Electro-Voice EVA Series User Manual
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6.0 Rigging-Strength Ratings and Safety Factors (cont’)
6.2 Structural rating Overview
Designing a safe structural array is ordinarily a very complex process best left to experienced profession-
als. There are two independent strength considerations that, together, give a complete description of the
overall structural capabilities of any loudspeaker system; these are:
1.
The strength of each individual enclosure rigging point; which is the combined strength of
the internal rigging straps, external tie plates, bolts and enclosure.
2.
The total strength of the overall array; which is a function of the combined forces from all of
the rigging points acting on the rigging components and the array as a whole.
For grids, there are also two independent strength considerations that, together, give a complete descrip-
tion of the overall structural capabilities of the grid; these are:
1.
The strength of each individual grid rigging point; which is the combined strength of the
bolts, grid side arms and spreader bars.
2.
The total strength of the overall grid; which is a function of the combined forces from all of
the rigging points acting on the rigging components and the grid as a whole.
In any system, the forces acting on each loudspeaker (on each individual rigging point and on the overall
enclosure) and the forces acting on each rigging accessory (grids and spreader bars) will vary with each
array configuration. Determining those forces throughout an array requires complex mathematical cal-
culations. Electro-Voice engineers have therefore defined a set of simplified structural-rating guidelines
for EVA systems that eliminate the need for complex calculations. The interaction of the complex forces
throughout EVA arrays was analyzed using a combination of destructive testing and computer modeling to
develop this set of conservative guidelines, presented below, to enable a rigger to immediately determine
on site whether or not an array is safe without having to make weight-distribution calculations.
To make EVA systems both safe and easy to use, Electro-Voice engineers have chosen to treat EVA arrays
as a single unified structure rather than individual components. All the complex factors listed below have
been taken into account to design a rigging system strong enough to maintain a minimum 8:1 safety fac-
tor up to a maximum suspended column weight of
720 lb (327 kg)
at any elevation (tilt) angle available on
the EVA-SG2 or EVA-EG2 grid with any combination of EVA-1151D and/or EVA-2082S modules. The
maximum suspended column weight for the EVA-CG coupler grid is
760 lb (345 kg)
. The EVA-2151D
may only be flown from the EVA-EG2 grid. The maximum single-point suspended column weight us-
ing EVA-2151D subwoofers is
840 lb (381 kg)
. See
SPECiAL ruLES WHEN fLyiNG EVA-2151D
SuBWOOfEr MODuLES
, section 6.4.
