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Old 21st June 2014, 10:32 AM   #1
solhaga is offline solhaga  Sweden
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Join Date: Jun 2009
Location: Värsta Götaland
Default Yet another DIY Planar Bass

It will be like a bookshelf with each shelf having one of these drivers:
Click the image to open in full size.

Yellow/blue part is the voice coil.

So it will only be a part of the pleat/shelf that will move.
The moving part, the membrane, will be 14 cm times 44 cm.
Every other driver will be flipped over so two of them will make a pseudo fold.

With a 10 cm spacing I reckon there will be 8 drivers in total.
The complete speaker will be 90 cm high and perhaps 70 cm wide footprint wise. The front baffle will probably be folded backwards to lower the OB cancellation frequency.

So far I have one question; is AWG30 a suitable dimension for a bass driver voice coil copper wire?

Last edited by solhaga; 14th July 2014 at 08:26 AM. Reason: Project has shifted from AMT and ripole to a plain bass planar.
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Old 21st June 2014, 11:12 AM   #2
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how thick is the membrane .. how heavy is the membrane.. what impedance are you targeting
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Old 21st June 2014, 11:45 AM   #3
solhaga is offline solhaga  Sweden
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Join Date: Jun 2009
Location: Värsta Götaland
Membrane is 0,1 mm thick and weighs about 5 grams not counting the voice coil.
I don´t think the inductance will be of any significance being that large of a coil.
When it comes the resistance, I am really at free will of choosing anything between 0,5 to 32 ohms depending on how I will wire the drivers.
I can have multiple amplifiers as well.

I aim for having about 20 turns of the coil wire though, fitting in the 2x2 mm voice coil space (blue part above).
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Old 21st June 2014, 11:48 AM   #4
solhaga is offline solhaga  Sweden
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Default Simulated the magnetic circuit

FEMM simulation gave some results:

Click the image to open in full size.

Click the image to open in full size.
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Old 21st June 2014, 02:11 PM   #5
solhaga is offline solhaga  Sweden
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Join Date: Jun 2009
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Default AWG26 calculations

I got the suggestion of AWG26, that is a diameter of 0,4 mm and an area of 0,125 square mm.
It then be 28 turns to get a nominal resistance of 8 ohms.
Bl will then be around 21 Tm.
The wire will weigh 33 grams so it will dominate over the weights of the membrane and (hopefully) the voice coil former although my recent calculations point to 30 grams.

Power handling will of course be lousy, but I reckon I will get by anyway as the complete speaker is an pseudo bass AMT that will not require much from each driver.

Last edited by solhaga; 21st June 2014 at 02:22 PM.
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Old 21st June 2014, 03:55 PM   #6
solhaga is offline solhaga  Sweden
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Join Date: Jun 2009
Location: Värsta Götaland
Default Sketch of complete speaker

Side view, front is to the left:

Click the image to open in full size.
Magnet assemblies are not shown. Sides are detached.

Front view, measures in mm:

Click the image to open in full size.

Last edited by solhaga; 21st June 2014 at 03:59 PM.
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Old 21st June 2014, 09:49 PM   #7
solhaga is offline solhaga  Sweden
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Quote:
Originally Posted by solhaga View Post
It will then be 28 turns to get a nominal resistance of 8 ohms.
It turned out that the value for aluminium was used instead copper, the resistance is of course somewhat below 4 ohws.
But that will probably not change the wire gauge nor the number of turns.

Last edited by solhaga; 21st June 2014 at 10:11 PM.
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Old 22nd June 2014, 09:20 AM   #8
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[IMG]Click the image to open in full size.[/IMG]
This one only uses 4 magnetsystems ,length 900mm.
You can buy 3mm adhesive alu.I got a link.

Bernt

Last edited by båndsei; 22nd June 2014 at 09:24 AM.
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Old 22nd June 2014, 09:28 AM   #9
solhaga is offline solhaga  Sweden
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Yes, exactly Bernt!
It will be a manifold ripole AMT.
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Old 22nd June 2014, 09:34 AM   #10
solhaga is offline solhaga  Sweden
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Join Date: Jun 2009
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Quote:
Originally Posted by båndsei View Post
You can buy 3mm adhesive alu.
I tried 10 mm adhesive aluminium tape, but it got too clumsy as I also had to have insulation tape between each layer of aluminium. Also, wouldn´t a 3 mm tape be very brittle and hard to handle when you are winding the coil?
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