Soundboard Panel Grain Angle

[Farrell]

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Comments below:

Some of my input below is playing the devil's advocate - I'm trying to =
push this so that I might understand some of this stuff.

Terry Farrell
 =20
----- Original Message -----=20
From: <A440A@aol.com>
To: <pianotech@ptg.org>
Sent: Friday, October 25, 2002 11:33 AM
Subject: Re: Soundboard Panel Grain Angle


> Greetings,=20
>    There are acoustic reasons for quarter sawn wood being used.  Sound =

> transmission is much better with the grain than across it, (something =
on the=20
> order of 3 times faster,too?)  I believe this is because there is a =
loss of=20
> acoustical energy every time there is a change from one medium to the =
next,=20
> and going across the grain requires the energy to go from one density =
of wood=20
> to another with every "ring line", effectively losing energy at every =
step.=20

Then it would seem that quarter sawn spruce would effectively =
stop/minimize sound transmission across the grain. If the boards were =
flat sawn, the sound would not have to cross between hard and soft =
layers. Going along the grain, it would seem as though there might not =
be much difference between flat and quarter sawn - just that quarter =
sawn would be lots of little hard grain strips and flat would be larger =
more continuous layers of hard wood for sound to "travel along".
=20
> Harder material transmits the sound faster, too, so the harder grain=20
> transmits the sound better and faster than the softer "summer" wood.=20

I'll buy that. That applies to the previous statement.
=20
>     The more truly quarter sawn it is, the more contact there will be =
between=20
> the harder grain and the bridge.

Yes, I see that. What about if you had flat sawn and simply planed it =
until you had a nice dense late-season growth ring near the surface? =
Then you would have 100% contact with the harder grain and the bridge.=20

>  There is a reason that the best sounding=20
> boards have the bridges directly connected to the ribs, since the ribs =

> transmit the energy to the entire board with greater efficiency than =
if all=20
> the energy had to spread across the grain from the bridge.=20

I suppose then this would get into advantages/disadvantages to having =
the ribs quarter sawn or flat sawn or somewhere in between. Should they =
be one way or another because of acoustical properties, or would/should =
that decision be based on strength/stiffness properties of the various =
cuts?

SNIP

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