X-Array™ Loudspeaker Systems
detailed discussion of the structural strength of
the rigging hardware.
Balancing the Grid: When using a grid, as
shown in
Figure 14
, the pickup point on the grid
(the hanger) must be positioned directly above
the combined center of gravity for the entire col-
umn of enclosures so that the grid will be bal-
anced and hang level. With enclosures facing
straight ahead or angled down, as shown in
Figure 14a
, the grid hanger must be shifted to-
wards the back to be located directly above the
combined center of gravity for the entire column,
so that the grid will be balanced and hang level.
With enclosures angled up, as shown in
Figure 14b
, the grid hanger must be shifted for-
ward. To ensure maximum stability, Electro-Voice
recommends that the grid be level ±5°. (See
Figure 8c
for hanger front-to-back adjustment
detail for the ATM grid.)
2.5 Using Pull-Up Lines
Pull-Up Line Techniques: In a column of
X-Array™ loudspeakers, the rear rigging hinges
allow the enclosures to pivot vertically (to angle
up or down) while the front rigging straps set the
vertical angles. The rigging straps can only con-
strain the downward angle to resist gravity. In
other words, if, in an array column, there were
only rear hinges and there were no front rigging
straps at all, each enclosure in the column would
naturally point downward due to gravity. The pre-
cise downward angle of each free-hanging enclo-
sure would be dependent on the center of gravity
of that enclosure and the weight of all of the en-
closures suspended beneath it. The front rigging
straps can be used to limit the angle to less than
that which gravity would dictate, but the front rig-
ging straps cannot be used to increase the angle
beyond which gravity would naturally allow the
enclosure to hang. Therefore, if a pair of front rig-
ging straps on an enclosure were installed in
track positions that would enable a greater down-
ward angle than gravity would allow, those rigging
straps would be slack when the enclosure was
free hanging. To force that enclosure to angle
down more than gravity would allow, a pull-up
line would need to be attached to the bottom
of the enclosure at the rear.
Pull-up lines are usually attached to the bottom
back corner of the bottom enclosure in an array
column. Pulling back and up will force the enclo-
sure to angle down more until the front straps are
taut. Even if the enclosure with the slack front
straps is not at the bottom of an array column,
pulling back and up on the bottom enclosure will
force that enclosure down until the straps are taut.
It should be noted that, because the relative
angles between the enclosures are limited by the
front rigging straps, a pull-up cannot further in-
crease the angles between the enclosures where
the front rigging straps were already taut, it will
only further tilt down the enclosures with the slack
straps. An example requiring a pull-up line is illus-
trated in
Figure 15
.
When the lower enclosures in a vertical array re-
quire relative downward angles greater than the
18° maximum permitted by the Xrsl long rigging
straps, the front straps may be omitted from those
enclosures. A pull-up line attached to the bottom
enclosure can then be used to set the downward
angles of the lower enclosures, as shown in
Figure 16
, as long as the working-load limit of the
Xrhl linking hinges is not exceeded.
When a significant downward angle is required for
the top enclosure in an array column, the top en-
closure should be attached directly to a structural
support (such as a building or a large custom
grid) using a pair of Xrhp pickup hinges at the
rear. A pull-up line can the be used to pull the
top enclosure to the required angle, as shown in
Figure 17
. Custom front wire-rope straps utilizing
the New Haven NH32102-2 double-stud fittings
can then be added to the front of the top of the
enclosure as redundant safety lines. Less then 1"
of slack in the front safety straps is recom-
mended. In applications where the total weight of
the column is no greater then 454 kg (1,000 lb),
custom wire-rope straps utilizing the New Haven
NH32102-2 double-stud fittings may be used in
place of the pickup hinges at the rear of the top.
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