Sidebar 3: Measurements
I used DRA Labs' MLSSA system to measure the ProAc Response D2R, using a calibrated DPA 4006 microphone for the farfield behavior and an Earthworks QTC-40 mike for the nearfield responses. Though ProAc specifies the Response D2R's sensitivity as 88.5dB, presumably for 1W at 1m, my estimate was somewhat lower, at 85dB(B)/2.83V/m.
The ProAc's specified impedance is 8 ohms; the solid trace in fig.1 reveals that, other than two regions in the midbass and lower midrange, the impedance remains above 8 ohms for the entire audioband. The minimum value is 6.22 ohms…