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Old 8th December 2001, 02:46 AM   #1
Ignite is offline Ignite  Canada
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I'm considering a little project in which I want to try using sperical enclosures. Knowing I will not be able to find pre-fabricated enclosures, I'm wondering about materials. I am considering fibreglass but I'd like to avoid it if possible. Suggestions?
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Old 8th December 2001, 03:03 AM   #2
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I havent tried it, though I've heard of DIYers casting the spheres with resin, and filling in voids with bondo.
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Old 8th December 2001, 06:22 AM   #3
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what about modelling clay with paper fibres?
with the proper thickness say 1cm or so, it may be pretty tough, and if you glaze it it'll be stronger. Or even cement.

Use a bowl or a soccer ball/netball/old bowling ball as a mould. I would prefer a bowl or even a hollowed out melon as its much easier to get a spherical shape.
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Old 8th December 2001, 11:54 AM   #4
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Default Spherical Enclosure

Good day,

I would recommend taking an soft rubber child's play ball, one of those cheap ones that you can get at Wal-mart or K-mart which if you kick it too hard it will burst, the size of the inside dimensions of the enclosure. Use that as a male mold and apply spackle or joint compound over in layers building up to the thickness that you want. It would be fairly easy to machine, but would also be very dead acoustically. It would not be strong enough for a sub-woofer driver but would be able to handle a small mid-bass or mid-range with out a hitch. You may also want to embed a reinforcing ring around the driver opening to strengthen it. With sufficient reinforcment you probably could use for a sub, especially if you use the fiberglass joint tape between layers. Remember to sand between each coat so the new coat has a keyed surfcae to adhere too. Keep the coats thin as if you make them too thick they will crack from shrinkage as they dry. When the enclosure is thick enough to meet your need and cured, you would pop the ball and let it collapse and remove it through the driver opening.

Using this method will allow you to vary the wall thickness if you want and also let you be a bit creative with the final external shape. And when you were done a fine sand and a couple of coats of primer and you could give it a very good paint job if you chose.

Here is a link to a gentleman who made concrete speakers. Quite intersting and he gives quite detailed instructons.

http://home.columbus.rr.com/dkuzma/concrete.htm

Best of luck, sounds interesting,

Surf, Sun & Sound
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Old 8th December 2001, 12:38 PM   #5
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Try encapsulating epoxy reinforced with glass fibers if you consider casting spherical enclosures.
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Old 8th December 2001, 02:08 PM   #6
tvi is offline tvi  Australia
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I saw some polycarb spheres in a lighting store, they come in a range of sizes, look very well cast, they are replacements for outdoor lighting fixtures, see below.
<img src="http://www.lightinguniverse.com/images/products/large_image/4892_product_l.jpg" >

I priced the 12-14 inch ones about Aust$60.

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James
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Old 8th December 2001, 04:50 PM   #7
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Lightbulb interesting idea....

James,
it's something worth considering...looks great too
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Old 9th December 2001, 01:23 AM   #8
Ignite is offline Ignite  Canada
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Thanks for the replies everyone. I think I will try surf,sun&sound's recommendation first since it sounds fairly easy to do. The drivers I am using are 6.5" midbass units, so it sounds like it will be strong enough.

Assuming I find a method that works well I will finish my set (5 channel MTM system, so 10 spheres in all) and of course post some details on how they turned out if anyone wants to try it too.
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Old 9th December 2001, 04:56 AM   #9
grataku is offline grataku  United States
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How about using layers of progressively smaller donuts of MDF glue them all and screw them together. If you do things right it shouldn't involve too much sanding at the end, you can cut out an 'half-moon' with plywood to check that the sphereshape is correct.
In principle the various holes could be built in each of the contours as you go.
It would be very heavy, strong, but it would take a fair amount of material.
I believe the Karma speaker use a similar technique to put their cabinet together using vertical slices. They make the the inner surface cavern-like with irregular surface to break up standing waves.

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Old 9th December 2001, 06:14 AM   #10
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Default MDF Spherical Enclosure

grataku's suggestion would be very easy if you had access to a lathe, metal or wood. After glue up you would use a 3 jaw chuck in the driver hole and turn and sand it smooth. If you have the right friends or equipment, you could make both of them in less than an hour.

If you are going to use the ball method, Ignite, make sure you scuff up the ball before you start so the compound has a surface to adhere too.

Surf, Sun & Sound
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