MEASUREMENTS

I used DRA Labs’ MLSSA system, a calibrated DPA 4006 microphone, and an Earthworks microphone preamplifier to measure the Bowers & Wilkins 804 D4’s frequency response in the farfield. My primary axis for the measurements was level with the tweeter, but I also performed a series of tests on an axis level with the midrange unit, which is 36" from the floor, the height of my ears in my listening chair. I used an Earthworks QTC-40 mike for the nearfield and in-room responses.

Bowers & Wilkins specifies the 804 D4’s anechoic sensitivity as 89dB/2.83V/m. My B-weighted estimate was the same. The 804 D4’s impedance is specified as 8 ohms, with a minimum value of 3 ohms. The solid trace in fig.1 indicates that the drops below 2 ohms between 22Hz and 33Hz, 62Hz and 116Hz, and 663Hz and 886Hz. The minimum EPDR is 1 ohm from 88Hz to 110Hz and 1.6 ohms at 886Hz. The 804 D4 must be used with amplifiers that don’t have problems driving 2 ohms.