Bridge Seating (was Re: Where to notch a bridge, & relative effects ????? (Advice sought)

[Ric Brekne]

List:


    "Exactly right William, thank you. Johnathan, when you hear a
    string that sounds like something you would typically seat,
    try this. Place a screwdriver tip against the speaking length
    bridge pin of that string, and apply a bit of pressure to the
    side of the pin opposite the string. Odds are, the sound will
    clean up as if you'd seated the string. Take the screwdriver
    away and the noise returns. Replace the screwdriver, and the
    sound cleans up again. Ask yourself why that is, when you
    haven't seated the string at all."


I'd suggest folks go a couple steps further with this advice.  Ask 
yourself why if you increase pressure on the screwdriver the beat starts 
up again.  Also actually count and write down which strings have false 
beats and which of these actually reacts to the screwdriver. Then figure 
your percentages.  The real odds are that the percentages are somewhat 
more a game of bingo then anything else.  More importantly, when you are 
done identifying all the strings that react to the screwdriver trick and 
have written down each note and string,  go back through and remove each 
of them one at a time and check to see whether the conditions given to 
explain both the false beat and the fact that the screwdriver trick 
works are present. If this explanation was correct then in nearly every 
(if not all) instance you should find   1:) a loose pin, and  2:)  a 
deepened string mark that effectively places the notch behind the pin
 
If you actually do this, as I have on several restringing jobs to date, 
you will find somewhat less then half of the pins are actually loose, 
and that the string mark factor shows up even less often.  Since the 
above quote is a leading  into the loose pin / false beat proposition 
again, we might as well go there right off and get it done with.  
Complete your researcher's ensemble by proceeding to add CA or epoxy to 
your pins.  Add it to ALL the pins.  When done re-identify all 
individual strings that show false beats.  What you will find is a 
general improvement of significant degree.  But closer examination of 
your data will indicate there is some other casual effect at work. The 
data shows that 1:) far from all of the original false strings are 
cured.  2:) some amount of the uncured are improved.  3:) there is a 
significant degree of new falseness on strings that were clean originally.

All this can lead you to try several different experiments in an attempt 
to better understand false beats.  And in the end you will still lack 
anything close to the definitive answer.  My experience shows clearly to 
me that a string is just as likely to display false beats (of the sort 
that reacts to the screwdriver) with the above conditions as without.  
Loose pins can be downright wobbly in there holes with the string 
propped up with a center pin under the strings 2-3 mm behind the pin and 
still there is no significant degree of assurance that a false beat will 
or wont appear.  Try it on 20 or so strings on the next beater you get 
in your shop. On the other hand pins that are tight as you can ever 
expect them to be can also display this same kind of beat. 

There is just plain too much randomness to the occurrence of false beats 
if the loose pin/crushed edge explanation is applied. 

What we do know (because the rest is pure conjecture) is that the 
introduction of CA or epoxy significantly improves the situation. Even 
more so then replacing with larger pins by accounts I've heard here.  So 
add the stuff and be glad for the improvement.  But as far as I can see 
we have not arrived at an explanation for false beats. 

Cheers
RicB










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