intro   the project   singing wood   the top    the back   the neck   assembling   tonebars adjustments     Finish/setup
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Tonebars adjustments


The goal of the operation  is to find the balance between the soundboard resistance and the strings pressure .
Neck , side and top are definitively glued together


I've built a jig able to compensate the back absence , and able to absorb the srings pressure and maintain all the structure in good conditions .

With this jig I've the possibility to work on the tonebars , as the strings are mounted .

Two calipers control the reactivity of the top during the process .
Strings action is higher than usual , to give a safety margin .

Calipers was adjusted on a value ( 5 mm )
Friday March/3/2205  I've string up the mando and tuned until the pitch was good
1- I start to tune the couple DD strings ,
                      then the bass caliper go from 5 mm ==> 4,90 mm
                      and the  treble caliper go from 5mm ==> 4,95 mm
2- I tune the couple AA strings and pitch again the AA
                       bass caliper go down to 4,87
                        treble caliper go down to 4,85
3- I tune the couple GG strings and pitch again the AA and DD
                        bass caliper go down to 4,70
                         treble caliper go down to 4,80
4- I tune the couple EE and tune again all the strings
                         bass caliper =====> 4,60
                          treble caliper ====> 4,50
Saturday 4 , I try to stay tuned and do nothing more
Sunday 5 , I've recorded  each strings ringing , before adjust the tonebars size .
then I've use exacto knife and chisels to remove wood on the tonebars .
I 've removed until the calipers react
then I've recorded the sound product .
I've use the same pick and try to play with the same force .
Below is the result of my observations
"before"  seem before adjust the tonebars size
"after" seem after adjustments

The microphone was at 30 cm in front of the instrument and the setup of the recorder
 was exactly the same for "before" and "after"

The second test is with the microphone placed behind the instrument at 30 cm from
 the sounboard .Then the result was heard, and analyzed with a " Fast fourier transform" software .

For read correctly the FFT diagramm , you must know that you find frequencies on the X  horizontal
and amplitude on the Y .  (vertical)
Open the new windows in a larger size for read easily the values .
FFT " Fast Fourier Transform"  is able to dissect a signal and find the frequencies and the amplitudes
of each frequ .
For example if we analyze the First G string below , FFT before , show that the fundamental frequ.
is at  392 hz  and harmonics are a low amplitude , except  a frequ. around 1200 hz .
in the FFT after , all the frequ. are more presents .
The pick position during playing , make varying the overtone presence .

G : hz
24,50 49,00 98,00 196,00 392,00 783,99 1567,98 3135,96

D : hz
18,35 36,71 73,42 146,83 293,66 587,33 1174,66 2349,32

A : hz
27,50 55,00 110,00 220,00 440,00 880,00 1760,00 3520,00

E : hz
20,60 41,20 82,41 164,81 329,623 659,26 1328,51 2637,02

First Test
listen    beforeafter                    first G string                        FFT before        FFT after


listen    beforeafter                 second G string                       FFT before        FFT after


listen    beforeafter                     first D string                        FFT before        FFT after


listen    beforeafter                    second D string                     FFT before        FFT after


listen    beforeafter                     first A string                         FFT before        FFT after


listen    beforeafter                   second A string                        FFT before        FFT after


listen    beforeafter                     first E string                        FFT before        FFT after


listen    beforeafter                     second E string                        FFT before        FFT after

Second test
 Microphone is  now behind the instrument

listen    beforeafter                    first G string                       FFT before        FFT after


listen    beforeafter                 second G string                       FFT before        FFT after


listen    beforeafter                     first D string                        FFT before        FFT after


listen    beforeafter                    second D string                     FFT before        FFT after


listen    beforeafter                     first A string                        FFT before        FFT after


listen    beforeafter                   second A string                        FFT before        FFT after


listen    beforeafter                     first E string                        FFT before        FFT after


listen    beforeafter                     second E string                       FFT before        FFT after


By listening , I've detected a much better balance between the different couple of strings "after" than "before"
and harmonics are more presents "after"
Sound is more rich after fitting tonebars , because of the harmonics presence more sensitive .