Isolated Air Movement, was: Rib Thinning

[Farrell]

Ron O. wrote:

"...the primary purpose of the panel is to prevent air leaking past the
ribs."

We all know the acoustic effects of placing a hi-fi speaker on a large panel
or on the panel of a sealed box compared to holding the speaker out in mid
air - especially mid-range and bass speakers. What about holes for nose
bolts through the soundboard and the limited distance from the top of the
soundboard on a grand, around the outside of the outer rim, to the underside
of the soundboard. Surely the two soundboard surfaces are not totally
isolated from one another. Perhaps the distance around the rim is large
enough that soundwaves do not interfere with one another. Perhaps the holes
in the panels are not large enough for a significant amount of air to pass
and cancel out soundwaves. But perhaps there is sound degradation from one
or both of these sources. Any insight into this?

Terry Farrell

----- Original Message ----- 
From: "Overs Pianos" <sec@overspianos.com.au>
To: "Pianotech" <pianotech@ptg.org>
Sent: Thursday, January 29, 2004 9:16 AM
Subject: Re: Rib Thinning


> Richard,
>
> >Do I understand you to say that dowels even just through the panel
> >and bridge are not all that great an idea ? ... or just through the
> >ribs ?
>
> Dowelling into ribs is the big no no, but it is more critical as
> Terry Farrell mentioned, when the ribs are designed entirely to
> support the down bearing. It doesn't matter at all to dowel through
> the panel, particularly with a rib crowned board where the primary
> purpose of the panel is to prevent air leaking past the ribs. It is
> quite common for manufacturers to dowel the bridges to the panel, but
> again it is not a great idea to use large dowels. While the bridge
> mass helps to produce sustain in an instrument, its stiffness helps
> to spread the support of the rib set evenly across the panel.
>
> There is so much development waiting to be done with sound boards.
> Its a very interesting area and I'm looking forward to some of the
> projects we are undertaking this year.
>
> By the way folks, we've got an Australasian convention coming up in
> the South Australian capital city of Adelaide this July. We've got a
> couple of visiting experts, Ron Nossaman and Roger Jolly, presenting
> classes. For further online details on the South Australian
> convention, please visit;
>
> http://aptta.org.au/sa_conv_news.html
>
> Best,
> Ron O.
> -- 
> OVERS PIANOS - SYDNEY
>     Grand Piano Manufacturers
> _______________________
>
> Web http://overspianos.com.au
> mailto:info@overspianos.com.au
> _______________________
> _______________________________________________
> pianotech list info: https://www.moypiano.com/resources/#archives
>