Line Arrays

Lately, after thinking over some audio concepts, I thought to my self. What makes line arrays so popular? Are they here to stay, or something that could soon be on the way out.

First of all, two main types of speaker arrangements are "summed" and "zonal". Let's start with the more popular system, zonal. Zonal splits up large spaces into smaller zones. With a zonal configuration the speakers are constructed in clusters and aimed at a region or zone, this way each of the speaker boxes can be EQ'd and the volume can be adjusted to get nice even coverage over the entire venue. With this type of system to get the best sound, you want as little an overlap in the box-to-box coverage patterns as possible. The problem is that it can be relatively hard to get excellent sonic transitions from zone to zone. In order to accomplish this, the system would be constructed such that listeners would not be exposed to sound emanating from boxes that are in close physical proximity to each other, yet different distances from the listener. In simple terms, sound from multiple sources arriving to the ear at different times is not good. When projecting sound over varying distances, some issues may arise. The coverage of each box increases in size over distance, meaning the angles between boxes pointed far away should be increased but since the volume naturally drops with distance it means that to maintain volume at distance, you would want to decrease the angles between the boxes to point more loudspeakers at each far away zone. Many times, zonal coverage systems will employ a long throw narrow dispersion cabinet to help counteract this issue.

Zonal Speaker Configurations

On the other hand, a summed configuration covers large acoustic spaces with multiple loud speakers hung together to act as one large loudspeaker covering the entire area. The coverage pattern then can be adjusted to cover the venue by adjusting angels between each individual box. The main challenge with a summed configuration is optimizing cooperation between the various loudspeakers, this is generally achieved by manually adjusting the loudspeakers very close together in order to minimize them acting as separate sources.

Summed Speaker Configurations

A goal with both types of configurations is to avoid having a listener hear two acoustically "separate" sources that are in close proximity to each other that are also not equidistant from the listener. Why does this matter? Well, because non-equidistant sound sources reproducing the same signal creates comb filtering issues that reduce output levels, messes up the frequency response and most importantly, does not sound good to the ear.

Some zonal configuration systems include Nexo's Alpha system, Electro-voice's X-array, and Turbosound's flashlight and Aspect systems are all examples of a zonal system. Much effort was put into these designs in order to achieve distinct and consistent vertical and horizontal coverage projected from each individual box. The building blocks for these zonal systems typically utilize a relatively few loudspeakers that are in each box that are mounted on some sort of horn to assist with pattern control.

The summed output system approach, until recently, was considerably less wide spread with some examples being the Clair Brothers S-4 and the Rat Sound Rat Trap 5, and to some degree the Showco Prism. These systems tended to rely on boxes with quite a few loudspeakers in each box placed in relatively close proximity to each other allowing them to unify their outputs. A major issue with these systems results from the physical space between the loudspeakers themselves which can cause the components to act as multiple sound sources creating box-to-box overlaps, comb filtering and inconsistencies in coverage patterns.

To be continued later...