarbon-based extrusion process aids like Dyneon. These are added at very low quantities and end up mostly on the surface of the film in (indeed) micro quantities. It's nothing unusual, I even use those process aids in extruding wine corks, but, hey, it's a feature.

As I said, it's just a guess, but I've gotten a bit cynical about technology claims in high end audio and have seen that kind of puffery over and over again.
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Old 8th April 2009, 03:24 PM   #52
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Sorry to resurrect this topic, but I'm researching coatings, and specifically suitability for a high humidity, and dusty environment. Indeed, whether ESLs are suitable at all in high humidity (daily swings from 40-50% to 80%, and frequently to 95-100%).

The options I see discussed are:

1) graphite power
2) PVC
3) hand soap, etc
4) elvamide (nylon in alcohol), or calaton as used originally by Quad
5) EC-coating (what is this, and where can I get it?)
6) Licron

I appreciate there are all kinds of other possibilities, which have been raised in this thread, but I'm looking for a proven solution, if I go ahead with a regular ESL (probably a hybrid using eggcrate and wire, crossed at 200-300Hz).


Also, for membrane, 12u (microns) or thinner mylar or hostaphan seem to be the recommendation with 6u, 4u, and lower mentioned as preferable, and saran also a possibility but not recommended. However, I see shackman are using a polypropylene film rather than PET. Are there better film choices than mylar now?


On ESL design, I've been doing plenty of reading, and the standard ESL approach is to bias the membrane, and put the audio signal on the stators, out of phase with each other. However, there is another way, used by Beveridge, which is to put the audio on stators AND membrane. This way seems to have plenty of merits, especially re: dust, etc.
Is there a reason ESL's follow the "static membrane" pattern? Even the reverse, ie biasing high-resistance stators, and sending the signal to a low-resistance membrane seems better for dust, etc.

The Beveridge stators appear to be a mixture of carbon and epoxy, with a foil backing on the outside; away from the membrane. Not entirely dissimilar to a PCB, in seems. Has anyone experimented with a DIY version of the Beveridge approach? I know he states in a thread that their method is not suitable for DIY, but I think their life production is only a few hundred units, so they must be using relatively DIY, or at least, small-run, production techniques. Not meaning to rip anyone off (I can't, and probably never will, afford $65k speakers), but I'm intrigued by their different approach.
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Old 9th April 2009, 08:04 AM   #53
Calvin is online now Calvin  Germany
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Hi,

All the named coatings have been extensively discussed before and from this list the EC-coating should meet Your demands best, if not the only usable one.

Mylar and Hostaphan (at least certain makes of these) are the best materials for diaphragms. I haven´t heard of a PP-material yet, that could hold the mechanical tension over a long time.

Any ESL applying the audio-signal to the membrane is of so called constant-voltage-type. Driving forces are highly non-linear and so distortion is high. It is only really usable at very small excursion levels, so maybe as Tweeter-panel.
Biasing the membrane and applying the audio signal to the stators leads to a constant-charge-type. Here the driving forces are highly linear and exceptional low distortion values are possible. Sonically its a vastly superior system.

To my taste the casted epoxy stators are very much DIY-style.
The clue behind these stators is the doping with a very high epsilon-valued doping agent to get a high-epsilon-dielectric. This allows for low voltage losses in the thick stator whilst lowering flashover problems by the sheer distance between conducting surface and membrane. As a sideaffect the high mass and strength of the panel should be work in favour too. It must be kept in mind though that a very smooth distribution of the doping agents is needed and that the voltage-current-relationships within the stator might not be linear anymore.
For a first step it might be much easier and more success-promising to use PCB-material and drill and etch a certain hole-pattern into this.

jauu
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Old 9th April 2009, 04:18 PM   #54
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Thanks Calvin, yes I know this has been done to death, but there wasn't so much discussion about which, if any, coatings were suitable for high humidity.

About ESL design, I don't understand why it matters whether the stator, or the membrane is "active", so long as whichever surface has the varying signal has low resistivity? ie a "reverse" esl should be just as effective as a standard one, partcularly in the case where there is just a single stator. I think the Beveridge have both stator and membrane variable though, I don't fully understand the system.

I think I will follow your advice and look at a fairly standard design - there is plenty to read and think about just with that.
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Old 10th April 2009, 08:30 AM   #55
Calvin is online now Calvin  Germany
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Hi,

the trick with a constant charge ESL is that it ´takes the membrane out of the electrical circuitry´. By this I mean, that the membrane is regarded as a ´piece of constant charge´. It wouldn´t need any electrical connection to a bias-supply or any other part of the electrical circuit at all. This is the case for so called electret materials which are used in electret microphones and electret Headphones.
The music signal which is connected out of phase to the two stators creates a homogenous electrical field between the stator-plates. This means that the force acting on a probe-charge is the same at any point between the stators! The system is perfectly linear as long as the stator plates remain fixed. The value of the charge has a influence on the forces acting upon the charge/membrane, but it can be shown, that this doesn´t effect the linearity of the system, but just creates a mechanical offset of the membrane off of the middle position.
If You change to a low resistance coating (constant voltage type) the membrane becomes an ´active part´ of the electrical system which is constantely charged and discharged. The forces acting upon the membrane are not linear any more since the membrane behaves like a moving stator itself. The forces vary quadratically with the distances of stator and membrane, hence non linearity, hence distortion. Distortions can only be kept small if the excursion can be kept very small.
The real expalanation is of course more complicated, but this should give You a rough idea.

jauu
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Old 10th April 2009, 10:43 AM   #56
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Quote:
Originally posted by jackpipe
Thanks Calvin, yes I know this has been done to death, but there wasn't so much discussion about which, if any, coatings were suitable for high humidity.


Hi Jackpipe,

The coating I used successfully in Thailand is graphite powder. Humidity in Thailand is quite high all year round.

Wachara C.
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Old 16th April 2009, 04:38 PM   #57
hafp is offline hafp  United States
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jackpipe,

ER Audio in Australia sells a proprietary conductive coating that works very well in high humidity conditions; although do not know of any ESL's that can stand up to near 100% humidity conditions for years on end without quirks.

Calvin gives you some excellent advice on ESL designs.

Good luck.
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Old 15th May 2009, 09:01 PM   #58
pongola is offline pongola  South Africa
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Default coatings

Does anyone have a comparison between the ER coating and the one that Martin supplies? What effect does altitude (if any) have
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Old 11th July 2009, 10:25 PM   #59
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Hi folks,

A modern coating works fine forever in any altitude, moisture and applied voltage.

The progress in electro-chemical substrates is far beyond that what is discussed since decades, especially about that "Nylon Myth", and, on the opposite, the ESL63 kind of graphite coating with Nylon pre-base coating.

That was yesterday. Today we have coating substrates light-years beyond all those discussions. So why live in the past. Better refer to the latest science developments. At least we do so since very quite a while.

Regards

reromanus
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Old 12th July 2009, 11:30 AM   #60
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Default sample

Reromanus, I understand that You make a coating that works, could it be possible to receive a free sample?

regards, Jonas
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