The Luthier said...

The making or fixing of an instrument often makes the luthier confront those problems concerning the instrument’s practical performance and the need to adapt it to the various requirements and perspectives of different-styled musicians. As far as the modern double bass is concerned, one of the central problems, in this sense, is the neck assembly, whether for an ancient or a modern instrument.

The modern double bass and the neck replacement

During the neck construction or replacement, the luthier must be aware of some important
points, allowing the musician to move easily from one instrument to another. Firstly, the exact proportion between the sounding board and the neck. Secondly, the exact neck curve in
correspondence of the fifth.

Since the majority of double bass players’ string length is 105 cm., the correct proportion between the length of the sounding board and the neck shall be obtained by taking the following reference
measures into account:

A=105 cm.
B=43 cm.
C=60 cm.

(60 cm. diapason + 43 cm. neck + 2 cm for the neck inclination = 105 cm.).

If it is necessary to make an instrument with longer strings, for example 108 cm., the right dimensions can be obtained by using the following proportions:

 

A : B = 108 : X

A : C = 108 : X

The neck replacement is linked to the diapason size. For example, if it is 61,5 cm., the following proportion should be applied:

61,5 : X = 60 : 43

This is the proper way to achieve the correct neck-sound board proportion and the instrument shall be in tune.

As for the exact curve of the neck, on which the thumb shall be placed to obtain the correct position of the index finger in order to play the fifth, the following pattern should be used, by following the horizontal line. The thumb shall correspond to the middle finger, close to the index finger. The correct measurement of the fifth is obtained by dividing the length of the strings by 3.
Proportion neck - body
Thumb's position at 5th
Model for the measure of the exact position of the interval of 5th.

Sergio Scaramelli
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