L-Acoustics V-DOSC, Operator'S Manual

Page: 102 / 158

L-ACOUSTICS V-DOSC Manual Version 4 6/29/2005 Page 102 of 158
3.5.4 LARGE FORMAT SUBWOOFER ARRAY CONFIGURATIONS
Electronic delay processing (see Section 3.5.2) is also useful for large format V-DOSC systems
consisting of LL, L, R and RR arrays with associated subwoofer arrays (flown or stacked) in conjunction
with a central horizontal line array (see Figure 79). The optimum arc radius is typically equal to half
the length of the central line array. Delay taps are calculated geometrically based on this arc radius and
the physical distance of a given subwoofer group off the center line reference (y-axis). An EXCEL
spreadsheet tool to help perform delay calculations is available in ARRAY2004 (SUB ARC). The LL and
RR subwoofer line arrays are then time aligned with respect to the central horizontal line by taking
measurements on their respective main axes.
In practice, the center subwoofer array acts as the time reference and the length of the line array
determines the arc radius. Predelay can be applied to compensate for the physical placement of the
centre line array and time align the system with the instrument backline, kick drum, monitor sidefills
or monitor front line as desired. This predelay is also applied to the relative arc delays T2, T3 and T4
that are calculated based on their physical XY coordinates. Once electronic delay processing has been
applied to all subwoofer arrays, individual V-DOSC arrays (LL, L, R, RR) are delayed to maintain
proper time alignment relative to their respective subwoofer arrays.
It is recommended that arc radii remain shallow so that the difference between T3 and T4 remains
less than 15 msec. Steeper arc radii will decorrelate LL versus L (and RR versus R) V-DOSC arrays to
the extent that the LL array will be perceived as an echo with respect to the L array. Apart from
smoother low frequency coverage in the horizontal plane, electronic delay processing of the main
arrays has the added benefit of improved stereo perception since psychoacoustically this helps to
localize the audience’s attention towards the stage and not the nearest loudspeaker array.
Figure 79: Large format subwoofer configuration with electronic delay processing