Line Array - Design and Rigging

Design and Rigging

Large-format line arrays are designed for large venues or outdoor festivals. These boxes typically included multiple vertically aligned high frequency compression drivers and multiple midrange and low drivers arranged symmetrically around the compression driver. The low frequency driver is typically 15 or 18 inches in diameter. Mid-format line arrays are typically two or three way and use 10 or 12 inch low-frequency drivers. The horizontal coverage is typically 90 degrees wide but some systems employ narrower boxes at the top or wider boxes at the bottom of the array. Using a transition frame (which aligns the rigging on dissimilar systems), system engineers may sometimes hang a mid-format box below a large-format box to cover the closest audience members. Speaker boxes from different manufacturers are not mixed because each system has a particular 'voicing' which may be common to a single manufacturer.

Manufacturers typically provide a spreadsheet or custom program to design arrays. Examples include L-Acoustics SOUNDVISION, Adamson Shooter, Electro-Voice LAPS (Line Array Prediction Software), and JBL Vertec Line Array Calculator. Renkus Heinz offers a program called EaseFocus. It is similar to EASE but has only features and calculations specific to Line arrays. EaseFocus has data for a large number of manufacturers allowing comparison of several loudspeaker systems. Meyer Sound offers a different solution by providing an online system called MAPP Online Pro

The design process starts by entering the dimensions of the room and the required sound pressure level. The program then suggests the number and arrangement of boxes. Alternatively some programs require you to enter the number of boxes and it will predict the resulting sound pressure levels in different parts of the room.

Once designed, the rigging points are hung from the structure, followed by chain motors (or blocks), flying frame and then the speakers. The individual boxes may be connected one at a time or rigged together on the ground and then pulled up. As the array is lifted, individual box angles are adjusted to match the array prediction program. The top frame may have an inclinometer to confirm the angle of the frame or laser attached which indicates the upper aiming point of the array.

If height or lack of rigging points does not permit flying the speakers, the speakers are typically stacked on the stage or on subwoofers using a custom stacking frame. Stacking of line arrays is common in smaller venues and in temporary installations. Compared to flown speakers, they require less vertical dispersion to cover front to back and the resulting array will have little curvature.