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Old 6th May 2013, 06:37 AM   #121
solhaga is offline solhaga  Sweden
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Join Date: Jun 2009
Location: Värsta Götaland
Default Wider membrane

If the membrane is 190 mm wide, that is 15 mm at the top and bottom are outside the field, the 7 mm horisontal strips will be 8 mm outside the field.
Hopefully I can do the sagittal fixation here as well.

I will use kapton tape to extend the membrane outside the 160 mm wide the 3M film is.
Hopefully the tape will stay folded after the bake.

One positive thing with this is that the active membrane surface has increased by 10 %.
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Old 6th May 2013, 05:45 PM   #122
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I dont think it is the horisontal conductors that resonates.
Maybe you could make a horisontal 30myx5-6mm ribbon one third up like this one:
[IMG]Click the image to open in full size.[/IMG]
Or make the pleats 6-7mm deep.
Or both
Or-----
Bernt
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Old 7th May 2013, 06:45 AM   #123
solhaga is offline solhaga  Sweden
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Quote:
Originally Posted by båndsei View Post
I dont think it is the horisontal conductors that resonates.
No, but they excites the iron bars as the membrane is fixed there.

Quote:
Originally Posted by båndsei View Post
Maybe you could make a horisontal 30myx5-6mm ribbon one third up
Is that for mechanical support or is the membrane divided into two circuits?
What´s the XO for this driver? Does it go as low as 150 Hz?

Quote:
Originally Posted by båndsei View Post
Or make the pleats 6-7mm deep.
Then I will have to make a new folding tool or at the least re-build the one I have. I´ll test this idea with a higher membrane first.

Maybe this is what everybody else that are making AMTs discovers; too high excursion at the low end.
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Old 7th May 2013, 05:25 PM   #124
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I think it is to break up resonances.It is only to 700hz.Is thre some sealing glue under the alu stripe?
http://www.lautsprechershop.de/index...amt_en.htm?xxx


Bernt

Last edited by båndsei; 7th May 2013 at 05:34 PM.
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Old 9th May 2013, 02:07 PM   #125
solhaga is offline solhaga  Sweden
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Join Date: Jun 2009
Location: Värsta Götaland
Default New membrane

New design of the membrane with the horisontal conductors outside the magnetic flux. The membrane is now 190 mm high and shall be inserted in the 160 mm high gap. Compare to the light yellow film:

Click the image to open in full size. Click the image to open in full size.

The 3m-film isn´t wide enough so some kapton tape has to cover the rest.
It is not thermo setting as the film but more robust on the other hand.
To hinder the alu-strips to fly against the film when applying it, the backside has been taped temporarily. The tape will be removed when the paper back is removed.
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Old 9th May 2013, 02:18 PM   #126
solhaga is offline solhaga  Sweden
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Cut out and baked:

Click the image to open in full size.

The first and last strip was one reason for the vibrations so they have been glued to the adjacent fold.

Mounted in the motor at the terminal´s side with a L-shaped support:

Click the image to open in full size.

The membrane now needs minimal support at the other end:

Click the image to open in full size.
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Old 9th May 2013, 02:42 PM   #127
solhaga is offline solhaga  Sweden
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Join Date: Jun 2009
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Had to make some more space in the baffle:

Click the image to open in full size.

Joyce Cooling: Revolving door. Loud and prolonged guitar notes that puts high requirements on resonance free membrane and motor.
The outermost folds still vibrates a lot, it is okay but they need to be fixed further.
Some scrap makes some vibrations, but with that gone it sounds okay; no more vibrations. Perhaps is 1 mm distance from the steel enough, next membrane will be 6-7 mm thick. But now I know that I am on the right track.

Norah Jonas: Sunrise.

Oooh, oooh.

No vibrations, that´s good!

I will assemble the other membrane before I measure and EQ.
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Old 9th May 2013, 05:14 PM   #128
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Quote:
Originally Posted by solhaga View Post
The outermost folds still vibrates a lot, it is okay but they need to be fixed further.
In my AMTs the outmost fold conducting current are 6 mm away from the magnet. If your outmost fold are to close to the magnet I think its magnet field are disturbed by the magnet and the fold are not behaving controlled.
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Old 9th May 2013, 05:28 PM   #129
solhaga is offline solhaga  Sweden
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You are correct.
Actually, it shows in the FEMM simulation:

Click the image to open in full size. Click the image to open in full size. Click the image to open in full size.
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Old 9th May 2013, 06:00 PM   #130
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The outmost fold have one additional issue...
All the other folds have another fold working in a counter way, but the outmost fold will have a different air "friction" due to the next surface do not move.
Due to that the outmost folds may move erratically.
I have the outmost fold placed at 1/2 distance to the folding cassette to give it a slightly better working point - still not perfect, but better....
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