I've been thinking about using spherical enclosures for a future speaker project. Now, I understand from reading on the forums that a spherical enclosure produces a single resonance that is strong.
What happens when you port a spherical enclosure? This would add a second resonance, if I am not mistaken.
What are the best ways of ameliorating the resonance issues? Stuffing with damping material, or just plain old EQ?
I am thinking about using one of these:
http://plasticfabrication.custom-division.com/viewitems/all-categories/acrylic-spheres?
They already have holes built-in that, given the right sized driver, would require nothing but mounting the driver. Boom, instant enclosure. If I get it a little larger than the desired volume, I could fill the bottom with some sand or lead shot to "tune" the enclosure.
Thoughts?
What happens when you port a spherical enclosure? This would add a second resonance, if I am not mistaken.
What are the best ways of ameliorating the resonance issues? Stuffing with damping material, or just plain old EQ?
I am thinking about using one of these:
http://plasticfabrication.custom-division.com/viewitems/all-categories/acrylic-spheres?
They already have holes built-in that, given the right sized driver, would require nothing but mounting the driver. Boom, instant enclosure. If I get it a little larger than the desired volume, I could fill the bottom with some sand or lead shot to "tune" the enclosure.
Thoughts?
going to be too thin for good enclosures. The key is to get damping material in the middle of the sphere. Less of an issue if the motor is stuck right in the middle, but if there's nothing in the middle, a single frequency will dominate.
I did wonder about the 1/8" acrylic being too thin. But there may be other spherical options.
What about having a tennis ball suspended exactly in the middle of the enclosure?
What about having a tennis ball suspended exactly in the middle of the enclosure?
I have sent a request asking how thick the 2 piece moulded ones can be made in sizes 6" - 18"
Will let you know.
Will let you know.
Hoooooeeeeeey! Them's some serious expensive.
6" globe, two piece acrylic, any size opening, 1" thickness. - $275.00 ea.
18" - $520.00 ea.
6" globe, two piece acrylic, any size opening, 1" thickness. - $275.00 ea.
18" - $520.00 ea.
standing wave and resonace of a Sphere is a myth, or better to say- not yet explained
with some drivers it works with some not, you got to try
with some drivers it works with some not, you got to try
Same issue- the difference from the outer surface to the surface of the tennis ball would be consistent all around. What you want is to vary this, or damp this mode. The tennis ball might raise the frequency and possible provide some damping but hard to say without testing.
Jeeez that's expensive for the two piece acrylic. Ok that is out. I will think about other spherical solutions.
Thanks for the replies!
Thanks for the replies!
Lighting fittings are a rich source of glass, acrylic and polycarbonate spheres. Most of them have a neck or rim around the opening which provides a good place to mount a driver or baffle. I have a selection of such spheres ranging from 6 inches to 2 feet in diameter , waiting for me to get a round tuit... They were very cheap, I found them at a junkyard.
The big polycarbonate ones are quite rigid, they are designed to withstand having rocks etc thrown at them - they are typically used in public spaces such as parks. I would think the main problem with such a sphere would be the driver's backwave mid and HF sound radiating out through the relatively thin surface. A coating of self-adhesive damping mat over the inside surface should reduce that. Or just pour in liquid damping material and swish it around until it hardens.
Another source of experimental enclosures is garden weed sprayers, the cheap pump-up ones with cylindrical tanks made of thick plastic. They come in sizes from about 3 litres to 8 litres. The tanks are thick walled and quite "dead" when rapped with knuckles. Cut an end off, screw in a round baffle board. Again, I have several in various sizes witing for my free time. They look ugly, but nothing a decorative sleeve won't fix. Check office supply stores for good-looking waste bins, and garden supply stores for decorative plant pot sleeves. Or just sew up a fabric pull-on sleeve.
