Article about bridge agraffes - function, types

[RicB]

Hi Calin

This is what I thought you were saying.  And, since much of your further 
reasoning depends on this being true or not I suppose I'll let myself 
get hung up here for the time being.  You make two declarations of fact 
here that I personally do not know as fact... simply because I have 
never run into any factual information on the subjects.  But then I've 
never looked in this direction either.

1st... you declare that the wood of the bridge surface is soft enough to 
cause significant damping -- to the point of purely absorbing string 
frequencies above some unspecified level.  You should footnote to some 
reference to research/data/ whathaveyou in your paper I should think. It 
is central to your paper. Frequencies response tables... etc..

2nd you declare that the larger footprint of the agraffe on the wood of 
the bridge itself will cause the rest of the assembly to vibrate more 
because the string will not be able to dig into the wood as it vibrates. 
This also needs documentation.   A couple of points on this... I would 
think this claim were were true... it would be true for all frequencies 
and you would be able to measure a significant output increase across 
the board.  I would also point out that the string is terminated at 
least as much by the pin itself, which while not having as big a 
footprint in the wood of the bridge as an agraffe... certainly is far 
harder then wood.  Then there is the matter of what degree the presumed 
lessened "efficiency" of the bridge/pin assembly becomes significant 
enough to make a measureable difference in this context.

3rd... which moves on a bit... you couple the above two to the increase 
in sustain seen in some agraffe pianos... presumably looking away from 
the added mass of the brass and other design issues that accompany such 
instruments that we already know significantly contribute to sustain.  I 
dont think you can do this without further ado without qualifying this 
as conjecture.

Without supporting documentation, none of this can be substantiated, 
and... if in the end it turns out you actually can not defend these 
claims thus... you will end up in a rather uncomfortable position I 
would think.

Interesting, and thought provoking to be sure....  I'd like to hear some 
opinion of others as to the validity of your two precepts above.

Cheers
RicB


    Ric,
    What I tried to say is that a wooden bridge cap, as found in a
    normal piano, is, when compared to the metal bridge agraffe, much
    softer. Now the frequencies of strings (including partials) at the
    top treble goes into the thousands of cycles per second. At those
    frequencies, anything that is somewhat flexible is likely to absorb
    them rather than  transmit them down to the soundboard . Keeping
    this in mind, you will also note that the string tends to dig into
    the wood cap, creating an unclean termination which further
    decreases efficiency. The bridge agraffe has a metal edge which
    allows for a very well
    defined termination. In addition, it has a much larger footprint on
    the wooden bridge, so rather than digging into the wood, the agraffe
    moves the whole bridge when it vibrates. The result is that the
    bridge agraffe transmits high frequencies better to the bridge and
    soundboard. It's actually quite simple.
    You might say this is just theory, but the pianos with bridge
    agraffes have, among other qualities, a sensibly longer sustain.