At 07:34 AM 4/25/2005 -0700, you wrote: >>Phil - >> >>Thanks for taking the time to pursue the experiments. I will try to >>replicate them. A few comments: >> >>Part of my own soapbox, so to speak, relates to the way measurements are >>taken with Lowell, though it would likely not alter your main >>observations. There are a number of ways the gauge readings can be >>misread, but that's mostly a different discussion. > >Perhaps we can have that now. What are the ways that the readings can be >misread? I'll give it a try. As already stated, pictures sometimes are much better at conveying ideas. Try making a drawing if my description is too confusing (of course such a description could, if rendered accurately, result in a confusing drawing). Apart from any heavy-handedness in its use, the traditional application has us either compare a zeroed reading on speaking length to a reading on the length between bridge and string rest (or visa versa), to make a conclusion regarding the implied angle. A positive angle would imply downbearing, a negative angle would imply negative bearing, and no angle would imply zero downbearing. The "component approach" isolates the front and rear angles relative to the top of the bridge. We are instructed to read the surface of the bridge with the gauge's feet spread just shy of the front and rear bridge pins (to avoid binding between pins), and then compare front and rear readings, relative to bridge top. A basic mis-assumption in this latter method is that the bridge surface is, in fact, flat. By spreading the feet as described in the instructions, the gauge assumes a straight line where, whether by the actions of wood crushing or by the original set up, there is not such. To test this, move the feet of the gauge as close together as possible. Zero the bubble in the rear-most graduations (closer to rear pins than front) and, making sure it is balanced on the string, slide it from contact with front pin to rear. You will see bubble movement, sometimes a few thousandths, but more often (for me) in the area of 12 graduations, which, I think, with the feet at about 1/4" would translate to about .009". Picture a diagram where the sounding length and the back scale are exactly the same plane. The gauge, zeroed on the first reads exactly the same on the latter. But instead of a flat bridge, the top is symmetrically arched. Either measuring method (front to rear or pin-to-pin component) would, in theory, show zero downbearing. This reading would be distorted by the string angle being "artificially" influenced by the bridge pins. Without the clamping influence of angled pins, there would be measurable downbearing, but the string contact with the bridge would be considerably behind the notch edge and the pin. I don't think we have a clear enough picture of the range of configurations that can occur at the bridge, nor is it clear what the acoustic differences are as the string / bridge notch interface moves from the idealized "point", through the lessening of force as the angle moves towards zero, through the phase where the force at the pin is actually (slightly) upward, and, through each of these phases, the effect of the string's contact with the notch either remaining intact or becoming compromised. All of these concepts and conjecture need to be tested in a way that can be considered definitive. You certainly have offered a starting point. David Skolnik
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