The "Test-A-Doo"

Test-A-Doo im Rötgen-Stil

The basic pitch, the trumpet and the tone quality depend mainly by the inner form of the didgeridoo. Therefore I constructed the "test A Doo", which is adjustable to simulate most possible forms of conical didgeridoos.

Einige Test-A-Doo Einstellungen mit der gleichen Rohrkombination
6 different forms with the same tube combination. With the "test A Doo" I can test the sound-characteristics of didgeridoo by try and error before making it.

Test-A-Doo Skalen
The instrument is made of of up to 7 plastic tubes with wall thickness from 4 mm to 12 mm. All tubes are present and replaceable in several lengths. For the necessary tightness rubbersealings and felt washers are used.
I can note down the test-result directly, fore that cm scales are milled in the tube-surface.
With the rods one can move the narrowings while he plays. The sound changes as like a flanger-effect from electronic effect devices, very interesting. 

Während des Spiels verschiebbare Verengung

Einzelne Verengung

Zwei getrennt voneinander bewegliche Verengungen

If the correct narrowings are placed at the correct place, a clear singing tone becomes audible - that is an overtone clearly audible beside the basic tone - a rare characteristic of special Didgeridoos and very attractive.

Testaufbau mit Analyser-Software

 Analyse von Veränderungen durch eine Verengung

In this example the FFT measurements with a Spectrum Analyzer software show substantial changes in the middle and high frequencies with a restriction in the inner channel.

With the new simulation method by Frank Geipel I can first check fundamental changes of the "test A Doo" first - e.g. different pipe diameters or narrowing forms. So I can make special tubeparts after testing it theoretical before.

Screenshot Test-A-Doo Einstellung

Screenshot (Kreis)Schablonen Positionierung

After I found my desired sound, I transfer the data of the tubes in a graphic software in which I have a 1:1 Version of the Instrument. Here I edit the surfaces, which correspond to the different diameters of the certain pipes. The centimetre-scale of the “Test-A-Doo” will be projected over the drawing and then printed out. So I get round templates corresponding to the position in the instrument. Cut out it is the perfect control-tool for the workout of the raw log.In Nierenform umgerechnete Schablonen
With some additional calculation one can make specific shapes, e.g. a kidney-form which is turning from mouthpiece to bell. The form of the templates changes, but their surface remains the same. This method I describe in detail in the Book “The Didgeridoo Phenomen”.

Plazierung von Nierenform-Schablonen mit Drall

Blick in das Bell eines nierenförmig (+ mit Drall) ausgehöhlten Didges If I work precisely, I receive a wood instrument, which corresponds to the "test A Doo" in its internal dimensions - and at least very near to important characteristics of the test equipment (e.g. basic tone, trumpet and a basic sound character).
 

View in a new Didgeridoo with a turnig kidney form.

For more detail I recommend the new book: "The Didgeridoo Phenomenon" by publisher David Lindner.

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