tade no esl

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so i have a panel that is eight inches by twenty two. a good tester. using gaphite on my saran wrap diaphram. i jacked a HV supply from a night vision camera, and it is capable of dragging the membrane into the stators. so that tells me that i am maxing out my voltage potential. i also bought a pair of tube otuput transformers to use as the step up. the secondary can be four eight or sixteen ohms. I tested with four. the primary is listed at 10000 ohms center tapped.
the volume was pretty pathetic. and when i turned up the amp to get a decent level, not rocking out, i could hear the transformer clicking and hissing. I hope this is just coils moving in the magnetic field and not laquer vaporizing, or layers arching... I am feeling a bit on the low side, any advice you could give would greatly help me!
many thanks
the diaphram was at about twenty hz i would guess. you could hear it vibrate, but it was very low. maybe tighten the heck out of it?i do not intend for these to be full range, maybe i could make the resonance yield a flatter response and high voltage tolerance. the spacing was probably four milimeters on either side. the thickness of the saran wrap is anyone's guess. quite thin i should think.
Well, most grocery-store Saran Wrap is about 5 times too thick. Finding 0.5mil Saran requires some hunting. Thinness for Saran is particularly important since its specific gravity (density, weight per unit volume) is considerably higher than Mylar.

For your geometry, a 20Hz resonance suggests that your tension is too low and (possibly) your diaphragm is too massy. If you really have 4mm of spacing on either side, that's pretty high, too. You'd be better off with 2-2.5, the lower number being more appropriate if you're not running full-range.
wow, i had no idea how thick saran wrap was in comparison to acceptable mylar, that and its density. The heavier diaphram will limit my high frequency and impulse response? I am going to build a new test panel today. 1.5mm spacing using double sided tape. and i will also stretch the **** out of the diaphram. Ill let you know how it works.
Thank you for the advise!

BTW, I greatly prefer your new look over the decomposing dwarf :)

I believe that the mass of the heavier Saran will only significantly effect the high frequency roll-off. This is where the diaphragm mass reactance exceeds the air radiation resistance. Therefore, we would expect an earlier roll-off in the treble with the heavier Saran. Well below that frequency, there would be no difference in sensitivity between heavy and light diaphragms because the air radiation resistance dominates. At low frequencies the diaphragm's stiffness interacts with the air mass reactance to determine the resonance, and not the relatively light diaphragm mass.
That's right- the mass part of the motor is dominated by the air load at lower frequencies. In tade's case, he's got an 8" wide panel which will (without eq) not go very low. If I were to guess, the combination of these two rolloffs is one contributing factor to his low output.

I've got some panels about the same width (rebuilt and heavily modified 1+1s) that are putting out very satisfactory levels, but it takes a lot of voltage swing for them to do so. The wussy 1kV direct drive amp I tried on them was fine for background music...
i started today on the bigguns. one by four feet. too me an hour to make one panel. i will need four... wish me luck

i was showing my neighbor the test esl i built. he was very impressed. then i showed him the sub i built, a wicked one. that was also impressive however, when i cranked it, it caused the panel resonate and the membrane to hit the stators with no charge on em! give and take.

more news later, and maybe some pics if you are lucky.
So i built a one by four foot panel. Sounds great. i really like the the beaming. allowa me to be further away with no reduction in quality. which is really neat. I don't notice anything lacking in the upper ranges due to the heavy saran wrap i used. i atribute that to either, rising trebel response caused by the transformer canelling out the damping by the wrap, or my prematurely aged ears!

I used double stick foam tape which is about one mm thick It sticks wonderfully to the stators and the membrane, which leads to another dilema. this panel's tention was too low. i probably got excited during its construction... anyway, this means sometimes i must shake or blow on the panel to stop popping and hissing sometimes. Ill have to tear it apart which i am not looking forward to. the next step will be housing them in such a way as to inspire awe in my fellow human being. this may be harder than i expect.

Also, i will need to pair it with a goldwood ten inch woofer. looking to do this scientifically with measurements and such, but i blew the fuse on my multimeter. so on to another day.

I have three weeks left til they come to school with me finished or not.

