Tonewoods and Shapes for Resonance? - diyAudio
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Old 15th December 2007, 07:25 PM   #1
patch is offline patch  United States
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Default Tonewoods and Shapes for Resonance?

I constructed an enclosure with intended resonant properties. This vented loudspeaker is made of wound bamboo strips, all curves. It sounds good when its single 4 inch driver is played at low dBs.

I wonder if anyone has a preference for resonant enclosures, and if so, what materials, what tonewoods, what shapes are preferred.

The enclosure is a slightly modified ornamental fiber vase made in Vietnam, found by chance and on sale at a local Fred Meyers. 7 inches wide, 14 inches tall. Approx. 1/4 to 3/8th-inch bamboo wood strips wound and glued. With a paper/wood/glue slurry applied to the inside. These have a sealed flat bottom that expands to a bowl shape and then narrows to a cone with and open end. Painted. The driver is mounted in a hole cut into the base. (I have since discovered that this same enclosure shape (but thicker materials) has been used by producer at www.norh.com

It is quite a resonant enclosure and musical. With the 4" midrange Seas that Jack Hidley is still selling on this forum, used as a full-range, and with a handful of poly stuffing, I get a nice open sound, good detail, not at all dark. And pretty good sub-middle-C sound coming out of the opening. The very top-end beams of course, but no unpleasant ringing. Interesting harmonics coming through and off the surface and filling the room, sort of like heat off a Class-A. Probably most critically, this design has a high family-acceptance coefficient.

I am thinking about making a larger enclosure of this type, primarily to bring good music back into the family living area where my other designs have been banned on grounds of poor aesthetics. Anyone else into this sort of thing and "good sounding wood"?
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Old 15th December 2007, 09:09 PM   #2
hermanv is offline hermanv  United States
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Drivers work their best in cabinets of certain volumes. Your example seems to be 0.3 cubic feet which is very small. this tends to significantly limit bass response. A more typical volume would be 2 to 4 cubic feet. Unfortunately this directly impacts the looks and acceptance factor. It is not an accident that most quality full range speakers are physically large.

Tuning a cabinet can be useful, the most famous brand I know of that does this is Sonus Faber. But the tuning should be used to add slight emphasis otherwise the speaker will sound hollow.

One alternative is in wall speakers that then make use of the hollow volume inside the wall.

A very large number of cabinet design programs are available free on the internet. they will help you visually determine the results of undersize cabinets.
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Old 16th December 2007, 09:16 AM   #3
Pano is offline Pano  United States
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You should have a look at this:
http://www.auditorium-23.de/Welcome/Intro.html

I have not heard Keith's designs, but he gets rave reviews, some of the best I've ever read. He's a really nice guy, too.

Certainly a different approach than what we are used to. He builds the cabinets FOR resonance.
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Old 17th December 2007, 03:49 PM   #4
patch is offline patch  United States
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Wow, panomaniac, the loudspeaker designs on the Auditorium 23 website are very neat. Just the kinds of ideas I am looking for. Thanks so much! (Too bad he hurts his credibility by presenting grossly overpriced cables, priced like a registered poodle when practically anyone can do the same for the price of a good old used hunting dog).

It's funny how my naive-design working donkeys and sketches look similar to those resonant-design and radically-vented commercial designs you've pointed me toward, panomaniac.

Maybe this moving toward similar baffle/OB designs is an almost-inevitable outcome when a person starts thinking sideways about loudspeakers and does something like what I've started to do: Sit in on services at some old traditional churches to hear the unamplified, big-hall, sounds of their instruments (choirs, huge pianos, pipe organs). Sit down and listen in a little differently when playing their piano, acoustic guitar, or whatever natural instruments they learned. Wipe the dust off Weems and buy and study some acoustics texts. And only then pull up to computer. Round up a basket of drivers, having ballparked and outright trespassed across the t/s parameters. Hit the sales and thrifts and select a bunch of all-sized objects made of promising materials. Spend some time at the workbench. Listen alone and with others, take notes; enjoy the positive feedback and apply negative.

Right you are hermanv, the small jug and that 4" driver really work best as soft of stand-along midrange speaker. When pushed, that speaker stalls out at something under concert A.

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Old 18th December 2007, 04:54 PM   #5
patch is offline patch  United States
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On good resonant designs: a suggestion was made to try cloning the ProAc Response 2.5s, unbraced. Said this was just simply a frame for a very high quality driver, and the wood vibrates with it. Never heard this one play; the sterophile review was positive. Not sure about the specs on that woofer, but that would be nice to know. Anyone happen to know what it is?

Sphereical enclosures are still being sold out there, small ones too, neat combinations, but few seem to have been vented. I very much like the looks of these egg-and-dart builds. : http://www.studio-electric.com/loudspekers3.html
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Old 18th December 2007, 05:43 PM   #6
hermanv is offline hermanv  United States
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My friend and I experimented with spherical driver enclosures. We found that the spherical shape caused more internal reflections to come out the driver front than others.

We lined the inside with felt and tried to suspend a felt ball at the focal point, but no joy.

Since internal reflections come out delayed in time, the response curve ends up with bumps and valleys equal to sum and differences at frequency multiples of the delay path length. Smoothing may make this look OK on a plotter, but the ears were not fooled.

Obviously some are making this work, but other shapes offer an easier solution IMHO
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Old 18th December 2007, 05:55 PM   #7
Nordic is offline Nordic  South Africa
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Well I think in this concept the idea is not to have they wood act as some kind of reflector of soundwaves only.... it literaly is supposed to resonate with the sounds....

Imagine a clasical guitar with a rubber body or a cement body for that matter (the two extremes).. it would in all likely hood sound very crap if at all...
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Old 18th December 2007, 06:50 PM   #8
freddi is offline freddi  United States
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I haven't tried flex cabinets but do like some Karlson couplers - heres one which sounded awful if the starting gap was 5/8" and real good when the wings were pivoted on the cleats to make the starting gap `1.2"

http://img406.imageshack.us/img406/7577/insert1lc8.jpg
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Old 18th December 2007, 08:18 PM   #9
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IMHO loudspeaker cabinets should be seen and not heard.

I believe it is physically impossible for a cabinet to improve the sound of a speaker - its vibrations are a passive reaction to the movement of the transducers, and resultant sound is an artifact of cabinet rather than transducer characteristics. One might hear "more" bass, but it will be unrealistic and distorted bass.

A vibrating cabinet produces a sound all its own - it has nothing to do with the music signal - they make sound, but it isn't music. A lot of work goes into making transducers that are accurate and distortion free - cabinets only introduce distortions that by their very definition are unwanted.

Drivers reproduce music - cabinets do not.
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Old 19th December 2007, 10:06 AM   #10
Pano is offline Pano  United States
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Quote:
Originally posted by sdclc126
A vibrating cabinet produces a sound all its own - it has nothing to do with the music signal - they make sound, but it isn't music. <snip>Drivers reproduce music - cabinets do not.

I would tend to agree with you there, that's the classic approach to loudspeaker design and the very best speakers I have heard follow those rules - sometimes to extremes. Massive heavy, dense plywood. Double walls sand filled, extensive bracing, large low pressure boxes, etc.

But here's the odd thing. Keith at Auditorium 23 has heard, built and owned many of the same systems I just referenced. Yet he chooses to built resonate cabinets. Why? Is he mad? Is it a market ploy? Or is it simply the Romantic approach vs. the Classical? Keith is not a man without taste, skill or knowledge - so that makes me curious of his building style, even if I've never heard his work.
Reviews of his products are glowing like not much I've read.

Strange, eh? Could it be there is no "one way" to audio Nirvana?
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