On the Design and Installation of Column Loudspeakers

Abstract

The economic utilization of available acoustic power is of major consideration particularly in sound reinforcement systems installed in theatres, auditoria, cinema halls, assemblies, etc. The advent of column loudspeakers has been welcome, as with the help of such speakers acoustic power may be beamed through a narrow angle to the desired audience.

The loudspeaker columns designed comprise six or seven elliptical cone speakers, 15 × 10 cm. diameter, mounted one above the other in the form of an array in a wooden cabinet, the inside of which is lined with sound absorbing material. In front of the cones is a long tapered slit which helps to diffuse high frequencies in the horizontal plane. Tests under fairly free-field conditions show that the vertical polar response is ±10° at 1000 c./s. and ±20° at 400 c./s., and the horizontal polar response is ±50° over the major part of the audio frequency band. The useful frequency response of the column is 100–7500 c./s.

While objective tests, conducted in typical indoor and outdoor installations, indicate fairly uniform sound distribution over the audience area, subjective tests reveal that listening conditions considerably improve with column loudspeakers.