Materials For Spherical Enclosure

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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?
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.
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.

Best of luck, sounds interesting,

Surf, Sun & Sound
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.
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I priced the 12-14 inch ones about Aust$60.

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.
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.
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
For the really absurd thought

How about throwing a pot? Like as in baked clay? You could get it pretty big, lots of mass, plus make it pretty for SAF. Could hide them in a matching vase or lamp design. WOuld take some practice to get what you want as it shrinks as it drys, but you could make it bigger than needed, then fill with something dead sonically to make your actual volume come out right - and take out any ringing that ceramics might have.

Hell, now that I think about it, this ain't a bad idea for surround speakers. Hidden in plain sight. Gonna have to ask a thrower I know. Wonder if its patentable? If so, I just released it into public domain...
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Joined 2001
maybe sphere internals only...

Well, it seems most suggestions are presuming that the sphere will also be part of the outside of the enclosure. To me it makes more sense to have a sphere/spherical internal cavity for the midwoofer/midrange. I have yet to build a pair using spherical internal cavity, but I have come up with several designs using parts from the local hardware store and Wal-Mart.

Use a flat and narrow front baffle made of MDF, etc, use 4"-6" or larger PVC pipe ripped into quarters(use a 1.5"-2" pvc the same length as the main piece and cut in half and use PVC cement and glue it inversed in the pipe before cutting or the large piece may curl after it is cut). for the front radius attached to the baffle so you have no diffraction problems with a wide overall dimension required to fit an adequate size sphere inside, use MDF or the board of your choice to make the rest of the enclosure. Do not u se the PVC for part of the structure, but construct the mdf so that their are notched sides for it to be glued onto the enclosure. For the speherical cavity you can do 3 things pretty easily...use a premade cermaic plant potter, get a custom size pot made at a pottery store(some make them to order), or...use 4 stainless steel bowls like you find in Kmart in 10 or 12" sizes...use silicone and attach the first two togher, then use lots of silicone or liquid nails and encapsulate the first layer with another layer of same size bowls..this is to give structural integrity. You can then cut a couple of shelf braces with for each end of the sphere and put the sphere in the middle to support it in the enclosure. Cut the holes you need in the sphere before using the adhesive, it will be easier. Use short piece of 6" or 8" PVC to tunnel to the sphere if wish from the front baffle to increae internal volum moderately without having to use a wider enclosure. If you really want to go overkill on damping, go ahead and fill the space between the sphere and outer enclosure shell with sand also. Cover enclosure with good ol' veneer or other flexible laminate that will shape around the radiuses. I am not sure of how well paint adheres to PVC.

You should now have an attractive enclosure with the benefits of minimal standing waves without having to resort to using dynamics robbing acoustic absorbers as you do in a boxed shape cavity.


[Edited by CHRIS8 on 12-12-2001 at 03:25 AM]
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Joined 2001
surf, sun & sound idea....

If you use surf's idea it may be a good idea to substitute spackle, etc for Rock Hard Water Putty, avaialbe at most hardware stores. It can be applied just like spackle but it cures to be avery hard and strong compound. Would even be suitable for a subwoofer. Comes in 5 lb containers usually, but you can order 25-100lb drums pretty cheap if you need them.
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