Article about bridge agraffes - function, types

[Alan R. Barnard]

Yeah, me too. A tuning fork sustains a lot longer if the end is not placed on something to amplify the sound. Same energy but a trade-off of power vs. sustain. You can't increase both unless you (a) put more energy into the system, i.e., play harder, or (b) reduced inefficiencies and resistances in the system, i.e., sound (energy) absorbing soft materials, string stiffness, bridge/soundboard stiffness, etc.

I think it's interesting that the violin family goes for the thinnest bridges possible, consistent with required sturdiness, and a small "footprint" actually touching the soundboard. Piano bridge construction kinda goes the other way. 

We could increase energy, thus volume AND sustain, by replacing the hammers with rotating wheels of horsehair! Think about it: A 9-foot Steinway & Sons Concert Hurdy-Gurdy!

Excellent work putting that together Calin.

Alan Barnard
Salem, MO
Joshua 24:15



----- Original message ----------------------------------------
From: RicB <ricb at pianostemmer.no>
To: pianotech at ptg.org
Received: 11/18/2006 6:07:40 PM
Subject: Article about bridge agraffes - function, types


>Hi Calin, Cy..  lots of points so I'll just comment on one for the time 
>being.

>I'm not entirely sure what exactly you mean in the below and the 
>corresponding part of your article.  What I'm hanging onto is the basic 
>impedance match between string and the bridge.  This is a pretty 
>complicated affair when you start mixing in the relative strengths of 
>partials.  Perhaps its just the wording that trips

>     "which are much stiffer and transmit high frequency vibration
>    better") 

>The inference being that the wood surface damps higher frequencies 
>earlier.   That would mean that if you constructed two bridges of equal 
>mass... the only difference being the stiffness of each... then you 
>could observe the same result.  I'm not really sure this is the case... 
>but then I havent really thought about it much either. In anycase I'm 
>not comfortable with the word transmit here.  The stiffer and more massy 
>a termination is... the less it transmits of vibrational energy through 
>it.  It will rather reflect this energy back through the input source 
>(strings) typically increasing sustain and lowering output amplitude.

>I'd assumed the filter was to minimize the audible effects of loss of 
>energy to the termination itself... much like braiding a front duplex to 
>quite capo noise.

>Cheers
>RicB

>     > This seems to counter your original assumption about standard 
>    bridge pins,  namely that the wood cap allows high frequencies to
>    pass  through, where > bridge agraffes do not.  Is that what you meant?

>    It actually supports my assumptions. Wood caps are weaker and more
>    flexible
>    than a bridge agraffe. So a bridge agraffe can be TOO EFFICIENT, in
>    that it
>    can make higher partials audible than what you'd get with standard
>    bridge
>    pins. Some of these higher partials are not always desireable
>    (especially
>    above the 7th). That's why they use the filter, to "tune" the harmonic
>    content.



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