The big polycarbonate ones are quite rigid, they are designed to withstand having rocks etc thrown at them - they are typically used in public spaces such as parks. I would think the main problem with such a sphere would be the driver's backwave mid and HF sound radiating out through the relatively thin surface. A coating of self-adhesive damping mat over the inside surface should reduce that. Or just pour in liquid damping material and swish it around until it hardens.
Another source of experimental enclosures is garden weed sprayers, the cheap pump-up ones with cylindrical tanks made of thick plastic. They come in sizes from about 3 litres to 8 litres. The tanks are thick walled and quite "dead" when rapped with knuckles. Cut an end off, screw in a round baffle board. Again, I have several in various sizes witing for my free time. They look ugly, but nothing a decorative sleeve won't fix. Check office supply stores for good-looking waste bins, and garden supply stores for decorative plant pot sleeves. Or just sew up a fabric pull-on sleeve.
Of course, garden weed sprayers.... that would be WAY cheaper than the schedule 40 pvc I've been using for my recent projects!
My orcus loudspeakers are made from schedule 40... I guess the upside is that I can run a pickup truck over them if I wanted to without them breaking lol.
I don't know why I never thought of those weed sprayers.
My orcus loudspeakers are made from schedule 40... I guess the upside is that I can run a pickup truck over them if I wanted to without them breaking lol.
I don't know why I never thought of those weed sprayers.
Again, I found some broken ones at a junkyard. Having the capacity marks on the side is handy... you just saw it off at the right mark and there's your desired enclosure volume.
What about 1/2"? Small ones you could likely get away with 3/8".
6, 8, 10" diameters (2, 4+, 8 litres). What about flangeless hemispheres (front half of teardrop)?
In Bronze?
dave
Well, I found 8" bronze spheres at:
RBWagner B2C | Silicon Bronze
..... for $601/ea!
$242 for a hemisphere the same size.
Brass is a little over half as much.
RBWagner B2C | Silicon Bronze
..... for $601/ea!
$242 for a hemisphere the same size.
Brass is a little over half as much.
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About a year ago, an army-surplus place near me had some large (approx 350mm diameter) plastic spherical fishing floats for sale. They had a moulded-in tube running through the middle for the fixing rope. With a bit of care you could cut out around one pole for the speaker, and leave a portion of the moulded tube opening at the other pole as a port. I regret not buying a couple to try out now.
Get two colanders, one smaller than the other. Fill the space with the same type of material used for making tabletop decoupage. Be sure to coat each colander with oil before assembly. Regards
Great ideas y'all. I'm sure I will get to a spherical enclosure at some point. I think there's some real merit to the fishing floats, the garden sprayers, the acrylic spheres... I dunno about the colanders, seems like filling all those holes would be a royal pain, and you may still end up with something rather thin (the original problem with the 1/8" acrylic).
In any case, I promise I will build some, it just may be a few months.
Would that nasty resonant frequency just be the equivalent volume rectangular enclosure's Fs? I am thinking that with the right sized sphere/speaker combo, it could just be crossed over above the Fs. Boom, no more resonance. Of course, it would require a sub. But I'm not a fullrange purist. Then there's always a notch filter, but I'd like to keep the design out of the electrical domain.
Actually, I wish I had the money for those brass spheres.... mmm I love brass. But plastic first for prototyping.
In any case, I promise I will build some, it just may be a few months.
Would that nasty resonant frequency just be the equivalent volume rectangular enclosure's Fs? I am thinking that with the right sized sphere/speaker combo, it could just be crossed over above the Fs. Boom, no more resonance. Of course, it would require a sub. But I'm not a fullrange purist. Then there's always a notch filter, but I'd like to keep the design out of the electrical domain.
Actually, I wish I had the money for those brass spheres.... mmm I love brass. But plastic first for prototyping.
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You can find stainless bowls with no holes. If the holes scare you, search for thoese instead. Wooden bowls would also work. regards
I asked for a lot of prices from 6" up to 18" from 1/8" up to 1"
What I posted is what she sent me.
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