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Old 2nd February 2013, 06:21 PM   #41
Legis is offline Legis  Finland
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Quote:
Originally Posted by bolserst View Post
Wow, your diaphragm tension must be extremely light if you are able to get resonance of 41hz with dots added to the sections.

Are you saying that the lowest resonance for some segments is 100Hz and others 41Hz? Or, that you measure resonances between these two extremes across the panel. It is possible that the added dots are accentuating some of the higher diaphragm resonance modes for sections that alos have a lower fundamental resonance.


I understand that you have minimal flattening to the rear with your current horizontal sectioning configuration. I was suggesting a way to that you could return to the vertical sectioning your mentioned in post#10 for which you were having the flattening problem.
dots or strips for spacers?

Using vertical sections with flat diaphragm facets allow the use of uniform tension which works better at LF where the diaphragm is moving a large % of the gap.
It has been a while since I measured the panels (been playing with 4" JBL compression drivers lately) but I think the fundamental modes of the sections were between 40 and 100Hz (narrowest section is ~9cm, largest ~20cm, width being 67cm). I will have to measure them better when I get the incredients of the membrane coating and can re-membrane them properly.

I did not read your post correctly. Yes, that would me to use vertical segmenting again, but I like "truly curved" membrane's sound more. The vertical segmented membrane acts like multiple ribbon tweeters and it's radiation pattern is very wide. Truly curved membrane is clearly more directive, with more pin-point imaging and so on.

At the beginning the vertical segmented membrane, with lots of tension (12m), had some residual/secondary resonances very high between 100 and 200Hz with the narrowet section. The fundametal resonance of the whole panel was somewhere at ~80Hz. Drum skin sound was present mucho-mucho due to the high resonances. Remembraining the panel with 6m, keeping the vertical spacing, dropped the main fundamental to ~55Hz, and the higher drum-skin resonances where also gone. I have not tried 3,5m with vertical spacing because I had already modified the spacer when I got that stuff.
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Old 20th October 2016, 09:29 PM   #42
ENCR is offline ENCR  Germany
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Thanks for this interesting tip Lukas. Can you say which brand of silicone you found which would stick to mylar? (Of course, it might not be available here in Germany.)

The other part of the story would be whether the silicone will stick to PVC stator wires. Many adhesives will form around the stator wires and hold them in place on the supporting cross bar without actually adhering to the PVC. The "ordinary" sanitary silicone I have tried does not adhere to PVC. If the silicone sticks to the PVC (and the cross bar) then the stiffness of the crossbars either side of the diaphragm would be much higher. Of course, one might achieve a satisfactory bond to the glue around the PVC.coated stator wires, without actually gluing to the PVC.
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Old 21st January 2017, 12:59 PM   #43
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Quote:
Originally Posted by harry_at View Post
Ahhh, thanks for the info.

What I would change first in this speaker construction, is to change the metallized membrane to one with a high resistance coating. Also in my Esl-63 I got better results (compared with the original graphite coating).

Harry
I am wondering: would it make sense to combine low resistive coatings with high resistive coatings? For example: use metallized mylar and apply a high resistive coating like antistatic spray to it? To allow for a fast charge up time but still avoid distortions that come with low resistive coatings ? Would results differ if one coating is applied to one side of the membrane and the other coating to the other side?
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