space blanket ribbon/planer advice needed - diyAudio
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Old 12th July 2006, 12:34 AM   #1
gon is offline gon  United States
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Join Date: Jul 2004
Location: indiana
Default space blanket ribbon/planer advice needed

Click the image to open in full size.

After reading about the left hand rule I finally have a good grasp of how a planer-magnetic speaker works. Current flows perpendicular to the field lines, and the movement of the membrane moves perpendicular to the current and field lines. The reason Quasi-Ribbon-Planers need to double back on the circuit is because the series of magnets will have field lines running in the opposite direction on the next pass of the circuit.

However, I have been tinkering with using a single sheet of space blanket as the membrane. Super thin, and having a minute amount of aluminum on one side has dual advantages in building a planer speaker. However, if the sheet is cut down, there is not enough aluminum, and it vaporizes quickly. So I need to utilize the entire sheet as one large “ribbon”. The resistance of the sheet is quite amplifier friendly.

See

http://groups.google.com/group/rec.c...080349808dbc47

A little math and science to add here:
Assuming the aluminum coating is 500 Angstroms, and the space blanket
is 5 feet wide:
The cross sectional area of the conductor is 0.0762 mm^2, which is
roughly equivalent to a 28.5 gauge aluminum wire.
Aluminum has a roughly 50% higher resistance than copper, so this is
equivalent to a 30 gauge copper wire.


However, there is the problem of getting all the field lines going in the same direction across the entire sheet. Hence my Quasi-Ribbon-ish diagram. If several magnets are arranged in bars across the back of the membrane (with spaces between the bars to maintain the dipole nature), will there still be enough field to produce movement? Quasi-Ribbons seem to say yes. Is there anyone with the expertise to quantify my idea here?

Hope this post makes some sense.
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Old 19th July 2006, 03:48 PM   #2
sreten is offline sreten  United Kingdom
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Join Date: Nov 2003
Location: Brighton UK
Hi,

spaced magnets and a slit pattern in the diaphragm, so the current
zig-zags across the diaphragm is how the lower frequency section
of Magneplanar loudspeakers work.

Click the image to open in full size.

You can see you haven't got your magnets right for the quasi,
they wiill simply form one big magnet, you need to do it as above.

/sreten.
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