----- Original Message ----- From: "Alan Forsyth" <alanforsyth@fortune4.fsnet.co.uk> To: "Pianotech" <pianotech@ptg.org> Sent: Saturday, April 12, 2003 9:04 PM Subject: Bridge pressure bar > Del wrote > > >"This system would certainly maintain good string contact with the bridge, > but that is not the function of string bearing. These are two quite > different issues. String bearing provides a way to increase soundboard > impedance without adding mass to the system." > > Del, > Can you please explain to me or define soundboard impedance. Not in a sentence or two. Basically impedance is a measure of how readily the soundboard assembly is able to accept energy from a vibrating string (or strings). A soundboard having low impedance will accept energy very easily and the resulting tone will be short and percussive. A soundboard assembly having high impedance will not accept energy as readily and the sound will be less loud but with longer sustain. It is a frequency-dependent function of the soundboard's overall stiffness, mass and mechanical resistance. The overall stiffness of a soundboard is dependent on the design of the assembly and physical characteristics of the materials used for the panel, the ribs, the bridges, etc., its mounting system (the characteristics of the rim, bellyrail, etc.) and whatever string loading exists. If you're a real glutten for punishment you can refer to my article, "Soundboard Damage Part I--A Guide to Soundboard Cracks and Other Maladies," Piano Technician's Journal, December 1997. Del
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