He is known for the commonly used Thiele/Small parameters for loudspeaker enclosure design, which are named after Small and his colleague Neville Thiele.
He gained experience in electronic circuit design for high-performance analytical instruments at the Bell & Howell Research Center in California from 1958 to 1964.
After a working visit to Japan in 1964, he moved to Australia, where he got a part-time job at the University of Sydney as a teaching assistant in the electronics lab.
Upon completion of his Ph.D., he published a series of nine papers—now considered classics—on the low-frequency analysis of closed-box, vented and passive radiator loudspeaker systems.
He taught for a number of years at that university, but returned to industry in 1986 as Head of Research at KEF Electronics Ltd. in Maidstone, England until 1993.