(horns) coupled to compression drivers. Each horn must have a very narrow vertical and a very wide horizontal dispersion. Rather than using constructive and destructive interference, horns achieve directionality by reflecting sound into a specified coverage pattern. In a properly designed line array system, that pattern should closely match the low-frequency directional characteristic of the array. If the array's vertical dispersion is 60 degrees and there are 12 boxes, then each horn would need to have 5 degree vertical coverage. (Narrow vertical coverage has the benefit that it minimizes multiple arrivals, which would harm intelligibility.) If this is achieved, then the wave guide elements can be integrated into the line array and, with proper equalization and crossovers, the beam from the high frequencies and the constructive interference of the low frequencies can be made to align so that the resulting arrayed system provides consistent coverage. Configurations Two configurations that are rarely used are the straight and curved array. The problem with curved arrays is that they are not very well suited to the average venue. While the bottom half will be angled down to provide extra coverage at locations close to the front of stage, the top half will be angled upwards at the ceiling. Also, the problem with straight line arrays is that the beam is far too narrow at high frequencies. A solution to utilize the best features of both arrays is to use a curvilinear or ‘J’ array. This is made up of a straight line portion and a curved portion, normally at the bottom. This provides a long throw straight line component for people relatively far away, while the curve at the bottom acts as an in-fill for the area underneath the array that would otherwise be neglected Spiral arrays are the next development from J-arrays, and have a superior frequency response due to their similar polar pattern at shifting frequencies, while still retaining the long throw and in-fill benefits that J-arrays provide. The concept is that spiral arrays are curved all the way along the array, but the curve is progressive. This means that the top of the array is almost straight with angles of 1° between boxes, and increases at the bottom to between 6° and about 10°. A well designed spiral array could have an almost constant directivity pattern with frequency, with some small lobes exhibited at low frequencies. Design and rigging Large-format