Dolby Laboratories CP65 manual Repeat, Action

5-10

B-Chain Alignment Procedures

a. Setting Room Equalization

Step			Action							Indication
No.
12		Cat. No.
		242
	mono eq
	mono
	gain
	non-syncL
		R								75-80 dBC
		L
	signal	C
	present R
		Ls
	gnd
		L
				FF
		C	O						0	30
	test			80		70	60	50
									4
	points R
		Ls
		L	Dolby
	gain	C
		R
		Ls
13	REPEAT 11		→ 12
		Cat. No.
		242
	mono eq
	mono
	gain									75-80 dBC
	non-syncL
		R
		L
	signal	C
	present R
		Ls
	gnd		FF
			O	0		0			0	30
				8	7		60	50	4
		L
	test	C
	points	R
		Ls
			Dolby
		L
	gain	C
		R
		Ls
	Cat. No.
		242
	mono eq
	mono									75-80 dBC
	gain
	non-syncL
		R
		L
	signal	C
	present R
	Ls		OFF
	gnd									0
				80	70		0	50	0	3
									4
							6
		L
	test	C
	points	R
	Ls		Dolby
		L
	gain	C
		R
	Ls

5-11

B-Chain Alignment Procedures

a. Setting Room Equalization

Notes

With a sound pressure level meter located at the position in the theatre used for step 6, adjust the center channel gain on the Cat. No. 242 card until the channel produces a reading of 75-80 dBC. (After room equalization for all channels is set, the sound pressure level will be set to 85 dBC.) The pink noise should be at least 20 dB above the background noise level of the theatre. If a level of 75-80 dBC cannot be obtained, adjust the gain of the amplifiers and and try again. A row of four LEDS, signal present L, C, R and S, is on the front edge of the Cat. No. 242 card. Each LED indicates the presence of signal for the appropriate channel and lights intermittently when pink noise is sent through the system from the Cat. No. 85C or from a film.

Repeat steps 11 and 12 for the left and right channels. Switch on the appropriate pink noise switch on the Cat. No. 85C pink noise generator, one channel at a time.

Compare the response displayed on the real time analyzer (RTA) for each channel (L, C, R). All should show a similar shape. Any large differences indicate faulty or misaligned crossovers or defective speakers. Speaker phasing could also be at fault. See Appendix A.