Dolby Laboratories CP65 manual Loudspeakers and Crossovers

Page 41

5-4

B-Chain Alignment Procedures

a. Setting Room Equalization

Step

Action

Indication

No.

 

 

4

Cat. No.

Cat. No.

85

150

5

5-5

B-Chain Alignment Procedures

a. Setting Room Equalization

Notes

Remove the Cat. No. 150 Card. Note that when the Cat. No. 150 card is removed, two card edge connectors are exposed on the backplane and that another slot to the immediate left of the Cat. No. 150 slot is accessible. This second slot and associated connector are for the Cat. No. 85C Pink Noise Generator.

Install the Cat. No. 85C Pink Noise Generator in the special slot to the left of the Cat. No. 150 slot. The switches in the Cat. No. 85C are up or down for ON and center for OFF. The phase is positive when the switches are in the up position and negative in the down position.

Loudspeakers and Crossovers

Thoroughly check the loudspeakers and power amplifiers for sources of poor performance:

•Check that the loudspeaker cables are in good condition and that they of a suitable gauge for the impedance of the speakers and the length of the run.

•Rattles (a leak in the woofer cabinet may appear to be a rattle).

•Loose bolts or other hardware.

•Open drivers.

In systems with pairs of drivers — woofers or tweeters — one of the pair may be open but the system will still function. Check the speakers with an ohmmeter. If one channel requires markedly more equalization than the other or if one speaker overloads at lower levels than the other speakers, an open driver circuit could be the cause.

•Missing drivers or other components.

•The settings of the crossovers to match the type of drivers in use and the acoustics of the theater.

The tweeter level control must be set for the best possible frequency response with the Cat. No. 64 controls all at mid-point before you attempt any equalization. (The same procedures should be followed if the system uses active crossovers with bi-amp equipment.) This check should be made with a real time analyzer.

•Phasing between the woofers and tweeters, and between the channels (see Appendix A).

•Aiming of speakers.

Check that the speakers are correctly aimed into the auditorium, and that they are not obstructed by the screen frame, struts or other obstructions.

Page 40 Page 42
Image 41
Page 40 Page 42
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 Two-channel Noise Slot Card Function Cat. NoReduction Module Channel DecoderContains 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
Top Page Image Contents