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<DIV>In a message dated 2/1/2004 12:51:33 PM Pacific Standard Time, fordpian=
o@earthlink.net writes:</DIV>
<BLOCKQUOTE style="PADDING-LEFT: 5px; MARGIN-LEFT: 5px; BORDER-LEFT: blue =
2px solid"><FONT face=Arial size=3>Ric writes</FONT></BLOCKQUOTE>
<DIV><FONT face="Times New Roman" color=#000040 size=3> </FONT><F=
ONT face=Arial><FONT size=3>My own degree of understanding of these matt=
ers still remains at a <BR>>rather young stage, yet one theme comes back =
again and again in <BR>>these discussions. That is that the sound that th=
e panel is able to <BR>>project is dependent upon its stiffness and mass.=
Certainly any <BR>>particular combination of these is in itself in=
dependent of string <BR>>coupling. John Hartman is correct in saying that=
down bearing can <BR>>increase the stiffness of the panel without added =
to the panels <BR>>mass... tho the strings have mass to... and these =
; things have a <BR>>habit of working both ways in some sense or another.=
.. Still <BR>>essentially John is correct</FONT>..........</FONT></DIV>
<DIV><FONT face="Times New Roman" color=#000040 size=4> I =
think I can hear Del gnashing his teeth. If stiffness was all that one wishe=
d then running ribs at 90 degrees to the grain is the least stiff configurat=
ion. If the ribs are run at substantially less than this the stiffness also =
goes up without adding mass.</FONT></DIV>
<BLOCKQUOTE style="PADDING-LEFT: 5px; MARGIN-LEFT: 5px; BORDER-LEFT: blue =
2px solid"><FONT face=Arial>The question remains then can good sound resul=
t without any <BR>>particular amount of down bearing.</FONT></BLOCKQUOTE>
<DIV><FONT face="Times New Roman" color=#000040 size=4>>>. Yes b=
ut it would be different. ie many uprights & other grands which have eit=
her lost crown or were designed with very little or i.e. My Own Mason AA wit=
h a minimal crown board (some crown presumably lost) and light bearing is on=
e of those pianos that works within the parameters being discussed &nbs=
p;but it also has a thick board & 15 ribs which equals mass and stiffnes=
s without great amounts of bearing. Also string scaling is another factor of=
course.</FONT></DIV>
<DIV><FONT face="Times New Roman" color=#000040 size=4> &n=
bsp;I just added new bridge caps & no I didn't, & wouldn't =
;set it up with 0 bearing which answer one of David's question. Wh=
y? Because I happen to think/know that a soundboard with crown or just =
mass & stiffness behaves like a compressible spring which makes it =
more reactive. </FONT></DIV>
<DIV><FONT face="Times New Roman" color=#000040 size=4> &nb=
sp; I also know that from a tactile sense when I'm prestressing board by pla=
cing wedges under the struts & pounding it down while wedging to simulat=
e some string preloading that the board simply gets <STRONG><U>so</U></STRON=
G> Stiff it's like pounding on the bridge top but hitting a gym floor. Its d=
ramatically different from before prestressing. </FONT></DIV>
<DIV><FONT face="Times New Roman" color=#000040 size=4> &nb=
sp; The amount of bearing does regulate the rate at which tonal en=
ergy leaves the board/system. Use a garden hose for an analogy turned on ful=
l blast then slowly pinch it to restrict water flow. This I belive is a simp=
le definition of mechanical imedance. Soundboard compression is a=
lso mechanical impedance but it's impeding soundwaves not water.&=
nbsp;Phil correct me if I'm wrong. </FONT></DIV>
<DIV><FONT face="Times New Roman" color=#000040 size=4> Da=
vid S's question which is ,"does bearing do anything other than make th=
e board stiffer" I think can be answered by saying I think so based on what =
I said above. Its more reactive. Any thing under stress is more reactive. Hu=
mans included</FONT></DIV>
<BLOCKQUOTE style="PADDING-LEFT: 5px; MARGIN-LEFT: 5px; BORDER-LEFT: blue =
2px solid"><FONT face=Arial><FONT face="Times New Roman" color=#000040=
> <FONT size=3>Phil writes</FONT></FONT><BR><BR><FONT size=3=
> I keep reading posts by various people stati=
ng that the <BR>soundboard gets 'stiffer' as downbearing is applied. B=
ut I have seen <BR>no experimental evidence to support this supposition.&nbs=
p; The only <BR>experimental evidence that I have seen was that presented by=
Ron <BR>Overs some time back in which he took a crowned ribbed panel, loade=
d <BR>it incrementally, and noted the deflections. His data showed jus=
t <BR>the opposite; that the panel was getting less stiff as the load <BR>(s=
imulated 'downbearing' if you will) was increased. If someone has <BR>=
some data to support the phenomenon of increased board stiffness with <BR>in=
creasing downbearing then please share it with us. The only <BR>suppor=
t for this position that I have heard has been anectodal <BR>stories along t=
he lines of, 'I pushed down on the new board and it <BR>deflected, then I le=
aned on it with all my weight and it wouldn't <BR>deflect any more, so it ob=
viously was getting stiffer'. </FONT></FONT></BLOCKQUOTE>
