Laminated sound boards, was Bridge design

Ron Overs ron@overspianos.com.au
Sat, 13 Jul 2002 01:37:11 +1000


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Greetings Del, Roger, Ron N. and all,

>----- Original Message -----
>From: Roger Jolly
>Sent: July 09, 2002 9:46 AM
>
>Hi Del,
>               I think Ron Overs has done some work in this area. 
>The laminated board in the Overs piano is outstanding. But there is 
>also attention to detail in every other area.
>
>regards Roger
>
>Yes. He managed to make a piano using a standard, off-the-shelf 
>Samick laminated soundboard sound very good.

Thank you for your complimentary remarks Del, Roger and Ron N (and 
others, I've really appreciated your private posts). It was very 
encouraging for us in Reno, and the positive comments really helped 
to keep me going. There have been times when I have seriously doubted 
the merits of this crazy roller coaster ride to sleeplessness, which 
has consumed me for the past two years.

As usual, I get around to completing my post long after everyone's 
moved on to new topics.

The sound board for piano 003 started out as a standard Samick board 
out of the piano case (although I did order deeper rib stock). It was 
ordered as a bare panel but it came ribbed - fortunately no bridges 
were fitted. I believe an important part of the tonal outcome of this 
instrument has to do with the preparation of the inner rim prior to 
installation of the sound board and the dimensions (more particularly 
the height) of the bridges. The inner rim was chamfered in specific 
areas to gain a greater radiating area in the low bass. We did not 
use a ring bridge, since it tends to affect the low bass performance, 
even though it helps to control impedance problems at the lower end 
of the treble bridge. Instead, we used an auxiliary rib, which 
stopped short of the bass bridge and the inner rim on the left side, 
to control  the lower end of the treble bridge.

>Given that, think what could be done starting from scratch and 
>actually designing a laminated soundboard from its conception on 
>with performance as the primary criteria.

Indeed Del - this is happening with our next 225 piano (under 
construction). We are taking a bare laminated panel (yes its a Samick 
panel), and ribbing it with ribs which are crowned on the upper 
surface and flat on the bottom. We are altering slightly the board 
impedance at the bass/treble crossover (relative to piano 003). This 
will be achieved through a redesign of the rib rigidity. I am looking 
to move the crossover tone slightly towards the narrower end of the 
spectrum (but not too far), with slightly less fundamental tone at 
the cross. I am quite satisfied with the treble and low bass 
sections, but the crossover area is just a little too wide toned in 
piano 003 for some repertoire. We will be incorporating a substantial 
curved bass corner cutoff for the next piano. The cutoff will be 
fitted to the piano prior to the installation of the board, and will 
be attached to the back braces. Here again, I can't understand why 
manufacturers persist in fitting cutoff bars which are not connected 
to the back braces. It just seems to fly in the face of good design. 
I suspect that the idea of not attaching the cutoff to the braces 
allows for the cutoff to be fitted together with the sound board. But 
I don't care for the idea at all. If a sound board cut off is to be 
included (and it is better if one can afford to include one -  a real 
one that is, not one like the excuse we used in no. 003), I believe 
it must be rigidly attached to the back beams. The bass corner, at 
the belly, for our next piano will not have the usual sound board 
spruce fill. It will be filled with a veneered structural grade 19 mm 
ply. This will greatly improve the rigidity of the cut off system. I 
don't see the sense in wasting good spruce just to fill the bass 
corner in.

Piano 005 will be an identical piano to 004, except that it will have 
a solid spruce panel. I am really looking forward to hearing these 
two compared. I am expecting the solid panel to sound no better, but 
we will see.  I think they both will be a significant improvement 
over piano 003. We are hoping to have 004 ready for the January 03 
Sydney Festival concert season.

Regards to all,
Ron O.
-- 
_______________________

OVERS PIANOS - SYDNEY
Grand Piano Manufacturers

Web: http://overspianos.com.au
mailto:info@overspianos.com.au
_______________________
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