Dolby Laboratories 737 User Manual
MAIN
Dolby
Model 737 Soundtrack
Loudness Meter – Leq(m)
Users’ Manual
Issue 3 Part No. 91533
Dolby Laboratories Inc
MAIN
www.dolby.com
United States
100 Potrero Avenue
San Francisco, CA 94103-4813
Telephone 415-558-0200
Facsimile 415-863-1373
United Kingdom
Wootton Bassett
Wiltshire SN4 8QJ England
Telephone (44) 1793-842100
Facsimile (44) 1793-842101
WARNING: Troubleshooting must be performed by trained technicians. Do not
attempt to service this equipment unless you are qualified to do so.
DISCLAIMER OF WARRANTIES
of one year from the date of purchase. All warranties, conditions or other terms implied by statute are excluded to the fullest extent allowed by law.
LIMITATION OF LIABILITY
or otherwise shall not exceed the cost of repair or replacement of the defective components and under no circumstances shall Dolby Laboratories be
liable for incidental, special, direct, indirect or consequential damages (including but not limited to damage to software or recorded audio or visual material), or loss of use, revenue or profit even if Dolby Laboratories or its agents have been advised, orally or in writing, of the possibility of such damages.
Dolby and the double-D symbol are registered trademarks of Dolby Laboratories.
©2000 Dolby Laboratories Inc; all rights reserved. W01/111
: Equipment manufactured by Dolby Laboratories is warranted against defects in materials and workmanship for a period
: It is understood and agreed that Dolby Laboratories’ liability whether in contract, in tort, under any warranty, in negligence
MAIN
Table of Contents
List of Figures
List of Tables
Chapter 1 Introduction
.........................................................................................................................v
..........................................................................................................................vi
............................................................................................... 1-1
Chapter 2 Operation and Features
2.1 Front Panel Controls................................................................................ 2-1
2.1.1 6/4 – 2 Channel Switch................................................................ 2-2
2.1.2 Input Trimpots ............................................................................. 2-2
2.1.3 Trip Set......................................................................................... 2-2
2.1.4 Pushbuttons.................................................................................. 2-2
2.2 Back Panel Connectors ............................................................................ 2-3
2.2.1 Analog Audio Inputs.................................................................... 2-3
2.2.2 Mon Out ....................................................................................... 2-4
2.2.3 DC Out ......................................................................................... 2-4
2.2.4 Power and Control ....................................................................... 2-5
2.3 Connection and Calibration ..................................................................... 2-5
...................................................................... 2-1
2.3.1 Connecting to an Audio Console ................................................. 2-5
2.3.2 Connecting to a Dolby Cinema Processor ................................... 2-6
2.3.3 Connecting to a DA10/20 Digital Adapter .................................. 2-6
2.3.4 Connecting to Non-Dolby Digital Adapters ................................ 2-7
2.3.5 Connecting to the SDU4 Surround Decoder................................ 2-7
2.3.6 Calibration Procedure .................................................................. 2-7
2.3.7 Automated Input Adapter Board (Cat. No. 448B)....................... 2-8
2.4 Mains Power ............................................................................................ 2-9
2.5 Interface ................................................................................................... 2-9
2.6 Block diagram........................................................................................ 2-10
iii
Chapter 3 Cat. No. 448B Input Adapter Board
MAIN
3.1 Introduction.............................................................................................. 3-1
3.2 Logic map ................................................................................................ 3-1
3.3 Component and Connector Layout.......................................................... 3-2
3.4 Preview Theatre ....................................................................................... 3-2
3.4.1 Concept ........................................................................................ 3-2
3.4.2 Installation.................................................................................... 3-2
3.4.3 Alignment .................................................................................... 3-3
3.5 Dubbing studio......................................................................................... 3-4
.............................................. 3-1
Chapter 4 Specifications
Appendix A Background
A.1 Loudness ................................................................................................. A-1
A.2 How Loud Is a Movie? ........................................................................... A-3
A.3 Standardizing a Measurement Technique for Soundtrack “Loudness” .. A-4
A.4 Analysis of the Data................................................................................ A-6
