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Old 2nd April 2007, 07:12 PM   #11
Few is offline Few  United States
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Can you figure out what the source of the lobing is in your current panels? That might help you decide whether to repeat that configuration. I'd also be interested to hear what you find.

If you only run the narrow tweeter strip, and disable the wider panels, is lobing still evident? If so, and the tweeter panel is quite narrow, then maybe diffraction or reflections from the support structure are to blame.

If lobing shows up when only the midrange panels are used then that would seem to suggest that the midrange needs to be rolled off at a lower frequency. Unfortunately, that might put too much strain on your tweeter.

If both the tweeter and midrange panels need to be running in order for lobing to be evident then interference between the two panels may be the culprit. Steeper filters to limit the range over which both panels contribute might solve the problem. Of course steeper filters aren't as easy to install as a single resistor in series with the midrange panel.
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Old 3rd April 2007, 03:57 PM   #12
Calvin is offline Calvin  Germany
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Hi,

"The diaphragm tension is critical on a curved ESL. Too much tension and it pulls in between the spacers-ruining the diaphragm to stator distance, too little tension and the diaphragm is wrinkled. There's just not enough room for error."
Actually its not that bad
Important is that You apply lots of tension in the straight direction and just enough tension in the curved direction to straighten out wrinkles ...thats all! It helps in the beginning to have a tensioning frame that is considerably longer than the panel and just to use the middle part of the diaphragm.

jauu
Calvin
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Old 5th April 2007, 02:00 AM   #13
BillH is offline BillH  United States
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Quote:
Calvin writes: It helps in the beginning to have a tensioning frame that is considerably longer than the panel and just to use the middle part of the diaphragm.
Hi, Calvin. My DIY stretching frame wasn't very effective. It was a collection of pine lumber, threaded rod, wood dowels, and double sided tape. I needed something like this jig from Shackman.de.

Hi, Few. Thanks for all the advice. I'm going to use the electronics from one of my current ESLs for this project and will be able to try out your ideas when I start testing. I'll let you know what happens.

Here's a picture of the latest version of the stators with a 500 gm roll of solder next to them for scale. It's going to be a simple flat panel built from 0.050" thick aluminum with 0.057 diameter holes, 35% open area and a 4-1/4" x 11-1/4" actual radiating area. The non-staggered hole pattern made cutting an edge with no sharp edges very easy.

The insulators are 0.025" thick acrylic sheet super glued to the stators with a divider that breaks up the diaphragm into 2-1/2" and 1-3/4" wide sections. The VHB tape from the first version didn't work out very well. It needed it to cover more area than I was willing to give it to be effective. I've used VHB in real life and it can perform extremely well when used correctly. My first try just wasn't a good usage of it.

I tried a couple of things that seemed like a good idea at the time. Each stator has an short edge bent at 90 degrees to the face to give it some rigidity and I added four legs for mounting. Each of the holes in the legs will have a rubber grommet added later. The legs should also make a good connection point for wires.
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Old 6th April 2007, 03:56 AM   #14
R. Jamm is offline R. Jamm  United States
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Default SMALL ESL

Does anyone have a simple DIY small size DIZ ESL project that they can share?

R.
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Old 7th April 2007, 04:19 AM   #15
BillH is offline BillH  United States
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Hi, R. A small ESL is built exactly the same as a large one. Have a look at ESL Projects at The Audio Circuit for a collection of ESL builds.

Stretching and attaching the diaphragm went without incident. The picture below shows my stretching jig. It's a piece of 3/4" MDF with a 6 micron Hostaphan diaphragm taped to the top on two sides. The free edges have wood strips clamped on and weights to give tension to the film. I gave it just enough weight to take out the wrinkles. After it was glued to the insulator, I had to use a hair dryer to get out a few small wrinkles.

I'm working on a new diaphragm coating, a glue based DIY formula that is a variation of the one used on my first ESL. A test film is coated and I want to check it tomorrow to see if it still measures OK. If it works I'll be able to put the small ESL together and try it out this weekend.
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Old 8th April 2007, 07:21 PM   #16
BillH is offline BillH  United States
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The small ESL is up and running and it sounds great. It has a very similar sound to my larger ESLs with less low end as would be expected from a smaller panel. The small ESL seems to be about as efficient as the larger panels, but plays louder. The smaller capacitance lets my amplifier deliver more power before its protection circuit kicks in.

The highs are crisp and extended, just how I like it. With a 12db/octave @100Hz crossover I can drive the diaphragm into the stators at loud volumes, but a 12db/octave @200Hz crossover cures that. My first guess at a good crossover point would be in the range of 1Khz to 2KHz. Without some help from a woofer in the lower midrange, male voices sound a bit thin. High frequency dispersion is still limited both vertically and horizontally, but that's not a huge problem for me.

The picture shows the small ESL on the right, large ESL in the center, and an 8" woofer on the right. The large ESLs are providing bias voltage and the audio step-up transformer.
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Old 8th April 2007, 07:35 PM   #17
BillH is offline BillH  United States
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Here's a screenshot of the small ESL without equalization. The microphone is 3" away from the center of the ESL and white noise is being fed to the ESL. The high end of the graph looks a lot like my larger ESL with a broad rise at 6Khz and a dip above 10KHz.
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Old 8th April 2007, 07:50 PM   #18
BillH is offline BillH  United States
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And here is the frequency response after equalization. Much better. There's a screenshot of the equalization I used on the left of the picture.
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Old 9th April 2007, 10:16 PM   #19
Few is offline Few  United States
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BillH-
Thanks for the updates. I'm surprised to hear that "The small ESL seems to be about as efficient as the larger panels, but plays louder." Can you remind me what the spacing and overall size are for the large panels? I'm assuming the small one keeps up with the large one because of a significantly smaller stator/diaphragm gap, but I'm still surprised the maximum loudness of the small one is greater. Is your amp's circuitry limiting the loudness of the large panels at fairly low SPLs?

Few
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Old 10th April 2007, 12:18 AM   #20
BillH is offline BillH  United States
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Quote:
Few writes:I'm surprised to hear that "The small ESL seems to be about as efficient as the larger panels, but plays louder."
Hi, Few. Me, too. Even though I was careful and checked my work, part of me was surprised it worked at all. This happened with a reduced bias voltage, too. When I first started the small ESL I forgot to turn down the bias voltage. It sounded like bacon frying. When I turned it off, I could hear the diaphragm that had stuck to the stator slowly deattaching itself. Fortunately there was no permanent damage.

Quote:
Can you remind me what the spacing and overall size are for the large panels?
About 0.060" diaphragm to stator spacing and about 3 square feet of radiating area.

Quote:
Is your amp's circuitry limiting the loudness of the large panels at fairly low SPLs?
I believe it is. The amp is nothing special, a Kenwood 100 watt x 4 home theater receiver. I am grateful for the protection circuit. Without it I would have left the magic smoke out of the amplifier several times.

I think the next step will be to make a new pair of small panels based on this one complete with bias supplies and step-up transformers so I can move on to enclosing the back wave. Has anyone tried the cheap CCFL power supplies for bias? I'd like to try to avoid building them from scratch if possible. I'm also looking for cheap toroids to try as audio transformers.
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