I used DRA Labs’ MLSSA system and a calibrated DPA 4006 microphone to measure the Bowers & Wilkins 705 S3’s behavior in the farfield, and an Earthworks QTC-40 mike for the nearfield responses. I left off the grille that covers the woofer for the measurements.
B&W specifies the 705 S3’s sensitivity as 88dB/2.83V/m. My B-weighted estimate was a little higher, at 88.9dB(B)/2.83V/m. The 705 S3’s nominal impedance is specified as 8 ohms, with a minimum value of 3.7 ohms. The speaker’s impedance magnitude (fig.1, solid trace) lies below 3 ohms in the bass and lower midrange, and below 2 ohms in the top two octaves. The minimum EPDR values are 2.63 ohms at 56Hz, 2.33 ohms at 117Hz, and 1.92 ohms at 8.6kHz. The 705 S3 needs to be paired with amplifiers that don’t have problems driving low impedances.
