Wavefront Sculpture In The Vertical Plane; Flat Dv-Dosc Array; Convex Curvature Dv-Dosc Array; Constant Curvature Dv-Dosc Array - L-Acoustics dV-DOSC Operator's Manual

2.2 WAVEFRONT SCULPTURE IN THE VERTICAL PLANE

Flat dV-DOSC Array

Flying or stacking dV-DOSC elements with zero degree angles between all enclosures produces a
flat array. In this case, the whole array behaves acoustically like a vertically-oriented, flat,
continuous, isophasic ribbon and radiates a CYLINDRICAL WAVEFIELD. The cylindrical wave
expands in the horizontal dimension only and is defined by the section of a vertical cylinder over a
predictable distance. The height of this section matches the height of the array (try to visualize a
120° cheese wedge). The overall vertical coverage angle of the array is equal to the angle defined by
a line that is perpendicular to the front of the top enclosure of the array (referenced to the top of
this enclosure) and a line that is perpendicular to the front of the bottom enclosure of the array
(referenced to the bottom wall of this enclosure - not the trapezoidal angle of the cabinet).
According to the Fresnel description of wavefields, a cylindrical wavefield expands from a source
over a certain distance then becomes a "classical" spherical wavefield. Detailed analysis shows that a
flat
dV-DOSC array radiates a spherical wavefront at the lowest frequencies and a cylindrical wavefront
at higher frequencies at any location within its coverage window. The boundary between the
cylindrical wavefield and the spherical wavefield is both frequency and height dependent.
In spherical mode, the wavefront expands in two dimensions, thus producing a SPL attenuation of
6dB with doubling of distance. In cylindrical mode, the wavefront expands linearly with distance, thus
producing only 3dB of attenuation when doubling the distance.
The net result is that at large distances, the tonal balance is progressively tilted by a HF
enhancement since the dV-DOSC system is, in essence, more efficient at projecting HF energy than
LF. This is an important benefit of the dV-DOSC system. With distance, this tilt in tonal balance is
offset by air absorption at large distances in open air situations and by both building material
absorption and air absorption indoors, resulting in tonally balanced sound over the largest audience
area possible.
Since the flat array configuration maximizes energy and intelligibility with distance, it should mainly
be used for long throw applications or in very reverberant rooms. It is also common to use a flat
array section at the top of a variable curved array for maximum throw in arena and stadium
installations.

Convex Curvature dV-DOSC Array

A convex or positive curvature dV-DOSC array (stacked or flown) is obtained by using dV-ANGLE
P1 or P2 bars to provide the desired angle between each element. If the angle between two
adjacent dV-DOSC elements is less than 7.5°, WST criteria are satisfied and the array behaves like a
continuous, curved radiating ribbon. If the angle between elements exceeds 7.5°, WST criteria are
no longer valid over the full audio frequency range. Practically, a larger angle produces neither
desirable nor predictable results - elements radiate individually and the benefits of collective coupling
are lost. That is why dV-ANGLE bars and the trapezoidal shape of the dV-DOSC enclosure itself
allows up to 7.5° maximum angle between enclosures.
There are two types of convex curvature V-DOSC array: constant curvature and variable curvature.
For the first case, the angle between all adjacent elements is constant while for the second case, it
varies within the defined range of 0° to 7.5°.

Constant Curvature dV-DOSC Array

For a constant curvature array, the vertical directivity is nominally N x A° where N is the number of
elements in the array and A° is the constant angle between each adjacent element. Therefore, a
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