help with round enclosures

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I really want to build some round enlosures and I have read that some of you have or are planning on it. I fond some round styrofoam balls at a craft store that are hollow and can be separated into two halves. The have them in 20cm, 25cm, 30cm and I think two size above that. I figured I could just encase the styrofoam with fiberglass. The question I have is should I use resin and fabric or just use fiberglass filler or filler and fabric or, or...I have never worked with this stuff. Tto me the resin and fabric approach seems to be more work but for whatever reason I suspect that it would be stronger. I'd appreciate any feedback unless it is to denounce rond enclosures ; ).

BTW my first post...
 
I don't about spherical enclosures. I did a small two-way with curved pannels. I used many layers of thin wood, with epoxy glue and lead layer in between. The result is great, both in apparence, rigidity and damping. I highly suggest this, but this is quite long to do
 

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tiroth said:
Remember, spherical inner chamber is quite possibly the worst possible enclosure shape...you may wish to build some kind of box inside the sphere. (spherical outer shape is great though)
I was under the impression that a spherical inner chamber is the most ideal enclosure design. :confused: I thought people didn't build them that way simply because it's very hard to implement.
 
My aim is something sphereical and the real heart of the question is purely structural, should i work with resin and some fabric or use filler or use both.

I like your design and had though about doing something similar but it would be a lot of work for a lot of tools I don't have.
 
A spherical chamber will have only one main resonance, but much more intense than the three main resonances in a rectangular box.

One could possibly make a helmholtz resonator tuned to the resonant frequency inside the spherical chamber, and place it where the resonace is at the most intense (in the center of the sphere) A tube placed from top to bottom inside the sphere with tuned holes in it should probably do the job, or a smaller sphere suspended inside... Well just an idea...


Peter
 
Yes, I think that option has been discussed as possible. I don't know that anyone has ever tried.

MarkMck did some great work where he demonstrated using real enclosures that rectangular prism was superior to egg/sphere shape. Think about it: if a cube is bad (three pairs of parallel sides with identical dimensions), how much worse is a sphere with an infinite number of parallel identical dimensions?
 
Yes, i totally agree with you, an infinite number of paralell dimensions would make an extremely strong resonance. But if we were able to kill that resonance, there would not be any other to worry about... Well, the multples of the main resonance could possibly make some trouble...:confused:
 
I have made spherical enclosures before. I was chief engineer at KEF, and involved in the Eureka project. I made the enclosures from fishing floats and mounted a specially built 5" Uni-Q driver to it.
These floats are available in a number of sizes, and are made from dense resin with a wall thickness of around 5mm, and are hollow inside. They come in two styles: 2 holes for the rope or 1 central hole.
I cut off a cap using a hacksaw, then put the cut edge on a sanding belt to smoothen and flatten it, then mounted the driver to the surface.
This method worked very well, and provided a very inert cabinet.
If you cut off the cap in the right place, the through hole can now function as a rear vent!
I have searched for a source, and so far found this supplier:
http://www.rainbownetrigging.com/page9.html

There are probably many others.
This will save you a lot of work compared to fiberglassing your own enclosure.
Good luck

Andrew
 

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gary f said:
I don't about spherical enclosures. I did a small two-way with curved pannels. I used many layers of thin wood, with epoxy glue and lead layer in between. The result is great, both in apparence, rigidity and damping. I highly suggest this, but this is quite long to do


Got any more pictures of those. THEY look super..
 
AndrewJ said:
I have made spherical enclosures before. I was chief engineer at KEF, and involved in the Eureka project. I made the enclosures from fishing floats and mounted a specially built 5" Uni-Q driver to it.
These floats are available in a number of sizes, and are made from dense resin with a wall thickness of around 5mm, and are hollow inside. They come in two styles: 2 holes for the rope or 1 central hole.
I cut off a cap using a hacksaw, then put the cut edge on a sanding belt to smoothen and flatten it, then mounted the driver to the surface.
This method worked very well, and provided a very inert cabinet.
If you cut off the cap in the right place, the through hole can now function as a rear vent!
I have searched for a source, and so far found this supplier:
http://www.rainbownetrigging.com/page9.html

There are probably many others.
This will save you a lot of work compared to fiberglassing your own enclosure.
Good luck

Andrew


Thanks for the suggestion I'll check that out. As for the negative feelings on the round enclosures. Don't waste your time I have heard so many claims in my life about the correct and incorrect way to build speakers, cabinets, crossovers etc. that I no longer care what anyone else thinks. If they suck then I'll replace them.
 
I'd use epoxy resin and chopped strand matt - not the woven stuff, the chopped mat shapes easier/will not crease on the curves.
Epoxy resin takes longer to cure than Polyester but easier to use and less agressive.

If the foam is desolving try a few good layers of cling film on a ball as a barrier, if that doesn't work I've had some luck with some brands of Gaffa/Duct tape - as a no stick barrier (dodgy roof flashing a few years back - but fglass spheres may be on horizon).

Unless you're going to play football with it, I think 2 layers of matt will be plenty for the sphere, you you may need to bulk it up with cheap filler.
Again if you use epoxy it should be easier to add/stiiffen sections later on if needed. (you can always glass in timber or similar to make tuff mounting flanges)

Filler by itself will not be strong enough, nor do I think it's thin enough to work through the fibres properly if you try a filler/ fibreglass combination.
 
tiroth said:
Yes, I think that option has been discussed as possible. I don't know that anyone has ever tried.

MarkMck did some great work where he demonstrated using real enclosures that rectangular prism was superior to egg/sphere shape. Think about it: if a cube is bad (three pairs of parallel sides with identical dimensions), how much worse is a sphere with an infinite number of parallel identical dimensions?


Are you referring to this thread?

Although he made a lengthly post, he was questioned about its accuracy (by several with sources) and never responded to the thread. I personally found the threads purpose to be mean spirited.
 
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Joined 2005
This thread couldn't have come at a better time. I'm a student at a university currently undertaking a group project of building a set of speakers, and an amplifier. The aim of the project is to teach as acoustics through practice. Right now I am researching the ideal shape for a loudspeaker. There seemed to be many opinions about the subject, and it is proving difficult to find professional literature.

Can anyone refer me to some literature? What are your opinions on the subject?

Currently I'm only researching the theoretical ideal shape. After I find that, I will research the ideal material. Hopefully when I'm done with this, I'll find a way to implement these results.

Thanks for the replies,
Eitan Waks
 
Jokes aside, I have been working with balls
that is spherical loudspeakers since the end of
the nineties. IMHO the ideal is the spherical outside
and egg inside. Coring the spheres with foam and
then adding rock wool seems to work. Adding weights
also makes life better and the speakers sit better.
So far have done 3inch and 4inch drivers and have
seen and heard the NHT 12inch drivers in a suspended
cored 24inch sphere. Adding barium filled cut plastic sheets
to the inside also is worth a try.
Apple's crystal sphere, Aq Dino, Anthony Gallo spheres,
Morel, Cabasse, Bouyer, The Ferguson Hill subwoofer
need I go on ! All are spheres and all seem to work well
especiilly the Gallo units (I once owned a pair). I enclose a
picture of an egg and cored sphere. You can embellish the
inside with rock wool and use reinforced household light spheres
to experiment with at low cost.

http://www.aq-czech.cz/en/baltic.htm
http://www.sound-e-motion.com/en/catalogue.shtml
http://www.sphearloudspeaker.com/specs.html


Good luck!

AnthonyPT
 
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