A form of pipe midway between reed and flute in tone,it is most often encountered as the 16′ extension of the Diapason.
The diaphone consists of a resonator atop a wooden block, with a boring which is covered by a metal disc mounted on a strip spring and known as a ‘vibrator’. As wind rushes past the valve into the resonator, the valve vibrates and creates an interrupted flow of air into the resonator resulting in a note being produced. The basic principle is therefore closely related to that of a reed pipe, and diaphones are sometimes referred to as ‘valvular reeds’.
Diaphones can produce a penetrating note with controlled harmonics and very prompt speech, almost in some cases a ‘honk’ but more kindly referred to by one respected organman as a ‘robust tonk’. The diaphone principle was also applied to maritime foghorns, an irrelevant fact often seized on with relief by would-be detractors of the theatre organ.
The diaphone principle was probably discovered in the mid-19th century, but first applied with enthusiasm by Hope-Jones who mainly applied the principle to Diapason basses, a habit perpetuated by Wurlitzers.
John Compton took the practical development of diaphones further and produced highly effective Tibia and String 16′ basses on a number of instruments.
Diaphones were also used for 32′ extensions, and some early examples were extended upwards to include all or part of the 8′ octave. Resonators are usually tapered, and of wood or metal, although Compton’s diaphonic metal Tibia basses were cylindrical and of wide scale.
Much has been written about the diaphone, but click here to read one article by John Compton which stands out for the lucidity (if not impartiality) of its analysis.