Throat Distortion: Rent Com Inc: Audio Visual, Video, Projection, Presentation Rental AV Equipment

Throat Distortion

Distortion is a prime consideration for our middle decade device, especially so since the existing array of commonly used devices (12- and 15-inch woofers, 2-inch compression drivers) have inherently high distortion levels due to operation at the fringes of their optimum passband.

Throat distortion, for a given horn flare, acoustic power level and frequency, is inversely proportional to the square root of the throat area. This means that as throat area decreases, distortion increases. The true "throat area" of a compression loudspeaker, however, is not the area at the throat of the horn (the exit of the driver). It is the area at the entrance to the phase plug, that is, the combined area of all the phase plug slits as seen by the diaphragm. This "phase plug throat" area, because it is smaller than the horn throat area, is the area that must be considered for the control of distortion and acoustic power output.

The M4's phase plug throat area is about 8 square inches. The phase plug throat area of a popular 2-inch exit driver (2-inch horn throat, that is) is about 1.25 square inches. Considering just this one factor, phase plug throat area, it would take more than six of this popular 2-inch driver to equal M4's acoustic power output and distortion level.