............................................................................................. A-1
.......................................................................................... 4-1
iv
MAIN
List of Figures
2-1 Model 737 front panel .................................................................................................... 2-1
2-2 Detail of front panel controls .......................................................................................... 2-1
2-3 Model 737 back panel ..................................................................................................... 2-3
2-4 Audio input connectors (detail of rear panel) ................................................................. 2-3
2-5 Mon and DC Out, and power/control connector ............................................................ 2-4
2-6 Model 737 block diagram ............................................................................................. 2-10
3-1 Cat. No. 448B Interface Adapter .................................................................................... 3-2
3-2 Installation of Cat. No. 448B .......................................................................................... 3-2
3-3 Typical UK setup ............................................................................................................3-4
3-4 Cat. No. 448B Interface Adapter schematic ................................................................... 3-7
A-1 Peak levels of photographic soundtrack formats. .......................................................... A-2
A-2 A-weighting vs. CCIR-weighting curve (offset by 5.6 dB) ........................................... A-5
A-3 CCIR-weighting (Leq(m)) shows influence of 2–6 kHz region. ................................... A-6
A-4 Comparison of weighted and un-weighted Leq. ............................................................ A-7
A-5 Comparison of Leq(m) and peak levels ......................................................................... A-8
A-6 Peak levels in reel 4 of Shine ......................................................................................... A-8
A-7 Comparison of Leq(m) with peak levels for UK commercials ...................................... A-9
v
List of Tables
MAIN
2-1 XLR input wiring convention for channels 1-6 ............................................................. 2-3
2-2 Mon Out wiring convention ........................................................................................... 2-4
2-3 DC Out wiring convention ............................................................................................. 2-4
2-4 Power and control connector wiring convention ........................................................... 2-5
2-5 DA10/20 Audio Out Conn. J8 Signal Assignments ...................................................... 2-6
2-6 Calibration levels for Dolby, Dolby SR, and Dolby Digital soundtracks ..................... 2-7
3-1 Logic map of Cat. No. 448B .......................................................................................... 3-1
3-2 Connecting the Cat. No. 448B to the CP65 and CP55 .................................................. 3-3
3-3 Pin convention ............................................................................................................... 3-3
3-4 Pin convention (continued) ............................................................................................ 3-3
vi
Model 737 Soundtrack Loudness Meter - Leq(m)
MAIN
Leq(m) is a term used by Dolby Laboratories to describe the level of annoyance in movie soundtracks. The Leq(m) value is a weighted true average of the audio power level
sent to the camera in optical or digital soundtracks, or the same weighted true average of
the audio power level passing through a cinema processor before equalization. The Dolby Model 737 Soundtrack Loudness Meter – Leq(m) provides a convenient method
of measuring soundtrack annoyance.
The phrase true average signifies that the meter measures the power at regular intervals,
adds these quantities together and then divides the result by the length of the measurement time. Since the measurement time is a critical factor in arriving at an accurate result, the measurement should start and stop at known points. These points can range
from the First Frame of Action (FFOA) and Last Frame of Action (LFOA) of a spot,
such as a ten-second clip, to the beginning and end of an entire movie. The degree of
repeatability of Model 737 measurements is dependent on the length of the measurement. For example, a ten-second spot requires about two frame accuracy whereas a
two-minute-thirty-second trailer needs only two-second accuracy for correct measurement. For an entire feature, the measurement can be started and stopped at a convenient
time, within two minutes of the opening and closing credits, to get repeatable results.
Measurements made within 1% of the stated time frame will compare accurately.
Chapter 1
Introduction
The Model 737 consists of six input channels with setup trims followed by five weighting filters, a true averaging power meter that can be remotely started and stopped, and a
trip circuit that indicates a preset maximum level has been exceeded. The unit is intended
for use on soundstages, optical recording facilities, and film QA installations to audition
the final two- and six-channel mixes that will be recorded on the film. It can also be
used in theatres to check levels during exhibition.
