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Electro-Voice® EVA Series User Manual
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. 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
factor up to a maximum suspended column weight of 720 lb (327 kg) at any elevation (tilt) angle available
on either of the two EVA grids. The following is a short synopsis of the considerations involved:
There are two independent strength ratings that, together, give a complete description of the overall struc-
tural capabilities of any loudspeaker system; which 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 ratings that, together, give a complete description of
the overall structural capabilities of the grid; which 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.
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