[CAUT] pre-stretching new string?

[David Love]

Grin
You will find in the example you listed below that since both speaking
lengths are equal, they will both yield equal break point percentages.
While you have to increase the tension in the string with the greater
diameter, it also has a higher break point so the break point percentage
does not change.  Set up your example using two notes different speaking
lengths to begin with so that the BPPs are not equal.  Then run your
calculations for an equal change in length.     

 

David Love
davidlovepianos at comcast.net
www.davidlovepianos.com 

-----Original Message-----
From: caut-bounces at ptg.org [mailto:caut-bounces at ptg.org] On Behalf Of
Richard Brekne
Sent: Sunday, June 10, 2007 3:53 PM
To: caut at ptg.org
Subject: [CAUT] pre-stretching new string?

 

Actually... grin... JD's post stopped me up and I broke out my handy dandy
spreadsheet and find he is right, and my last post in which I stated 

"As for your two different strings below... of COURSE  a similar change 
in length will affect differently two dissimilar strings that were 
originally tuned to the same pitch."
  

is wrong.

Take for example the two following strings.  
1:   9 mm Ø, 100 mm long speaking length, 50 mm back length, and 192.3750
lbs 
2:   8 mm Ø, 100 mm long speaking length, 50 mm back length, and 152 lbs

Both yeild starting pitch undeflected at 2070,6484 hz  and both if deflected
1 mm upwards at the <<bridge>> will have their pitch altered to 2104,7860
hz.

Thanks JD.  Spoke to fast in my last.

Cheers
RicB

 


At 10:11 am -0700 10/6/07, David Love wrote:

>Sorry, but itÕs not quite a complete enough formula for purposes of 
>this discussion.  When comparing two strings that produce the same 
>pitch but with different tensions, either the original length will 
>be different or the diameter will be different (or both), thus a 
>similar change in length will yield a different change in tension 
>and thus pitch.


If this were so, then the whole basis upon which musical instruments 
are designed would crumble.  When you halve the length of a vibrating 
string, no matter how much strain is on it etc., you double the 
frequency, and if you stop two unison strings of identical length but 
of different mass, and thus tension, at the same point, you will make 
precisely the same change in their frequency and they will still 
sound in unison.  If this were not so it would be impossible to play 
a guitar in tune unless the tension of all six strings were identical.

According to Wolfenden, if the temperature changes, and one of the 
strings is well below its yield point whereas the second is close the 
yield point, then the strings will produce a beat because the less 
strained string is more sensitive to the change in temperature.  This 
is easy enough to verify by a simple experiment, which I shall do in 
the next few weeks once the new workshop is up and running.

JD

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