Note: See Appendix A – Background for a complete discussion of the factors that led
to the creation of the Model 737 Soundtrack Loudness Meter – Leq(m).
1-1
Model 737 Soundtrack Loudness Meter - Leq(m)
MAIN
The Model 737 Soundtrack Loudness Meter – Leq(m) is a simple 1U, rack-mountable
device that measures the equivalent loudness of one-, two-, four-, or six-channel inputs,
typically from the non-equalized outputs of a cinema processor or mixing console.
Since the time available for averaging is several hours, a soundtrack can be evaluated
in small sections or in its entirety. The current Leq(m) value is displayed in the LED
window. The circuit consists of a set of six input stages, five CCIR (2K) filters, five
square law detectors, and a display driver that takes the average of the squared signal
voltage and then extracts the square root/log of the resultant DC signal. A separately
processed average DC circuit outputs a signal that is buffered for use with a chart recorder/
moving coil meter for trend analysis.
The Trip Se t adjustment sets the level that lights the Trip LE D and triggers a signal
to the Trip Output. The Trip Output can activate a more noticeable device (such as
a light or sound) to alert the user that a preset level has been exceeded at the end of
the measurement.
Chapter 2
Operation and Features
2.1 Front Panel Controls
The front panel has three pushbuttons (Cal, Start, Stop), a two-digit LED that displays
the current Leq(m) value, a screwdriver-accessible hex switch to set the trip level, trimpots for the six analog inputs, and a 6/4 – 2 channel switch.
Leq (m)
Soundtrack Loudness Meter -- Leq (m)
Model 737
The right side of the front panel is shown in detail below.
Start
Start
Stop
Cal
Cal
Cal
85
Figure 2-1
Calibration LEDs
Stop
Stop
Trip
4
5
Trip
6
3
7
2
8
1
9
0
C
A
F
B
E
C
D
Set
Set
Model 737 front panel
-
Cal
Stop
Start
Audio Input Trimpots
Mon Out Trimpot
LCR
26/4 -
+
Ls RsSwMon
Trip
-
4
5
Trip
+
6
3
7
2
8
1
9
0
C
A
F
B
E
C
D
Set
26/4 -
LCR
Ls RsSwMon
Start Trip Set
Figure 2-2
Detail of front panel controls
6/4 - 2 channel switch
2-1
Model 737 Soundtrack Loudness Meter - Leq(m) Operation and Features
MAIN
2.1.1 6/4 – 2 Channel Switch
Located to the left of the input trimpots (see Figure 2-2), this switch may be used in
future versions to introduce a fixed offset in the measurement of two-channel encoded
material. Presently (version 1), the offset is set to zero so the switch has no effect on
the measurement.
2.1.2 Input Trimpots
To derive accurate and repeatable Leq(m) measurements, the input trimpots are used to
calibrate the Model 737 to standard input levels. The input trimpots are screwdriveradjustable and allow sensitivity adjustments from -12 to +4 dBu for Dolby Level to suit
a wide variety of console setup levels and cinema processor types. See Section 2.3 Connection and Calibration for a complete discussion of how to connect and calibrate
the Model 737 to different signal sources.
2.1.3 Trip Set
Trip Set is a 16-position switch that sets a value from 78 Leq(m) at position 0 to 92 Leq(m)
at position E in 1 unit increments. When Stop is pressed to end the measurement, if the
Trip Set level has been exceeded, the Trip LED lights and a signal is sent to Trip Out.
The Trip LED does not light during the measurement to allow transient Leq(m) values
to exceed the Trip Set value without triggering Trip Out.
Note: The Trip circuit can be disabled by setting the switch to position F.
