# Soundboard Materials



## Enthalpy

Hello nice people! I propose to discuss *soundboard materials* here.

========== Figure-of-merit, Kiri

I used E/rho^3 to compare woods for a soundboard, there
scienceforums​This figure of merit indicates how light a soundboard is at identical size and resonant frequencies, adapting the thickness.








It tells that the commonly used spruce _Picea abies_ makes the lightest soundboards among traditional European woods, with near equivalents in America. The same figure of merit suggests that kiri _Paulownia tomentosa_, which makes music instruments in Asia, may outperform _Picea abies_. At least one guitar maker in America confirms.


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## Enthalpy

*Kiri Paulownia tomentosa grows in Hungary, Portugal and Turkey* too, maybe Spain, not just in Japan, China and Australia.
researchgate.net - mdpi.com

Some radial and azimuthal moduli are reproduced there from the Wood Industry Handbook
core.ac.uk
_Picea abies_ and _Acer pseudoplatanus_ bought by luthiers are grown, selected, harvested, sawn and dried to their high demands, which improves much the performance. Kiri isn't to my knowledge, biassing the comparison. Selecting the logs may suffice for experiments and to start a series. Koto makers know certainly a lot on the topic.

_Tomentosa_ is adult in 20 years, so luthiers can compare growth conditions in less than two centuries, nice. Big production exists in Australia and supposedly in Asia. Unclear to me: the species is considered invasive in Europe but is sold and grown in gardens and plantations.

The first linked paper measures _Paulownia tomentosa x elongata_, and more _Paulownia_ exist
Paulownia - tomentosa at Wikipedia
but _tomentosa_ is the one that makes instruments in Asia, so maybe the others don't sound well. Again, koto makers must know it better.

The squared reciprocal of the soundboard mass influences the radiated sound power, which varies like E/rho^3 hence. So 200 for kiri versus 156 for spruce brings a clear loudness advantage, like a 4-notes chord versus a 3-notes one.


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## Nate Miller

I can't talk about soundboards on that level, but assuming we're talking guitar soundboards, I do have some first hand experience there. I do know that there are alot of woods used by lutheirs that are no longer allowed to be imported. I have the paperwork to prove my concert instrument was made and imported before the bans went into effect. I'm sure its mostly the East Indian Rosewood that make up the back and sides, though. It's an Alpine Spruce top, which I think is still legal to import.

One thing about soundboards...its like baseball bats....the tighter the grains, the better. That means that trees grown in the extreme north or at altitude make the best sound boards. Thus the Alpine spruce in my instrument and the wide use of Canadian cedar.

Spruce brings out the highs and projects better, but cedar has a warmth to it. Both are great materials, its purely personal preference. 

What you were saying about soundboard mass is what's behind the double top guitars. The two layers are thinner than any single soundboard you can make, and then they are braced together. The thing is that a single layer guitar can still be just as loud as a double top. When I bought my instrument, I tried out a couple double tops and the one I went home with was every bit as loud as the double tops, so you can make guitars with a single layer top that are still every bit as loud as a double top.


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## Enthalpy

Hi Nate Miller, thanks for your interest!

Acoustics is useful only of it serves music, and acoustics is still a _very_ incomplete science, so once theories, models and figures like the ones I put tell "there might be something interesting", only experiments can tell if the idea has some value.

As you play the guitar, I suggest to read the comment about kiri by Carla Kelly, a guitar maker, there:
Paulownia | The Wood Database (Hardwood)
Just enthusiastic.


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