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

[Stéphane Collin]

Hi Vladan.

This makes much sense, of course.
But then, those old Steinway A pianos, with no fish and no cutoff bar, 
produce nice bass enough, and long lasting high trebble, don't they ?  Why 
doesn't the real world obey our theories ?  Nothing is simple.

Best regards,

Stéphane Collin.



----- Original Message ----- 
From: "V T" <pianovt@yahoo.com>
To: <pianotech@ptg.org>
Sent: Saturday, February 19, 2005 2:57 AM
Subject: "Fish"....my best guess...


>
> 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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