PSB Alpha A/V loudspeaker Measurements part 3

Nevertheless, when you look at the plot of the Alpha's spatially averaged in-room response (fig.7), lacks of energy can still be seen in the middle of the midrange and between 1.25kHz and 3kHz. In my auditioning, I picked up on this as an upper-midrange forwardness.

Fig.7 PSB Alpha A/V, spatially averaged, 1/3-octave, free-field response in JA's listening room.

In the time domain, the step response (fig.8) indicates that the Alpha's drive-units are connected with the same positive acoustic polarity, with the HF unit leading the woofer slightly in time. The discontinuity in the step response around the 5ms mark indicates a strong reflection, possibly the woofer's backwave bouncing off the inside of the cabinet and coming back through the cone. The PSB's cumulative spectral-decay plot (fig.9) does indicate a dip, and then some delayed energy just above the upper-midrange peak, both of which might be associated with this reflection. Other than some hash at the top of the tweeter's passband, this plot is quite clean. It also is definitely cleaner overall than that of the 1992 Alpha.---John Atkinson

Fig.8 PSB Alpha A/V, on-axis step response at 50" (5ms time window, 30kHz bandwidth).

Fig.9 PSB Alpha A/V, cumulative spectral-decay plot at 50" (0.15ms risetime).

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