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Old 12th April 2002, 07:35 AM   #1
jmiyake is offline jmiyake  United States
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Default What is the ideal enclosure shape?

Theoretically: What is the ideal shape for an enclosure?

OK...Now how close can you come to that using mdf or like materials?

James
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Old 12th April 2002, 03:34 PM   #2
Bill F. is offline Bill F.  United States
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You want to avoid two things: air mass resonances within the enclosure and reflections back out through the cone.

To cut resonance, it's a good idea to make sure no length dimension is equal to (or a multiple of) another. Also resonant standing waves can be attenuated by making interior surfaces non-parallel. This also helps disperse midrange/treble reflections.

Have you ever seen pictures of those anechoic chambers with foam wedges everywhere? That kind of treatment with random acute angles would probably work well to diffuse the mid/treble backwave.

I've thought of taking the scraps left over after making a cabinet, cutting them into wedges, and gluing them in alternating patterns to the inside back wall of the enclosure. Then you could coat them with a good layer of rubberizing spray, like vehicle undercoating from the local Auto Zone. They would also add mass to the enclosure wall--not a bad thing.

Bill
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Old 12th April 2002, 04:07 PM   #3
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Default Enclosure shape

Basil says: amphibious landing craft shape
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Old 12th April 2002, 04:41 PM   #4
jam is offline jam  United States
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How about our favourite Christmas tree shape?

Jam

P.S. Seriously I believe it is a sphere or egg shaped.
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Old 12th April 2002, 04:59 PM   #5
jam is offline jam  United States
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James,

See Olsen's work on acoustics.

Jam
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Old 12th April 2002, 05:08 PM   #6
Nisbeth is offline Nisbeth  Denmark
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The optimum enclosure shape is a sphere. (tough to do in mdf). Vance Dickason discusses this subject in "The loudspeaker design cookbook". If you have access to this book, look it up.
I donīt have it handy at the moment, but I believe the best shape possible in a wooden enclosure would be something like the "christmas tree" shape (i.e. no parallel surfaces).

HTH
/Uffe
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Old 12th April 2002, 09:14 PM   #7
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Default Dual tapered Octagon

Well obviously Iím biased a bit but I believe that my latest project (SST8) has the perfect (well almost) shape, I did over a year of research and testing to come to this conclusion, I tested equilateral triangles, boxes, spheres, eggs (ovoid) and three different octagons until I finally came up with a dual tapered octagon. After living with these a few months and finally getting the crossover point right I couldnít be happier with these. Also a shape like this needs no internal bracing and they are as dead as any cabinet I have ever heard or should I say not heard.

SST8 MTMís
http://64.33.91.28/kingdaddysst8/index.html
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Old 12th April 2002, 10:55 PM   #8
Bill F. is offline Bill F.  United States
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Purty work, KD

Looks like you gave some thought to baffle step, too. What's that white stuff that sorta reminds me of drum skins? Is it a decorative touch to sorta remind people of drumskins?

Bill
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Old 12th April 2002, 11:18 PM   #9
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Didn't realy intend to go for the drum skin look, or drums at all in fact, just turned out all the research and expermints led to this design, sound was first and formost looks came second, or some might say not at all. the finish is bleached stone textured paint and oak inlays. interesting thing about baffle step is that with these I dont need any compensation at all.
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Old 13th April 2002, 01:40 AM   #10
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Default I vote for the egg

About 20 years ago I believe someone like Madisound had focal
speaker kits with what they clamed was the best enclosure shape
namley the egg. They had fiber glass reinforsed plaster of parris
enclosures for sale. I don't recall the name but there is a speaker
enclosure company that has a pattent on spherical enclosures. They sell them in many sizes. Besides hard to set a drink down
on the top of either these shapes!


Keep up the posting


bob
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