Dolby Laboratories CP650 Installation Manual download pdf (Page 53)

Dolby

Model CP650 Installation Manual

4-1

Chapter 4

B-Chain Alignment

4.1 Check Theatre Equipment

Thoroughly check the loudspeakers and power amplifiers for any sources of poor

performance, using the suggested checklists below as a guide.

Speakers

• Loudspeaker cables—Check that they are in good condition and that they are the

correct gauge for the impedance of the speakers and the length of the run.

• Speaker wiring—Check that the speakers are connected to the correct power amp

channel.

• Rattles—A leak in the low-frequency driver cabinet may sound like a rattle.

• Also check for loose bolts or other hardware.

• Open drivers—In systems with pairs of drivers, one voice coil of the pair may be

open but the system will still function. Check the speakers with an ohm meter. 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.

• Check for missing drivers or other components.

• Crossover settings matching the type of drivers in use and the acoustics of the

theatre—The high-frequency driver level control must be set for the best possible

frequency response before you attempt any equalization. This is especially true if

the system uses active crossovers with bi-amp equipment. If your CP650 is

equipped with a Cat. No. 791 Crossover Board, please refer to

Section 4.4 for information on settings.

• Check for proper polarity between the low- and high-frequency drivers, and

between the channels.

• Aiming of speakers—Ensure that the speakers are correctly aimed into the

auditorium, and that they are not obstructed by the screen frame, struts, or other

obstructions.

Amplifiers

• Check for distortion.

• Gross gain differences among amplifiers—If one amplifier differs in performance

from the others, it should be checked and repaired if necessary, before proceeding

further. Input gain controls should all be at the same setting.

• Check for blown fuses.

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Dolby Laboratories CP650 Installation Manual Page 53