9th AES MEMBERS SHOWCASE

BRIEF:

Simple truncation of the reflections in the impulse response of loudspeakers measured in normal rooms will increasingly falsify the response below about 500 Hz for typical situations. Well-known experience and guidance from loudspeaker models allow the determination of the lowest frequency for which truncation suffices. This paper proposes two additional strategies for achieving much improved low-frequency responses that are complementary to the easily-obtained high-frequency response: (a) a previously published nearfield measurement which can be diffractively transformed to a farfield response with appropriate calculations, here presented with greatly simplified computations, and (b) a measurement setup that admits only a single floor reflection which can be iteratively corrected at low frequencies. Theory and examples of each method are presented.

BIOGRAPHY: 
John hails from the Netherlands but received all of his education in Canada, with a B.Eng. in 1963 and Ph.D. in physics in 1967, both from McMaster. After a two-year postdoc in Cambridge, UK, he came to the fledgling University of Waterloo.  Early research in high magnetic-field low-temperature properties changed to audio in the 1970’s.  John is a Fellow of the Audio Engineering Society, a recipient of its Silver Medal and several Publication Awards. Together with his colleague Stanley Lipshitz and a number of graduate students they formed the Audio Research Group at the University of Waterloo, studying topics such as crossover design, measurement techniques, dithered quantizers, and acoustics. John retired in 2006 but still had a few graduate students and he also continues with some projects such as today’s topic.