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RE: Averaging of multiple locations

Posted by Dave_K on December 11, 2014 at 08:57:35

In Reply to: RE: Averaging of multiple locations posted by Inmate51 on December 10, 2014 at 20:42:43:

On the contrary, in a home environment it might be "good enough" to take a single measurement, but in a control room I think it's more important to make measurements over the full listening area. First, because performance is more critical. Second, because a working engineer is not stationary; they need to move around a bit especially in front of a big console.

Even if you lock your head in a vice at the sweet spot, your ears aren't in the same location. They are ~7" apart and if you place the microphone at the location of your two ear openings, there will be differences between the two responses which are visible on plots of amplitude and phase vs. frequency. These differences are meaningless. And in every system I've listened to, with the possible exception of extreme nearfield setups, I can move my head left and right a foot and the only significant changes in the sound are a shift in the center of the soundstage because you're not equidistant between the speakers, and subtle shifts in treble balance as the effective toe-in angle changes. The measured responses at the left-of-center and right-of-center positions will show changes in the pattern of peaks and nulls, but these differences aren't audible.

My point is that a single unsmoothed, unaveraged in-room measurement is dominated by features which are inaudible. These aren't details, they are 'noise' obscuring the things that are actually important. You want to suppress this 'noise' so that the 'signal' is more apparent. That requires smoothing the response with a filter, or averaging multiple measurements from different locations around the listening position, or a combination of both. Spatial averaging helps separate the response deviations that are really audible from those that aren't, and it also allows you to use less smoothing. A spatially averaged result with 1/12 octave or even 1/24 octave smoothing will reveal more meaningful detail than a single point measurement with 1/3 or 1/6 octave smoothing.

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