"Fish"....my best guess...

[V T]

Actually, part of what you wrote is quite close to
what I think is happening.

When the pulse from the string hits the bridge and
therefore the soundboard, it travels in the board
until it gets to a place on the board that no longer
can move because it's attached to the rim or something
hard.  There, the pulse reflects and part of it
travels back towards the bridge.  If you do it right,
that returning wave reinforces a later pulse that is
just entering the board at the bridge.  Obviously,
that distance and the time required for the round trip
is a function of the frequency, so the fish has to
progressively move away from the bridge as the
frequency gets lower.

The cut-off serves the same function on the other side
of the bridge.  My guess would be that the cutoff
should be the same distance from the bridge as the rim
or fish is on the other side of the bridge, so you get
a double effect.  So the bridge should follow a path
right in the middle between the rim and the cutoff.

If the distance is wrong, you get a pulse that returns
just in time to cancel the next pulse (or some later
pulse), and the impedance of the board will look very
wrong.

If the distance from the fish or cutoff is too long,
you will get some interference and some notes will
cancel while others will enhance.

Any comments?

Vladan

=========================================
is that it stiffens this area of the rim so that
vibrations travelling from the board are not creating
friction, and lost as heat energy (  due to molecular 
"wiggling"  )  but are more likely kicked, or
otherwise ransmitted,  back into the board. Right ?
   ( Praise Be to the Circle of Sound! )
     Thump



		
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