---------------------- multipart/alternative attachment
Hi Clarke,
At 9:05 AM -0500 18/2/05, Clark Sprague wrote:
>
>Also, Ron, I noticed that the bridge in your D has the treble and
>bass bridges connected in a U shape. We have a used Yamaha C-7 from
>the 1970's, I think, that has the same configuration.
Yes, and Steinway used it long before Yamaha took it up.
> What is that all about? For stiffness, or what? Clark
The bridge shown in the image was the original Steinway D 'ring'
bridge (which we did not use for the new sound board - we designed
new bridges, with a new string scale). In the 'ring' design both the
bass and treble bridges are joined. I do not use this system since I
want the low bass to be more flexible than the lower end of the
treble bridge, so I always use separate bridges without the join. The
original ring is fitted to help impedance at the lower end of the
long bridge, but it has the disadvantage of killing the low bass.
And in another post Clark wrote:
>. . . how do you figure how big this "fish" should be, and how do
>you come up with what size the soundboard should be?
When rebuilding a piano, I stand at the instrument and think about
the original distribution of area, and think about what distribution
area might yield an improved result. For this D, I drew in a spring
lathed 'ideal' position for the 'fish' on the old board before
removing it. Then I drew a second fish area which reverted about 30%
back towards the original area. I didn't want to risk going too far
in one step. The next board reduction will probably conform very
closely to the first area reduction I drew onto the old board.
> (ie: where to place the cutoff bars?)
I consider the cut-off bar placement similarly. Another unachievable
but desirable feature is placing the long bridge to run more or less
down the centre of the belly. The bridge itself can't be moved since
the string scale is dependent upon its position, but a cut-off will
help. Another significant cut-off benefit is that it will allow for
considerably reduced rib lengths for the middle order ribs. These are
typically grossly overloaded in a conventional non-cut-off design.
> Why should the manufacturers, for many decades advertise that the
>bigger the soundboard area, the bigger the sound, and then we put in
>cutoff bars to decrease that "essential " size?
Because we live with many myths in our industry, and that's another
one of them. Bigger can be better but it depends on where it is
bigger. The well established convention with Hi-fi speakers is that a
large-area woofer is used for the low frequencies, where a larger
surface area is required to achieve air movement at lower
frequencies, and a smaller area tweeter to produce the higher
frequencies. The woofer, with its relatively high area-to-mass
diaphragm would be incapable of the relatively faster reaction
required to produce the higher frequencies, causing the large
diaphragm to distort across its face if asked to do so. The high
frequency driver, with its relatively small surface-area-to-mass
rigid diaphragm is designed to react extremely quickly to faithfully
reproduce the higher frequencies which it handles.
You can simplistically think of a piano sound board as a multi-range
speaker diaphragm, which is expected to reproduce frequencies from
27.5 to 4186. Its a big ask. Ideally, as with speaker design, it
should have a larger area for the lower frequencies, with a
progressively reducing area as the frequency increases. A sound board
without a cut-off won't remotely conform to this objective. If you
look at a grand piano in its typical concert grand form with a very
small or no cut-off, you have a large area around the bass bridge, an
even larger area in the middle where it could be reduced to
significant advantage, and a top area which sometimes has 'half a
football field' out behind the bridge - which also could be reduced
to advantage. Typically, the longer the piano, the bigger the area
behind the long bridge at the top. I suspect that makers have done
this for two reasons. Firstly, because of the myth that bigger is
better, and secondly to keep the proportions of the piano looking
'right' from a styling perspective.
I like to think of the ideal grand piano sound board area as a 'bent
tear drop' shape. The bass should have the largest surface area
because it is being asked to produce the lowest frequencies.
Similarly, the mid areas should be of less area and the high treble
should have the least of all. When designing a new piano, we have the
most flexibility, but we still have to ask the same questions and
come to a decision, and it will be from our experience and judgement
only that we derive the final dimensions. Unless of course, we take
the more ordinary route of copying what someone else has done before
us. Of course, we should consider the design decisions of those who
have come before, but we should not feel bound by their decisions.
Their idea at the time was just that. They had to make the same
decisions then, as we are making today. We should not constrain
today's possibilities by cloning what has gone before. By all means
look at and consider the design parameters of the dinosaur, but don't
replicate the entire beast. Evolution must properly make, from the
current crop of front runners, the champion of the new age. The new
champion may or may not be your creation, but its judgement day will
surely come.
> There are others out there who would like to "tool up" to do
>soundboards, as well, and do them well.
The more the better.
> How do you figure out how to design soundboards with the knowledge
>that seems to be expanding all the time?
It will always be an evolving process based on current knowledge and
experience. I have been thinking about piano design parameters,
including sound board area, since my first year as a piano technician
in 1975. I remember spending so many years tuning on 'autopilot',
pondering about the design and layout of the piano I was tuning, and
considering how the various design parameters were influencing the
tonal outcome.
Knowledge in our discipline is expanding all the time. We are living
at a time when 300 years of combined thinking has resulted in what we
have come to know as the modern piano. It is essential that this
thinking and evolution should be allowed to continue. Further
progress remains possible as long as we don't let the politics of the
currently-successful ones get in the way. We must always endeavour to
work out what is a worthwhile design feature, and what might be a
dead end idea. The black art of piano design is fascinating, and
there remains an ocean of improvements waiting to be found. As with
the evolution of species, many subspecies will come and go like the
Dodo. Not all will be bad ideas, and some may be worthy of
resurrection. But new Dodos will come along as well. We must use our
judgement to establish what we believe to be the best combination of
established practice, past practice and future possibilities. Getting
the three together in the best proportion, when building a new
instrument, can be somewhat akin to jumping off a cliff in the hope
that there is a soft landing at the bottom, and not just rocks.
You also have to contend with a multitude of 'technical' opinion,
which sometimes hasn't even been down the 'thinking road' you have
taken. So often this chorus will discount the new idea just because
it is different and 'not the way' their favourite manufacturer does
it. It doesn't necessarily mean that the new idea hasn't got merit,
but you have to somehow carry on through the 'thunderstorm' of
disbelief which surrounds you.
Ron O.
--
OVERS PIANOS - SYDNEY
Grand Piano Manufacturers
_______________________
Web http://overspianos.com.au
mailto:ron@overspianos.com.au
_______________________
---------------------- multipart/alternative attachment
An HTML attachment was scrubbed...
URL: https://www.moypiano.com/ptg/pianotech.php/attachments/50/a6/38/e6/attachment.htm
---------------------- multipart/alternative attachment--
This PTG archive page provided courtesy of Moy Piano Service, LLC