I think the biggest problem with saran type film is the low spring constant will keep you from ever getting enough tension to run them at high bias voltage. The reason you have to shake/blow on the panel to stop the hissing is the diaphragm is being pulled over and sticking to the stator due to the low tension or large unsupported area of the diaphragm. If you can't get the tension any higher, add more support to the diaphrgam. With only 1mm diaphragm to stator spacing you should be supporting the diaphragm every 2-3 inches- i.e. if you should not have any unsupported diaphragm area with a smallest dimension of more that 2" or so. You can have a long strip 2" (maybe 3" max) wide that is unsupported, but 4" is probably too wide. That's the fun thing about these drivers. You can experiment a lot and find the optimum size for very low cost. Try 4" spacing. If it's too big, go to 3". It only takes a few minutes to make another driver.

Double stick foam tape is OK except that the stuff normally dries up and crumbles to dust after about a year. In an ESL with high voltage applied and resulting increase in ozone (there is always some especially around corona points) it's liable to break down sooner. I would look for a more permanent solution unless you don't mind rebuilding the drivers every year or so.

The other problem with foam tape is its softness. When you sandwich the whole thing together it will still be pretty flexible which can easily lead to wrinkles in the diaphragm. Wrinkles will lead to hissing and noise problems, and will make rattling sounds when the speaker plays.

you are exactly right of course! i did have to put some supports in the middle of the panel.

another problem i had on a smaller test panel was resonance. it was not audible, from the panel itself, but if stimulated externally, the membrane would wail on the stators creating a buzzing noise. maybe more supports are needed.

yes, the low cost is an insentive. i figure i have made something which is more sonically acurate than something i could have bought for a similar price. that is terriffic!

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I don't really like seeing the panel being excited by the bass, so I would favor a physical separation somehow. Perhaps have a framework so the panel straddles the woofer. But having said that, I really like the way the Final 0.3 looked. Otherwise, what can you really do with an enormous skinny panel and a woofer housing? Let us know.

If you NOT dilute liquid soap, you will achieve a resistance between 20 and 100 Mega-Ohm. This is not too high. The resistance may increase when the humidity of air lowers, but in the case of soap this is within the limit most of the time.
So you may add another layer of (undiluted soap). Ofcourse, it is not transparant at all and it adds more mass, but since you use it on a test-panel I suppose this is not a problem.
Because of limited chemical stability and poor adhesion of soap, I recommend buying the EC-coating for the final project.
Since you won't be using the ESLs full-range, you might consider using graphite for the diaphragm coating. My experience with detergent solutions is that they don't stay on the diaphragm long (maybe a couple months). My experience with graphite is that it works for a looooong time. I have test drivers and speakers made >15 years ago that still work fine.

Graphite is mainly undesirable because the resistance of the coating will be a bit low. This isn't a problem if you're not trying to reproduce very low frequencies.

Graphite is very cheap and readily available.

The stuiff I used is lock lube also.

There is no way to make it even so practically speaking, uneven coating doesn't matter. When you apply the stuff, the diaphragm should be under tension and against a hard surface such as a very clean table. If the surface of the table is white, it will be easy to see where the graphite is and is not. It takes very little of the stuff to cause some discoloration of the diaphragm.

Put a little on the diaphragm, take a cotton ball (or polyester ball, or whatever you are using, it is not critical as long as it is soft and won't tear the diaphragm) and rub the graphite into the diaphragm. After you have covered the entire diaphragm with some graphite (it won't be even), use a clean cotton ball or two or three to rub off some of the graphite.

That's really all there is to it. Don't try to make it even- you can't do it.

If you are heat shrinking the diaphragm to tension it, good luck. I don't know how you can apply a graphite coating to a heat shrunk diaphragm because it will already be attached to the insulators (and maybe one of the stators).

Back when I was using graphite to coat diaphragms, I used a mechanical stretcher table to tension the film, apply graphite, then finally glued the diaphragm to the insulator/stator. These days I use the mechanical stretcher to tension the film, then glue the film to the insulator/stator, then spray with Licron. Licron is very easy to apply and very effective, even for full range speakers, due to the very high resistivity of the coating.

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