Dolby Laboratories CP65 manual 90 dBC, 85 dBC

				5-24
			B-Chain Alignment Procedures
d. Subwoofer Alignment (Cat. No. 441)
Step			Action						Indication
No.
4		Cat. No.
		441		90 dBC					➝	85 dBC
	signal
	present
		tp
Subwoofer		on
		cut
	auto	freq
	off	Q	Dolby
				F
n-sync	opt gain			OF	70	60	50	4	30
				8
				0				0
surr	mag/dig
gain	gain
Surround	treble
		cut
	mid	freq
Left		Q
		bass
		tp
	treble
Surround		cut
	mid	Q
		freq
Right		bass
		gain
		gnd
	signal
	present
5		Cat. No.
		441

5-25

B-Chain Alignment Procedures

d. Subwoofer Alignment (Cat. No. 441)

Notes

Adjust the mag/dig gain control on the Cat. No. 441 card for a 90 dBC SPL (sound pressure level) in the theatre. (If this level cannot be obtained it may be necessary to change the J2 jumper setting to increase or decrease the output - - see page 2-5). When you have obtained this level turn the mag/dig gain control down for an 85 dBC SPL.

Note

This level is only an approximation. Sound pressure level meters are not appropriate for setting accurate levels of narrow band signals. The correct final level will be set later in this procedure using an RTA.

Turn the cut control at the top of the Cat. No. 441 card to the fully clockwise (CW) position

6

		signal
		present
				tp
Subwoofer				on
				cut
	auto			freq
		off		Q
n-sync		opt gain
surr		mag/dig
gain		gain
Surround		treble
				cut
	mid			freq
Left				Q
			bass
				tp
		treble
Surround	mid			cut
				Q
				freq
Right			bass
				gain
				gnd
		signal
		present

Cat. No.

441

Dolby

								+10
								+5
								0
								–5
								–10
.05	.1	.2	.4	.8	1.6	3.15	6.3	12.5 kHz

for minimum cut. This disables the subwoofer equalizer circuit.

Note the frequency of the peak in the response. You will need this information in Step 9 following.

Turn the Q control on the Cat. No. 441 card to its mid point (for a moderately wide notch).

	signal
	present
		tp
Subwoofer		on
		cut	Dolby
		freq
	auto
	off	Q
n-sync	opt gain
surr	mag/dig
gain	gain
Surround	treble
		cut
	mid	freq
Left		Q
		bass
		tp
	treble
Surround		cut
	mid	Q
		freq
Right		bass
		gain
		gnd
	signal
	present

7		Cat. No.
		441
	signal
	present
		tp
Subwoofer		on
		cut
	auto	freq	Dolby
	off	Q
n-sync	opt gain
surr	mag/dig
gain	gain
Surround	treble
		cut
	mid	freq
Left		Q
		bass
		tp
	treble
Surround		cut
	mid	Q
		freq
Right		bass
		gain
		gnd
	signal
	present

Turn the cut control back to the fully counterclockwise (CCW) position for full cut.