Effect of bridge height on tone?

[gordon stelter]

It seems to me that energy is transferred to the board
from the string via "bell-crank" motion, NOT the
direct waving of the board ( heavy and stiff ) by the
string ( light and flexible).  As the string
oscillates it expands and contracts in lenghth, and it
is this motion, yanking the top surface of the bridge
for and aft, that is transmitted into an up-and-down
motion of the board near the bridge 
( alternately adjacent to its sides )  and these
vibrations are then sent rippling along the grain to
the rest of the board surface.
     Therefore, could it be that increased bearing
mainly improves the mechanical advantage, via
leverage, that the string has in tranfessing its
motion to this most immediate portion of the board,
and that this is as ( or more ? ) important than any
increased stiffness to to compression?
     If my theory is correct, then bridge height would
probably also be a significant factor in tone, as it
would also have marked effect on the mechanical
advantage the string has as it vibrates.
     Has anyone studied the effect of bridge height on
tone, all else being equal?
     Thump

     
--- Richard Brekne <Richard.Brekne@grieg.uib.no>
wrote:

> Overs Pianos wrote:
> 
> >
> > At 8:29 PM +0100 24/1/05, Richard Brekne wrote:
> >
> >>
> >> . . . that compression damage is not really
> (necessarilly) damage per 
> >> se at all, that a CC board that has lived a very
> successfully life 
> >> and slowly but very evenly been compressed flat
> will retain (exactly 
> >> because of said compression) a substantial part
> of its initial 
> >> stiffness, explaining why so many old boards seem
> to perform so 
> >> acceptably well . . .
> >
> >
> > I totally disagree that an evenly compressed board
> will have retained 
> > its stiffness. If the cellular compression has
> gone out of a panel 
> > enough to allow it to lose crown, it will also
> have lost a significant 
> > degree of stiffness at the same time. In CC
> boards, panel compression 
> > adds to the stiffness of the whole. If you're
> looking for a floppy 
> > non-stiff panel that has front-end-punch with less
> sustain, the sunken 
> > CC item will do it. There are numerous S-bent
> killer octaves out there 
> > to prove this point (which were overloaded because
> they were 
> > under-engineered in the first place). There may be
> instruments which 
> > sound acceptable, which have what some would
> describe as an ordinary 
> > board. But I have no doubt that these instruments
> would have a longer 
> > tone (which, in my opinion, I happen to
> subjectively like) if the 
> > board had retained that higher level of stiffness,
> which might have 
> > been built into it at the time of construction.
> 
> I am aware that you, and some particular others on
> the list 
> disagree...and before going on let me just say I am
> certainly not any 
> authority on the matter and can not confirm or not
> whether you and 
> fellow minded are correct on this issue, or whether
> the opposing camp 
> is.  But I can observe that there are two (at least)
> schools of thought 
> on the matter and the neither has seemed to come up
> with any unrefutable 
> conclusive argumentation on this matter down through
> the years.
> 
> I can also observe pianos out there... ones that
> have flattened out 
> boards that are not caved in so that some areas of
> localized reverse 
> crown exist... but simply pressed slowly and evenly
> down through the 
> years.  I find no lack of sustain in these, no lack
> of volume or power, 
> no killer octave type of sound anywhere.  On the
> subjective side I'd 
> have to add that I find nothing that I personally
> would term as <<tonal 
> negatives>> at all.  The difference I do observe is
> a mellowed more 
> rounded sound then I find in new pianos.
> 
> What I'd like to see, tho perhaps may never... is
> someone actually 
> measuring stiffness levels in various boards of
> various age and 
> condition.  Thats concrete enough.. quantifiable..
> and can be easily put 
> into a larger puzzle of other quantifiables to bring
> better into focus 
> just what it is that some people seem to like so
> well about older 
> boards... and some  seem not to.
> 
> None of this is meant in any way as a lack of
> respect for anyones 
> knowledge, experience, whathave you...  quite the
> opposite  really....
> 
> >
> > On several occasions I've had technicians claim
> that "provided there 
> > was an initial angle of downbearing set into an
> instrument, there will 
> > still be a down bearing force on the board even
> after significant 
> > soundboard drop has occurred". It isn't so. No
> down bearing angle 
> > results in no loading on the board. Similarly, if
> a CC board has lost 
> > its crown, it will have lost significant
> stiffness. Sunken boards 
> > might sound OK if there is a working balance
> between 
> > mass/stiffness/sound board area remaining.
> 
> I will buy that it must have lost significant
> stiffness, but it also 
> seems sensable that it has retained significant
> stiffness. Also as the 
> crown decreases and thereby the upward pressure
> against the strings 
> decrease... so does the downward pressure of the
> strings decrease.  So 
> as long as a kind of equilibrium is maintained I
> would imagine that tho 
> the sound may indeed be changed somewhat.. this need
> not be seen as 
> anything particularilly negative by many.  Tho, I am
> the amature here... 
> and my reasonings are based on ponderings of the
> many arguements on both 
> sides of this fence I've tried to sift through down
> through the years.
> 
> >
> > I strongly suspect that there is some sort of
> important relationship 
> > between mass/stiffness/soundboard area which
> fundamentally influences 
> > the tonal qualities of an instrument. Please don't
> ask me to elaborate 
> > on this matter at this time. This theory remains
> just that, at present.
> 
> Dont need to elaborate to be in agreement here. 
> Whether or not any 
> particular configuration results in influences that
> cause agreeable or 
> disagreable acoustic charachteristics is another
> matter tho. 
> 
> >
> > Ron O.
> >
> 
> Cheers
> RicB
> 
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> 



		
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