Midband THD and midband fluctuations in the frequency response (ripple) are both caused by transverse waves being excited in the cone body. Midband distortion and ripple are both dependent upon the amplitude of the transverse waves. The amplitude of the transverse waves monotonically decrease as the internal friction of the cone body and/or surround increase. Therefore, in order to decrease the midband THD and ripple, the internal friction of the cone body and/or surround must be increased. Finite-element analysis, doppler laser vibrometer modal analysis, and simple experimentation support this hypothesis.
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