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 > > > > > __________________________________ > Do you Yahoo!? > Meet the all-new My Yahoo! - Try it today! > http://my.yahoo.com > > > _______________________________________________ > pianotech list info: https://www.moypiano.com/resources/#archives > >
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