The line array effect of the narrowing of the beam with increasing frequency was first demonstrated by acoustical pioneer Harry Olson. He published his findings in his 1957 text, Acoustical Engineering. Olson used line array concepts to develop the column speaker in which vertically aligned drivers in a single enclosure produced mid-range output in a wide horizontal and narrow vertical pattern. Line arrays have been around for over half a century but until recently most were voice range only. The application for these were for highly reverberant spaces where a narrow vertical design kept from exciting the reverberant field.