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<DIV style="FONT: 10pt arial">----- Original Message ----- </DIV>
<DIV
style="BACKGROUND: #e4e4e4; FONT: 10pt arial; font-color: =
black"><B>From:</B>
<A title=rbrekne@broadpark.no =
href="mailto:rbrekne@broadpark.no">Richard
Brekne</A> </DIV>
<DIV style="FONT: 10pt arial"><B>To:</B> <A =
title=pianotech@ptg.org
href="mailto:pianotech@ptg.org">pianotech@ptg.org</A> </DIV>
<DIV style="FONT: 10pt arial"><B>Sent:</B> June 15, 2001 1:37 =
PM</DIV>
<DIV style="FONT: 10pt arial"><B>Subject:</B> Re: Soundboard =
Evaluation</DIV>
<DIV><FONT color=#800080 size=2></FONT><FONT color=#800080 =
size=2></FONT><FONT
color=#800080 size=2></FONT><BR></DIV>
<BLOCKQUOTE><FONT color=#cc33cc>"If there is still enough structural =
integrity</FONT> <FONT color=#cc33cc>left in the original panel to =
hold
itself together I see no reason why this</FONT> <FONT =
color=#cc33cc>won't
work. And work just about as well as a panel made out of new wood.
The</FONT> <FONT color=#cc33cc>age of the wood is purely =
incidental. The
only thing of any real consequence</FONT> <FONT =
color=#cc33cc>would be the
fiber compression that has taken place over the =
years."</FONT></BLOCKQUOTE>
<DIV>Then I begin wondering where we are going with this point about =
the
"consequences of fiber compression".... Follow me for a bit and you =
may see my
problem.... Given three rib crowned panels, one of new wood, and one =
of old
compression damaged wood, and an old panel that was rib crowned =
origionally.
If fiber compression damage is of consequence with respect to acoustic =
performance then the board that was made from compression damaged wood =
should
clearly be inferior sounding.... right ?... </DIV></BLOCKQUOTE>
<DIV dir=ltr><FONT color=#800080 size=2>I'm not sure. First you =
say, "Given
three rib-crowned panels..." Then you say, "If fiber compression damage =
is of
consequence with respect to acoustic performance then the board that was =
made
from compression damaged wood should clearly be inferior sounding... =
right?"
Which one are you referring to? And why are you assuming that any of the =
three
should "clearly be inferior sounding...?" How old is that third example =
of your?
It might still be sounding great.</FONT></DIV>
<DIV dir=ltr><FONT color=#800080 size=2></FONT> </DIV>
<DIV dir=ltr><FONT color=#800080 size=2></FONT> </DIV>
<BLOCKQUOTE dir=ltr
style="PADDING-RIGHT: 0px; PADDING-LEFT: 5px; MARGIN-LEFT: 5px; =
BORDER-LEFT: #800080 2px solid; MARGIN-RIGHT: 0px">
<DIV>and if then all three sound very much the same...then doesnt it =
follow
that this fiber compression damage is then, in itself, of no real =
consequence
at all in this perspective. ? Do you see my quandry with this ?
</DIV></BLOCKQUOTE>
<DIV dir=ltr><FONT color=#800080 size=2>No, I don't. Read again =
what I said:
"The only thing of any real consequence would be the fiber compression =
that has
taken place over the years." I didn't say that this had any appreciable =
effect
on it's performance as part of a working rib-crowned soundboard =
assembly. The
compression damage now exists. When the panel was new, it didn't. That's =
all.
</FONT></DIV>
<DIV dir=ltr><FONT color=#800080 size=2></FONT> </DIV>
<DIV dir=ltr><FONT color=#800080 size=2>I repeat, this fiber =
compression damage
will probably have little effect, if any, on the panels =
performance as
a diaphragm in a rib-crowned soundboard assembly. Just the fact that the =
fiber
damage is there shouldn't really matter all that much.</FONT></DIV>
<DIV dir=ltr><FONT color=#800080 size=2></FONT> </DIV>
<DIV dir=ltr><FONT color=#800080 size=2>You're just confusing =
yourself with what
is really a fairly simple concept and you seem to be trying to blend the =
two
systems together. Can't do that. </FONT></DIV>
<DIV dir=ltr><FONT color=#800080 size=2></FONT> </DIV>
<DIV dir=ltr><FONT color=#800080 size=2>The rib-crowned soundboard =
assembly does
not depend on the across-grain compression strength of the wood panel to =
either
form or maintain crown. It is simply a wave-carrying diaphragm. The
compression-crowned soundboard does depend on this across-grain =
compression
strength. If you take the ribs off of a compression-crowned soundboard =
assembly
and replace them with a set of properly crowned ribs you no longer have =
a
compression-crowned soundboard assembly. You now have a rib-crowned =
soundboard
assembly.</FONT></DIV>
<DIV dir=ltr><FONT color=#800080 size=2></FONT> </DIV>
<DIV dir=ltr><FONT color=#800080 size=2>This is a fundamental =
difference you
must understand if you are be able to knowledgably discuss the =
two.
</FONT></DIV>
<DIV dir=ltr><FONT color=#800080 size=2></FONT> </DIV>
<DIV dir=ltr><FONT color=#800080 size=2>You still seem to be =
assuming that the
wood panel in the rib-crowned soundboard assembly you describe (#2, =
above)
somehow depends on its being compressed to perform properly as a piano
soundboard. It does not. It is now simply a diaphragm that happens to be =
made of
a material that is anisotropic in nature. The wood panel made of =
somewhat
damaged wood started out that way and now, having been damaged somewhat =
by being
held under compression for a few decades, it is just a bit more so. As =
it turns
out with a rib-crowned soundboard assembly this does not matter all that =
much.
