Neville Thiele (left), Richard Small
Speaker design has long been considered some kind of black magic. Yet a major step forward came when two researchers, following earlier work by Leo Beranek, published their findings regarding the relationship of loudspeaker parameters to low-frequency performance in vented cabinet enclosures and simple methods of measuring them. Among these were the driver’s free-air resonance, electrical and mechanical Q, DC resistance, efficiency, piston area, thermal power rating, etc.
In 1961, an Australian broadcast engineer named Neville Thiele published a paper in a radio/electronics journal describing his work in simulating loudspeaker response as electrical filters as a means for speaker design. Several years later, Richard Small, an American studying in Sydney read the paper and convinced the University of Sydney to let him enroll for a Ph.D., expanding and refining its premise. With the help of colleague Robert Ashley, Small convinced the AES to reprint Thiele’s original paper in 1971 and followed it up with a series of his own papers. The effect of the Thiele-Small research was dramatic, not only influencing manufacturers to provide more details about the drivers they built, but also bringing about a new era in the predictability of loudspeaker response based on enclosure volume and port dimensions.