Trim And Angle Adjustments - L-Acoustics dV-DOSC Operator's Manual

Trim and Angle Adjustments

At this point there are only two adjustments left - trim height of the array and tilt angle of the entire
flown system. If two motors are used for standalone flying, the front motor is used to set the proper
height of the whole array. Controlling the tilt angle is then performed by the relative action of the
two chain-motors, i.e., once the proper height has been set the front motor is fixed and activating
the rear motor only varies the tilt angle.
Note: For dV-DOSC, do not use the top and bottom of the cabinet as a visual reference (as for V-DOSC).
The radiated wavefront is parallel to the front of the cabinet and is not defined by the trapezoidal enclosure
walls. Adding a 3.75 degree angle at the rear of the top element allows dV-BUMP to be used as a site angle
reference for the top element.
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 fixed to the lower wall of
the bottom dV-DOSC element at the front of the enclosure (by using some duct tape). The tape
measure is then used to raise the array to the proper height (referenced to the floor) based on the
bottom element elevation which was pre-calculated using ARRAY 2000. Once the array is at trim
and focussed, the tape measure can be pulled free.
For angle adjustment, under dark conditions (indoors), a small flashlight can be attached at the
junction between the top and the second elements. The final trim angle adjustment can then be
checked from the rearmost seats of the audience: when the light can be seen through the small gap
separating the first and the second elements, the angle of the array is correct.
A more precise technique for far field focus is to use a laser attached to dV-BUMP (provided that a
3.75 degree angle is used at the rear of the top dV-DOSC). Trim angle adjustments are then directly
given by the focus of the laser on the audience (no walking to the back of the venue is required
although a set of binoculars can be useful in locating the laser beam). Obviously, array focus using
lasers is difficult to perform outdoors under daylight conditions.
For both alternatives, two pieces of light rope can be run from the floor, one over dV-BUMP and
the other routed through a hole in dV-BUMP. Both lines attach to the Maglite or laser device in
order to pull the instrument free then lower it after measurements have been performed (one string
is a pull line, the other is used to lower the instrument). As a final check, mute mid and low channels
and run pink noise through the system and listen to the high section coverage throughout the venue
to verify that installation is correct.
Under daylight conditions (outdoors), the trim angle can be visually checked from the rearmost
audience section. If the gap between the top and second elements is clearly visible then the focus is
correct. At long distances, binoculars can help to visualize this gap and for final angle adjustments, a
dV-DOSC dV-SUB Manual V2.0 Nov 2001 99