The ability to choose the most appropriate loudspeaker for a particular enclosure is directly related to your understanding of the performance data that manufacturers provide with their products. Prior to 1970, there were no easy or affordable methods accepted as standard in the industry for obtaining this data. The recognized methods were expensive and often unrealistic for the thousands of individuals needing loudspeaker performance information.

Thiele-Small Parameters

In the early seventies, several technical papers were presented to the AES (Audio Engineering Society) that resulted in the development of what we know today as ‘Thiele-Small Parameters’. These papers were authored by A.N.Thiele and Richard H. Small. Thiele was the senior engineer of design and development for the Australian Broadcasting Commission and was responsible at the time for the Federal Engineering Laboratory, as well as for analyzing the design of equipment and systems for sound and vision broadcasting. Small was, at the time, a Commonwealth Post-graduate Research Student in the School of Electrical Engineering at the University of Sydney.

Thiele and Small devoted considerable effort to show how the following parameters define the relationship between a speaker and a particular enclosure. However, they can be invaluable in making choices because they tell you far more about the transducer’s real performance than the basic benchmarks of size, maximum power rating or average sensitivity.