Wave Fronts And Source Curvature - PROEL AXIOM - VERSION 2.0 Manual

A.2. WAVE FRONTS AND SOURCE CURVATURE
Figure A.1: Simulation of the radiation along the vertical axis of an array composed of 16 omnidirectional sources
with a step of 32cm.
while off axis these contributions tend to cancel out due to the differences in radiation path and, conse-
quently, in phase.
Furthermore, it can be verified that the control of directivity at low frequencies is dependent on the
overall length of the array.
Therefore, at low frequencies it is possible to make constructive use of interference in order to obtain
a combined output from the sources with a resultant increase in sound pressure level. The dependence
of the maximum frequency for this phenomenon on the step could incite designers to reduce the step to
a minimum, but the problem of finding components with the required characteristics within the required
dimensions becomes insurmountable. In actual vertical array systems therefore, the interference is
exploited at the low end of the frequency spectrum while it is carefully reduced in the high end by using
HF sources that are extremely directive.
A.2 Wave Fronts and Source Curvature
Vertical arrays are the physical approximation of theoretical linear sources, whether they are linear
or variably curved. Portions of the system exist which do not radiate- gaps- due to the physical structure
and the spacing of the source elements. Moreover, the radiating elements of real systems emit wave
fronts that can be quite different from the flat wave fronts of sources.
Here, we discuss only the effect of the curvature of the wave fronts of the sources
The HF components of a vertical array system that are based on a conical waveguide produce curved
wave fronts. When combined in and array, these sources appear more as a series of superimposed arcs
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For a more detailed treatment please see the already mentioned Ureda review, Analysis of Loudspeaker Line Arrays. JAES,
Vol. 52, No. 5, May 2004.
Figure A.2: Structure of an array using curvilinear sources.
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A. Vertical Array theory
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