The Soundboard bit.. RC&S

[Ron Nossaman]

> My speculation was based on a small and simple experiment anyone could 
> try at home (else I couldn't have done it).  Take a panel with no ribs, 
> made in wood chosen for it's presumably good acoustic properties.  Do 
> with the panel what they did to choose that wood : knock on it and hear 
> how it sounds (average pitch, sustain, volume and, why not, subjective 
> aesthetical value). Now, put the panel straight up, lean on it with all 
> your weight (this asks a little practice to do safely) and again knock 
> on it.  Hear again how it sounds (average pitch, sustain, volume and 
> aesthetical value).  In my experiment, it was clear that the second 
> version had more aesthetical value than the first one.
> 
> Now how this experiment relates to the real world of piano soundboard in 
> situ, you will most certainly be much more able to tell with some 
> pertinence, absolutely no doubt.  I'm just trying to understand.
> 
> Best regards.
> 
> Stéphane Collin.

Hi Stéphane,
If I were making xylophone bars, I'd most certainly be 
concerned with the tap tone and resonance of the wood I was 
using. For soundboards, I'd really prefer the wood exhibit as 
little specific resonance as possible. Besides supporting 
downbearing in the type of system I'm currently building, I 
see the soundboard doing basically two things. It acts as an 
energy reservoir, cycling the string energy between string 
plane and itself. It also provides a large surface to move 
air, providing sound volume. If it were to be ringing (loud 
enough) at it's own resonant frequency at the same time, it 
would stand out and be a voicing problem that you couldn't 
cure with voicing. Soundboards do have unavoidable resonances, 
but I'd prefer to keep them at an absolute minimum if I can.

What, incidentally, is tapping soundboard planks supposed tell 
us anyway? A dense close grained plank, say 20 grains per 
inch, will ring clearer and longer than a lighter less dense 
plank of, say 10 grains per inch. The 20gpi plank would be 
better suited for a CC board than the 10gpi plank because the 
denser plank will be more resistant to compression. For my 
RC&S boards, I'd want the 10gpi plank. The ring tone and 
duration of the planks doesn't have much specifically to do 
with their general suitability as soundboard panel stock, but 
is rather a secondary indication of a primary characteristic 
that very well could make a difference. Take a common rip saw 
and whack the blade with a stick. Not a very musical clunk. 
Now clamp the handle between your knees and, holding the tip 
with one hand, spring the blade into an "S" curve. Whack it 
again and it sings long and sweet. The musical tone means 
nothing to the process of sawing wood (perhaps even 
*soundboard* wood <G>), but indicates a steel of required 
physical characteristics to do the job. The tone is not 
consulted either during the manufacturing process, nor by the 
prospective purchaser. Terry, are you out there? Do you 
assemble soundboard panels by tap tone, or by grain density 
and orientation? For instance, if I ordered a tap tone 
assembled panel and said "gimme an F"...

Ron N