d&b D80 - Manual (Page 58)

3. As a next step, execute a System calibration.
Þ The calibration process identifies the actual load
impedances for each channel. The result will be stored as
a reference and used to calculate the upper and lower
limits for the tolerance band.
To verify the correct connection of cabinets and amplifiers,
the calibration result can be compared with the typical
impedance values for d&b loudspeakers as listed in the
Þ Appendix: " Typical impedance (Z) values" on page
76.
4. Run System check
Þ Executing a System check after the event will repeat the
measurement and display all values that are outside of the
tolerance band, indicating a possible damage to the
system components.
When a sound system is repeatedly used in the same
configuration for which a calibration file exists, the System
check procedure can also be used before the show to
verify the system's correct setup.
A System check will only provide valid impedance values,
if the amplifier has been calibrated before the check with
the load connected or if a valid calibration file has been
loaded using R1.
10.7.2. Load monitoring (LM)
Features
The d&b Load monitoring function is related to the System check
function and serves to identify a possible loudspeaker malfunction.
Function
The calibration process, performed from the System check menu
with the completely set up system, determines the impedance for
each channel and calculates the related upper and lower
impedance limits.
While the system is operating, d&b Load monitoring continuously
monitors the load impedance separately for both frequencies. It
detects any changes in loudspeaker impedance and reports an
error if the limits are exceeded. For this purpose, Load monitoring
uses inaudible pilot signals which are faded in for approximately 2
seconds in user defined intervals.
NOTICE!
The resolution of Load monitoring regarding failures of single
components depends on the type and the number of loudspeakers
connected to each channel.
The maximum number of cabinets which can be operated in
parallel by one amplifier channel in order to be able to detect a
failure of a loudspeaker component is listed in the Þ Appendix:
" Max. number of cabinets operated in parallel" on page 78.
Load monitoring does not work if:
–
the amplifier is switched off or switched to standby mode.
– the respective channel is muted.
– the pilot signal level is too low.
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