The current Trip level can be checked by holding down the Cal button then pressing
and holding the Stop button. This test always sends a signal to Trip Out to check the
circuit operation. Push the Run button to cancel the trip indication. In position F, the
display is blank.
2.1.4 Pushbuttons
• Cal – Push to enter calibration mode to set audio input levels using the trim-
pots. In calibration mode, Mon Out sends a mono mix of the channels instead
of the output of the filter. Push Start to return to measurement mode.
• Start – Push to begin a measurement.
• Stop – Push to stop a measurement and display the final level of the measurement.
2-2
Model 737 Soundtrack Loudness Meter - Leq(m) Operation and Features
Ch 1
Lt
Left
Dolby and the double-D symbol are trademarks of Dolby Laboratories.
Ch 3 Rt
Right
Ch 2
Center
Ch 4
Left Surround
Ch 5
Right Surround
Ch 6
Subwoofer
Analog Audio Inputs
MAIN
2.2 Back Panel Connectors
The back panel has six audio input connectors (shown in detail in Figure 2-4), two output
connectors, and a power/control signal connector (shown in detail in Figure 2-5).
Analog Audio Inputs
Left
Ch 2
Ch 1
Lt
Dolby and the double-D symbol are trademarks of Dolby Laboratories.
Center
Right
Ch 3 Rt
Left Surround
Ch 4
Right Surround
Ch 5
Ch 6
Figure 2-3
2.2.1 Analog Audio Inputs
Although the input stages of Left, Center, Right, and Left Surround are identical, it is
recommended that Left and Right (Ch 1 and Ch 3, also labeled Lt and Rt, respectively)
be used for Lt/Rt measurements of two-channel encoded material. The Right Surround
and Subwoofer channels share a common filter and rectifier so the Subwoofer input is
not normally used except when measuring 5.1-channel material.
Subwoofer
Mon Out DC Out
Model 737 back panel
24Vac
500mA
Gnd
Gnd
AC In ~
Start / Stop
AC In ~
Trip Out
Trip Out
Trip Out
Ref
Model 737
Dolby Laboratories Inc.
San Francisco U.S.A.
Wootton Bassett U.K.
WARNING:
No user serviceable parts inside.
Refer all service
to qualified
personnel.
Figure 2-4
Audio input connectors (detail of rear panel)
The XLR input connectors for channels 1–6 use the following wiring convention:
Table 2-1
XLR input wiring convention for channels 1-6
Pin Connection
1Chassis
2Audio +
3 Audio -
2-3
Model 737 Soundtrack Loudness Meter - Leq(m) Operation and Features
MAIN
2.2.2 Mon Out
Mon Out DC Out
Figure 2-5
Mon and DC Out, and power/control connector
Start / Stop
Gnd
Trip Out
Trip Out
Trip Out
Gnd
Ref
24Vac
500mA
AC In ~
AC In ~
Model 737
Mon Out is an unbalanced output which, in calibration mode, provides an unweighted
mono mix of channels. In measurement mode, Mon Out carries a mono mix of the outputs
of the weighting filters. Listening to the filtered output can help the mixer find the effect
or equalizer setting that is raising the average above the standard. Mon Out is adjustable
on the front panel from -20 to 0 dBu for Dolby Level so that it can be balanced with the
studio monitor level.
Mon Out uses the following wiring convention:
Table 2-2
Mon Out wiring convention
Pin Connection
2.2.3 DC Out
DC Out is an unbalanced output to drive an optional moving coil meter/chart recorder.
Using a 1 mA moving coil meter with a calibrating potentiometer across its terminals
is a useful method to observe measurement trends. DC Out uses the following wiring
convention:
1Chassis
2 Mon signal out
3 Mon signal common
Table 2-3
DC Out wiring convention
Pin Connection
1Chassis
2 DC out
3 DC return
1 V is equivalent to 91 Leq(m); the range is 0–1.25 VDC; 0 VDC corresponds to
70 Leq(m); output resistance is 1 kΩ.
2-4
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