Originally Posted by bolserst
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 (12µm), 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 6µm, keeping the vertical spacing, dropped the main fundamental to ~55Hz, and the higher drum-skin resonances where also gone. I have not tried 3,5µm with vertical spacing because I had already modified the spacer when I got that stuff.