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Old 21st April 2013, 11:24 AM   #91
solhaga is offline solhaga  Sweden
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Folded the membrane:

Click the image to open in full size.

Baked and out from the tool:

Click the image to open in full size.
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Old 21st April 2013, 03:01 PM   #92
solhaga is offline solhaga  Sweden
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Default AMT playing

The suspension was a little tricky to apply, but I managed in the end.
I think I have some work to do on that:

Click the image to open in full size.

Anyway, AMT is playing. Some resonanses in the low but from 300 Hz there´s usable output.
A couple of dBs rise per octave up to 13 kHz where acoustic lense of 3 mm makes the directional output drop.
It´s a totally different soundstage compared to my focused line arrays

Next step is to come up with a better solution for the suspension, hopefully the resonances in the low will be fewer, and build a complete pair.
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Old 22nd April 2013, 06:02 AM   #93
solhaga is offline solhaga  Sweden
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The bad lf response is probably due to that the membrane is too stiff in the folds.
So I´ll make the next membrane with only one film layer.

The suspension will be from the middle of each pleat, so there will be a second layer on that pleat.
Also I will try to remove the glue in the folds, I noticed that it accidently came off in some folds when I did the first membrane.

I don´t know if the hf response is desirable or not.
I guess I´ll know better when I have a stereo pair.
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Old 22nd April 2013, 06:50 AM   #94
solhaga is offline solhaga  Sweden
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"The suspension will be from the middle of each pleat, so there will be a second layer on that pleat."

I´ll change the suspension to having pieces of yarn on both sides of the membrane at the top and bottom. That ought to keep the membrane centered but still allow the membrane some sideways movement, especially a bit in the membrane.
The yarn has to be supported at the bottom of course, perhaps with some tape.
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Old 22nd April 2013, 09:35 PM   #95
solhaga is offline solhaga  Sweden
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So I did a new membrane with another alu/paper combo (see båndsei´n thread for picture). Film only on one side.

It´s 10 um aluminium and the finished membrane´s resistance is below 4 ohms.

The new membrane weighs 8,12 grams.
The alu weighs 56 % of the total alu/paper weight.
So I guess it´ll be under 5 grams if I can peel the paper off.
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Old 22nd April 2013, 09:56 PM   #96
solhaga is offline solhaga  Sweden
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The paper came off really easy.
The membrane weighs 6 grams without the paper and the resistance is 3,6 ohms.

Feels like this membrane really gonna hit the lows.
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Old 23rd April 2013, 05:31 AM   #97
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If you remove the glue in the cuttings,it is more flexible

Bernt
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Old 23rd April 2013, 05:33 AM   #98
solhaga is offline solhaga  Sweden
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I guess that you mean where the folds are.
Any suggestions on how to do that?
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Old 23rd April 2013, 05:44 AM   #99
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Use "Renset Benzin" petrol cleaned.Use a cloth an soak it.
I have tested diaphragms with and without the glue in the folds and goes deeper without.
Test om a piece of 3m tape.

Bernt
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Old 23rd April 2013, 06:00 AM   #100
solhaga is offline solhaga  Sweden
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Ok, I got it. It is called "Kemiskt ren bensin" in Sweden.
No danger to the glue under the alu I guess?
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