Three instruments of Ad Sax were specifically taken as an example for the design of the bore profile: the soprano 19575 in Bb from 1859, the incomplete alto AIS 341 in F the date of which is not known and the altos 24495 and 25095 in Eb from 1861 and 1862.
To make them commensurable, the soprano 19575 in Bb and the alto AIS 341 in F were both converted to the acoustical length of the altos in Eb. From the graphs, it will be noted easily that Sax's designs show a clear resemblance as to their make-up: in the bore profile, there are different consecutive concities to be discerned which are narrower each time. At the same time the final execution of this idea most certainly is not uniform: both the concities themselves and the lengths over which these concities are valid show different proportions in the different instruments.
There are three conicities to be discerned, succesively:
|sheet with bore profiles.|
Probably in the alto AIS 341 a fourth conicity was present, but because the instrument is no longer complete, no desicive statements can be made on this point. The table gives a survey. For the soprano 19575 in Bb and the alto AIS 341 in F the table gives converted values to the Eb acoustical length.This conversion is based on the position of tone hole nr. 6. The truncated lenghts and volumes of these converted instruments is of such a magnitude, that it can safely be concluded that both the soprano and the alto in F have relatively much larger trunations than the alto in Eb.
Conicity is expressed as a ratio: the number of millimeters length needed for a millimeter gain in width.
|Adolphe Sax sr.|
|1st conicity (neck)||12,8||15,1||13,3||13,4|
|relative length (%)||22½||36½||17||19|
|truncated length (mm)||167½||195||160||155|
|truncated volume (cc)||8,9||8,6||6,0||5,4|
|relative length (%)||21||32½||37||32|
|truncated length (mm)||317||290||242||246|
|truncated volume (cc)||31,6||20,3||14,1||13,7|
|relative length (%)||56½||31||46||49|
|acoustistical length (mm)||1209||1213||1224||1185|
The bore of all four example instruments in their central parts is most certainly wider than the bore of a modern instrument. This is mainly caused by both the neck and the upper part of the body having a wider conicty than with instruments with a straight cone. Especially at the end of the second conicity, at about two thirds of the length of the body, these instruments are wider than a modern instrument. Measuring 50½ millimeter, Sax's alto is at the beginning of the bottom bow wider still than an instrument with a straight cone and the usual concity of 1:18. Note that the intersection of the main concity and the x-axis is yet always in the same spot (and has to be in the same spot, at least for both the altos in Eb. The two smaller instruments that were converted to Eb have, as has been said, a greater truncation of the cone). This intersection is related to the sounding length of the instrument and acts as the acoustical top of the cone.
But there is not only the difference between Sax's instruments and the modern ones. Also among themselves there is a marked difference in relative width of the bore, because where the two altos appear to be of more or less equal width, the soprano clearly is relatively much wider. Sax's designs appear not to be proportioned uniformly for the different instrument sizes.