L-Acoustics V-DOSC, Operator'S Manual

Page: 121 / 158

L-ACOUSTICS V-DOSC Manual Version 4 6/29/2005 Page 121 of 158
be close to zero (with no ratchet) when the system is flown and focussed downwards.
Moderate ratcheting then introduces the possibility of continuously variable angles between
0 to 0.75 degrees and the progression is monotonic as a function of height. For example, if a
16 enclosure array is pointing 4 degrees down and 0.75 degree straps are used for the first 8
enclosures (combined with moderate ratcheting), actual values on the order of 0, 0, 0.25,
0.25, 0.5, 0.5,0.75, 0.75 will be obtained for enclosures 1-8. This provides better spacing of
enclosure impact zones over the audience in flat open air situations.
♦
When the array is pointing upwards, the centre of gravity shifts forwards and V-DOSC
enclosures tend to open naturally, providing the nominal angle values (0.75, 1.3, 2.0, 3.0, 4.0
and 5.5). Therefore, for a V-DOSC array with upwards tilt, very little ratchet strap tension is
required. Typically, the bottom 2-3 enclosures will need to open up slightly and spacer
blocks can be used for this purpose (or moderate ratcheting).
To summarize, the most precise way to work with ratchet straps is to have a remote
inclinometer on top of the array to measure Site Angle #1 and a handheld digital inclinometer to
measure the bottom enclosure site angle. Fly the array using the angle strap values calculated in
ARRAY 2004 or SOUNDVISION and raise the array above ground level at a height where the
ratchet strap handle is accessible. While referring to the remote inclinometer, adjust the
front/rear motors to give the correct Site #1 angle. Allow the array to settle then measure the
site angle of the bottom enclosure. Adjust the tension of the ratchet strap until the site angle of
the bottom enclosure agrees with the value determined in ARRAY 2004 or SOUNDVISION. At
this point, the vertical coverage of the array is correct. Next, raise the array to the calculated
bumper elevation (or bottom enclosure elevation). Since front and rear chain motors can run at
different speeds, once you are at trim, you must reset the focus angle of the array using either
the remote inclinometer or by referring to a laser mounted on the top enclosure. Repeat this
process to ensure that the vertical coverage and focus of Left and Right arrays are exactly
matched.
Trim and Site Angle Adjustments
After the ratchet straps have been tensioned there are only two adjustments left: trim height of
the array and the site angle of the top enclosure which is performed by the relative action of the
front and rear chain-motors. Due to different geometric coordinates in ARRAY2004 and
SOUNDVISION, the trim and site angle adjustment procedures are different.
ARRAY2004 installation data (see Figs 48 and 94): The rear motor is used to set the elevation of
the array and the front motor controls the site angle. A tape measure should be attached at the
upper rear corner of the top V-DOSC enclosure (bumper elevation = 10.0 m in Fig 94) or
lower rear corner of the bottom V-DOSC enclosure (bottom element elevation=4.78 m in Fig
94). Once the proper height has been set, the rear motor is turned off and the front motor used
to adjust the site angle of the top V-DOSC enclosure (-1.5 degrees in Fig 94 - see also below).
SOUNDVISION installation data (see Figs 51 and 93): The front motor is used to set the
elevation of the array and the rear motor controls the site angle. A tape measure should be
attached at the upper front corner of the top V-DOSC enclosure (elevation = 10.0 m in Fig 93)
or lower front corner of the bottom V-DOSC enclosure (bottom element elevation=4.73 m in
Fig 93). Once the proper height has been set, the front motor is turned off and the rear motor
used to adjust the site angle of the top V-DOSC enclosure (-1.5 degrees in Fig 93 - see also
below)
NOTE: For larger arrays (12-16 V-DOSC), always fly the system without tilt initially. Applying tilt
before the array is entirely flown can produce too much stress on angle strap fittings – especially if
excessive upwards tilt is applied. Always refer to the mechanical data provided in ARRAY 2004 or
SOUNDVISION to confirm that rigging limits are not exceeded