Soundboard Resonces and the Wogram Article

[David Love]

I don't think false beats are quite the same thing as an oscillating
resonance which seems to take place mostly (if I read the diagram correctly)
in the lower frequencies.  Clearly there are other reasons to build boards
with cutoffs and rib crowned and supported than simply for controlling
resonances.  Those reasons (which I am inclined to agree with) may very well
trump any acoustical differences between the two.  I'm really just wondering
what those acoustical differences in terms of overall effect might be
between a soundboard constructed with the bridge precisely located between
the functional inner rim in a uniform shape and one that isn't as it relates
to the resonances pictured in those diagrams at various frequencies.
Moreover, I'm wondering how those differences might manifest themselves in
our experience of listening to the piano.  My assumption is that the pattern
produced will be more uniform and predictable.  But sometimes
unpredictability and randomness can be a positive thing.  So my question is
first, if that's the case, and second, if so, what are we trading for what
and is it something that's worth considering?

David Love
davidlovepianos@comcast.net 

-----Original Message-----
From: pianotech-bounces@ptg.org [mailto:pianotech-bounces@ptg.org] On Behalf
Of Ron Nossaman
Sent: Saturday, February 04, 2006 10:16 AM
To: Pianotech List
Subject: Re: Soundboard Resonces and the Wogram Article


> If the board without the cutoff gives rise to some
> more random pattern of resonances, might not that translate to a somewhat
> more random or, expressed differently, more complex sounding tone in the
> piano.  

Or a less organized more chaotically vibrating membrane, with 
more self-canceling movement. If techs want complex sound, why 
do they spend so much time and effort trying to fix false 
beats? The more likely effect of not having that cutoff is 
"voicing" problems when certain frequencies correspond and are 
enhanced, or oppose and are retarded by soundboard resonances. 
We don't put in the bass cutoff arbitrarily or randomly. It's 
for a couple of good reasons. This is one of them. The other 
is structural. Given the desire to build a rib supported 
board, the difference between a 1200mm long rib and an 850mm 
long rib that can support a given load at a given crown height 
is substantial.


>While controlling random resonances on the surface of it seems like
> a good thing, might it not have the effect of making the piano, to some
> ears, sound somewhat too pure or somewhat more sterile.  Now I'm not
> suggesting that's the case, btw, I'm just wondering if I'm reading these
> diagrams correctly and what this means in terms of the choices about to
> cutoff or not to cutoff.
>  
> David Love

I see no choice at all if we want to build rib supported 
boards. We have to build a structure that will support the 
load, and we have to do it within some existing physical 
constraints - like clearance of the bracing beams. And it 
doesn't matter what is done or not done, or what sound is or 
isn't produced, "some" ears won't like it even if they are 
miraculously capable of listening to it honestly without 
hearing it through the name on the fallboard. Pleasing 
everyone isn't possible, and I wouldn't care to try. I also 
didn't see any mention of how this test soundboard was 
constructed. Did he say? If anyone has ever done modal 
analysis on rib crowned and supported boards, I sure haven't 
heard of it, and would love to see the results.

Ron N
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