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Old 18th October 2005, 12:00 AM   #21
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What do you use to attach the film when you use PVC spacers.
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Old 20th October 2005, 10:12 AM   #22
Calvin is offline Calvin  Germany
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Hi,

I used to use double sided tape made to glue carpets. The brand TESA manufactures a strong bond tape in a whitish-yellowish colour called ´universal´ (50mm wide, 25m long). Cut into half the width I used it on 30mm wide PVC with very good results.

jauu
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Old 29th November 2005, 09:36 AM   #23
el`Ol is offline el`Ol  Germany
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Quote:
Originally posted by Calvin


If You want to build a hybrid with lower mechanical tension You may use a film down to 1/8mil.
Hello everybody! The talk about cylindrical ESLs in other threads lead me to this discussion about mylar thickness.

I am currently working on dynamic omnidirectional speakers. I am using fullrangers with a treble-dominated frequency response looking to the ceiling and no reflector. I made the experience that for the superior spatial image is essential to have the drivers on the level of my ears. My conclusion is that the most important point about omnidiredtionals is coherence of the direct part of the signal, not the fact that they show so much indirect reflections.
So I believe for a cylindrical ESL it is better to have many segments that are relatively narrow. A membrane with less tension may probably allow to manufacture this construction in one piece.


A good omni is worth any effort!


Greets, Oliver
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Old 29th November 2005, 10:43 AM   #24
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Hi el'ol,

segmenting the cylinder has two disadvantages.

1. if you really want to come close to a cylinder you need to arrange a lot of small cells, which will suffer from a high frequency resonance. e.g.
a cell having 2" width will show a resonance @ about 400-800 Hz, even with low tension.

2. Cells which are angled to each other will show the venetian blind effect, which lead to significant interferences of higher frequencies, causing a lot of ripple in response. Could be that the omnidirectionality is ditributing those effects.

since 10 years the cylinder-ESL is in my mind . Maybe igonna try it. I am sure that the imaging will be breathtaking.

capaciti
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Old 29th November 2005, 11:00 AM   #25
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hi folks,

regarding membran material, there is a new material called teonex, which is considered to outperfrom mylar.

Look here :

www.dupontteijinfilms.com/Teonex/Brochure/2.htm

Hi Calvin,

i read your post regarding your curvilinear panel. It would be interesting to see some frequency response measurements depending on the off-axis angle. I expect it to be very homogeneous between -10 and +10 °, with an significant loss of level @ larger angles.

my segmented panels are designed the same way. I intentionally try to have a good dispersion within +/10 °,which reduces at larger angles. imo too much dispersion is worse, since the first wave energy is reduced and wall reflexions are increased. As long you have sufficient dispersion in between the speakers base witdh, its OK. There is no need for further dispersion.

capaciti
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Old 29th November 2005, 11:08 AM   #26
Calvin is offline Calvin  Germany
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exactly
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Old 30th November 2005, 08:02 AM   #27
wrl is offline wrl  United States
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From what I've read, segmented cylindrical panels will tend to suffer from a "venitian blind" effect. This makes sense when you consider how strongly traditional panels beam... especially in the high frequency. It would be difficult to get around this affect.

What angles were you looking to offset each segment?

-Wes
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Old 30th November 2005, 09:09 AM   #28
Calvin is offline Calvin  Germany
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Hi,

even with 2 of my curved panels placed side-by-side togeteher I can clearly hear and measure the venetian blind effect. With an array of flat panels it should be even more distinct. That leaves You with the problem of producing a truely 360° circular. How´s about a elliptical shape with two curved panels facing each other? The panels could be connected and the space between them be sealed by frame that holds both panels. The sound pattern would be changed from a dipolar cylindrical shape to a bipolar one. The ´cabinet´ could provide for some damping mechanisms as suggested earlier.
Still, I doubt that it´ll be possible to handle the reflection problem with the backside sound waves sufficiently. The lower the freqs the bigger the prob.

While a unidirectional speaker has its merits and friends, there are a lot of people -me included- who prefer a highly directive sound pattern. A cylindrical sound pattern is imo the best for a lot of rooms, because the nasty early reflections from the rooms sidewalls, ceiling and ground are minimized, thereby emphasizig on precize location of soundstage and fine dynamics (resolution of details). Of course is this concept less good for occasional istening, but on the other hand industry provides us with cheap dynamic speakers for ceiling or inwall use for this application A second advantage is the the more constant soundpressure over distance than with global patterns.


jauu
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Old 30th November 2005, 12:25 PM   #29
el`Ol is offline el`Ol  Germany
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Quote:
Originally posted by wrl
From what I've read, segmented cylindrical panels will tend to suffer from a "venitian blind" effect. This makes sense when you consider how strongly traditional panels beam... especially in the high frequency. It would be difficult to get around this affect.

What angles were you looking to offset each segment?

-Wes
J thought about twelve 50mm segments.
Here are the frequency responses of a 50mm fullranger at 0 and 30°. Beaming doesn`t seem to be a big problem at that size. The problem that remains is to find a material with far less tension than mylar. I considered a nylon/latex compound in an other thread but I have strong doubts about linearity.
http://www.ejjordan.co.uk/drivers/jx53.html
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Old 1st December 2005, 06:32 AM   #30
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Hi el' ol,

you cannot compare directivity of the 50mm jordan to that of a 50mm ESL-stripe. The jordan's effective sound radiating diameter decreases with higher frequencies, while a ESL-membran do not.

A 50mm ESL-stripe will start to roll-off at about 2000 Hz and should have a level drop of more than 20dB at 20000Hz (30° angled).

capaciti
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