Measuring Speakers. The Map Is Not The Territory.

Here is something that I believe is very relevant to several of the questions being debated about how to measure speakers to achieve good subjective correlation.

Remember, all these types of measurements, Allison’s, Toole’s, Beck’s, Geddes’, mine, anyone’s, are based on models of system behavior. They are not measurements of fundamental physical quantities that we like to imagine they are.  Thus, any of these measurement sets, can at best only approximate the perceptual response certain types of music, under certain conditions.  Take just one example: Music has both sharp transients, and legato, steady-state elements. Even at a fixed point in space, even in an anechoic chamber, the signal envelope of music or speech has modulation time-constants that span a wide range.

Some musical events are much shorter than typical early room reflections, some are much longer than typical listening room decay times.  Why should it be that any one model of room interaction is “best?”  Even if it is statistically most often correlated somehow with listener preference, that DOES NOT MEAN that it is necessarily the measurement model that best quantifies the reproduction of each and every piece of music or recording method. There simply cannot be one perfect measurement technique. If there was, certainly, there would be fewer design approaches on the market.

This hints at the same dimensional transformation problem I was discussing earlier. Ultimately, its about transform reversibility and information entropy. It can be mathematically shown that there exists an infinite set of distinct and different transducers which can satisfy any given criteria of accuracy, if the number of channels is finite. Thus, there cannot be either one perfect measurement, or one perfect loudspeaker response.

(Edited from a post of mine a few years ago at www.classicspeakerpages.net.)

 

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