All La Systems - Renkus-Heinz STXLA User Manual

Line Array User's Manual

ALL LA SYSTEMS

RH Engineering has developed an acoustic lens of the "path length refractor" type in order to change the output of
a horn/driver into a planar wavefront. A schematic of the HF section of a Renkus-Heinz Line Array Module looks
like this:
Renkus-Heinz line array modules use pattern control techniques that have been borrowed from microwave
research. Since microwaves have characteristics similiar to high frequency sound waves, these techniques are useful
for creating continuous HF wavefronts. The Path Length Equalization Technology used in this device has a significant
advantage over other techniques (such as reflectors and obstacle arrays). Reflectors and obstacle arrays operate
over a relatively narrow bandwidth: perhaps four octaves. This limitation is due to the transition from the "ray
model" (reflection) to the "wave model" (refraction and diffraction) that occurs as wavelengths become long in
relation to the reflector or the obstacles.
The path length refractor, however, can generate planar wavefronts over a wide operating band. When higher
frequencies pass through the device, it operates on the "ray model, " as illustrated below:
When the "wave model" takes over due to the longer wavelengths, the path length refractor lens functions as
closely spaced array of diffraction slots, as illustrated on the next page.
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