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keith -> RE: Filed saddle for 2.6mm action-- WOW!!! (Jun. 18 2014 13:40:44)
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alan carruth has some interesting thoughts on break angle--see the post, in quotes, from another forum. i am posting a link to his website at the end of this post for his articles he mentions in the post.
Alan Carruth: "If you look on my web site, under 'Acoustics', there's a PDF of a paper I did on measurments of the string forces on the top of the saddle. What I found was the the translational motion of the bridge and top, caused by the transverse string force when the string is vibrating 'vertically' with respect to the plane of the top, is far more important in producing sound than the torqewise motion of the bridge caused by the change in tension. However, the tension change signal does contribute to 'tone color' at least.
In my recent experiments, raising the saddle height so that the strings went from 11mm off the top to 18mm (don't try this at home!) increased the amplitude of the second partial, and decreased that of the fundamental, of the strings. The increase in the second partial is due to the increased leverage for the tension change signal to drive the top. The cut in the fundamental probably has to do with an increase in top deformation, which seems to have had the effect of making the top stiffer in translation.
I did see a small change in the static deformation of the top that varied with the break angle, even when the string height off the top was kept the same. This was a bit of a surprise. This could possibly alter the way the top vibrates, and thus change the sound.
I made a mechanical plucker, and recorded six plucks on each open string for each case (low break-low saddle, high break-low saddle, and high break-high saddle) that I tested, and analysed the partial content of the sound of each string for each case. My statistics guru is careful to say that we don't have enough data to say whether there is a difference between the two low-saddle cases, but there does seem to be a clear difference in the sound with the taller saddle.
We're now in the proccess of getting listening data to see if people can hear any differences. There are some other measurements we could make as well.
The bottom line is that, so far, it looks as though any changes in sound from changing the _only_ the break angle are likely to be small compared with those from changing the height of the strings off the top. I'd say that would be 'negligable', but given the sensitivity of a good classical guitar, that might be a losing bet."
http://www.alcarruthluthier.com/Acoustics.htm
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