Designing a Goban (Go Board) with Sound Hole

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Greg Kennedy
Posts: 3
Joined: Sat Feb 25, 2012 11:27 am

Designing a Goban (Go Board) with Sound Hole

Post by Greg Kennedy »

I know, this doesn't directly relate to acoustic guitars... bear with me for a moment! And feel free to move the topic if there's a better location for it, though I couldn't find one.

The game of Go is played on a large, mostly-rectangular board of these (outside) dimensions:

Code: Select all

Dimension                  SI       Imperial      Japanese
                           (mm)       (inch)
 Board width               424.2     16 23/32     1.4  shaku 尺
 Board length              454.5     17 29/32     1.5  shaku 尺
 Board thickness           151.5      5 31/32     0.5  shaku 尺
Additionally, floor boards are mounted on feet which stand approx. 4 inches off the floor.

Now, the traditional Goban is made of a single solid hunk of wood, cut to the proper size. The best boards are made from some particular kinds of wood and dry for several years after being cut. Oh, and this is very expensive - on the order of $1000+ for a solid wood Goban.

But! Another very important factor in a nice Go board is the loud "chunk/snap" sound emitted when a player places a stone on the board. It lends some psychological heft to the act of making a move. So I thought, what if I designed a board in every way dimensionally exact, except it was hollow and had a sound hole at the bottom to really amplify the noise? That way it would be far less expensive to construct and still just as much fun to play. So who better to ask about "a large-volume hollow box with sound hole designed for amplifying noises" than flat-top acoustic guitar builders?

Just to show I'm not all talk, here's a work-in-progress Sketchup design showing the basic idea. It's just a mitered box made from six pieces of wood, and I plan to glue it along the edges so as not to show any joining hardware. Now let the questions begin:

* Wood thickness. My design is using 1/8" wood for now. How is that for sound transmission and sturdiness? I assume it depends on the type of wood - I plan to use "something cheap from Home Depot" and stain / varnish it in the end. Should I go thinner? Can I go thicker?
* Sound hole size - how big do I make the hole? How does diameter affect the sound?
* Internal Bracing and Baffles - that's a large area top to support just on the corners. I imagine some braces or posts might be a good way to support it, but which is best? Where do I place them? What about "baffles" inside to direct the sound, would that be necessary? Is there a way to help the sound be "consistent" whether the stone is placed near an edge or the center?
* Internal Corner blocks - would these adversely affect the sound? They might make construction easier.

That's all I have for now. I'd appreciate any insight you guys could share.
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Greg Kennedy
Posts: 3
Joined: Sat Feb 25, 2012 11:27 am

Re: Designing a Goban (Go Board) with Sound Hole

Post by Greg Kennedy »

Followup on sound hole size:
http://www.cigarboxnation.com/group/the ... ation-size
Formula for calculating sound hole diameter
1.) Calculate box volume(V) = Length * Width * Height
2.) Solve for the radius of a sphere of the same volume: radius = ((3*V)/4*pi)^(1/3)
3.) Divide the radius by 4.
4.) This resulting value is the new radius of the sound hole.
5.) So, 2 x radius is the new sound hole diameter.
Wikipedia gives this information about Acoustic Resonance, which includes a model for a "closed box". Unsure at this point if venting the box changes the resonant frequency. I also have no idea what the frequency of a stone placement would be... I guess I'd need some stones first, which I would then record and FFT analyze, and then cut the sound hole to maximize amplitude of that particular sound. Essentially I'd be tuning the board to the "note" of a stone placement.
http://en.wikipedia.org/wiki/Acoustic_r ... ngular_box
Randy Roberts
Posts: 465
Joined: Sat Jan 07, 2012 9:11 pm
Location: Omaha, NE (a suburb of Iowa)

Re: Designing a Goban (Go Board) with Sound Hole

Post by Randy Roberts »

Corner blocks will be fine. Baffles would be pointless. I'll come back to your braces or posts in a moment.

Top thickness: The freedom of the top to vibrate and produce sound is a factor of mass, surface area free to move, the stiffness (thickness) , how and to what degree you brace it, what wood is used, etc. If you are going to have a bunch of rocks sitting on it then there’s no point in worrying about it… just build the box and see if you like the sound.
Your determination of Soundhole size should be fine. It would not need to be round, you could do any shape as long as your total surface area of hole is roughly the same as that for the round hole.
As far as your plans for tuning the box by analyzing by recording stones and subsequent FFT etc., I think you may be looking at this backwards. The described resonance is for the main air resonance of the box structure itself, not the stones. Theoretically your box with a sound hole most closely approximates a Heimholtz resonator (“sphere with a necked sound hole” in your referenced Wikipedia citation) However this is just an approximation of your box, and it only gives you the air resonance for the structure. This air resonance in turn interacts with the top’s resonance and the back’s resonance. Unfortunately for any analysis, you are continually changing the top’s resonance with each placement of a stone (mass).
My considered opinion is: just make the box and forget the analysis stuff. You cannot control anything you want to control adequately enough to be wasting your effort there. A box with a hole in it will give you a louder clunk of the stones than a solid block of wood the same size. If you want a louder clunk your box will give it to you.


Back to the braces or posts: It might be an interesting experiment to, when you are making the sides, to make several posts exactly the same heigth as the sides are. embed a small magnet in the end of these posts. Then once the box is finished but before gluing on the top, just clamp it on and move these posts around by way of magnets on the outside to see what effect varying the placement of the posts has on the sound. This may allow you to smooth out the variation of sound from placeing the stones on different locations. It will definitely affect the response of the top and back a great deal. This might let you do some of the "tuning" that it appears you want to do.

Just my 2 cents.
Greg Kennedy
Posts: 3
Joined: Sat Feb 25, 2012 11:27 am

Re: Designing a Goban (Go Board) with Sound Hole

Post by Greg Kennedy »

Thanks so much for the feedback, that is exactly what I'm looking for.

Here's the latest iteration of my design, using diagonal-cut 4x4 posts as corner braces. The wood is all 1/4" thick now (thinnest available from Home Depot) and the sound hole is sized using the formula above. I added a rosette too : ) This is probably what I'll end up building, though I may add long braces beneath the top board from side to side, to aid consistency of the sound.
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