Grand piano soundboards.

The soundboard is the acoustic heart of the piano. When a hammer strikes a string, the vibration travels through the bridge and into the soundboard. Because the soundboard has a far greater surface area than the string, it moves a much larger volume of air, amplifying the vibration and creating the rich, powerful tone we recognise as the voice of the piano.

A well-made soundboard is formed with a shallow upward curve known as the crown. Together with the supporting ribs beneath it, this crown gives the board the correct strength, flexibility and resistance to the downward pressure of the strings. When these elements are properly balanced, the soundboard can vibrate freely and evenly, producing greater resonance, projection and sustained tone.

As a soundboard ages, its crown can reduce, flatten or even reverse. Wood is principally composed of cellulose fibres, which provide strength, and lignin, which binds those fibres together. Over many decades, repeated changes in humidity, temperature and mechanical loading can gradually alter this structure. The timber may become drier, more brittle and less elastic, making it increasingly susceptible to splitting and cracking. As the soundboard loses elasticity, it becomes less able to vibrate freely and efficiently, resulting in weaker projection, reduced sustain and a loss of tonal richness and resonance.

A properly crowned soundboard has a gentle convex curve. The strings rise over the bridge and descend towards the frame, creating the correct downbearing. When the crown, bridge height, string tension and bearing angles are correctly set, this geometry allows the soundboard to vibrate freely and produce a strong, sustained resonance.

A soundboard that has lost its crown may become flat or develop a reverse, concave curve. Although the string rises onto the bridge, it then continues upwards towards the frame, reducing or eliminating the correct downbearing. As a result, the string may lose firm contact with the bridge cap and pins, causing unwanted overtones, reduced sustain and a noticeable loss of resonance.

The condition and geometry of each piano are assessed before the work is agreed. Ask Paul to explain the findings for your instrument.