I used DRA Labs' MLSSA system and a calibrated DPA 4006 microphone to measure the Stirling Broadcast BBC LS3/6's frequency response in the farfield, and an Earthworks QTC-40 for the nearfield responses. (I measured S/N SB88019A.) The testing was primarily performed without the speaker's grille; I did repeat some of the farfield measurements with the grille in place. Stirling specifies the LS3/6's voltage sensitivity as 87dB/W/m; my estimate was significantly lower, at 84dB(B)/2.83V/m.
How the LS3/6's impedance magnitude and electrical phase angle vary with…