Toa FS-970 SERIES - Manual (Page 46)

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13.3. Speaker Line Adjustment and Measurement
13.3.1. Speaker line impedance measurement (using impedance meter)
Measure the impedance of each speaker line, then measure the total impedance of all lines. Record the
planned impedance and measured impedance for future maintenance and inspection. If the planned
impedance is notably different from the total impedance, inspect individual lines again to find and remove the
cause.
Impedance of arbitrary wattage can be calculated using the formula below.
Z = E 2 /P (
Ω)
where E = Rated line voltage (100 V)
P = Speaker wattage (per line)
Note: Disconnect each speaker line from the terminal block inside the main rack, and measure the impedance
of each line.
When the speaker lines are connected to the terminal block inside the main rack, remove the terminal block
by loosening two screws indicated by the arrow in the figure below, and disconnect the speaker lines from the
main rack.
Measure the impedance between C and N and between C and R of the speaker line using an impedance
meter (ZM-104, etc.).
JP-0410 front panel