Quote:
Originally Posted by dekutree64
Yeah, the focus is mostly on monopole, but the trebles don't just automatically sound good. Here's an example of what not to do  15" lower bout, 2mm (.080") plate thickness (rather dense, very stiff sitka with zero runout), and braced like this:
It actually did survive just fine, in the sense that the central area was plenty stiff not to cave into the soundhole, and the large bridge plate prevented deformation and bridge peeling there. But carving the braces so low at the perimeter with such a thin plate allowed the whole central area to pull upward, creating a fairly intense "radius" in the last inch or two before the perimeter. Hollow, nasal sounding trebles. Sort of archtop-like. But the bass was excellent. I think Ervin actually did mention in the book that the perimeter has a lot to do with treble response, and I agree  |
Fascinating to see an example that actually failed. Did you thickness the plate using a deflection test? Or did you thickness it to a specific dimension?
Quote:
Originally Posted by dekutree64
In fact, the main difference between thin plate style and thick plate style seems to be whether the central stiffness comes more from the plate or bracing. With thin plate, it's often equal thickness all over. With thick plate, it's thinned at the perimeter... to about the same thickness as it would be all over in thin plate style. My .080" was too far, though I suspect it could have worked if I left all the braces taller as they approach the edge, and notched them into the linings at maybe 1mm tall to gain back a little perimeter stiffness. I have another in progress to test that theory...
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Is that a classical? The heel block looks interesting. And is that redwood? And same question regarding the plate thickness. Did you do so with a deflection test, or to a dimension?
Good stuff man. Do you have a build thread somewhere I can follow?