Acoustic Memory

[Tony Caught]

Hi Del,

Tony wrote

> >  It is my impression that the tone of a modern new piano remains the
same
> > for the first few years then in pianos starts to deteriorate, slowly in
> > quality pianos and faster in others. Yet in the older pianos where the
> > soundboard timber was open air seasoned (as against the modern kiln
> drying)
> > does not deteriorate to the same degree and possibly not at all except
for
> > grain compression problems.
>
Del wrote

> This is certainly a question that is open to debate. Those manufacturers
> that use only air-dried lumber certainly make a big deal out of it. Those
> that don't obviously don't. The wood technologists I know tell me that if
> wood is properly kiln-dried it is impossible to tell the difference. The
key
> word being 'properly.' Kiln operators are getting better at this as
> computers more and more take over the drying schedule.
>
> Keep in mind, as well, that any manufacturer that compression-crowns their
> boards get the wood up to a fairly high temperature and hold it there for
> some considerable period of time--until the wood moisture content
stabilizes
> at around 4.0%. From the woods perspective there is not a lot of
difference
> between this practice and traditional kiln-drying.
>
A piano manufacturer in Sydney, Australia, used a method of drying out
soundboards by putting them in a very large flat drying oven. I was told
that they would draw a line across the grain of the board and mark a set
distance of say 4 foot then dry the board until it had shrunk by 3/4 inch
then install the board. When fitted of course is  under very high
compression.

Question.  A board that is dried to compress fit is going to expand more in
some areas than others. I mean, the treble in a grand, the board is a lot
shorter than in the bass and mid sections. The compression taken on as the
board absorbs moisture is going to compress the treble more or less due to
the shortness of the board in this area. Is the grand's treble curve
designed to give even compression. ????


Tony