Blat Distortion in Loudspeakers

Unacceptable distortion, sounding like a “blat” on bass notes was reported for some models of 4 X 6-inch loudspeakers in certain 1992 prototype vehicles. A study was initiated to find the cause of this distortion and to develop a specification to limit it to acceptable values. The cause of the distortion was determined to be a rapid increase in suspension stiffness at large cone excursion. The specification is based on the sum of the weighted acoustic amplitudes of the 4th through 10th harmonics of a sine wave input at 8.0 volts.