Dolby CP750 Digital Cinema Processor Manual - Projectionniste.net

Final Output-Level Calibration
x‐curve without overcompensating. Remember that the SMPTE tolerance is ±3 dB,
although closer results are often easily achieved.
5.6.4 Adjusting LFE Channel EQ
Begin with zero cut and observe the worst peak within the spectrum. Adjust the Center
slider until the frequency matches the peak, and then adjust the Cut to flatten that region.
Adjust the Q (width) and Cut, until the smoothest response is achieved.
Equalization facilities for the subwoofer channel are different than for the other channels.
The process in this manual is designed to correct the principal room resonance in the
operating range of the subwoofer. The subwoofer equalizer is a cut‐only filter, with
adjustable center frequency (25 to 125 Hz), Q (center width, selectable among four values),
and amount of cut (0 to 12 dB).
After all the full‐range channels have been equalized, follow these steps:
1. Click LFE to make it the active channel.
2. Using the slider reduce Cut to 0 dB. This disables EQ so that you can determine the
low‐frequency resonant peak to be equalized. Note the band where the unequalized
peak appears.
3. Using the slider increase Cut to its maximum, 12 dB.
Using the Center slider moves the dip in the frequency response along the frequency
axis of the RTA display.
4. Adjust the center frequency so that the center of the dip is in the same band as the
peak displayed in the previous unequalized frequency response.
5. Using the Cut slider, slowly reduce the amount of cut to flatten the dip. The center of
the dip should be at the same level as the skirts.
6. Click to check other Q values for the flattest possible frequency response.
5.7 Final Output-Level Calibration
Once room equalization is complete, the sound pressure level in the theatre can be set
accurately.
5.7.1 Main Channels
If a microphone multiplexer is being used in your auditorium, move Mic 1 to room center
two‐thirds back from the screen.
1. Click the Room Levels tab to activate it.
2. Using the sliders, set L, C, R to 85 dB, and the surround channels to 82 dB.
Note:
Because the sound pressure level calibration was performed earlier, a recalibration
is not required unless the microphone placement has changed. Repeat the steps in
Section 5.4 if necessary.
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