L-Acoustics ARCS, Руководство оператора

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L-ACOUSTICS ARCS Manual V2.0 2/13/2003
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orientation). The orientation of the ARCS enclosures (normal or inverted) will depend on the trim
height of the array (flown or stacked) and the audience geometry. In most cases, there is no need to
tilt a flown array - if tilt is required, it is typically by a much smaller angle than is required for
symmetrically radiating systems (see also ARRAY AIMING).
DOUBLE ROW ARRAYS
For larger scale applications with expanded vertical coverage requirements, ARCS is used in a double
row configuration with top row cabinets oriented in the normal position for up-fill and the bottom
row cabinets inverted for down-fill. When arrayed in this manner (logos together as a quick visual
reference), all 15'' loudspeakers satisfy Wavefront Sculpture Technology Criteria and couple over their
entire operating bandwidth, thus providing maximum low frequency impact and throw due to
enhanced directivity control at lower frequencies. The HF sections are oriented with +40/-20
degrees coverage for the top row and +20/-40 degrees for the bottom row providing an overall
vertical coverage angle of 80 degrees total. Given the physical separation of the HF sections, the 20
degree coverage angles of the top and bottom sections do not start to interact until a distance of 10
meters and interference effects at greater distances tend to be masked by room reverberation and the
psychoacoustics of tightly spaced comb filtering at higher frequencies which is difficult for the ear to
resolve. However, to help minimize this interaction it can be useful to apply a separate time delay to
the bottom row of ARCS enclosures so that the bottom row is time aligned with respect to the top
row at the FOH mix position (or approximately 30 metres from the system as a reference point).
4.2 ARRAY AIMING
The first task is to map the coverage of an ARCS array in the vertical plane (i.e., section cutview) in
order to see how it matches the audience area to be covered. L-ACOUSTICS' proprietary ARRAY
software is useful for this purpose – although specific ARCS modeling is not included, the following
procedure will give an estimate as to the vertical coverage:
Enter: X1, Z1, X2, Z2 in the Cut-view 1 cells (X = range, Z = elevation) to define to a section profile of
the given audience geometry (see the V-DOSC or dV-DOSC manuals for further details)
Enter: 3 for “# of Elements”
Enter: 40 for “#1 to next” for the normal orientation (or 20 for “#1 to next” for inverted)
Enter: 20 for “#2 to next” for the normal orientation (or 40 for “#2 to next” for inverted)
Adjust: “Bumper elevation”, “Autofocus Adjust” parameters until audience coverage is satisfactory
Refer to: “Site” for “#2 to next” and the ARCS Rigging Reference Chart in Section 4 to determine the
appropriate BUMP3 / LIFTBAR pick point.
Refer to: “Bumper elevation” to determine the system trim height.
When ARCS is used in the vertical orientation, it is easy to visually check the horizontal coverage of an
ARCS array since the coverage area is effectively defined by the outer walls of the outer cabinets of
the array. Basically, if you can see the outside cabinet wall (onstage or offstage), you are outside of the
coverage pattern.
Note: A useful technique in theatres or conference rooms is to align the outside wall of the offstage ARCS
enclosure parallel to the wall surface in order to avoid wall reflections.