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Old 30th May 2009, 08:37 PM   #131
Kontra is offline Kontra  Russian Federation
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Default About width of a film and a bass

Hi, Wachara

Quote:
Originally posted by chinsettawong
Last night I had a chance to try the 0.9 microns mylar which I bought from the USA. Interestingly, I didn't find the diaphragm to be more efficient than the 6 microns one. Overall, the mid and high sounded about the same as the 6 microns. But the low frequency wasn't as good.

I'll try the 1.4 micron mylar tonight, and will report soon.
Wachara C.
It seems to me, I know, why so it seems to you.
The thin film is more inclined to be shaded slide as the piston
" Wants or can " do it better than thin.
Because " it is easier to thick film to be the piston "
The the film is more thin, the it is more on it than tracks of movement between two perforated leafs.

Adout roud loudspeakers: I think round better than rectangular, because it is not necessary to undertake express methods to kill rezonance. First of all.
I think, that round it is better because issues " a magic sound "
And as this authoritative judgement for me thinks Staxx.
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Old 31st May 2009, 02:36 PM   #132
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Default Re: About width of a film and a bass

Quote:
Originally posted by Kontra
Hi, Wachara



It seems to me, I know, why so it seems to you.
The thin film is more inclined to be shaded slide as the piston
" Wants or can " do it better than thin.
Because " it is easier to thick film to be the piston "
The the film is more thin, the it is more on it than tracks of movement between two perforated leafs.

Adout roud loudspeakers: I think round better than rectangular, because it is not necessary to undertake express methods to kill rezonance. First of all.
I think, that round it is better because issues " a magic sound "
And as this authoritative judgement for me thinks Staxx.
The first version of my headphone is a round one. I like it very much. However, I don't feel that it sounds better than my oval shape version.

Wachara C.
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Old 2nd June 2009, 02:38 PM   #133
Calvin is offline Calvin  Germany
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Hi,

aaah, You found the glue-formula
Instead of graphite You may try black writing ink.

my recipe for 100mL of coating is:
1 volume part glue (Tesa brand)
4 volume parts destilled, deionized water
2 tiny drops of black writing ink

The black ink contains extremely fine particles of carbon black in a water based solution. So it dissolves easily and You can taylor the resistance to Your needs depending on the number of drops of ink and the thickness of the wet coating.
It can be brushed on (extremely thin) or sprayed onto the film and the film can be coated a 2nd or 3rd time to reduce the resistance, if the resistance of a single coating prooves too high.
Films coated this way are working stable for many years.
The color of the solution is slightly greyish and the dryed coating is almost invisible.


jauu
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Old 2nd June 2009, 08:31 PM   #134
Few is offline Few  United States
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Thanks Calvin. Tesa seems to make lots of different types of adhesive. Is this the one you're referring to?
Click the image to open in full size.

Few
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Old 3rd June 2009, 01:48 AM   #135
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Hi Calvin,

Thanks a lot for your formula. Now we have at least two easy to apply formulas that prove to work well.

Wachara
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Old 3rd June 2009, 06:16 AM   #136
Calvin is offline Calvin  Germany
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Hi,

the link is not the right Tesa. It´s the bottle with the red cap, which reads ´Alleskleber´ i.e ´all-purpose glue´ and `wasserfest´ i.e ´waterproof´ on the label.
The correct Tesa comes in the bottle with a blue cap and reads ´Vielzweckkleber´´i.e ´multi-purpose glue´ and ´ohne Lösungsmittel´ i.e ´free of solvents´ on the label.
The kind of glue makes the difference. Tests with UHU glue which looks smells and tastes the same failed completely.

jauu
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Old 3rd June 2009, 06:38 AM   #137
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Quote:
Originally posted by Calvin
Hi,

the link is not the right Tesa. It´s the bottle with the red cap, which reads ´Alleskleber´ i.e ´all-purpose glue´ and `wasserfest´ i.e ´waterproof´ on the label.
The correct Tesa comes in the bottle with a blue cap and reads ´Vielzweckkleber´´i.e ´multi-purpose glue´ and ´ohne Lösungsmittel´ i.e ´free of solvents´ on the label.
The kind of glue makes the difference. Tests with UHU glue which looks smells and tastes the same failed completely.

jauu
Calvin
Wow! Did you really try to taste it, Calvin?

Wachara C.
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Old 3rd June 2009, 07:06 AM   #138
Calvin is offline Calvin  Germany
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Hi,

Yeah, why not? It´s not poisonous if swallowed (I assume it was intended as child friendly hobby-glue), but You don´t need to swallow it when You just wanna taste ;-)
There seem to be no ill effects, but I sometimes wonder about the fact that my communication has reduced to hammering words into a keyboard *lol*

jauu
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Old 4th June 2009, 01:49 PM   #139
Calvin is offline Calvin  Germany
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Hi,

regarding wachara´s Q in post #101:
The high valued resistance has the purpose to keep the charge constant. Done as a simple series resistance and using a highly conductive membrane coating the charge would remain constant, but not the distribution of charge over the membrane area. The charge would concentrate at points which are closer to a stator. This concentration would mean a higher force on the membrane at this point, pulling the membrane closer to the stator, more charge concentrating at this spot and so on. This is a self energizing effect and introduces non-linearities, hence distortion.
Therefore it has become quite a standard to use a highly resistive coating that ´fixes´ the charge at its place. Besides this reduces the energy of a flashover, so that it remains a ´cold´ flashover and doesn´t turn into a hot spark that could melt holes into the film.

A lower resistance reduces charging time, that´s right, but this only plays a role when You power-up the system the first time. Assuming a well build panel with low leakage (ideally no leakage) the charge remains constant for several seconds if not a few minutes (ideally it stays on forever). Even a rather slow highvoltage cascade (50Hz/60Hz) together with a high series resistance is fast enough to make up for the loss of charge on the membrane.
Still though a too high valued coating seems not to be able to hold enough charge to reach field saturation (-->lower force, lower efficiency), since it forms a voltage divider with the air resistance, i.e. leakage path, towards the stators. The best compromise seems to be around 10^8---10^11Ohms/sqr of surface resistance.

jauu
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Old 4th June 2009, 01:58 PM   #140
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Hi Calvin,

Thank you so much for your explanation. I had actually proved it to myself that high surface resistance was actually better. I did an experiment to coat the diaphragm with very low resistive value - less than 1k ohms. I tried to listen to the music and the music was very distorted.

Wachara C.
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