Replacing the Soundboard

Replacing the Soundboard

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A good quality soundboard can last 100 years or more.  The pianos that have their soundboards replaced are often vintage pianos or pianos that have been exposed to adverse conditions.  Cracks in a piano soundboard are common and often are not sufficient reason to replace a soundboard.  Cracks can be repaired, retaining the original soundboard.  Cracks and rib separations are usually repaired at the same time the piano is restrung.  It takes an experienced rebuilder to determine if a soundboard needs replacement. When it is decided that the original soundboard is at the end of its useful life, a new soundboard can restore the piano's projection and tone quality to what it was when it was new.  This photograph section focuses on the soundboard replacement process.

In order to remove the old soundboard, the piano has to be almost completely disassembled.  The rebuilder first takes a series of measurements of all the critical dimensions.  Some of these measurements include the thickness and grain direction of the original soundboard and the exact location of bridges, the width, thickness and position of the original ribs. The tuning pins are backed out of the pinblock, the plate, strings and action are removed.  A paper pattern of the original soundboard is made and then sent to the soundboard supplier. Other replacement parts and felts are ordered at this time as well so that they will be ready when needed.  Parts and supplies are ordered from the sources the rebuilder determines will best contribute to and achieve the greatest authenticity of restoration and the best musical results.

One of the suppliers that Piano Finders orders our new soundboard blanks from is North Hudson Woodcraft in Dolgeville, New York.  This company at one time supplied 90% of the soundboards to the U.S. piano industry.  It was established  by a man named Dolge (for whom the town is named).  Dolge invented or built many pieces of equipment that are used in piano factories today, including a machine that would make piano hammers (called a hammer press).  Dolge at one time searched through the country to find a planer large enough to surface an entire soundboard.  No one would build it for him. It needed to be 5 feet wide, and nobody in the machine tool industry thought that such a large planer could be built, let alone be safe to operate.  Dolge ended up building the machine himself, and it was quite successful.  It enabled his craftsmen to make many times more soundboards in a day than were possible by the laborious technique of planing by hand.

The rebuilder uses the hot box to lower the moisture content of the soundboard to between 4% and 6% prior to installation.  This is done so that  the board will not continue to shrink after installation in the piano.  Reducing the water content of the wood to a minimal amount before its glued to the rim of the piano helps ensure this.  The ribs are also placed in the hot box, and together with the soundboard, they are conditioned for between several days to a couple of weeks, however long it takes to get the moisture content down to the proper level.  During the conditioning process, the rebuilder takes periodic readings with a moisture meter, and the humidity and temperature in the hot box are monitored carefully.

After the old soundboard is removed, the rebuilder selects the ribs that will go in the various locations, and cuts them to length.  At this time, the ribs are cut and shaped  to their proper width and depth.  The grain is also oriented in the proper direction.  The ribs may be made of either spruce or sugar pine, depending on the piano.

Several processes help maintain the soundboard curvature (or crown). After cutting the ribs to the correct thickness and width and then crowning them, they are ready to be fit into the notches in the case inner rim.  The soundboard should have as airtight a bond to the inner rim as possible, and so the more carefully fitted the ribs are to the notches, the better the bond, and the better the ultimate sound.   The rebuilder uses the holes visible in the end of the ribs for aligning the ribs to the correct point on the soundboard, so that when the ribs are glued to the soundboard outside the case or rim, they will fit exactly into the notches when the soundboard and rib assembly is installed.

Before the rebuilder installs the soundboard, he cuts it to the exact size to fit tightly in the inner rim of the piano.  The final stages of fitting the soundboard are accomplished with a belt sander or a sharp knife.  The act of pressing a soundboard down into the curved forms while gluing curved ribs to it, imparts a curvature to the soundboard.  When the glue is dry and the soundboard is removed from the cauls, it retains this curvature.

Because of the importance of having good terminations (anchor points) for the string when the piano is restrung, the rebuilder recaps the bridges with rock maple, a very strong, dense hardwood, the same type of wood that was originally used as the bridge cap on quality pianos. 

To read more about the soundboard replacement process, click on the first photo in this section to see a larger version and then click next to scroll through the rest of the photos. At the bottom of each photo is a description of the process featured in the photograph.

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