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Multi-Way Conventional loudspeakers with crossovers

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Old 26th November 2001, 04:48 PM   #1
jouch is offline jouch  Sweden
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I'm wondering if somebody have some good construction tips about building round speakers box, like the JBL txi series.
Thanks for your help
Christopher
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Old 28th November 2001, 02:16 AM   #2
BAM is offline BAM
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Sonotube.
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Old 2nd December 2001, 06:33 PM   #3
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Default what kinda round?

if you meant cylindrical, yes, the sono-tubes work well, see here: http://terryctheater.tripod.com/shiv...um/page12.html

if you mean spherical, like these:

Click the image to open in full size.

i'm thinking of making a spherical enclosure for my 12" woofers... i'd start with a child's ball (a cheap one from Toys-R-Us) of the appropriate volume, then wrap it with several layers of fiber-reinforced resin (fiberglass) and attach an MDF mounting surface for the woofer. Then bondo, then lotsa sanding, then paint.
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Old 2nd December 2001, 10:15 PM   #4
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If cylindrical, consider PVC pipe.
Spherical will be a problem unless you have a friend who can cast resin for you.

Grey
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Old 3rd December 2001, 04:15 AM   #5
Æ is offline Æ
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Default PVC pipe is not cheap,

Not when it comes to the larger diameters. Boy is it pricey!
I recently went to a concrete supply place, they had cardboard forms (sonotubes) in just about every conceivable diameter in 12 foot lengths. I bought 10" diameter for a little more than $3 per lineal foot.
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Old 3rd December 2001, 11:50 AM   #6
Per is offline Per
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In Denmark some companies has recently come up with mdf wich has been routed on the one side, kind of like the type of cardboard you use around glass as rappings. Yóu the make the inner shelves in the speaker, and glue the mdf on to the shelves. Maybe you can get that kind of mdf at a lokal hardwarestore?

Kindly Per.
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Old 3rd December 2001, 12:04 PM   #7
jouch is offline jouch  Sweden
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Default Thanks

Thanks for your help.
I'm not looking for cylinder or all round speakers, but for a flat surface on the front, where the drivers are moúnted, and rounded face att the back, like JBL.
Thanks
Christopher
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Old 3rd December 2001, 11:25 PM   #8
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I am in the process of finishing up a similar project myself!

I wanted to get a 5" radius edge on my speakers to minimize diffraction effects. Indeed, it is highly effective.

I went through three methods before hitting on a successful one.

First was to use 10" PVC pipe, cut it in quarters and glue the quarter pices to the edge of a box that has been built with a "step" of sorts on the edges. Unfortunately, I found that once I cut the PVC, it curled in some to a smaller diameter, making the box I had built the wrong size.

Scratch that. Didn't seem like the best idea.

Next idea was to laminate six 4.5" wide pieces of mdf together for a billet 4.5" square. Then I drew the arc on the end of the stock and ran it through the table saw 5 degrees at a time. After that, sand with an orbital sander until it is smooth instead of faceted.

This worked pretty well, but the radius was not perfectly linear in spots, and it produces an INCREDIBLE amount of MDF dust, which is hell to work with.

Current method; and this is working quite well now... I made a box with a skeletal rib-work for the cuves on the edges. Every 5 inches or so there is a routed curved piece. (I added more ribs after the shown picture)

http://www.hoppehome.com/Rounded%20Cab.jpg

I then used double-stick tape to attach a plastic sheet to the ribwork (similar material to overhead transparencies) and fiberglassed it from the inside. Peel off the plastic when it dries and there you have a nice smooth form to veneer over! Also, it is very strong and will not resonate, due to it's curved shape.

I will need to do a little bondo and sanding to get it just right, but this method is workind well.

Another good possibility is to use the flexible bending plywood that can be found at good lumber stores.

Also, you could cut deep scores down the length of a piece of veneered MDF of some kind and bend that around a form as well.

Hard work, but I think it's going to be worth it...

[Edited by Phloodpants on 12-03-2001 at 06:27 PM]
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Old 4th December 2001, 08:31 AM   #9
Per is offline Per
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jouch

The mdf I described above, IS the kind JBL uses to make kabinets(jbl kabinet are (also) made in Denmark). Lots of routes lines on the one side makes it bendable.

Per.
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Old 4th December 2001, 02:43 PM   #10
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It's cheaper, faster, and safer to use a table saw to score the MDF. The spacing and depth of the scores will determine the radius you can obtain when you bend the sheet.

Grey
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