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

[David Love]

The cut-off bar and fish don’t really have much to do with the bass
sound.  The fish certainly doesn't as it's located at the opposite end
of the piano.  Many pianos employ a full cut-off.   A Boesendorfer I
tuned only yesterday (225 cm ?) employs a full cut-off bar extending to
the middle of the straight side.  The long lasting high treble on an old
piano doesn't seem as long lasting when you are able to compare it with
something that really is long lasting.  The installation of the fish I
have found to improve the musical quality of the high treble
considerably.  Much less extraneous noise.  

David Love
davidlovepianos@comcast.net 

-----Original Message-----
From: pianotech-bounces@ptg.org [mailto:pianotech-bounces@ptg.org] On
Behalf Of Stéphane Collin
Sent: Saturday, February 19, 2005 12:44 AM
To: Pianotech
Subject: Re: "Fish"....my best guess...

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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