Mass versus Stiffness was RE: false beats from ?? -...

[David Love]

This discussion directs us into an area that I've often wondered about and
that's the mass/stiffness ratio and how changes in soundboard design might
effect that balance.  My experience with the RC&S boards suggests that some
mass loading is often required in order to keep that balance right and
perhaps avoid what you describe.  While I haven't ever encountered the tone
that you describe, I have found that mass loading is often necessary to a
greater or lesser degree and have heard the same thing described by those
who are redesigning soundboards.  There several questions that come to mind:

1.  Is there a target mass/stiffness ratio and how is it described
numerically?
2.  How does it differ in different parts of the piano?    
3.  Does adding a cut-off bar and/or treble fish reduce the mass by virtue
of a decrease in the area of the board such that some compensation is always
required to rebalance that ratio?
4.  Does changing the rib width to height relationship influence mass
stiffness ratio?

For starters anyway.  

David Love
davidlovepianos@comcast.net 

-----Original Message-----
From: pianotech-bounces@ptg.org [mailto:pianotech-bounces@ptg.org] On Behalf
Of Overs Pianos
Sent: Monday, December 19, 2005 5:44 AM
To: Pianotech
Subject: Re: false beats from ?? -...

A very stiff sound board with insufficient mass in the treble 
produces a most unflattering tone which is shocky and intense with 
short sustain. Furthermore, there is an increased propensity towards 
falseness. When the mass of such a board is strategically increased, 
the overall tonal improvement and reduction in falseness is most 
remarkable.