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CURVED ARRAY
A curved array is comprised of radiating elements arranged along a segment of a circle. It generally provides a wider
directivity response than a straight-line array. At high frequency, it provides a polar pattern corresponding to the included
angle of the arc. There exist limitations with respect to the maximum allowable splay angles to comply with the theory.
One of the conditions is specifi ed on the following sentences: a) for curved arrays, the vertical splay angles must vary
inversely with the distance to the listening location. I.e., for the farthest positions the splay angle will be small, and will
widen progressively as the listening point gets closer to the “line array”. b) the vertical coverage of a curved array is
given by the size or height of each box, the splay angles between boxes and the number of units being fl own.
“J” ARRAY
A J-Array is comprised of a straight line array and a curved array. Gen-
erally the straight segment is located above the curved segment and is
intended to provide the long throw component of the polar response.
The curved segment is intended to provide coverage in the relative
near fi eld(f) below and in front of the array. Together, the segments
provide an asymmetric polar response in the vertical plane.
SPIRAL ARRAY
Like the J-array, a spiral array provides an asymmetric polar response
in the vertical plane. However, unlike the J-array, it is a continuous
curve rather than two distinct segments. The curvature increases
with distance along the curve. This results in an upper portion that is
largely - but not perfectly - straight, and a lower portion that is curved
downward. There are many types of spirals providing various rates of
curvature. The relevant set of spirals for arrays of loudspeaker enclo-
sures are those for which the curvature changes at predetermined
intervals of length along the spiral. This length interval corresponds
to the height of the enclosure. An arithmetic spiral is one for which
the angle between successive enclosures changes by a predetermined
angle ∆-. For example, the top box might be hung at 0°, the next box
at 1°, the next at 2° and so on. This defi nes a spiral where the angle of
the nth box is oriented to the vertical axis by 0°, 1°, 3°, 6°, 10° and so
on - an arithmetic expansion. An incremental angle of 2° would yield
0°, 2°, 6°, 12°, 20° and so on.
RCF Shape Designer calculates the optimum progressive curvature for a given audience area. The progressive
curvature produces a more consistent frequency response from the front rows to the rear seats than often used
J-shaped arrays having a straight, long throw section at the top and a curved lower section. An over-angular
J-shaped array acts like a foreshortened straight array above a point source array and creates vertical lobes that
result in irregular coverage.
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