How do I make spherical enclosures?

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hi roch
i´m interested too in designing something spherical. if possible i would choose the seas Tr18. a coax is probably the only choice, or you take some broadband driver.
for the enclosure my idea would have been to take glass-fiber or sliced wood in shapes that build a sphere together. the fiber should be reinforced with wood too. no more thoughts about it at the moment.
I've forgotten the name of it, but there is a tube that is used for pouring cement columns,.......Spiro-tube, or something to that effect. It has been used several times recently by DIYers. I assume it is strong enough to work for you, and you can get it in different diameters too.

Oh, I remember, SonoTube. I assume that you can get it locally without any trouble.

Nice low tech solution.

Get a sphrical object of a size your like.... stryo ball, beach ball or etc. Can't find the right size, then make one of paper mache.

Then lay up a fiberglass cloth and resin shell over the ouside of said object. Test first to be sure your resin doesn't ruin the form.

When done, either dig the form out of the shell or split the shell, remove the form and reglass the shell, adding driver mounting details in the process.

Someone on the forum recently suggested wooden bowls from IKEA use in pairs to form a sphere.

Somewhere at home I have an article re:- building speakers from styrofoam spheres used in handicrafts. It used a small and medium for the tweeter and mid with a trapezoid box for bass.
Ok, I did a google search on Sonotube and speakerbuilding and I came up with the following:

Building a Sonotube Subwoofer

Sonotube FAQ for speakerbuilding

This one is from AudioKarma, and is about 5 years old, Building an Acoustic Wave Cannon

Sonotube Sub Design Help

Where to buy Sonotube for building a subwoofer?

DIY Project # 11 - A Subwoofer Made from Sonotube and the Hsu 12" Driver - September, 1999

And from right here at DIY

Sonotube RL-p15 Project with questions...

"SDSS 1.1"
Single-Driver, Ported Tube Speakers

Ok, that should be enough for anyone as a starter. YOu can Google for more information. Just insert Sonotube in the search, and you will find much more. ;)
planet10 said:

They make great raw material for woofer boxes. I have a push-push sub project on the TL site and they sent me all sorts of legal mumbo-jumbo to have me remove the trade-marked SonoTube from the pages (and in the future if i have the choice i'll buy a different brand)


Good for you Dave. Any business that does not appreciate unsolicited good will does not deserve further encouragement.
The one critical question hasn't been asked by anyone - How big?

Softball? Soccer Ball? Beach Ball? Deep Sea Diving Sphere?

Somewhere here in this grup is a link to a South American guy who build 'snail shell' shaped woofers. Similar to these Bower Wilkins Nautilus speakers -

He built a central frame with speaker mounts out of MDF, then added ribs. He filled the gaps on the inside with fiberglass lay-up, then did the same to the outside.

Is your project on this scale that you could fabricate a framework and fill in the gaps?


A styrofoam ball will not withstand a concrete pour, concrete's wet mass, hydrostatic pressure, nor will it stay submerged if done in halves. And styrofoam is porous.

You will have better chance of success if you do this in spherical halves and then join them. This is quite easy to fabricate with moderate success, and also offers easy assembly of your internals as well as design potential for a contrasting center piece / partial stand support.

For the cavity try a bowling ball, 5 or 10 pin depending on required spherical volume. You can drill into it and insert mold supports.

For the shell visit restaurant supply store and select a large stainless steel mixing or maybe even a large wooden salad bowl. Even with this I would suggest fully setting it in sand or water as setting concrete's hydrostatic pressure is immense.

Read up on concrete kitchen countertops and furniture. Commercial readimixes are available for very fine, dense and coloured concrete including how-to guides: concrete pouring for dummies!
For a bigger mould an exercise ball would be cheap .

I made a pair of cheap speakers using IKEA vase (12.95 €) and Tangband W3-871S drivers (~20 €). Internal volume is about 6,5 litres and the neck/mouth gives Fb=75 Hz. I intend to add some bitumen inside to reduse ringing of the enclosure but the enclosure sounds quite dead allready with some polyfill in it.

IKEA steel bowls look great also and there are many sizes.


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