About perceptivity of narrow-band frequency response variations of loudspeakers

Abstract

Many loudspeakers show peaks and gaps at 1 kHz caused by the connection of the hard cone and soft surround, which produces interferences and complex vibrational modes. Great efforts are made by the speaker manufacturer to avoid this by changing the surround geometry and material, whereas primarily knowledge about the perceptive limits of the peaks and gaps in frequency response would be necessary. For this investigation line spectra with equal amplitudes and statistical phases between 1 Hz and 20 kHz were calculated by a personal computer. At 1 kHz spectral enhancements or gaps with a bandwidth of 1 Hz or of a half, one, or two critical bands were realized with five different critical band levels. Ten test persons had to compare the first line spectrum with equal amplitudes (anchor) with the second signal with spectral changes in a yes–no procedure presented by an earphone with free-field equalizer at a SPL of 70 dB. The just-noticeable changes in spectral envelope are different for enhancements and gaps and depend on the bandwidth and the critical band level of the variations. They can be explained with calculated masking patterns and literature data.