Testing KF740 Transducers

The only way to test them without removing the transducers from the enclosure is to measure the impedance at the input (not resistance, but  impedance). Per the attached spec sheet, you should measure about 6.7 ohms on the HF input. If you measure 13-15 ohms, then one of the
HF diaphragms is blown.

The LF transducers are wired in series. The front pair on one input, the side pair on another, so if one of the front transducers is blown, then neither will work. Same for the side pair. Impedance for each pair should measure about 8 ohms.