L-Acoustics V-DOSC, Operator'S Manual

Page: 122 / 158

L-ACOUSTICS V-DOSC Manual Version 4 6/29/2005 Page 122 of 158
Depending on the tools available, there are a number of possible techniques for trimming and
angling the array.
For trim height measurement, one end of a tape measure can be attached using some duct tape.
The tape measure is used to raise the array to the proper height (based on the geometrical data
which was pre-calculated using ARRAY2004 or SOUNDVISION – see above) and can be pulled
loose afterwards.
Under dark conditions (indoors), a laser pointer or laser level can be attached to the top of the
upper V-DOSC enclosure. Trim angle adjustments are then given by the focus of the laser on
the audience - no walking to the back of the venue is required although laser glasses or a set of
binoculars can be useful in locating the laser beam). Coverage up close can be checked by
attaching the laser device to the lower wall of the bottom enclosure or visually looking for the
bottom wall of the bottom V-DOSC enclosure to see where coverage starts.
As described above, mounting a remote digital inclinometer on the top enclosure and using a
handheld digital inclinometer is very useful for tensioning ratchet straps and verifying that the
overall vertical coverage angle of the array matches what was simulated in ARRAY 2004. Once
the system is flown to trim, the tilt of the array can be set using the remote inclinometer and
setting the tilt = Site Angle #1 (-1.5 degrees in Figs. 93 and 94). It is important to perform this
final adjustment once the array is at the correct trim height since chain motors typically do not
run at exactly the same speed if the front and rear load distribution is different.
Alternatively, under dark conditions (indoors), a small flashlight can be attached at the junction
between the top and second enclosures. The final trim angle adjustment is checked from the
rearmost seats of the audience: when the light can be seen through the gap separating the first
and the second enclosures, the angle of the array is correct.
Under daylight conditions (outdoors), the trim angle can be visually checked from the rearmost
audience section (flashlight not required). If the gap between the top and second enclosures is
clearly visible then the focus is correct. Note: Bushnell Rangefinder glasses can be useful for
checking gaps between cabinets at long distances. Coverage up close can be visually verified to
ensure that the top wall of the bottom enclosure is in line with the desired aiming angle for the
closest members of the audience. For final angle adjustments, a pair of radios is useful while one
person walks the venue and visually inspects the array while a second person operates the site
angle adjustment motor (front motor for ARRAY2004, rear motor for SOUNDVISION).
For all of the above alternatives, several pieces of string or light rope can be run from the floor,
over the BUMP2 and to the Maglite, laser device or remote inclinometer in order to pull the
instrument free and lower it after measurements have been performed.
If a DELTA PLATE is used, on- or off-stage rotation of the entire array can also be adjusted.
Three motors are used in this case, and a rotating shackle connects the DELTA PLATE to the
BUMP2. With reference to ARRAY2004 installation data, the two rear motors control the height
of the array and the relative action between them controls the rotation. As before, the front
motor controls the tilt angle.
Use these techniques to verify L and R arrays are matched (plus L-L vs R-R arrays, if installed).
Rigging Amplifier Racks
In some cases, it is desirable to rig amplifier racks behind the V-DOSC array. Shorter speaker
cable runs have the advantage of lower cable resistance resulting in more effective signal transfer
since there is less energy dissipated as heat in the cable. Reduced cable runs can also improve
damping factor and potential frequency-dependent losses due to the skin effect (in extreme
situations).