The Meyer Sound MM-4XP Miniature Loudspeaker (Fig.7) is a self-powered speaker that provides an approximate four-inch by four-inch cell. Thus, with this speaker we can make either a line array or a 2D grid with four-inch spacing. While this speaker is relatively expensive, it exhibits excellent power and linearity for its size.
The MM-4XP power output is 113 dB at 120 Hz. Extending the low end beyond the spatial-hearing range down one octave requires a 6 to 12 dB sacrifice in power for the same peak diaphragm excursion.18Thus, the extended-low-end array is plenty loud--and we may cross over to a subwoofer below the spatial hearing range.