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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 href="mailto:BobDavis88@aol.com"
title=BobDavis88@aol.com>BobDavis88@aol.com</A> </DIV>
<DIV style="FONT: 10pt arial"><B>To:</B> <A =
href="mailto:pianotech@ptg.org"
title=pianotech@ptg.org>pianotech@ptg.org</A> </DIV>
<DIV style="FONT: 10pt arial"><B>Sent:</B> Thursday, April 24, 2003 =
8:51
AM</DIV>
<DIV style="FONT: 10pt arial"><B>Subject:</B> Soundboard =
re-engineering
priorities</DIV>
<DIV><BR></DIV>
<DIV><FONT face=arial,helvetica><FONT face=Arial lang=0 size=2 =
FAMILY="SANSSERIF">One really needs to START with 50 installations =
under his
belt, to try out parameter changes one at a time and throw them all =
away.
However, since this is impossible, it would be nice to have guidance =
on the
order of precedence. Rather than throwing fifty experimental boards at =
one
piano, I'm going to have to make small changes in the next fifty =
pianos. I am
willing to accept that they may not be their
ultimate.</FONT></FONT></DIV></BLOCKQUOTE>
<DIV><FONT size=2>This is a generally good and safe way to proceed. It =
also has
the advantage of allowing you to quantify the improvements (or lack =
thereof)
made by one specific change. </FONT></DIV>
<DIV> </DIV>
<BLOCKQUOTE
style="BORDER-LEFT: #000000 2px solid; MARGIN-LEFT: 5px; MARGIN-RIGHT: =
0px; PADDING-LEFT: 5px; PADDING-RIGHT: 0px">
<DIV><FONT face=arial,helvetica><FONT face=Arial lang=0 size=2 =
FAMILY="SANSSERIF">I have previously used crowned ribs, glued on in =
a bellied
press, in a moderate EMC environment, and they sound good and should
presumably last longer. I have (for now!) four specific questions: =
<BR><BR>1)
Is there some small change to try next, to improve the treble sustain =
and
projection, without changing the rib layout, or making a new bridge
root?</FONT></FONT></DIV></BLOCKQUOTE>
<DIV><FONT lang=0 size=2 FAMILY="SANSSERIF">You might try a =
soundboard cutoff
bar. It won't help the high treble any but will help through the upper =
tenor and
lower treble. Don't forget to adjust the rib specification to compensate =
for
their shorter length. Sooner or later, however, you're going to have to =
tackle
those bridges. You might start by recapping the top two treble sections =
to
accommodate something resembling semi-log scaling.</FONT></DIV>
<DIV> </DIV>
<DIV> </DIV>
<BLOCKQUOTE
style="BORDER-LEFT: #000000 2px solid; MARGIN-LEFT: 5px; MARGIN-RIGHT: =
0px; PADDING-LEFT: 5px; PADDING-RIGHT: 0px">
<DIV><FONT face=arial,helvetica><FONT face=Arial lang=0 size=2 =
FAMILY="SANSSERIF">2) I thought the general deal was that =
stiffer=softer
tone/longer sustain and less stiff=louder, more abrupt. We recently =
strung a
Chickering 109C, the treble of which had both weak output AND a very =
short
sustain in the top section. The scale lengths and sizes looked normal. =
Whassup? Too much mass?</FONT></FONT></DIV></BLOCKQUOTE>
<DIV><FONT lang=0 size=2 FAMILY="SANSSERIF">What do you mean, "The =
scale lengths
and sizes looked normal....?" What is normal? Where is the hammer =
striking
point? What are the hammers like? </FONT></DIV>
<DIV> </DIV>
<DIV> </DIV>
<BLOCKQUOTE
style="BORDER-LEFT: #000000 2px solid; MARGIN-LEFT: 5px; MARGIN-RIGHT: =
0px; PADDING-LEFT: 5px; PADDING-RIGHT: 0px">
<DIV><FONT face=arial,helvetica><FONT face=Arial lang=0 size=2 =
FAMILY="SANSSERIF">3) A third bridge obviously goes on a different =
spot on the
soundboard, with different impedance, and loudness, characteristics =
from the
hockey-stick area of the tenor bridge it replaces. How does one figure =
that
difference into the string scale the FIRST time? And would you leave =
the
hockey stick area or cut it away?</FONT></FONT></DIV></BLOCKQUOTE>
<DIV><FONT lang=0 size=2 FAMILY="SANSSERIF">Are you going to be in =
Dallas come
July?</FONT></DIV>
<DIV> </DIV>
<DIV> </DIV>
<BLOCKQUOTE
style="BORDER-LEFT: #000000 2px solid; MARGIN-LEFT: 5px; MARGIN-RIGHT: =
0px; PADDING-LEFT: 5px; PADDING-RIGHT: 0px">
<DIV><FONT face=arial,helvetica><FONT face=Arial lang=0 size=2 =
FAMILY="SANSSERIF">4) What difference do you think the grain angle =
to the
belly rail makes?</FONT></FONT></DIV></BLOCKQUOTE>
<DIV><FONT lang=0 size=2 FAMILY="SANSSERIF">In general, as the =
grain angle
becomes closer to perpendicular to the bellyrail the stiffness felt by =
the
bridge increases (i.e., the stiffness component of impedance increases) =
wherever
the bridge is close enough to the belly rail or the rim for this =
stiffness to be
felt. This by virtue of the physical characteristics of the spruce =
panel. It is
stiffer along the grain line than it is across the grain line. Changing =
the
grain angle (relative to the belly rail) from the normal 45º to =
something like
60º or 70º (depending on the length and design of the piano) can be =
particularly
helpful through the killer octave region. In practical terms, and all =
other
factors being equal, this change works to increase sustain of the =
treble. In
theory it may also reduce slightly the available potential power, though =
this
may not be noticeable. Of course, this change has the same effect =
on the
bass to a greater or lesser degree depending on the design of the bass =
bridge
and its location on the soundboard. Around the bass bridge this added =
stiffness
may not be desirable since it will work to increase the sustain of the =
higher
partials, something rarely desirable in the bass section. Compensation =
can be
made </FONT><FONT lang=0 size=2 FAMILY="SANSSERIF">by thinning the =
board out
through the bass region o<FONT lang=0 size=2 FAMILY="SANSSERIF">r, =
better yet,
partially or fully floating the bass region.</FONT></FONT></DIV>
<DIV><FONT lang=0 size=2 FAMILY="SANSSERIF"></FONT> </DIV>
<DIV><FONT size=2>It is a good idea to re-orient the ribs to take =
advantage of
any changes made to the soundboard grain angle. Though we don't
always.</FONT></DIV>
<DIV><FONT lang=0 size=2 FAMILY="SANSSERIF"></FONT> </DIV>
<DIV><FONT size=2>Del</FONT><FONT face=arial,helvetica><FONT =
lang=0 size=2
FAMILY="SANSSERIF"></DIV></FONT></FONT></BODY></HTML>