No downbearing ? REVISITED

[David Skolnik]

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Almost one month ago, this a question regarding downbearing was raised:

At 04:09 PM 12/31/2003 +0100, Jean-Jacques Granas wrote:

>I have come across a puzzling suggestion a few weeks ago: Namely, that=20
>downbearing is not really necessary in order to transfer the vibration of=
=20
>the string to the soundboard panel, the mere "grip" that the string has on=
=20
>the bridge being sufficient to assure this transfer. Would anyone of you=20
>with experience in such issues care to comment?


Then, At 10:48 AM 12/31/2003 -0500, John Hartman wrote:

>Yes I believe this is correct. Bearing does not directly influence the=20
>transfer of vibrations. What it does is alter the apparent stiffness of=20
>the Soundboard and thereby help to control the rate at which the=20
>vibrations move from the strings into soundboard. Check the archives for=20
>soundbaord impedance.

Then, At 05:25 PM 12/31/2003 +0100, Isaac sur Noos wrote:
>I should say that indeed downbearing is not indispensable, but on most=20
>pianos, front bearing particularly produce a more pleasing (fuller) tone.
>
>Bearing being not discernable after the strings have been installed, it is=
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>often confused with "distance bearing" which indeed is the proof that some=
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>pressure exist when it is seen, but on some pianos the soundboard look=20
>flat after the strings have been tense (while down bearing exist absorbed=
=20
>by the soundboard) .
>
>All depend of the kind of ribbing and construction used (flat ribbing vs.=
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>crowned ribbing). Most German made pianos are using flat ribs and are very=
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>sensitive to humidity changes when the soundboard is in good condition, so=
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>the go out of tune easily in that case. these instruments need less down=20
>bearing than the ones which are using crowned ribbing (B=F6sendorfer for=20
>instance).
>The flat ribbing method "is said" to produce stiffer soundboard assembly,=
=20
>while curved ribs need to be pressured more to obtain the necessary=20
>stiffness. That is what I have understood, very crudely  I confess, from=20
>the different conversations on those matters.


By the second (Isaac sur Noos's) response, what was a potentially=20
illuminating or controversial discussion, was re-routed to yet another=20
review of crown and the crowning process.  None of the subsequent=20
contributions sought to address the original question (in fact or in=20
spirit), or to clarify John's response.  Here is some of what I felt was=20
missing:

Jean-Jacques, what was the original source of your 'puzzling=20
suggestion'?  (previous posting?)  The mere "grip" , as you described=20
would, presumably, refer to the side bearing of the bridge pins.  This=20
would seem to promote  the theoretical conclusion that the energy is=20
channeled from string to bridge exclusively by the bridge pins; that the=20
function of the front  edge of the bridge top may simply be to limit the=20
downward excursion of the string.  Does it have any role in creating a=20
reflective terminus of the string? And if so, how much force is required to=
=20
prevent  (or control?) energy leakage to rear string segment?  Is it=20
presumed that  the transfer of energy would be unaffected by the presence=20
of either positive bearing, no bearing, or, for that matter,  negative=20
bearing, as long as the bridge pins held onto that string,?

John's response is, I think, unintentionally misleading. He first suggests=
=20
that Jean-Jacques's  statement is correct, but then immediately attributes=
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to downbearing the [important?]ability of controlling "the rate at which=20
the vibrations move from the strings into soundboard".  If there is a point=
=20
of differentiation to be made here, it seems inordinately subtle, compared=
=20
to the resulting impression conveyed that downbearing is not an essential=20
component in piano design and engineering. Unless that is the meaning that=
=20
is intended!?

Finally, before Isaac Sur Noos directed the discussion towards crown, he=20
made some comments which, if I understand them correctly, are additionally=
=20
confused:
>I should say that indeed downbearing is not indispensable  but on most=20
>pianos, front bearing particularly produce a more pleasing (fuller) tone.

To summarize then, downbearing isn't essential, unless you want the piano=20
to sound good.??

With regard to downbearing being discernable, or measurable  (see quote=20
above)... what IS measurable is, as he puts it, distance, or string=20
deflection,  I may not be able to tell how much the board has flattened in=
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response to X amount of original downbearing, but if there is no measurable=
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deflection, there is no downbearing.  Is this not true?

Thoughts?


David Skolnik




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