Impedance measurements – problems and solutions
PROBLEMATICS
The problem of impedance measurement is the need to use a special device that generates alternating voltage (AC).
Impedance measurement should always precede connecting the loudspeaker line to the amplifier in 100V audio systems. The problem of impedance measurement is the need to use a special device that generates alternating voltage (AC). Impedance measurement, although its value is given in ohms (Ω), cannot be performed using a regular multimeter due to the direct current (DC) used. Impedance measurement using modern meters is virtually immediate and non-invasive. The meter emits a signal with a frequency of 1kHz, less often 700Hz, to the loudspeaker line and measures their impedance. The sound of the same frequency is heard on the entire line. Depending on the meter used, the reading may refer to the power of the loudspeaker line, expressed in watts, or to the impedance, expressed in ohms, which then needs to be converted to power, expressed in watts, using a formula.
R = U² / P
solution
Performing the measurement is limited to connecting the meter to both wires of the loudspeaker line and pressing the "test" button, then reading the values from the display. In the case of automatic meters, the device changes the measurement ranges itself, in the case of less advanced devices it is necessary to select the measurement range to match the loudspeaker line. Depending on the meter, we obtain the result in watts or ohms.
