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Old 31st January 2010, 03:32 AM   #21
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Originally Posted by MJL21193 View Post
No room - too much beer in there.
Oh darn.
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Old 31st January 2010, 04:10 AM   #22
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I'm impressed...

I know that means nothing to you, but trust me, it takes some effort to accomplish...
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Old 31st January 2010, 12:59 PM   #23
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Thank you Jarrett,

You are wrong, it means a lot to me - I see some of your own work and I know your skill level is high.

At this moment the negative is in my oven where I'm trying to dry it out a bit faster. Sitting in the plastic bag all night was probably a good move - the inside of the bag was dripping wet. If plaster is anything like cement (it is) it helps if the initial drying after casting is slowed.
The oven is set for 200 degrees F, 3 minutes at a time every 30 minutes. It keeps it summer day hot inside the oven.

I'll give it a couple of hours in there (it's already had 1) while I work on the form for the new positive casting. I'm on the fence about the mounting flange shape: rectangular (as shown in my render) or elliptical, following the shape of the horn itself. The rectangular shape is easier to route into the baffle when I mount it but I haven't let things like that bother me before. The elliptical shape may resemble an eye too much - I can't abide anyone staring at me, even my own speakers.
A pair of Cyclops?
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Old 31st January 2010, 01:08 PM   #24
mightym is offline mightym  United States
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Neat sub-project.

What are you going to use for the horn/waveguide when you construct it?

Back to lurking

John
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Old 31st January 2010, 01:21 PM   #25
SunRa is offline SunRa  Romania
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Ok, this might look stupid and offtopic but I'll give it a try .

This waveguide molding makes me wanna try it but first I'd like to try some sketchups. Now, do you think you can upload the sketchup files, I'd like to figure out how did you drawn the horn. If you used a tutorial or something form the web, a link would be great.

Thank you!
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Old 31st January 2010, 01:43 PM   #26
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Quote:
Originally Posted by mightym View Post
Neat sub-project.

What are you going to use for the horn/waveguide when you construct it?
Thanks,
I will try the high density foam I have coming to start, just to see how it turns out. If everything looks good, I will order some black casting resin - 2 part polyurethane for the final pieces.

Quote:
Originally Posted by SunRa View Post
Ok, this might look stupid and offtopic but I'll give it a try .

This waveguide molding makes me wanna try it but first I'd like to try some sketchups. Now, do you think you can upload the sketchup files, I'd like to figure out how did you drawn the horn. If you used a tutorial or something form the web, a link would be great.
It's good if someone can be inspired by this.
I can do a mini-tutorial here on how I did it. I'm no expert in Sketchup by any means. Give me an hour or so and I'll post it.
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Old 31st January 2010, 01:58 PM   #27
SunRa is offline SunRa  Romania
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Thank you for your help, don't wanna take much of your time though...
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Old 31st January 2010, 02:54 PM   #28
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Quote:
Originally Posted by SunRa View Post
Thank you for your help, don't wanna take much of your time though...
No problem. The time I needed wasn't to get do the tutorial but to go out to my shop and let the reality of -12 hit me I'm better off in here where it is warm...

I'll show specifically how to do a round 3-D shape, assuming you know how to do the basics.
First, make your design in 2D (use the Top view to lay it out) and create a centre point (the intersection of the 2 dotted lines):

118.PNG

Add as much detail as you want here - see it as a thin slide through the object but erase all internal lines so you have one flat shape.
Create a circle vertically (on the blue axis) with it's centre point on the intersection of the dotted lines and make the radius half the total width of the object:

119.PNG

Erase half of the pattern and use the "follow me" tool (arrow in pic) to build the pattern around the circle:

120.PNG

You get something like this:

121.PNG

Use the select tool and select the entire object, Right click and click "make group". This makes an object:

122.PNG

Then you can use the "scale" tool to resize the object:

123.png

To improve the appearance, change the view, edge style to "display edges" uncheck that box:

124.png

Rotate and study your new baby!:

125.png

Have fun but for Gods sake build something! - don't lose yourself in the virtual world of Sketchup!
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Old 31st January 2010, 04:12 PM   #29
SunRa is offline SunRa  Romania
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Thanks for the info John,

I am now looking for plaster and the other materials needed on our market. I am willing to give it a try, even if for a smaller model, just to gain experience working with this stuff.

Regarding the shape of the flange, I guess that if the horn and the baffle will have the same color/clear coating, this pretty much negates the need for a specific shape (especially if you glue the waveguide or clip in a manner not to show of the screws on the front).
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Old 31st January 2010, 06:12 PM   #30
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Plaster should be easy to find. I used ordinary building type in a 10kg bag, less than $10 here. It's interesting to do.

I've settled on a rectangular flange with round corners:

NPX_143.JPG

That's the negative sitting on a heat register drying out.

The casting is really easy to cut on the tablesaw:

NPX_148.JPG

an old dull carbide blade zipped thru it like a hot knife through butter It has to be cut and the corners rounded to fit part way down in the form shown above.
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