<DIV><FONT face="Times New Roman" color=#000040 size=4><STRONG>>>=
; I believe it was getting stiffer but remember we're talking abou=
t a light weight system with limited ability to carry loads so great as to c=
rush them altogether.</STRONG></FONT></DIV>
<BLOCKQUOTE style="PADDING-LEFT: 5px; MARGIN-LEFT: 5px; BORDER-LEFT: blue =
2px solid"><FONT face=Arial><FONT size=3>It was <BR>reaching a state of =
equilibrium for the applied load based on the <BR>stiffness of the system.&n=
bsp; That doesn't mean it was getting 'stiffer'.<BR> The=
re is a difference between preload and stiffness. </FONT></FONT></BLOCK=
QUOTE>
<DIV><FONT face="Times New Roman" color=#000040 size=4>>>I'm hon=
estly not sure about that. It seems like to me it's both.</FONT></DIV>
<DIV><FONT face="Times New Roman" color=#000040 size=4> Was Ron =
Os demonstation on a board glued to the case liner? For the board&=
nbsp;will certainly react differently if the test is out of the piano with o=
ut the edges glued down.</FONT></DIV>
<BLOCKQUOTE style="PADDING-LEFT: 5px; MARGIN-LEFT: 5px; BORDER-LEFT: blue =
2px solid"><FONT face=Arial><FONT size=3>As you <BR>apply more downbeari=
ng load to the board then the preload (or <BR>prestress if you prefer) will =
increase. It's not hard to believe <BR>that this could have some affec=
t on the vibrational characteristics <BR>of the board and experience tells u=
s that it does. Putting <BR>downbearing on the board usually seems to =
have a beneficial effect.</FONT></FONT></BLOCKQUOTE>
<DIV><FONT face="Times New Roman" color=#000040 size=4>>> And to=
o much makes for a stingy sound especially in the treble</FONT></DIV>
<BLOCKQUOTE style="PADDING-LEFT: 5px; MARGIN-LEFT: 5px; BORDER-LEFT: blue =
2px solid"><FONT face=Arial><FONT size=3><BR> Stiffne=
ss is a relationship between load and deflection. If two <BR>beams hav=
e the same load applied to them, then the one that deflects <BR>less is 'sti=
ffer' for a load applied at that particular spot. <BR>Increasing stiffness u=
nder load would mean that there was <BR>incrementally less deflection for un=
it increases in load. If a beam <BR>deflects down 1/10 of an inch for =
an applied load of 1000 lbs, then <BR>if it is getting 'stiffer' under incre=
asing load, when you applied an <BR>additional 1000 lbs of load the addition=
al deflection would be less <BR>than 1/10 of an inch.</FONT></FONT></BLOCKQU=
OTE>
<DIV><FONT face="Times New Roman" color=#000040 size=4> <STRONG>&=
nbsp;<FONT size=2> </FONT><FONT size=3>This is exactly what a board is d=
oing when it is being compressed up to a point & then it will fail just =
as the beam will.</FONT></STRONG></FONT></DIV>
<BLOCKQUOTE style="PADDING-LEFT: 5px; MARGIN-LEFT: 5px; BORDER-LEFT: blue =
2px solid"><FONT face=Arial><FONT size=3> I see no reason why a ri=
bbed panel would <BR>behave in this way. That's not to say that I can'=
t be wrong and that <BR>there's not something about this particular system t=
hat I've <BR>overlooked or don't understand. But I'd like to see some =
<BR>experimental evidence to prove it.<BR> This distinct=
ion is important to potential soundboard design. <BR>If the important thing =
is increasing the stiffness without increasing <BR>the mass, then an alterna=
tive soundboard made of something like <BR>honeycomb sandwich might give the=
desired performance without any <BR>downbearing. If the important thi=
ng is preload or prestress in the <BR>panel then the honeycomb panel might b=
e a waste of time and <BR>downbearing would be essential regardless of the t=
ype of panel you <BR>used.<BR> Also, if the board is not=
getting stiffer as a result of <BR>deflection, it raises the question of wh=
at function the crown is <BR>performing. </FONT></FONT></BLOCKQUOTE>
<DIV><FONT face="Times New Roman" color=#000040 size=4><STRONG>>>=
;The way I look at it is that putting boards under some modest amount o=
f strain via compression or tension for that matter makes the boar=
d more reactive and tonally efficient because of the impeding effect, w=
hich moves air & thet's why soundboards are built this way. If it wasn't=
Ron O would be building a flat board.</STRONG></FONT></DIV>
<BLOCKQUOTE style="PADDING-LEFT: 5px; MARGIN-LEFT: 5px; BORDER-LEFT: blue =
2px solid"><FONT face=Arial><FONT size=3>If the crowned board is not get=
ting stiffer as it <BR>deflects down, then a flat board would be just as sti=
ff as a crowned <BR>board. So, the reason for the crown would not be '=
stiffness'.</FONT></FONT></BLOCKQUOTE>
<DIV><FONT face="Times New Roman" color=#000040>Phil</FONT></DIV>
<DIV><FONT face="Times New Roman" color=#000040 size=4><STRONG>>>=
; But I think it is getting stiffer.</STRONG></FONT></DIV>
<DIV><STRONG><FONT face="Times New Roman" color=#000040 size=4> &=
nbsp; Dale</FONT></STRONG></DIV>
<BLOCKQUOTE style="PADDING-LEFT: 5px; MARGIN-LEFT: 5px; BORDER-LEFT: blue =
2px solid"><FONT face=Arial size=4>PS I hope somewhere in here is =
something of an answer/opinion David S was looking for.</FONT></BLOCKQUOTE>
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ML>