The soundboard is one of the most important parts of a piano. Soundboards have traditionally been made of thin planks of solid spruce, about 1/2 inch thick and the width of your hand, glued together on the edges to form a very large surface. While this traditional approach has been used throughout the history of the industry, there are some very well known problems with this approach.
The problems have to do with changes in humidity. Solid wood moves with humidity levels, swelling in periods of high humidity and shrinking as humidity drops. This, along with the stretching of the steel strings, is the primary cause of pianos going out of tune. While this is annoying, it is corrected by tuning.
A more serious problem is caused by GREAT swings in humidity. During periods of high humidity, the fibers in the wood swell to the point of crushing themselves, leading to weak areas that, when they then experience very low humidity, tend to turn into cracks. A crack in the soundboard, while unsightly, usually has no impact on the overall tone of a piano. However a cracked soundboard has a major detrimental affect on the resale value of a piano and is very expensive to repair.
There have evolved 2 alternatives to solid, or “traditional” soundboards and the most common is to use a layered construction, adding 1 or 2 layers with the wood grain at a cross pattern. This construction absolutely resists humidity changes and usually eliminates the possibility of cracks developing and has been used by various makers over the years.
While this construction has a lot to offer piano makers, there a couple of problems. In the past it was offered only in lower price pianos (Kimball was a pioneer in laminated soundboards) and was seen as not being as tonally responsive as solid boards. Another problem is what to call it. It is truly “laminated” but that word is seen as negative, bringing up images of soundboards being made of ordinary plywood.
I prefer the term “modern” as opposed to “traditional”. The technology of layering thin pieces of wood together has come a very long way and has gained greater value and acceptance with the rise in the price of high quality spruce and the increase in the sophistication of piano design and construction. Among piano technicians and designers, modern soundboard construction has become accepted as long as other aspects of the piano are designed with the soundboard construction in mind.
Modern soundboards don’t crack and are much more stable in periods of changing humidity. And it is generally, though not universally, accepted that they perform perfectly well in pianos where string tension and hammer weight compliment the qualities of the soundboard.
It is argued that since the finest piano makers all use solid spruce, traditional boards must be better. But remember, the makers being referred to are at the highest ends of the price spectrum and choose to purchase high quality spruce which is both scarce and expensive. It is my contention, and that of a number of makers, designers and technicians that a well made modern board performs better than a traditional board made out of lower quality spruce.
Don’t be put off by a salesperson dismissing modern boards. They have a lot to offer.