An old truism of audio wisdom states, “point the loud side toward the audience.” It’s good advice for a single speaker. With two or more, a powerful new force arises that can steer the sound to parts unknown: summation. It’s hard enough to visualize the shape of sound from a single speaker, but we must dig much deeper to understand combinations. The interactions differ at every frequency and every location. Although complex, they are predictable and we have the decoder keys: level and phase offset.
summation n. addition, finding of total or sum; summing up.
sum n. & v. total amount resulting from addition of items.
Concise Oxford Dictionary
Understanding summation is a big challenge but an even bigger payoff. The understanding ...