Electro-Voice X1-212/90, Руководство по установке

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Figure 6.13: Comparing Array Structural Strengths
The arrays in Figures 3a and 3b are the weakest. The highest force in both of these arrays will
be on the rear rigging points of the top box. The long length of the X12TE-GRID extended
behind the loudspeaker acts as a large lever arm (like a wrench) that significantly increases
the force on the top enclosure rear rigging. Another way to visualize this is to think of the grid
being held in a fixed position. Because the center of gravity of the entire loudspeaker column
is so far towards the back, the column will tend to rotate counterclockwise to tilt up. The rear
rigging of the top enclosure will be in tension resisting the rotation.
Whenever a large portion of grid is extended behind the top loudspeaker as shown in Figures
3a and 3b, fewer boxes will be allowed to be suspended before the working-load limit of the
top box rear rigging is exceeded. This condition most commonly occurs with the X12TE-GRID
with the loudspeakers are in the A position. The same condition can occur when a large
portion of grid is extended in front of the top loudspeaker. This could occur with a steep up-
tilt angle with the X12TE-GRID with the loudspeakers in the C position on the grid. The X12TC-
GRID is not subject to this condition, because the grid is just slightly longer than the
loudspeaker enclosures.
The array in Figure 3d is the strongest because the load is shared between the top and bottom
of the array. This configuration will allow the highest number of boxes to be suspended and is
most commonly employed when a greater down-tilt angle is required.
Unless extreme down-tilt angles are employed, the highest forces in the array in Figure 3d will
be on the rigging of the top box. The X12PU-BGK bottom grid does not have as high of
strength rating as the top grids X12TC-GRID or X12TE-GRID. In the unlikely event that the
working-load limits of the X12PU-BGK are exceeded, one of the top grids may be substituted.
The array configuration shown in Figure 3c has greater capability than those shown in Figure
3a and 3b, but less capability than the array shown in Figure 3d. In this case, the load of the
loudspeaker column is shared between the rigging attachment points of the top box and the
pull-up assembly. However, the pull-up to the grid introduces forces that otherwise would not
exist due to gravity alone. For the array configuration in Figure 3c, the highest forces typically
occur at either the top box or at one of the boxes near the bottom of the array.
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Electro-Voice Installation Manual 2015.04 | 02 | F.01U.310.953