Impedance Matching... John

[Brian Trout]

 Hi John,

Would you mind expounding upon these two things a bit more?

 >7: Tapering the edges of the panel and scalloping the ribs.

I've known of a number of people who taper certain parts of the panel,
usually around the nose end, in an effort to make the board less 'clamped'
by the stationary rim.  I'm curious about scalloping the ribs?  It's not a
term I've been familiar with.  Is that the portion on the end where it's cut
out thin, as in 1/4" thick or so?  I've wondered how varying the length of
this 'tail' would affect the way a board speaks, especially in the upper
treble end of the piano.

  11: the grain direction of the panel and the angle and spacing of the
  >ribs.

In most of the panels I've seen, the grain of the panel appears to have been
placed so that the grain is pretty much parallel with the general direction
of the long bridge, and the ribs usually are not too far from 90 deg. from
the grain direction.  I'm curious if you have some general kinds of thoughts
as to what happens when those things are moved from the 'norms', or whether
one can 'tweek' those positions.

Very interesting stuff!  Thanks for your input.

Brian Trout
Quarryville, PA
btrout@desupernet.net
>
><We can effect change in these resonance frequencies by increasing or
>decreasing stiffness to the board by
>
>1: increasing / decreasing the height of the ribs, particularily in the
>middel area of the board.
>2: increasing / decreasing the height of the bridge.
>3: increasing / decreasing the downward pressure exerted by the strings
>on the bridge
>4: adding / subtracting mass at various points on the board.
>5: changing the tension of the strings.
>
>(anything else ?)>
>
>6: changing the material used in the ribs, panel and bridges. What
>species of wood.
>7: Tapering the edges of the panel and scalloping the ribs.
>7-1/2: the general thickness of the panel.
>8: Amount of soundboard crown and how formed.
>9: The length of the back string scale.
>10: The construction and shape of the rim and belly rail. The size of
>the board.
>11: the grain direction of the panel and the angle and spacing of the
>ribs.
>