Saddest O of the Week

[Piano Builders Northwest]

A440A wrote:

>    ....What is the acoustical difference between those cases glued up with hide
> glue, and the cases with the later developed stuff that is cured with
> microwave?
>
> Just a case in point, or a point,  just in case.
>
> Regards,
>
> Ed Foote
> -----------------------------------------------------------------

Ed,

It's not the glue that counts here. It's the wood. Steinway (as well as pianos like Knabe, Chickering, M&H, etc.) has always
used hard maple in the rims of their pianos. Baldwin used to, but now uses a combination of maple (inner rim) and poplar
(outer rim). If you haven't personally bent a hard maple rim you can't really appreciate how difficult a process this can be.
That stuff is really stiff.

Pianos that are intended for high volume production most frequently use what is euphemistically called "Select Hardwood."
This can be anything that meets the legal definition of a "hardwood." That is, the tree must lose its leaves in the winter.
The most critical characteristic of this wood is that it must bend easily and quickly. It also must not exhibit a great deal
of springback. I don't know how long Steinway leaves their rims in the press after gluing, Baldwin leaves them in for 24
hours. Minimum. I expect that Steinway's press cycle time is similar. At Baldwin, once the rims are taken from the press they
are placed in a fixture that physically holds their shape and they are cured in a heated environment for some four weeks
before they are entered into production. Again, Steinway probably does something similar. By comparison high production rims
can come out of the presses within minutes and be entered into production immediately.

There is a reason why Steinway (and Walter and a few others) still use hard maple for rim making. As well, Walter uses maple
for the belly and rim braces. Maple is also used (at least by Walter) for the belly rail. Structurally, the difference is a
rim of high stiffness and mass (presenting a high impedance load to the vibrating energy found in the soundboard) vs. one of
relatively low stiffness and mass (presenting a lower impedance load to the vibrating energy in the soundboard).

Acoustically, the differences are most often detectable in sustain. Pianos with relatively light, relatively flexible rims do
not offer the same resistance to energy transfer that stiff, massive rims do. The tend to accept energy from the soundboard
more readily. Energy that enters the rim is largely lost, acoustically. (And, yes, I realize that some companies -- for some
inexplicable reason -- do this intentionally.) Pianos like the Steinway can achieve good sustain with a soundboard that is
very thin and light. Treated right, these boards can be made to produce great depth of tone and dynamics. Pianos using
lighter, more flexible rims must find sustain some other way. Usually by using somewhat stiffer and heavier soundboards,
along with the requisite denser and less flexible hammers. The acoustical and structural differences between these two rim
making philosophies are found throughout the respective designs.

Del