How to construct a cube louver (Acoustat) - Page 4 - diyAudio
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Old 10th April 2010, 06:11 PM   #31
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The material at home depot is made of styrene.

As the frequency goes up the capacitive reactance goes down.
The impedance refelcted to the amplifier is determined by the transformation ratio of the transformer.
cacacitve reactance / (ratio*ratio)=reflectd impedeance
This gives you a basic idea as ther are other factors involved also that determine the total impedance.
check out the thread "step-up transformer design".
most all of these factors have been either pionted out, or discussed. jer

Last edited by geraldfryjr; 10th April 2010 at 06:14 PM.
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Old 10th April 2010, 06:45 PM   #32
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Default Capacitance and Stator wire spacing

Quote:
Originally Posted by pforeman View Post
so, increasing wires/inch = more capacitive reactance. This will be an overall higher impedance as seen by the amplifier?
Easier, or harder speaker to drive I guess is my real question.
As this is one of my design goals.
Paul
The higher the capacitance, the lower the reactance. That is, harder to drive with a high step up ratio. The impedance gets lower with increasing frequency. Note however, that there is a resonance with capacity and leakage reactance of the transformer. This will cause a rise in impedance peaking above the audio range with a decent audio transformer. A low value select resistor in series with the primary will cause a roll -off at a frequency lower than this peak resonance.
The sum of the 2 frequency responses creates a maximally flat response with a smooth roll-off without the peak.

One more thing about stator wires. Doubling the number of wires does not double the capacitance with close spacing. At some point, a wire mesh is nearly equal to a solid surface when it comes to capacitance.
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Old 10th April 2010, 07:11 PM   #33
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Paul more wires per linear inch means you are increasing the density of your electrostatic field which is what is driving your diaphragm. More wires per linear inch means more efficiency, its a good thing. Cube louvres basically come in two materials Styrene (everywhere) and Acrylic (special order).The louvres you see at the home supply shops are going to be Styrene.

Hey Allen would you please email me directly not via the gmail or asylum mail as every time I try to reply to you my mail is bounced back. Perhaps my mail is seen as spam by your machine. We need to connect buddy.
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Old 10th April 2010, 07:31 PM   #34
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As an aside note you need to sand the surface of the Styrene louvre before you glue or solvent weld. This will remove any mould release agents and plasticizers on the surface of the louvre. It will also remove any surface irregularities that exist. Regards.
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Old 10th April 2010, 11:15 PM   #35
a.wayne is offline a.wayne  United States
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Quote:
Originally Posted by pforeman View Post
Is there a way to look at louver panels and tell what they are made of.
At Home Depot their product doesn't say, and the kid obviously doesn't either.
Paul
I have used the standard light fixture screens ( that's what they are ) and have had no issues. To those questioning the design , wired stators IMO are the way to go, more work, absolutely time consuming , but worth it.

If manufacturing it is much easier and cheaper to make perf metal stators, Hence there popularity , if not I'm sure there would be more wired units.....



Hello Moray : What advantage is there in using the acrylic vs the standard Styrene.



regards,
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Old 11th April 2010, 12:39 AM   #36
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Well the Acrylic material is stronger than Styrene so a 3/8 thick louvre is probably close to the strength of a 1/2 inch Styrene. The Acrylic is also much better damped when compared to the Styrene. The Acrylic is a much higher quality material and does not have the plasticizer issues that the Styrene has and it can be glued or painted with out issues. It is a much nicer material all around. For a lot less money you can work with Styrene if you solvent weld and don't mess with adhesives and you will achieve results equal to Acoustat and they will last a good long time. So Styrene is great for a low cost easily available material to do prototype work or just to build inexpensive yet solid panels with. Acrylic will make a better panel that will last longer with less resonances than Styrene but it does cost more and you will probably have to special order it in. Consider Acrylic louvre the top of the line material choice. A flat perf metal (insulated) bonded to an Acrylic louvre would be the best of both worlds as long as you have the perf metal properly coated. Aside from that it is next to impossible to better an insulated wire stator for all around performance and cost (on a diy level).
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Old 11th April 2010, 03:15 PM   #37
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I'll have to look into the cost of ordering acrylic panels, but I'm still not sure if the consensus is that pvc coated wire is the best way to go, or to use
magnet wire.
Magnet wire looks to be easier to cut all the loops, and solder at the ends (of the panel)
Also, I have a spray enamel. Could I go over the wires with this after they are tensioned to "improve" them
Paul
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Old 11th April 2010, 04:06 PM   #38
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Click the image to open in full size.
This is how I handle the frame end wires. It is one continuous wire. I used a Dremel to cut slots. The panel is laid with the ends supported to give it a slight concave shape. I have constructed a curved jig for this layup. The wires are pulled back and forth with slight, but equal tension. I then use my styrene syrup to anchor the ends where the wires are in the slots. After a few minutes of drying, the frames are laid flat. The wire tension increases and the wires are now laying against the frame. Then I apply my syrup across all wires. I use the edge of a foam brush. I can do several wires at once this way. You gently touch the surface of the wires and the syrup bleeds out. The solvent in the mixture also melts the wires into the frame slightly.

Note that I am using acrylic spacers along the edge. I solvent weld these and apply syrup fillets to hold them in place. They have been clamped all the way around during the drying process.

Jim
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Old 11th April 2010, 07:12 PM   #39
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Default wire stator

here is a wire stator with 24 wires per inch painted black for cosmetics hope you can see clearly there is a lot of reflection unfortunately it is the best shot I have.
Attached Images
File Type: jpg wire stator.jpg (87.7 KB, 374 views)
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Old 11th April 2010, 08:45 PM   #40
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One thing I failed to mention.. I have a rig with a hot-wire and springs on each side. I use a variac and high current filament transformer to cut off the edges of the lighting louvers. I am going to construct a jig for small magnet wire grid to slightly melt the grid wires into the louver. I will then of course have to use thinner spacers.

BTW, my 3 wire per section "Acoustat Clone" panel is about 310pf. Also, I was able to create a paint-on carbon black formula that actually sticks to the mylar. Unfortunately, I don't remember the recipe. I do however remember the ingredients. I am going to make a few test batches and re-learn and report the recipe.

If you will notice, the top center wire loop exits the frame. I did this to make it easy to cut it if one wants a split stator for use with delay lines.

Jim
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