[CAUT] More on Single String Beats

[Fred Sturm]

On Apr 16, 2007, at 5:29 AM, RicB wrote:

> There is so much micro movement going on between the bridge /  
> bridge pins / bridge interface with the soundboard that is on a  
> scale large enough to contribute directly to a single string beat  
> condition that it is actually quite surprising the loose pin  
> explanation got started in the first place... let alone gained so  
> much steam.

Hi Ric,
	Interesting thoughts on the "false beat" phenomenon. As to why the  
loose pin explanation got started: when it is possible in many, many  
cases to clear up false beats by adding a "filler" material next to  
the pin, one begins to make assumptions <g>. I guess your contention  
is that in applying those materials (CA, epoxy) you are doing more to  
stiffen the termination area than to fill the gap. Could be. One way  
or another, it has a lot to do with the pin being firmly (relatively  
speaking) rooted.
	I think some high speed videography might yield real information on  
this issue, as opposed to the conjectures we mostly deal with. Taking  
a string that is producing a noticeable false beat, focusing close up  
on the bridge pin, seeing whether the pin itself moves, and whether  
there is a regular frequency that can be associated with the  
frequency of the false beat.
	In any event, from a practical standpoint CA and epoxy are good  
cures for much falseness. Crisp terminations (well shaped capo or  
machined/polished agraffes, new bridge pins without nicks and  
grooves, pins firmly held by the bridge, good notching) yield clean  
sound, in my experience.
	As to your experiment of placing a centerpin between string and  
bridge cap, I'm not sure it proves anything about loose bridge pins  
(maybe it says something about notching). By raising the string up  
the angled pin, you are greatly increasing the side pressure on that  
pin, hence "stiffening it against the side of its hole." You are also  
somewhat increasing the lever advantage of the string versus the pin,  
increasing that effect (of pushing it firmly against the far side of  
the hole). So I think, contrary to your reasoning, that you are  
reducing the likelihood of flagpoling.
Regards,
Fred Sturm
University of New Mexico
fssturm at unm.edu



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