MEASUREMENTprocedures
measuring a saxophone
Measuring a saxophone is quite simple, actually, yet quite some work. If you've never done it before, count on a day for an alto, a day and a half or more for a baritone.
You need some simple measuring tools, like callipers and a slender tape measure (take a tailor's tape measure of which you cut off a narrow ribbon), a felt-tip pen (felt pen ink can be removed easily with methylated spirits), a spreadsheet for the necessary calculations (which you can get from me) and a worksheet (which you can download from this website). Measure both bore and tone holes. Only such a 'complete picture' can make reveals relationships between different instruments.
BORE
- Start with measuring key lift heights. As you'll have to take off keys in a later stage, this can best be done as a first step. Next mark lengths in centimetres on the neck and body. Zero length is at the entrance to the neck
- Next, take outside diameters and subtract twice the wall thickness. The tube will not be accessible at all places because of ribbons or pillars and you will have to search and choose. Try to take a measurement each centimetre in the neck; at least every five centimetres on the body; bottom bow every 2 or 3 centimetres; the bell five, except for the final few centimetres.
- Wall thickness can be hard to establish. I made myself a special vernier calliper which can work around a bulge, so that I can take a wall thickness even at a rolled tone hole. 0.6 millimetre is a common size in sopranos, altos and tenors, which makes: outer diameter minus 1.2 (antique instruments are sometimes built out of 0.5). Baritones are often built out of 0.8 mm. Sometimes there is a subtle shift in wall thickness, for instance in the neck from 0.7 to 0.6, caused by the production process (forging..) Simply neglect this.
- Important: everything is always out–of–round. You can tackle this problem by taking diameters in different directions and calculating an average value. In wide tube parts (a bell) with a pronounced out–of–roundness, take the circumference with a tape measure and recalculate this to a diameter. For accuracy, you should take care that the tape measure is as thin as possible, preferable made out of paper.
- Accuracy
- length: I use a unit of a centimetre – in bows anyway you will very soon lose any greater accuracy.
- diameter: here I use a unit of a millimetre. In both cases these units are divided into tenths. The inexactitude of the object makes that a tenth of a millimetre is already the maximum that can be accounted for. Only in the neck I sometimes use pluses or minuses for a an undefined 'something more than' or 'slightly less than', without wanting to attach a numerical value to it.
- Mark down in the table where one tube part ends and where another one begins. The end size of one tube part certainly is not the same as the opening size of the next, although you might expect so.
TONE HOLES
- In hand made instruments and instruments with hand made tone hole rings, tone hole diameters cannot always be measured accurately because of out–of–roundness. In those cases, two measurements are taken perpendicular and averaged out. The out–of–roundness of the tone hole in many cases exceeds a millimetre.
- A ratio tone-hole-size/tube-size is calculated on the ground of surface areas of both. For this I take an extra width measurement of the tube at the tone hole. The ratio is given as a percentage (say 23).
- Tone hole length measurements have their zero at the entrance of the neck and are measured to the centre of the tone hole. Although accuracy is aimed for, measuring length especially of the tone holes in the bottom bow is no easy job. Therefore differences in length are of first of any meaning when larger than ½ centimetre. In many cases I take such measurements several times and calculate an average.
Measuring a bore profile. The easiest way to determine lengths in a bow is to first mark the central axis and only then mark lengths. Looking at reflections on the bow can be helpful.
A tape measure for circumference measurements.
Callipers like these come in handy, but you'll have to make them yourself. |
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measuring intonation
In intonation measurements we have to deal with the natural flexibility of the saxophone. The most reliable method I've found thus far, is in using FMIT-software (free musical instrument tuner) which is available for Windows, Apple and Linux systems (native). FMIT itself calculates averages of intonation over a longer period of playing (in the 'statistics'-screen), which is very helpful. You can use it while playing your daily exercises. Next, make screenshots to save the results.
a worksheet for instrument measurements
a spreadsheet supporting all kinds of instrument measurements