L-Acoustics V-DOSC, Руководство оператора

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L-ACOUSTICS V-DOSC Manual Version 4 6/29/2005 Page 65 of 158
Constant Curvature V-DOSC Array
The constant curvature array is the simplest type of curved V-DOSC array. The vertical coverage
angle is nominally (N-1) x A° where N is the number of enclosures in the array and A° is the constant
angle between adjacent enclosures. For example, a constant curvature array of 8 V-DOSC enclosures
can provide a maximum vertical coverage angle of (8-1) x 5.5° = 38.5° while still satisfying WST
criteria.
Figure 44 shows the influence of array curvature on the A-weighted and unweighted SPL for three
different constant curvature arrays. (Note: this example is for the purpose of illustrating WST
concepts - 2.5 and 2.14 degree angles are not available as standard angle strap values).
7.5 deg
15 deg
15 deg
8 x 2.14 deg
7.5 deg
15 deg
15 deg
8 x 2.14 deg
Figure 44: Constant Curvature Array Examples.
Comparing the two 4 enclosure arrays in Fig 44 (90° x 7.5° versus 90° x 15°), the same unweighted
SPL will be observed at 30 m since both arrays contain the same number of 15” loudspeaker
components and the unweighted SPL is largely determined by the amount of low frequency energy.
However, a 3 dB increase in the A-weighted SPL will be observed for the 90° x 7.5° array since the
same amount of mid/high energy is focused over half the vertical angle (i.e., 7.5° versus 15°).
Comparing the two 90° x 15° coverage arrays (4 versus 8 enclosures), for the 8 enclosure array there
will be a 6 dB increase in the unweighted SPL (since there are twice as many 15” loudspeaker
components) and a 3 dB increase in the A weighted SPL (since twice as much mid/high energy is
focused over the same solid angle).
Finally, when comparing the 4 enclosure 90° x 7.5° array versus the 8 enclosure 90° x 15° array, it is
interesting to note that it is possible to obtain the same A-weighted SPL using half the number of V-
DOSC enclosures. By focusing half the amount of mid/high energy (4 enclosures versus 8) over half
the vertical angle (i.e., 7.5° versus 15°) the same A-weighted SPL is observed at 30 m for both arrays.
Note: Since a constant curvature array radiates the same amount of energy in all directions over its nominal
vertical coverage angle of (N-1) x A°, this type of array is of practical use only when the entire audience is
sitting at the same distance from the array. However, in most venues, a V-DOSC array will have to cover an
audience sitting at varying distances from the system and a constant curvature array would produce
excessive SPLs in the first rows compared to the furthest rows (even if the vertical coverage angle is correctly
matched to the audience geometry). Therefore, a constant curvature array is generally not useful for most
applications. If this configuration is used, the gain of the amplifiers powering the high frequency section of
the lower V-DOSC enclosures may need to be progressively reduced (however, such attenuation results in a
global loss of energy).