L-Acoustics V-DOSC, Руководство оператора

Страница: 70 / 158

L-ACOUSTICS V-DOSC Manual Version 4 6/29/2005 Page 70 of 158
Typically, optimum coverage is obtained iteratively by varying the height of the array and the
enclosure angles (#1 to next, #2 to next, etc). The designer manually performs the optimization by
visually referring to the spacing between impacts after making changes to the array. Once equal
spacing has been achieved, the designer has successfully optimized the performance of the system by
shaping the array’s vertical isocontour to match the audience geometry. Angle strap values, bottom
enclosure elevation, site angles for top and bottom enclosures and trim height parameters are then
recorded and used for installation of the system (see Output Data).
Note: There is a difference between nominal angles for flown versus stacked arrays. When V-DOSC
enclosures are stacked, the rear corners of cabinets are touching (due to gravity) and when flown there is a
small gap. This difference (approx 1 cm over the depth of the cabinet) corresponds to an additional 1 degree
for stacked versus flown systems. Therefore, to simulate stacked system coverage users should enter: 1.75,
2.3, 3.0, 4.0, 5.0, (do not use) instead of 0.75, 1.3, 2.0, 3.0, 4.0, 5.5.
Output Data
In the columns adjacent to where angle strap values are entered, the site angles (i.e., what you would
measure if you put a digital inclinometer on each enclosure) and the wavepath (throw distance) for
each enclosure are tabulated.
Note: The site angle for enclosure #1 is essentially equal to the V-DOSC bumper site angle since the first
enclosure is attached to the BUMP2 with minimum separation (within physical tolerance limits) using the
BUMP angle strap. When the system is pointing down (negative site angle for #1) the top enclosure will
close against the bumper - normally this is indicated by a negative 2-Angle Stress value in MECHANICAL
DATA cells. When pointing upwards, there will be a small gap between the top V-DOSC enclosure and the
bumper and therefore a difference between site angle #1 and the BUMP2 site angle. For this reason,
always attach a laser and/or remote digital inclinometer to the top of V-DOSC enclosure #1, not the V-
DOSC bumper, in order to accurately measure the true focus of the top enclosure.
Also tabulated are continuous A-weighted SPL estimates throughout the coverage of the array on an
enclosure-by-enclosure basis. These dBA estimates are derived using a Fresnel-type calculation (see
Appendix 2) using a 2 kHz reference frequency for a +4 dBu nominal input signal level (17 dB of
headroom remains). Since the dBA calculation considers discrete V-DOSC enclosures (not sections of
the continuous radiating line source) the resolution of this calculation is not sufficient for the user to
attempt to design for constant dBA throughout the audience area. Users are advised to refer to the
visual spacing between audience impacts and use the dBA estimates as a guideline only.
In ARRAY GEOMETRICAL DATA cells, the physical dimensions of the array are displayed including:
the Overall Depth of the Array (in the x dimension), the Overall Height of the Array (in the z
dimension), and the Bottom Enclosure Elevation (rear corner of the bottom enclosure, referenced to
floor level). The bottom enclosure elevation is used as a reference for installing the system and the
Depth/Height information is useful to determine if the array will physically fit in a given space (scaffold
bay, clearance to proscenium wall etc). Please see Figure 48 for further details.
ACOUSTICAL PREDICTION data gives the unweighted SPL of the array at a user-selected distance
(enter the distance in the black cell). This calculation is based on a 200 Hz reference frequency and
correlates well with the unweighted SPL (as opposed to the A-weighted enclosure-by-enclosure SPL
estimate). The peak unweighted SPL for a single array as well as an estimate of the peak unweighted
SPL for 2 arrays is also given.
Note: unweighted SPL estimates do not include additional contributions due to subwoofers.