<STRONG>Soundboards systems that are primarily rib-crowned do =
not depend on
the compression of the wood across-grain to either form or maintain =
crown.
</STRONG></FONT></DIV>
<DIV dir=ltr><FONT color=#800080 size=2></FONT> </DIV>
<DIV dir=ltr><FONT color=#800080 size=2>The fact that the specific =
wood used to
make this rib-crowned soundboard panel--the wood taken from that =
old
compression-crowned soundboard assembly--now has less compression =
strength than
it had when it was fresh, new wood simply doesn't matter all that much. =
We are
not going to use the across-grain compression strength characteristic to =
structurally stiffen the soundboard assembly.</FONT></DIV>
<DIV dir=ltr><FONT color=#800080 size=2></FONT> </DIV>
<DIV dir=ltr><FONT color=#800080 size=2>Your question, "If fiber =
compression
damage is of consequence with respect to acoustic performance then the =
board
that was made from compression damaged wood should clearly be inferior
sounding...right?" shows that you still have a very fundamental =
misunderstanding
about the differences between a compression-crowned and a rib-crowned =
soundboard
assembly. This fiber compression damage would only be of consequence if =
I were
going to use this panel to form another compression-crowned soundboard =
assembly.
In this case it would indeed be inferior sounding simply because no =
matter how
much I dried out the old panel I probably couldn't get enough expansion =
to
create the stress interface between it and the ribs to form the required =
crown.
</FONT></DIV>
<DIV dir=ltr><FONT color=#800080 size=2></FONT> </DIV>
<DIV dir=ltr><FONT color=#800080 size=2>There is no quandry or =
magic smoke here.
There are simply basic differences between two quite different systems =
to be
understood. </FONT></DIV>
<DIV dir=ltr><FONT color=#800080 size=2></FONT> </DIV>
<DIV dir=ltr><FONT color=#800080 size=2></FONT> </DIV>
<BLOCKQUOTE dir=ltr
style="PADDING-RIGHT: 0px; PADDING-LEFT: 5px; MARGIN-LEFT: 5px; =
BORDER-LEFT: #800080 2px solid; MARGIN-RIGHT: 0px">
<P>Ok to take things a step further then... if it turns out that fiber =
compression damage then is of little or no consequence to acoustic =
performance
of said panel... then isnt this a rather large point removed in the
argumentation against compression crowning to begin with ? =
</P></BLOCKQUOTE>
<P dir=ltr><FONT color=#800080 size=2>There is a structural =
difference between
compression-crowned soundboard assemblies and rib-crowned soundboard
assemblies.</FONT>
<P dir=ltr><FONT color=#800080 size=2>How do you suppose the wood =
panel acquired
that compression damage in the first place? As has been explained =
before, the
compression damage got there because during manufacture the soundboard =
panel was
made very dry (it was shrunk) prior to ribbing with the result that it =
later
became heavily compressed (something between 1% and 2.5%) to =
form the
stress interface with the ribs that formed the initial crown. Without =
that
compression there would have been no compression damage. Even then, it =
is not
the compression damage per se that causes the loss of tone performance, =
it is
the loss of crown in the soundboard assembly (the loss of stiffness) =
that
results from that compression damage that causes the loss of tone =
performance.
</FONT>
<P dir=ltr><FONT color=#800080 size=2>In other words, the loss =
tone performance
is the result of the loss of crown that is the result of the compression =
damage
that is the result of compressing the wood to form the crown in the =
first
place.</FONT>
<P dir=ltr><FONT color=#800080 size=2></FONT>
<BLOCKQUOTE dir=ltr
style="PADDING-RIGHT: 0px; PADDING-LEFT: 5px; MARGIN-LEFT: 5px; =
BORDER-LEFT: #800080 2px solid; MARGIN-RIGHT: 0px">
<P>(we arent into the structural integrity / strength of the panel =
assembly
question just yet ok ?... ..cuz I will conceed that point no problem
anyways..I first want to get at how this fiber damage eventually =
affect the
performance capabilities of the wood isolated from all other factors.) =
</P></BLOCKQUOTE>
<P dir=ltr><FONT color=#800080 size=2>What?</FONT></P>
<P dir=ltr><FONT color=#800080 size=2></FONT> </P>
<BLOCKQUOTE dir=ltr
style="PADDING-RIGHT: 0px; PADDING-LEFT: 5px; MARGIN-LEFT: 5px; =
BORDER-LEFT: #800080 2px solid; MARGIN-RIGHT: 0px">
<P>Ok... so then we would have to confront the strength of these =
panels over
time..and if you dont mind... can we take this one step at a time... =
dealing
with the above first and as isolated as possible... and get into the =
structual
strength issue in the next episode ? </P></BLOCKQUOTE>
<P dir=ltr><FONT color=#800080 size=2>Sure. Just keep it civil. =
Don't assume I'm
blowing some kind of magical smoke just because you don't understand
something.</FONT></P>
<P dir=ltr><FONT color=#800080 size=2>Del</FONT></P>
<P dir=ltr><FONT color=#800080 =
size=2></FONT> </P></BODY></HTML>