soundboardinstal again

[Isaac sur Noos]

Aggreed from most of the workshop guys there and there.

But indeed it should be done anyway.

And about the large articles of the Journal "with formulas" I always
have find that in the next isssue someone wad other formulas just to
prove the opposite.

Piano trade is a wondeeful word (and i am the only one to know what
tones well !)

Best Regards.

Isaac OLEG

Entretien et réparation de pianos.

PianoTech
17 rue de Choisy
94400 VITRY sur SEINE
FRANCE
tel : 033 01 47 18 06 98
fax : 033 01 47 18 06 90
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> -----Message d'origine-----
> De : pianotech-bounces@ptg.org
> [mailto:pianotech-bounces@ptg.org]De la
> part de Delwin D Fandrich
> Envoyé : mercredi 30 juillet 2003 21:53
> À : Pianotech
> Objet : Re: soundboardinstal again
>
>
>
> ----- Original Message -----
> From: <ranjacob@umich.edu>
> To: "Pianotech" <pianotech@ptg.org>
> Sent: July 30, 2003 10:11 AM
> Subject: RE: soundboardinstal again
>
>
> > Right, bridges serve to distribute load among the ribs, and don't
> > support crown, and I was asking whether or not a counter-bridge or
> "sister
> > bridge" had ever been intended, at least partly, to
> support crown. Or if,
> > without adding way too much stiffness and mass, a set of
> counterbridges
> (or
> > better, quasi-ribs parallel to the grain of the panel) *could* be
> designed
> > to support crown, so that, *assuming* there was anything
> to be gained
> from
> > it, ribs could be designed without having to have all of the crown
> support
> > as one of their functions.
>
> Yes, a bridge system could be designed such that it would
> "support crown."
> As to whether that is desirable or not is another question.
> With this
> subject coming up so regularly it has given me some reason
> to think about
> it some. I'm not at all sure this would be a good thing. A
> bridge that
> would be so stiff and structural as to be effective as a
> crown-supporting
> member would (regardless of the mass involved) also be an
> overly effective
> acoustical bridge. That is, it would spread the energy from
> a particular
> string set (at a particular frequency) over too broad an
> area. There is a
> reason why the flugal, or wing-shape, design has won out
> over the years.
>
>
> >
> > I think that due to Del's reply and yours, I see better
> why this might
> not
> > work, or, at least, might be wholly unnecessary.
> (Understand, by the way,
> > that I am after grand piano tone, not, what might result
> if we tried to
> > "simplify" matters by pretending that we are trying to
> reproduce string
> > oscillations as found at the bridge cap, in the same way
> that an audio
> > engineer tries to reproduce air oscillations arriving at
> a microphone.)
>
> Gosh, and here all the time I thought that was just what we
> were trying to
> do.
>
>
> >
> > One way of visualizing the problem lies in considering
> the consequences
> of
> > the fact that the gaining of downbearing necessarily
> changes, from a
> right
> > angle, the angle of the string to the downward vector of
> board assembly
> > movement. (The assembly does have very high resistance to
> any change in
> the
> > exact angle at which its own deflection, as a complex of
> end-supported
> > beams, operates in response to the "live load" bearing
> down on it. ((Now,
> > *there's* a simplification...)) :) .)  Rather than being
> merely "just a
> > very small change of angle", this lessening of the right angle
> > fundamentally alters the right angle that is shown in a
> drawing, on
> > acoustic theory of the string, of the string as having
> one vertically
> fixed
> > termination (the capo or agraffe) and one termination
> that is fixed
> > horizontally, but whose vertical "quasi"-fixing is to a
> mass that is free
> > to move vertically -- e.g., a mass free to move
> vertically because, in
> > fact, in that dimension, it is a spring.  That is, the
> change from that
> > right angle to a smaller angle in the grand piano will
> cause the string
> to
> > have more tension than its resting tension at the top of
> its complete
> cycle
> > of vertical oscillation, and less tension than its
> resting tension at the
> > bottom of the complete cycle. These differences cancel
> each other out,
> > yielding a tone that is steady in pitch, just as the
> process of the
> > formation of the string's standing wave after the upward
> blow of the
> hammer
> > is, in part, a process of cancelling out certain of the
> effects of the
> > blow's having been upward rather than downward.
> >
> > It is, therefore, this lessening from the right angle to the
> > assembly's vector as a spring that makes the string itself
> > an *opposing* string, in the sense that, at the required times
> > in the course of the fundamental's cycle (and,
> correspondingly, of the
> > cycles of the harmonics), the string is a not "simply" a
> > spring that hardens when moving upward from the rest position
> > of zero amplitude, but a spring that has the required degrees of
> > stiffness at that rest position and at all higher amplitudes.
> > The provision and adjustment of the adjustment of
> downbearing, therefore,
> > is a means to control the rate of vertical transmission
> "beyond", and, so
> > to speak, horizontal reflection backward from,
> > the coupling of the string to the bridge.
>
> This is a good way to go nuts! It's time for a little
> simplicity. Varying
> string bearing against the bridge controls (varies) the
> amount of string
> loading against the soundboard system, hence the spring
> rate of the system,
> hence mechanical impedance of the system, hence the rate at
> which energy is
> transfered from the strings to the soundboard system.
>
> If you're really determined to add in some complexity this
> would be a good
> time to consider the effect of the string backscale on the
> bridge/soundboard system.
>
>
> >
> > If I haven't made a new mistake here, my next question is:
> > are *lateral* transverse vibrations of the string (or,
> large lateral
> > vectors of vibrations that are significantly "slanted"
> from the vertical)
> > thought to be transmitted in any way that the theory
> > of the board assembly, and of the interaction of its components,
> > has been able to explain, or (usefully) speculate about?
>
> This would depend on your defination of "usefully." In
> terms of piano
> design I can't see how pondering this line of speculation
> could be usefully
> applied. From a purely scientific perspective it may well
> be usefully
> considered and studied. This all goes back to something I
> have observed
> several times in the past--there is much scientific
> exploration into the
> physics of musical instruments that has been largely useless in the
> development of those instruments. That doesn't mean it
> shouldn't be done,
> it just all needs to be kept in perspective.
>
> Del
>
>
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