Dolby Laboratories CP65 manual Paul

Page 47

5-16

B-Chain Alignment Procedures

a. Setting Room Equalization

Step	Action	Indication
No.

18

Paul

19

20

5-17

B-Chain Alignment Procedures

a. Setting Room Equalization

Notes

When equalization is completed, the average of the 27 third-octave band controls should be approximately 12 o’clock (not mostly up or down). If you find the controls are set differently, repeat the equalization procedure until you obtain the proper equalization; settings that diverge from this average may result in unpleasant sound.

Although the equalization may be set correctly for the chosen microphone position, it still may not be correct for providing the best sound to the greatest number of seats in the theater. You should therefore check the sound quality at several locations (three or more) in the auditorium with the calibrated microphone and RTA system. If time does not permit this procedure, walk around the theater with pink noise playing. If necessary, adjust the equalizer for a compromise at several seat positions so that all of them sound acceptable.

Mark the settings for each control on the white card provided inside the Cat. No. 64 module.

If the sound quality varies significantly as you walk around, the equalization has not been adequate:

•You may have over equalized. Check the positions of the controls; all should be as close to 12 o’clock as possible.

•There may be phase shift present if the adjacent controls are pointed in opposite directions, especially if you did so to eliminate a sharp dip that resulted from physical problems in the auditorium (horn location, speaker orientation).

•The size of the room may be a multiple of a given wavelength, wall surfaces are parallel, or there may be a severe balcony overhang.There may be reflection off the walls behind the screen or crosstalk from adjacent theatres.

•The seat and seat materials may be too reflective.

•The microphone may have been placed in an untypical position.

Repeat the procedure with the microphone in other average locations in the auditorium. Adjust the controls for the best compromise to fit all of the locations of the microphone.

Image 47

Contents Model CP65 Cinema Processor Dolby Laboratories Inc Headquarters Table of Contents Section Reference Block Diagrams Introduction Page Section Equipment Required Jiffy Test Film Cat. No 2 Listen . . . Film Cat. No Smpte Buzz Track Stereo Optical Surround Level Cat. NoSection Initial SET-UP and Installation Voltage Acceptable Setting Voltage Range Fuse Type Next, check the jumpers in the following locations Cat. No , B-Chain Card Cat. No , Power Supply ModuleJ2 NON-SYNC Cat. No , Control Logic CardStandard CP65 or CP65A CP65 BackplaneCP65-300 High Low Subwoofer subwoofer Output output These Modules are Necessary for Bypass Operation Channel Decoder Slot Card Function Cat. NoTwo-channel Noise Reduction ModuleContains a semi-regulated power supply with International Voltage Setting Fuse TypeIEC Notices Room lighting dimmer controls SCR-TYPE HUM ProblemsPage Aligning the B-Chain Section AN Overview of the Alignment ProcedurePage Page Section Chain Alignment Action Indication Preliminary ProceduresLamp Voltage Optical Preamplifier Adjustments Chain Alignment Procedures Optical Preamplifier Adjustments 222 CAT. no Test Film Oscilloscope Traces Repeat Repeat 1 → CAT noMagnetic Preamplifier Adjustments Magnetic Alignment 100mV Section Chain Alignment Bypass Setting Room EqualizationLoudspeakers and Crossovers General AmplifiersOff Chain Alignment ProceduresAction RepeatChain Alignment Procedures Setting Room Equalization Do not adjust Paul 14 → 21 R 14 → Setting Room Equalization b. Adjusting L,C,R Gain79 dBC Setting Mono GainChain Alignment Procedures Subwoofer Alignment Cat. No 85 dBC 90 dBCStep No FromSelect format 04 Dolby Stereo A-Type 441 Same ASSurround Equalization Alignment Cat. No Cat. No 441 Surround Equalization Alignment Cat. No NotesDesired 88 dBC Bypass Msec Setting Adjustment of Surround DelayThumbwheel Switch Xx dBC Chain Alignment Procedures Adjustment of Bypass GainXx dBC -3 dB Yy dBC FromPress the format 60 non sync switch Adjustment of Non-sync GainAuto Freq Repeat page 5-20 Step Adjustment of Mono Gain and Equalization NotesPress the format 04 Dolby Stereo A-type switch Chain Alignment Procedures Final ChecksSection 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 +15M Cat. No +24V +15V15V +12B Appendix a Checking Phasing of Speakers Appendix B Effect of Changes in Slit Height on Slit Losses Cat. No a Circuit Description Appendix C CP65M Mono InstructionsOperation Schematic Cat. No a Terminal Block TB3 Appendix D Backplane Connections ListConnector J18