Dolby Laboratories CP65 - Manual (Page 41)

B-Chain Alignment Procedures
Action Indication Step
No.
5-4
a. Setting Room Equalization
4
5
Cat. No.
85
Cat. No.
150
B-Chain Alignment Procedures
Notes
5-5
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.
a. Setting Room Equalization
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.