AES British Section lectures - February 2007
Experiments with a Multi-Element Steerable Loudspeaker Array
Laurie Fincham, THX
www.thx.com
A two-dimensional loudspeaker array, with both rows and columns of drive units, is capable of providing directivity control in all directions. The design of such systems is difficult and not until relatively recently has the processing power needed to provide good directional control over a wide frequency range been viable. The design of suitable transducers for inclusion in such an array is another matter altogether. The dual design requirements of close spacing, for accurate high-frequency control, and the need for a large effective radiating area for good bass output are not inconsiderable. Most of the existing products on the market claiming some form of directional control use miniature drivers that are neither small enough for high-frequency control nor large enough for adequate bass output. This paper will present theoretical and practical design criteria for line arrays with controllable directivity, including techniques for eliminating spatial aliasing over the audible bandwidth. Demonstrations will be given of such a line capable of real time changes in both directivity and beam direction with multiple beam overlays.
Laurie has spent almost the whole of his working career, spanning more than four decades, in speaker design. During that time he has designed drivers and systems for professional, domestic and musical instrument applications. After working for Goodmans Loudspeakers and Celestion he was for 25 years the technical director for KEF Electronics before moving to the USA in 1993 to work first with Infinity Systems and then, since 1998, with THX. He has a keen interest in measuring and modelling methods and while with KEF he developed, along with Mike Berman and Rex Leedham, the first FFT-based measurement system in 1971. At THX he continues to pursue a lifetime passion for designing speaker systems and associated electronics. He is a life fellow of the AES and a member of the Acoustical Society of America, and has served as the chairman of the British Section and as a governor and VP International of the AES. A keen jazz fan he worked, in between loudspeaker design assignments, as a semi-professional musician, playing the double bass with many soon-to-be famous jazz musicians who he remembers fondly but it is doubtful that they do him.
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