Soundboard Crown measurement and evaluation

[Overs Pianos]

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Hello John,
At 3:44 PM -0500 25/11/05, John Alsina wrote:
>
>Your recent post describes re-crowning the soundboard in a 
>relatively new instrument.
>Would this technique be worth considering for older instruments?

Very much so, provided that the overall scope of required repairs 
makes it a viable proposition. The thing about 20-30 year old Kawai, 
Steinway and Yamaha pianos in particular is that there are thousands 
out there in the field, many of them have sunken sound boards. If you 
find this hard to imagine, just hold a 150 mm metal rule under the 
bridge position on the under side of the board (and for some pianos 
at the feathered rib ends also). The rule can be rocked. Sure, they 
might sound OK now in some cases, but some will sound very ordinary 
and rib extensions will fix the problem provided the instruments are 
otherwise structurally sound. You will even find pianos on showroom 
floors with inside out boards which already are exhibiting signs of 
significant shortness of tone.

>For example: an 80-year-old compression crowned instrument whose 
>soundboard is visually
>in good condition but flat in the mid-treble, resulting in short 
>sustain in that range.
>On the one hand, the SB might already be crushed and "dead."

Certainly the grain in the panel will be crushed, relative to its 
condition when new, but it won't be dead if you fit rib extensions. 
The stiffness and tonal improvement is astounding. One of the 
limitations with older instruments would be where the finish on the 
underside of the board has deteriorated. The top surface and set bolt 
holes can be refinished, but the area over the belly rail will be 
almost impossible to access for re-coating.

>On the other hand, if new built-up ribs could provide sufficient 
>springiness by themselves,
>the soundboard would only have to serve as a diaphragm, so perhaps 
>even a dead SB would do.

Exactly, just as it does with rib crowned and supported new soundboards.

Provided the original ribs are firmly glued to the panel and the 
panel is firmly glued to the rim, I don't think it matters how dead 
the board is, it will response very well to rib crowning. What we are 
creating is a rib-supported assembly which originally was compression 
crowned. It it will work very well.  We're currently charging about 
A$15K - 16 to build a new soundboard and bridges, while the last two 
rib extension jobs cost the clients around A$5K (US$3.6K) each for 
the rib extension part of the work.

At present it takes us a whole week to do a full rib extension job. 
The preparation, particularly the removal of original rib height with 
a rasp, involves hard back-breaking work, but the excellent result 
makes it all worthwhile.

Best regards,
Ron O.
-- 
OVERS PIANOS - SYDNEY
    Grand Piano Manufacturers
_______________________

Web http://overspianos.com.au
mailto:ron@overspianos.com.au
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