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Old 22nd October 2013, 10:35 AM   #1
hesener is offline hesener  Germany
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Default DIY tweeter

Hi, looking at building a box speaker using a couple SEAS F8, and I am looking at adding a (super) tweeter to them. It may not entirely be necessary as the highs of these speakers are fine, its also for the looks I guess.... Would like to build my own tweeter:

- Electrostatic
- Diameter 20mm
- Frequency range 5...10kHz upwards (or so), tbd
- Separate case Nautilus style, with a closed back side and damped interior

But at this point I am just thinking..... The docs over at the B&W website talk about the tapered tube in the back of the tweeter, which is loading the speaker similar to a horn, only that its getting smaller instead of wider, and that the damping material is getting progressively more dense along the tube, all in an effort to dampen the back wave. But I am no expert in horns by any means....

Has anybody tried this? What could be a good material for damping high frequency sound at the backside of the tweeter? All inputs welcome.....
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Old 22nd October 2013, 04:39 PM   #2
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The best material for damping is wool. Use the Visaton material or other available at your location.
LAMB'S WOOL
Visaton 5069 | Lambs Wool
Technical instructions relating to your project might be available in the forum,
Planars & Exotics - diyAudio
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Old 22nd October 2013, 06:46 PM   #3
hesener is offline hesener  Germany
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Many thanks for the suggestions and the reference. What makes it the "best" material?

I do not have experience with damping material on the back side of an ESL, guess I should keep some distance there else the fibers might be attracted by the high voltage. In fact, I was thinking of a piece of carpet, with 5mm "hair" length, and glue this to the walls of the cavity behind the tweeter, not so much stuffing it with damping material.

And yes, I did search both forums and here were more inputs regarding the design that B&W is using. In search of an efficient and good-sounding way of damping the back wave of a tweeter.....
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Old 22nd October 2013, 07:25 PM   #4
sreten is offline sreten  United Kingdom
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Hi,

No-one has ever made one for very good reasons.
You are hopelessly technically way out of your depth.

rgds, sreten.
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Old 22nd October 2013, 09:53 PM   #5
tvrgeek is offline tvrgeek  United States
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I would second sreten here. Spend the next few years getting the tweeter to work (it will take that long) and then worry about a tuning cavity. An ES moves a very small distance, so you will find you will need a much larger radiating surface. An old Xerox machine can supply the HV supply. This is DIY, so by all means, go for it as you will learn something. I was never brave enough to build an ES, I had enough of it building a crona effect tweeter. It did produce sound with no moving parts, as well as enough ozone to kill me and the planet. People have built DIY AMT's, and as replacement membranes are available, that saves trying to etch and fold one yourself. Ribbons have been built and I see no reason you could not build a planer electrodynamic.

I tested stuffing a while ago. I found wool, cotton and Acousta-Stuff to be about equal overall, each with some advantages over others. I guess I prefer wool for it's ability to reduce reflections back through the cone. Splitting hairs though. I was surprised that for a simple sealed sub, plain old pink FG worked better to increase the bottom end. Foam and that slippery cheap polyfill were far worse in all respects.
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Old 23rd October 2013, 06:52 AM   #6
hesener is offline hesener  Germany
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Thanks for the encouragement. The ELS cell and driver electronics are not so much of an issue here (built some of these , admittedly a while back), I am trying to understand the acoustic side of it.

What is "pink FG"?
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Old 23rd October 2013, 07:01 AM   #7
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If I'm not mistaken must be FG fiberglass pink from OC, construction insulation material.
http://insulation.owenscorning.com/h...as-insulation/
Test other materials you have in mind...
http://www.bobgolds.com/AbsorptionCoefficients.htm

Last edited by Inductor; 23rd October 2013 at 07:07 AM. Reason: Frequency Absorption Coefficients
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Old 23rd October 2013, 05:23 PM   #8
hesener is offline hesener  Germany
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many thanks, thats very helpful
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Old 23rd October 2013, 06:11 PM   #9
sreten is offline sreten  United Kingdom
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Quote:
Originally Posted by hesener View Post
I am trying to understand the acoustic side of it.
Hi,

You cant understand the acoustics without first understanding
the physics of electrostatics. Assuming the tweeter is dipole
(no rear loading) on a baffle, what sensitivity and max SPL
can you reasonably expect from a 20mm electrostatic ?

What is the difference between rear loading an electrostatic
and rear loading a dome or cone ? Why are there no rear
loaded electrostatics ? Or horn loaded electrostatics ?

rgds, sreten.
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Old 23rd October 2013, 06:24 PM   #10
tvi is offline tvi  Australia
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B&W made an ESL tweeter

Click the image to open in full size.

Maybe you need something like Sony SA-S1 to play with...

Click the image to open in full size.

regards
james
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