Way back in 1930 a paper appeared in the “Journal Of the Acoustical Society” entitled “Directional Radiation of Sound”(1) which discussed the essential elements and concepts behind what became known as column arrays or line source arrays, both straight vertical and curved versions.
In 1940, Harry F. Olsen in his legendary book “Elements of Acoustical Engineering” (2) presented all the mathematics and technology needed to produce 60-, 90- and 120-degree arc line sources.
In 1954 Leo Beranek, in his book “Acoustics” (3) showed the measured responses of both line sources and curved line sources variations.
In 1963 David Klepper and Douglas Steele (4), published a paper in the “Journal Of the Audio Engineering Society” titled “Constant Directional Characteristics from a Line Source Array” and showcased a number of actual installation and application of the theories offered almost 30 years earlier.
A considerable number of additional technical papers, white papers and research papers have been published in the more than eight decades since the original 1930 presentation. This information is important because the products in this roundup are the great grandchildren of those early concepts, theories and the initial implementations they produced. (Note: there is short list of references is at the end of this article, and any online search will produce many, many more.)
Many of the ideas and concepts developed by the early practitioners were simply not fully achievable with the technology and hardware available at the time. The digitally steered, DSP-controlled products listed here are can finally fully implement all the theory and concepts and realize the kind of performance and speech intelligibility originally predicted.
One of the most important capabilities of these products is to produce one or more “steerable beams” above roughly 1 kHz. These beams are just like spotlights, they can be tilted, aimed,