Dolby Laboratories CP650 Installation Manual download pdf (Page 55)

Dolby

CP650 Installation Manual B-Chain Alignment

4-5

Mic Level Too Low

or Too High

Proceeding

Uncalibrated

6. The CP650 is shipped from the factory with the mic input-level control set to

minimum. If necessary, adjust the mic input-level pot until the center area of the

displayed pink noise moves to the middle of the scope screen. The trimpot is

accessible through an opening in the setup panel.

7. With a sound pressure level meter, measure the noise level in the

room. Hold the sound pressure level meter near the location of

mic 1.

8. Rotate the CP650 front-panel knob until the room reading is shown on the front-panel

screen. The adjustment range is from 45 to 108.5 dB, in 0.5 dB steps. Press OK.

9. Wait while the system automatically calibrates to the room reading. The calibration is

retained in CP650 memory and can be used in future alignments. However, it is

advisable to recalibrate the system when rearranging microphones because the sound

pressure level will vary slightly with microphone placement.

Note: The spectrum analyzer built into the CP650 has automatic

level control covering a range of mic input levels. If,

however, you see an error message reporting mic level too

low or too high, the microphones may require phantom

power.

If the microphone requires phantom power, move DIP switch 3 up (to turn on

phantom power), then press and hold , and rotate the main fader counterclockwise

one step back to the Calibrate SPL menu. Repeat steps 1–9. Or, while watching the

oscilloscope RTA display, adjust the mic gain control to place the flat part of the

signal in the approximate center of the screen. Then press and hold while rotating

the main fader counterclockwise one step back to the Calibrate SPL menu, then

repeat steps 1–9.

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Dolby Laboratories CP650 Installation Manual Page 55