more bridge design

[Barbara J. Fandrich]

>
> ----- Original Message -----
> From: "Don" <pianotuna@accesscomm.ca>
> To: "Pianotech" <pianotech@ptg.org>
> Sent: Wednesday, March 26, 2003 8:18 AM
> Subject: Re: more bridge design
>
>
> > Hi David,
> >
> > I would not call 30 pounds of downbearing a humungeous burden. The
"holes"
> > in a violin bridge are there to "filter" the sound. Downbearing on a
fiddle
> > is almost as much as that on a piano.
> >

I'm assuming you are refering to the 'downbearing' on just the bass bridge.
While it is true that the string bearing on many bass bridges is not much
higher than this, the soundboard is affected by the string bearing on the
tenor bridge as well. It is the complete, integrated system we have to
consider.

Generally, holes are put in bass bridges to reduce their mass. That these
holes are ineffective goes to the basic principles of soundboard impedance.
This impedance is not linear across the frequency spectrum. In other words,
it is frequency dependent. It is primarily mass-controlled at high
frequencies and primarily spring-controlled at low frequencies. Drilling a
few holes in the body of a bass bridge generally will not affect mass enough
to make an audible change in the tone quality of the typical piano.

Del