Today's Lesson

One big way comb filtering can be created is by using multiple loudspeakers. In stereophonic reproduction, left and right loudspeakers are placed equidistant from each other. Both direct sounds will reach the listening position and your ears at the same time with all frequencies perfectly in phase. No comb filtering will happen. 

However, in any non-ideal environment where the listening does not take place precisely at the defined listening position, comb filtering will occur as the listener is sitting closer to one loudspeaker than the other, causing some frequencies to cancel and others to sum together. This is very common when using a stereo configuration in a live sound setting and unfortunately cannot be completely avoided. Sorry.

If the goal is to cover a large area using point-source loudspeakers like QSC CP, K.2 or KW Series, make sure to select loudspeaker models that have a very controlled directivity. For example the K12.2 has a dispersion radius of 75 degrees in all directions. This is good. We can use this information to direct the two loudspeakers so that the sound emitted from each will not interfere with the other and comb filtering will not be possible. If the two loudspeakers are too close together or angled towards each other, the signals from each will overlap and create comb filtering.  By placing, each loudspeaker in such a way that there is the least possible overlap between their coverage, we will ensure there is almost no comb filtering occurring.

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