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A simple method for measuring the peak linear excursion capability (Xmax) of loudspeaker drive units is presented. The method measures the acoustic amplitude modulation of a small high-frequency signal by a very low-frequency signal. The low-frequency signal is increased to produce a target peak-to-peak modulation. A physical measurement of the peak-to-peak diaphragm excursion is made and defined to be twice Xmax.

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.

Delayed arrivals of a stereo source are manipulated to suppress undesirable vehicle cabin acoustics and replace them with optimum acoustics for reproduction of commercial recordings. These optimum playback acoustics are derived from concert hall and listening room measurements. An experimental vehicle sound system implementing these concepts is described.