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The Asymmetrical Soundboard
Wm. Rees Instruments builds harps which are especially unusual in that William has refined a trademark asymmetrical soundboard. Traditional harps, including those William has built in the past, have a symmetrical shape. In the case of a harp, the soundboard is evenly divided by the strings.
Why Asymmetry?
The perfectly symmetrical nature of the traditional harp soundboard lends itself to wave canceling. Wave canceling occurs when two wave frequencies (sounds, in this case) are modulated equally but are opposite. The high point in one wave is canceled out (attenuated) by the low point in another wave and either no sound or a much diminished sound is produced. The other failing of a symmetrical soundboard is that if the soundboard on one side is not sensitive to a specific tone, the usually bookmatched piece on the other side will also not be sensitive to that tone because the two sides are identical.
An asymmetrical soundboard breaks up both of these patterns. Wave canceling is reduced because the various parts of each side of the soundboard are so radically different in configuration that they carry the wave frequencies in a purposefully mismatched manner. Equal and opposite waves are not produced so they do not cancel. Further, the division of the soundboard into two unequal portions means that the two sides of the soundboard are not identical and one side can pick up the tones which the other side omits. The asymmetrical nature of the soundboard makes it possible for harps to have a full range, strong harmonics and a clean voice which plays throughout all of the strings.
Other Asymmetrical Instruments
Guitars and the entire violin family appear to have symmetrical soundboards but internally this is not the case. Guitar luthiers use some or all of a combination of asymmetrical bracing, soundboard thinning and bridge adjustments to eliminate the symmetrical performance of a guitar soundboard. Luthiers of the violin family use some of these techniques and add to them the offcenter placement of the soundpost and bass bar, therefore giving their violins the asymmetrical advantage.
Bracing Symmetry
Traditional harps have symmetrical internal bracing which serves to distribute the high string pressure throughout the bearing frame of the instrument. Harp bridges cannot be placed asymmetrically without creating havoc in string spacing and a tuned soundboard is not enough in and of itself. The asymmetrical needs of a harp are best met by dividing the soundboard into two different sized portions with the midrib and strings. When played sidebyside, the asymmetrical designs have a bit more sparkle than the older symmetrical harps and the treble strings have added volume. Overall, testing has shown that Rees asymmetrical instruments have a greater overall sensitivity to a wider range of tones than do comparable symmetrical instruments.
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222 Main Street, Rising Sun, Indiana 47040 • voice: (812) 438-3032 • web: http://traditionalharps.com
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