Part 1 of this article presented experimental evidence from a study conducted by the author demonstrating that trained and untrained listeners prefer the same loudspeakers (see reference 1). Part 2 showed that the trained listeners performed 3 to 20 times better than untrained listeners based on their ability to give discriminating and reliable loudspeaker ratings. In part 3, we examine the relationship between the listeners' loudspeaker preferences and a set of anechoic measurements performed on the loudspeakers used in that study.
The mean loudspeaker preference ratings and 95% confidence intervals, averaged across all listeners, are plotted for each of the four loudspeakers (see the graph to the right). According to the definition of the preference scale, listeners liked loudspeakers P and I, were relatively neutral towards loudspeaker B, and they disliked loudspeaker M.
The next graph on the right shows a set of anechoic measurements for each of the four loudspeakers P, I, B, and M, shown in descending order based on their subjective preference rating. Each loudspeaker was measured at 70 different angles around its horizontal and vertical orbits in order to fully characterize the quality of its on and off-axis sounds, and allow removal of acoustical interference effects from resonances, which can cause harmful colorations to the reproduced sound. These resonances are visually presented as peaks and dips in the frequency response. In each graph, the frequency curves represent, from top to bottom, the quality of the direct sound, the average listening window, the first reflections, the sound power, and the directivity indices for the first reflections and the sound power. The reader is referred to references 2-4 for more background on how these measurements were derived and experimentally validated through controlled listening tests.
There are clear visual correlations between listeners' loudspeaker preferences and the set of frequency graphs. Both trained and untrained listeners clearly preferred the loudspeakers with the flattest, smoothest and most extended frequency response curves, as exhibited in the measurements of loudspeakers P and I. Loudspeaker B was rated lower due to its less extended, bumpy bass, and a large hole centered at 3 kHz in its sound power curve. The measurements of Loudspeaker M indicate it has a lack of low bass, and has a non-smooth frequency response in all of its measured curves. Both the direct and reflected sounds produced by this loudspeaker will contribute serious colorations to the timbre of reproduced sounds.
It is both satisfying and reassuring to know that both trained and untrained listeners recognize and prefer accurate loudspeakers, and that the accuracy can be characterized with a set of comprehensive anechoic measurements. The next logical step is to use these technical measurements as the basis for modeling and predicting listeners' preference ratings. This will be the topic of a future post in this blog.
 Sean E. Olive, "Differences in Performance and Preference of Trained Versus Untrained Listeners in Loudspeaker Tests: A Case Study," J. AES, Vol. 51, issue 9, pp. 806-825, September 2003. (download for free courtesy of Harman International)
 Floyd E. Toole, "" J. AES Vol. 23, issue 4, pp. 227-235, April 1986. (download for free courtesy of Harman International).
 Floyd E. Toole, "Loudspeaker Measurements and Their Relationship to Listener Preferences: Part 2," J. AES, Vol. 34, Issue 5, pp. 323-248, May 1986. (download for free courtesy of Harman International)
 Allan Devantier, "Characterizing the Amplitude Response of Loudspeaker Systems," presented at the 113th AES Convention, October 2002.