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Old 14th July 2012, 01:53 AM   #11
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Originally Posted by Richard Ellis View Post
The sphere is NOT the best! In order of worst to best..1) Sphere 2) cube....3) all others 4) A calculated best Acoustic ratio 1.2599-1- .7937.
Think about it... the sphere will reflect internal waves from a point source to the walls (At equal distances) & all arrive back to the same place, in phase, equal intensity....This will compound & concentrate the back-wave...Same somewhat with the cube. An acoustic ratio breaks up these frequencies by a mathmatically derived proportion.


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The sphere enclousure is the best sound why it had no flat walls inside to amplify the resonances, which funnel down.
I fell you would say rectangular Golden Ratio box is good, but these proportions you mention are strange.
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Old 14th July 2012, 09:53 AM   #12
lejaybo is offline lejaybo  United Kingdom
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Originally Posted by planet10 View Post
One potential complication: the cone needs to be the same diameter as the bowl, no dimensions are given.

dave

hi,

so the hemi-sphere bowl is Dia 28cm with a 13cm height

and the cone shape bowl is Dia 28cm with 13cm height


my first thoughts of using these was to make a crude B&W'esc teardrop cabinet


going to buy some this weekend so i can measure the internals
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Old 14th July 2012, 10:35 AM   #13
ODougbo is offline ODougbo  United States
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Default Cylinder Subs

Few years back I found a huge PVC drain pipe, 15" ID 1/2" wall (still have 4' left). I made several BR subs with 8" and 12" woofers.

They worked okay, I didn't see any advantage over a rectangle box. I had some pics, but must have delated them.

I would add if sphere is the ideal speaker inclosure, there would be 100s of them available in stores, web, etc.
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Old 14th July 2012, 10:48 AM   #14
tvrgeek is offline tvrgeek  United States
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The sphere is ideal only in how it manages baffle step and diffraction. We can beat boxes into submission and they pass the WAF easier. There are spherical speakers on the market.

This is pretty simple physics. Just go read Olson's paper. It has ONLY to do with diffraction and baffle step. No magic, golden, Fib sequence, smoke and mirrors. Like I said before, his original work stands so well, no one has needed to revisit the subject. Just read it.

BTW, a sphere with a wad of damping in the center works exceedingly well. Also note that internal reflections are no where near as important as the external problems Olson addresses. Not unimportant, just not as.
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Old 14th July 2012, 04:36 PM   #15
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Quote:
Originally Posted by tvrgeek View Post
Just go read Olson's paper.
The paper is a book. Acoustics.

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Old 14th July 2012, 04:59 PM   #16
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Here's the equation you need to work out what freq your spheres will work down to in terms of removing defraction issues:

required sphere radius = 13500 / lowest frequency / 2 / pi



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Old 14th July 2012, 05:13 PM   #17
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Mr Groog's formula spits out inches

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Old 14th July 2012, 05:16 PM   #18
Ron E is offline Ron E  United States
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Quote:
Originally Posted by tvrgeek View Post
Like I said before, his original work stands so well, no one has needed to revisit the subject.
Bews and Hawksford, Lipshitz and Vanderkooy, Juha Backman, just a few who have published analytical papers in the JAES since Olson's rather crude empirical work.
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Old 14th July 2012, 08:17 PM   #19
tvrgeek is offline tvrgeek  United States
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I went through all 4 volumes. You know, his "crude" work has everything this thread needs except getting a few people to actually read it. If you can mention a specific paper that adds to this conversation, let me know and I will revisit it.

So for those too lazy to do a simple search:

Diffraction Information & Graphs
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Old 14th July 2012, 08:36 PM   #20
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OK......howbout a box for your low-end & a sphere for your mids???




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