As some, or most of you know, I'm a scientist by profession. As JA also has an engineering background, I thought I would post my experiences with using Design of Experiments as a way to assess integration of subwoofers into a "mains" system.
In recently acquiring a REL subwoofer, and with the data acquisition system that my friend Tim helped (greatly..thanks, Tim) to set me up with, it naturally occured to me that one could use a formal system of experimentation called Design of Experiments (henceforth referred to here as DOE) to formally and reproducibly optimize the integration of the sub with the mains to provide the ideal room response.
Design of Experiments is different than the classic scientific "change one factor, leave everything else the same" (One Factor At A Time or OFAT) approach that scientists and engineers were taught in school and are still primarily using to this day (much to their detriment in many cases). While the basic concepts of DOE have been around since the 1700s, it was originally formalized by the statistician R.A. Fisher. The difference between DOE and the classic OFAT approach is that you can change [i]multiple factors[/i] at a time, set the the factors different "levels" (effectively, high or low), and run a series of a defined pattern of experiments (even in random order), measure the response (the effect you are interested in) and the DOE will tell you which factors are most important to get the response you want, and more importantly, what, if any INTERACTIONS there are between factors.
The ability to examine interactions between factors is one of the most important aspects of DOE, because if there are interactions involved between complex set factors and their resultant responses, you will never be able to deconvolute them without DOE, or if you can, it will not usually be without pure chance or luck, or without spending a lot more time, money, and effort in trying to figure them out, and often, you will still not figure them out in terms of which of the factors have the biggest effect from a statistically valid point of view.
Given this, I set out to to perform a set of experiment to see if I could determine the optimal settings of speakers, REL sub settings and other factors, like grilles on or off, speaker toe-in, port plugs, etc. that would optimize the in-room response.
My next post will be a brief introduction to DOE, and setting up the precepts of the experiments.