Of soundboards, bridges and ribs

[iumonito]

I am interested in a conversation about what makes a soundboard great or not so great.  Ribs, bridges, size, tapering, crown, age of wood; if you have something to say I would love to hear it.

A few of specifics to get things started:

Does a non-buzzing crack in the soundboard affect its transducer properties?

Are there any essential differences between a soundboard and a violin belly (and back plate, for that matter) that would explain why it would be crazy for a fine violin to have this wood replaced but it is entirely common to replace old soundboards that have lost their crown and may present cracks?

Why do soundboards shrink, rather than spread, when they loose their crown?

[Bob]

I have heard -- for violins -- that the wood for Strads came from a forest that grew very slowly.  The wood is very dense and vibrates to sound better.  I would think the same would go for piano.

[kamike]

Soundboard performance is a very complex thing.  Shape ("scale" design), materials (wood species, selection, moisture content, aging), location of bridges, connection details.  Up until the last few years success was more the result of years of trial and error and art rather than science.

Some rebuilders refuse to replace soundboards because it is such an integral part of the sound of the instrument opting, instead, for repair or simply to not proceed with reconstruction.

Soundboards shrinkage can be due to changes in water content of the wood.  Wood shrinkage is mostly perpendicular to the wood grain due to the alignment of cells.  Wood tensile strength across the grain is much less than the tensile strength parallel to grain.  Cracks form when tensile stress exceeds the tensile strength of the wood. 

This is one reason why humidity control is so important for pianos.  Cyclic seasonal variations in humidity can cause progressive damage.  Formation of even a very small crack significantly reduces the cross sectional area of the soundboard in the plane of that crack, thus significantly reducing the available tensile strength and increasing the likelihood of crack propagation the next dry season.  So, as the years go by, the crack increases in size. 

Because wood is not a naturally homogeneous material, there will always be small imperfections causing zones of stress concentration, and these are the most likely areas for crack initiation.

Lateral spread is restrained by the connection of the soundboard to the rim and/or frame.  Crown reduction is due to gradual collapse of the crown as the wood shrinks.

[faulty_damper]

One of the problems with instrument construction that uses wood as a main material is that wood is a poor conductor of everything.  It doesn't vibrate well, is ready to warp and shrink with alternating climate, and can break easily.  And this is the main reason why manufacturers still choose wood to make pianos from.   Actually, it's just cheaper to continue using a poor material than to innovate the technology.

One way to combate the poor accoustics of wood is to use more wood, that is to have a larger area for vibrations.  Another is to add more ribs to stiffen the sound board and transfer vibrations to other parts of the board.  And a soundboard is a terrible conductor of vibrations due to its shape which isn't round which means more ribs.

Anyway, the point I am getting to is that wood is a naturally bad material to use even though there are alternatives that will end the conversation about this topic.

Imagine using a material that virtually never alters in shape, is virtually never affected by different climates however extreme, doesn't damp vibrations to such a great extent that current technology does... what you would achieve is not only a superior sounding instrument but one that would last virtually forever and require virtually no maintenance.  But who wants a superior instrument if it isn't "hand-made" and "traditional"?

[nsvppp]

faulty_damper,

could you please continue? What's that material you are writing about. Are there piano's built with it yet?
 

[kamike]

Has another material has ever been used that can provide the warmth and resonance of real wood?  While there are challenges due to the fact that wood is non-homogeneous and has natural defects,  I am unaware of a better man-made substitute. 

[faulty_damper]

The material has been used successfully on string instruments, violins, violas, cellos, et al, and surprisingly (maybe not so suprisingly) has a vibrant and larger tone.  Instruments made out of this material, due to the lighter and stiffer material, sound like a much larger instrument.  Violins have to vibrancy like a viola, viola like a cello, and cello like a bass.  Or perhaps in more common terms, they are more powerful and resonant.  And if you should need a floatation device, they float!

Kawaii has actually used this material in the action parts, which in my own opinion from playing them, is quite successful.  The action was the fastest action I have ever played on, and this was compared to a Fazioli 308 the same day which couldn't compare to the repetition rate of the Kawaii.

This material is carbon fiber, a material that is superior to wood in ALL areas except for moisture absorbancy, flamability, and heaviness... things you wouldn't want anyway.

Here is a link to a manufacturer of carbon fiber string instruments and includes sound and video clips of the instruments.  The instruments are suprisingly cheap compared to the handmade 'natural' alternatives.  If this is what this material can do for string instruments, imagine what it can do for the piano.
https://www.luisandclark.com/

[kamike]

It would be very interesting to hear comparisons (I mean actual playing of them, side-by-side) of sound boards made of wood and made of carbon fiber.   You seem to imply that a carbon fiber sound board would be rejected on the basis of tradition.  I think that is nonsense.  If it sounded that much better, pianists would be beating down the doors...

Carbon fiber is truly a miracle material in many ways.  But it also has limitations.  Good carbon fiber structures require very skilled labor and lots of it.  Carbon strips would have to be oriented in very precise directions to achieve the desired frequency response and strength.  That requires significant R & D and construction of prototypes for testing, which requires elaborate and sophisticated instrumentation and experiment design.   All this, while wood continues to deliver reasonable performance at a reasonable cost. 

At some point, however, it seems reasonable that there could be outstanding instruments that use such a sound board.   My guess is that development is, for now, just to expensive and the ultimate cost too high for the consumer.

[chickering9]

...You seem to imply that a carbon fiber sound board would be rejected on the basis of tradition.  I think that is nonsense.  If it sounded that much better, pianists would be beating down the doors...

I was particularly interested in the idea of a carbon fiber soundboard many years ago when a friend of mine who is an award-winning leading scientist in nanotechnology was working with C-60 "nanotubes".  At the time, the material was prohibitively expensive for such a use.  (I tried to talk him into building me one.   )  Since then, the cost has come down.

Then, recently, I read the comments of a world-class tech and commercial piano designer about his experience with a carbon-fiber board prototype made by a major manufacturer.  He said it simply did not sound like a piano at all.  Yes, it tranduced the vibrations from the strings to audible sound, but the sound was like a computer-generated tone, as he put it.  No color or timbre or texture at all.

Which leaves me thinking that the familiar and acceptible tonal envelope of what we think of as a piano sound is quite dependent on that inefficient and imperfect transducer material--spruce.  That inherent "distortion" or resonance in the spruce modifies the sound in its ineffcient conversion of the strings' energy and the resulting resonance we hear is what we think of as piano tonal "color".  Certainly variations in soundboard condition (and even wood selection) and design significantly alter the particular tonal development even when using spruce.  Straying too far from that convention may well take us entirely away from any sound we might recognize as a "piano". 

That said, I still wonder if it would be possible to engineer a carbon material at the molecular level that could effectively mimic the characteristics of spruce while still delivering the longevity and atmospheric impermeability of wood.  But clearly carbon materials as currently used in cellos and violins and so on are not going to cut it for piano.  The point to bear in mind when thinking about this is that the soundboard is not an amplifier, but a transducer.  And the sound is not a product of the strings alone, but of the combination of those strings with that arcane wooden soundboard.