Dolby Laboratories CP65 manual Do not adjust

Page 46

5-14

B-Chain Alignment Procedures

a. Setting Room Equalization

Step

Action

Indication

No.

 

 

16

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

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+10

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

+5

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

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2.0

 

 

 

 

 

 

 

 

 

8.0

 

 

 

 

.05

 

 

.1

 

 

 

 

.2

 

 

 

 

 

.4

 

 

 

 

 

.8

 

 

 

 

1.6

3.15

 

6.3

 

 

 

 

 

12.5 kHz

17

✓ X X

 

 

 

 

 

dB

 

 

 

 

 

+10

 

 

 

 

 

+5

 

 

 

 

 

0

x

 

 

 

 

 

Do not adjust

 

 

 

 

–5

 

 

 

 

2.0

–10

 

 

 

 

8.0

.05 .1

.2

.4

.8

1.6 3.15

6.3 12.5 kHz

5-15

B-Chain Alignment Procedures

a. Setting Room Equalization

Notes

While observing the frequency response curve on the RTA, adjust the treble control on the Cat. No. 64 for a flat response as close as possible up to 2 kHz, followed by a 3 dB per octave roll-off above 2 kHz (the frequency response specified in ISO Standard 2969). Once you set this control, do not change the setting during the rest of the room equalization procedure.

The next step is to fine-tune the equalization by adjusting the third-octave controls on the Cat. No. 64 equalizer. There are certain rules to keep in mind:

•The object is to achieve the final adjustment of room equalization with all of the controls as close to the 12 o’clock position as is possible.

•All of the equalizer controls interact with each other so you should not start at the low end of the response curve and merely work your way to the high end. As each control is adjusted, the response obtained by adjustment of adjacent controls is affected.

•Start at the center frequency and attempt to achieve results with cut rather than with boost. The desired curve is a flat frequency response up to 2 kHz,falling at 3 dB per octave to 8 kHz (1dB per third-octave band). Do not change the position of the 50 Hz or 40 Hz band controls nor turn the controls for bands above 8 kHz unless you have modern loudspeakers. This protects the loudspeakers and power amplifiers from damage and prevents distortion of the reproduced sound.

•If modern woofer systems (vented-box direct radiator enclosures) are installed in the theatre , moderate bass equalization down to 40 Hz may be used.

•Once an adjustment seems OK, work on the frequencies to either side of it. You may find that a cut at one frequency is followed by a slight boost at adjacent frequencies.

•Control settings should not fall outside the band between the 9 o’clock and the 3 o’clock positions.

•Avoid diametrically opposed adjacent control settings.

Adjust for the response that is closest to the curve shown. The diagrams show a typical equalization procedure, from the response before equalization to the final equalization.

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Contents Model CP65 Cinema Processor Dolby Laboratories Inc Headquarters Table of Contents Section Reference Block Diagrams Introduction Page Section Equipment Required Smpte Buzz Track Stereo Optical Surround Level Cat. No Jiffy Test Film Cat. No 2 Listen . . . Film Cat. NoSection Initial SET-UP and Installation Voltage Acceptable Setting Voltage Range Fuse Type Next, check the jumpers in the following locations Cat. No , Power Supply Module Cat. No , B-Chain CardCat. No , Control Logic Card J2 NON-SYNCCP65 Backplane Standard CP65 or CP65ACP65-300 High Low Subwoofer subwoofer Output output These Modules are Necessary for Bypass Operation Reduction Module Slot Card Function Cat. NoTwo-channel Noise Channel DecoderContains a semi-regulated power supply with Voltage Setting Fuse Type InternationalIEC Notices HUM Problems Room lighting dimmer controls SCR-TYPEPage Section AN Overview of the Alignment Procedure Aligning the B-ChainPage Page Section Chain Alignment Preliminary Procedures Action IndicationLamp Voltage Optical Preamplifier Adjustments Chain Alignment Procedures Optical Preamplifier Adjustments 222 CAT. no Test Film Oscilloscope Traces Repeat CAT no Repeat 1 →Magnetic Preamplifier Adjustments Magnetic Alignment 100mV Section Chain Alignment Setting Room Equalization BypassLoudspeakers and Crossovers Amplifiers GeneralChain Alignment Procedures OffRepeat ActionChain Alignment Procedures Setting Room Equalization Do not adjust Paul Setting Room Equalization b. Adjusting L,C,R Gain 14 → 21 R 14 →Setting Mono Gain 79 dBCChain Alignment Procedures Subwoofer Alignment Cat. No 90 dBC 85 dBCFrom Step NoSelect format 04 Dolby Stereo A-Type Same AS 441Surround Equalization Alignment Cat. No Surround Equalization Alignment Cat. No Notes Cat. No 441Desired 88 dBC Bypass Thumbwheel Switch Adjustment of Surround DelayMsec Setting Chain Alignment Procedures Adjustment of Bypass Gain Xx dBCFrom Xx dBC -3 dB Yy dBCAdjustment of Non-sync Gain Press the format 60 non sync switchAuto Freq Adjustment of Mono Gain and Equalization Notes Repeat page 5-20 StepChain Alignment Procedures Final Checks Press the format 04 Dolby Stereo A-type switchSection Reference Diagrams Cat. No Dual Noise Reduction Module Inputs Cat. No Optical Bass Extension and Surround Equalizer Card Cat. No B-Chain Facilities Card Cat. No Power Supply Card Cat. No Transformer Module Inputs Cat. No Control Logic Card 15V +12B Cat. No +24V +15V+15M Appendix a Checking Phasing of Speakers Appendix B Effect of Changes in Slit Height on Slit Losses Operation Appendix C CP65M Mono InstructionsCat. No a Circuit Description Schematic Cat. No a Appendix D Backplane Connections List Terminal Block TB3Connector J18
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