Tonewoods and Shapes for Resonance?

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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"?
 
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.
 
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.

patch
 
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
 
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
 
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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sdclc126 said:
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?
 
Thanks hermanv, I see what you mean. I am getting a dull result with a sphere made of two very large wooden bowls glued rim to rim, about 1.5 cubic feet under there. Looks great to my kids, but I only got the bowls barely listenable. Instead of bass it rather sounds like a truck changing gears, the otherwise stable jbl/consumer-grade driver beams tin at lower frequencies, crossed or not.

Maybe I need to install my under-fluxed Jensen 15" at the open end of one, to look like a short horn-in-reverse. Then again, not.
 
sdclc126 said:
IMHO loudspeaker cabinets should be seen and not heard.
<snip>
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.
<snip>
Drivers reproduce music - cabinets do not.
In general I agree, but it not impossible to visualize a situation where a given speaker design has a notch and the cabinet resonant at that notch frequency fills it in.

Like all other narrow filters, regardless of how they are made, making the Q the same is vitally important. In this case the resonant rise and fall times must match exactly for this to work. A very difficult feat, but not impossible.

If I need a narrow filter I'll stick to ones in my crossovers, thank you, but not dismiss alternatives out of hand. As I said earlier Sonus Faber is one believer in cabinet resonance, their speakers are arguably in the top tier of commercial designs.
 
hermanv -

I did not mean to sound as though I was dismissing alternative speaker theories out of hand - it was based on experience and my understanding of physics.

I would not second guess what a manufacturer such as Sonus Faber is doing - however what I would do is want to listen to, and measure, both a resonating speaker (cabinet) and a non-resonating one of the same design; can't be done because they don't make both, but for me that would be the litmus test.

Panomaniac -

Yes there is no one way to achive "Nirvana" because we all have different tastes and what is Nirvana to one is garbage to another. The beauty of DIY is that we can make speakers to sound the way we WANT them to, and we all want something different.

I am speaking from my approach - I want to hear reproduced sound that is as faithful to the original as possible - nothing added, nothing taken away. I want to hear a reproduced violin that sounds no different from a real violin, and that extrapolates out to every other musical instument, type of music, etc.

Back in the 80s I purchased a set of devices by a company called Microscan, that attached to the back of loudspeaker cabinets. They converted cabinet resonance into heat - conversion of mechanical energy into heat energy. I listened to a set of good speakers that had the device on one and not on the other. There was a decided reduction of midbass "boom" in the speaker with the device - the difference was quite audible, going back and forth from one speaker to the other. For me the preference was obvious.

As for deliberately tuning a cabinet for resonance, I do see merit if it compensates for a dip in frequency response of the drivers, but not if it creates a rise in the response curve. I am still guarded about this sort of "tuning" - again because of the basic physics - cabinet panels are not transducers and when they vibrate they produce their own secondary sound outside of the reproduced music signal - this, at least to me, by definition is not "high fidelity."
 
Speakers as musical instruments!

Although I haven't listened to any of them, apparently Bosendorpher deliberately exploit cabinet resonances, and the properties of the materials used (like wood), in their quite expensive loudspeakers.

For anyone who may not know, they also make very well thought-of grand pianos, so they should know a thing or two about this subject.

Regards,
 
I suspected this argument would come up.

A musical instrument and a loudspeaker are not the same. In a violin there is no conversion of an electrical signal into mechanical movement. In the case of string instruments, the wooden chamber resonates and amplifies the sound of the strings and gives a particular character to the instrument - making the chamber out of a different material imparts a different sound quality to the instrument. But ALL of that is recorded in the studio and reproduced by the drivers in a loudspeaker. Anything a cabinet adds to that is something that was not in the orignal recording!

To say that you need a resonating wooden speaker cabinet to accurately reproduce a violin is like saying you need a metal cabinet to accurately reproduce a trumpet. Indeed, how can transducers reproduce the sound of any instrument when they are not shaped or built like any of them?

A loudspeaker cabinet at best could mimic perhaps one instrument, but it can't be a catch-all - whatever resonance it has will react to the entire music signal at its resonant frequency, imparting characteritics to any and all musical instruments playing in the recording in that region, characteristics those instruments do not generate by themselves.
 
Re: Speakers as musical instruments!

Bobken said:
Although I haven't listened to any of them, apparently Bosendorpher deliberately exploit cabinet resonances, and the properties of the materials used (like wood), in their quite expensive loudspeakers.

For anyone who may not know, they also make very well thought-of grand pianos, so they should know a thing or two about this subject.

Regards,


I have heard them. They reproduces piano VERY well !!

no matter what instrument is playing !!!
 
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