Quantification of Subwoofer Requirements, Part II: The Influence of Lower System Cut-Off Frequency and Slope and Pass-Band Amplitude and Group Delay Ripple
The audibility of changes in the lower system cutoff frequency and slope and in passband amplitude and group delay ripple has been investigated for a subwoofer system for two situations: a real loudspeaker in an anechoic chamber and a simulated system reproduced via headphones. The signals were program material, selected to ensure a sufficient energy content at the relevant frequencies. The experiments were conducted with six subjects with normal hearing using a paired comparisons procedure. The subjects evaluated the magnitude of lower bass and upper bass in relation to a fixed reference condition. The first experiment investigated the influence of filter order (second, fourth, and sixth) and lower cutoff frequency (20, 35, and 50 Hz) at three reproduction levels and for four programs. The second experiment examined the influence of amplitude and delay ripple corresponding to four reverberation times at three reproduction levels and for four programs. The results of the first experiment show that the lower cutoff frequency has a significant influence on the perceived level of lower and upper bass reproduction, independent of reproduction levels. The filter order was found not to be of significant importance to the conditions investigated. The results of the second experiment show that the amplitude ripple has a significant influence on the perceived level of lower and upper bass reproduction. The results further show that there were no significant differences between the data produced by the two reproduction methods.:
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