Mackie HR824 Service Manual page 17

LOW FREQUENCY AMP TESTS continued
LOW FREQ SWITCH TEST
Set your audio signal generator for an output of 300mVrms (-10.46dBV)
Set the Acoustic Space switch to position A (Quarter Space).
Measure the output into the 4 ohm load for the three positions of the LOW FREQ switch.
Do these measurements fairly quickly because the amplifier will be warming up.
The level of the output may be different from that shown, due to the factory settings of
the calibration pots. Just make sure that the speaker under test follow the overall shapes
and the switch is working.
NOTE: the graph of the 37 Hz position is the same as measured on the previous page
(position A), so no need to repeat it, just do 47 Hz and 80 Hz.
30
20
25
15
10
20
15
5
10
5
1
0.0
20
LOW FREQUENCY AMPLIFIER OUTPUT
30 40 50 60
FREQ(Hz)
ACOUSTIC SPACE LOW FREQ
(Keep on A) (Vary during test)
70 80 90 100
30
20
25
15
10
20
15
5
10
5
1
0.0
200
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