This chapter explores the dark side of speaker summation: cancellation. The most well-known cancellation mechanism is polarity reversal between adjacent elements. The normal placement rules for full-range speakers do not apply to subwoofer arrays. The beam bends toward the synchronous time center unless the level side provides a resistive force, i.e. isolation. A coupled line source is used in the vertical plane. The TM array is a unique solution to the challenge of large-scale "in the round" applications. The end-fire is the superior cardioid steering configuration for its high efficiency and minimum phase offset on the front side. Delay-induced beam steering is essentially a willfully misaligned spatial crossover. The spectral variance of proportional beamwidth strikes again. The gradient's operating principle is to sync by delay and cancel by polarity. The lowest/widest frequencies are steered more while the highest/narrowest are steered less, which nets a balanced cardioid pattern.