Kienle Resonator System
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The Kienle Resonator System (also known as Kienle Sound System or Kienle Resonator Organ) has been developed by Ewald Kienle since 1970 to replace the loudspeaker reproduction used for digital organs which is regarded as unsatisfactory by many churchgoers.
Loudspeakers often disturb the aesthetic overall impression in churches since, for acoustic reasons, they can only be hidden or covered insufficiently. More importantly, a loudspeaker cannot reproduce the sound characteristics of a pipe organ, such as the lively, spatially sound impression which is created by the tones moving between the organ pipes, or the high energetic efficiency factor and the projection of those tones into a space.
Furthermore, for the higher tones, the circular sound emittance characteristic for organ pipes can only be achieved to a very limited extent as loudspeakers become more directional at higher frequencies.
So, in some cases, several loudspeakers are located next to each other in a (semi) circle to obtain a more even emittance. Another possibility is to install the loudspeaker with the diaphragm facing up, and down and to divert the sound from the loudspeaker using a cone fixed above and below it (a so-called circular emitter). Although the area of even emittance is extended on the horizontal plane, the problem of an even sound distribution cannot be solved in a satisfactory way if the audience is seated at different heights with respect to the emitting device.
Function
Ewald Kienle found the solution to the emittance problem by using the resonating bodies of the organ pipes for the sound emittance, while avoiding the usual complexities of airflow stimulation in the organ pipes. Instead, the air columns in the resonating bodies are stimulated by loudspeakers, a method which has been used in loudspeaker cabinet design since the middle of the 20th century, i.e. for transmission line housings.
The diagram shows the sound generation processes in an organ pipe and in the resonator of the Kienle Resonator System. To activate the organ pipe, the required air flow (black arrow) must be generated first in a sufficient quantity and supplied from below through the pipe foot. The air flow is directed through the windway against the upper labium where air vortexes replace each other, alternatingly between the inside and the outside.[1] This process stimulates the air column in the tube and it starts to oscillate.
An example of the distribution of the sound wave's fundamental tone created in the tube is shown in the diagram by red curves. The node is located at the height of the curve intersection, the anti-nodes occur close to the openings emitting the main part of the sound. The oscillation of the air column and the sound emittance of the Kienle Resonator System occur in the same manner as in a traditional organ pipe. However, the air column in the tube is stimulated by a small loudspeaker which is installed at the lower end of the resonator and which provides the stimulating air flow by the reciprocating movement of its diaphragm.