Soundpost and bassbar create asymmetric plate modes to boost radiation

Evidence

Three key components remain to be described: the bridge, the soundpost, and the bassbar (see figure 18.2). These each play a role separately and also act together to transfer energy directly from the foot of the bridge sitting above the soundpost, which presses against the top and back plates. The other foot transfers energy to the top plate. The bassbar stiffens the top plate, and together with the soundpost acts to increase the impedance mismatch between the bridge and the body (not to mention strengthen the whole against the 50 or so pounds of string tension force). The mismatch is controlled as a function of frequency using bridge resonances where they are needed (see the following). The soundpost and bassbar placement have a role in making the vibrational modes of the top and bottom plates asymmetric, which as we know will partially foil short-circuiting and increase the radiated sound power. — Eric J. Heller, Why You Hear What You Hear- An…, 1743

Categorization

• DEFINE: Crisp definition of bridge, soundpost, and bassbar functions in one passage.