Dolby Laboratories 737 User Manual
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Dolby Laboratories 737 User Manual

Dolby Laboratories 737 User Manual

Soundtrack loudness meter – leq(m)
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Dolby
Model 737 Soundtrack
Loudness Meter – Leq(m)
Users' Manual
Issue 3
Part No. 91533
MAIN

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  • Page 1 Dolby Model 737 Soundtrack Loudness Meter – Leq(m) Users’ Manual Issue 3 Part No. 91533 MAIN...

  • Page 2: United States

    (including but not limited to damage to software or recorded audio or visual mate- rial), 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.

  • Page 3: Table Of Contents

    List of Figures ...v List of Tables ...vi Chapter 1 Introduction 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 ...
  • Page 4 Chapter 3 Cat. No. 448B Input Adapter Board 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 Chapter 4 Specifications Appendix A Background...

  • Page 5: List Of Figures

    Model 737 front panel ... 2-1 Detail of front panel controls ... 2-1 Model 737 back panel ... 2-3 Audio input connectors (detail of rear panel) ... 2-3 Mon and DC Out, and power/control connector ... 2-4 Model 737 block diagram ... 2-10 Cat.
  • Page 6 XLR input wiring convention for channels 1-6 ... 2-3 Mon Out wiring convention ... 2-4 DC Out wiring convention ... 2-4 Power and control connector wiring convention ... 2-5 DA10/20 Audio Out Conn. J8 Signal Assignments ... 2-6 Calibration levels for Dolby, Dolby SR, and Dolby Digital soundtracks ... 2-7 Logic map of Cat.

  • Page 7: Chapter 1 Introduction

    Chapter 1 Introduction Leq(m) is a term used by Dolby Laboratories to describe the level of annoyance in mov- ie 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.

  • Page 8: Chapter 2 Operation And Features

    Model 737 Soundtrack Loudness Meter - Leq(m) 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.

  • Page 9: 6/4 - 2 Channel Switch

    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 screwdriver- adjustable 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.

  • Page 10: Back Panel Connectors

    Ch 1 Ch 2 Ch 3 Ch 4 Dolby and the double-D symbol are trademarks of Dolby Laboratories. 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.

  • Page 11: Mon Out Wiring Convention

    Model 737 Soundtrack Loudness Meter - Leq(m) 2.2.2 Mon Out Mon Out Figure 2-5 Mon and DC Out, and power/control connector 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.

  • Page 12: Power And Control Connector Wiring Convention

    Connect the Left, Center, Right, Left Surround, Right Surround, and Subwoofer outputs from the audio console into the appropriate inputs on the Model 737. Use a 1 kHz tone at Dolby Level as the test signal to each full-band input. Use a Dolby Level tone at approx- imately 100 Hz for the Subwoofer input.

  • Page 13: Connecting To A Dolby Cinema Processor

    Model 737 and the digital adapter. If the Model 737 is not in the same rack, there must be a connection between any of the ground pins (1, 4–13) of J8 and one of the ground pins on the 8-pin power and control connector on the rear panel of the Model 737.

  • Page 14: Connecting To Non-Dolby Digital Adapters

    With the digital adapter connected to the Dolby cinema processor, make a parallel con- nection from the cinema processor to the audio inputs on the Model 737, and use the test media from that manufacturer as the signal source to apply Dolby Level to each channel.

  • Page 15: Automated Input Adapter Board (Cat. No. 448B)

    Model 737 Soundtrack Loudness Meter - Leq(m) Notes: The null circuit has two points of transition (at 82 and 85), so the + and - LEDs should be used in conjunction with the numerical display to set the correct levels for that input.

  • Page 16: Mains Power

    Model 737 Soundtrack Loudness Meter - Leq(m) Mains Power The Model 737 uses a mains transformer that converts incoming AC to 24 VAC. The transformer has 1 meter leads and should be placed at the base of the equipment rack in which the unit is mounted.

  • Page 17: Block Diagram

    Model 737 Soundtrack Loudness Meter - Leq(m) Block diagram in - L / Lt in + in - in + in - in + in - R / Rt in + in - in + in - in + The six input channels each have a balanced to unbalanced stage buffering the input sig- nal.
  • Page 18 Model 737 Soundtrack Loudness Meter - Leq(m) Operation and Features The selection switches are followed by five ideal rectifiers and squaring circuits. The five squared signals are added and short term averaged. The resultant varying DC signal passes to an analog long-term averaging circuit. This requires a logic signal from the pushbutton logic section to start and stop the average measurement.

  • Page 19: Logic Map Of Cat. No. 448B

    CP65, CP55, or DS4-E (UK). Format calibration and routing requirements are therefore met automatically. The Cat. No. 448B passes six balanced channels on to the Model 737 with a 3-dB L and R channel attenuation. The Model 737 is then calibrated to compensate for this attenuation with 3 dB more gain on the L and R input trim pots.

  • Page 20: Component And Connector Layout

    Model 737 Soundtrack Loudness Meter - Leq(m) Component and Connector Layout TO MODEL 737 Lt, Rt 1 & 3 (LK1-4) FROM DA20 / MON BUSS Lt, Rt 2 & 3 (LK1-4) CAT. NO. 448B INTERFACE ADAPTOR FOR MODEL 737 A2A7463 REV A Figure 3-1 Cat.

  • Page 21: Alignment

    (L, R) and adjust RV1 (L) and RV2 (R) trim pots of the Cat. No. 448B to obtain a null-point at 85 dB for each channel. 4. Check that the Model 737 reads 3 dB higher when in Format 05 than in Format 04 for each channel.

  • Page 22: Dubbing Studio

    Model 737 Soundtrack Loudness Meter - Leq(m) Dubbing studio Dubbing Studio set-ups may vary depending upon location. Contact a Dolby sound consultant or Dolby office to resolve any uncertainties. Installation of the Cat. No. 448B can be optimized using the logic map in Table 3-1 and Figure 3-4, the Cat. No. 448B schematic diagram.
  • Page 23 OPT logic line SR logic line From DA20/Mon Bus tags To DS4-E Lt/Rt tags 6. Connect the Cat. No. 448B output to the Model 737. 7. Mount the dubbing interface (Cat. No. 448) on top of the Cat. No. 448B. CP65 CP55...
  • Page 24 Alignment 1. Set the DS4-E into Discrete mode (one green LED). 2. Send tone at Dolby Level to the studio monitor bus and align the Model 737 as described in Section 2.3.6 - Calibration Procedure (Dolby Digital). Note: If LK1-4 are in the lower position, the L & C input trimpots on the Model 737 will be reversed.
  • Page 25 Model 737 Soundtrack Loudness Meter - Leq(m) Cat. No. 448B Input Adapter Board Figure 3-4 Cat. No. 448B Interface Adapter Schematic MAIN...

  • Page 26: Temperature And Humidity

    Model 737 Soundtrack Loudness Meter - Leq(m) Temperature and Humidity Operating Non-Operating (Storage) Humidity EMC Limits AC power line conducted Radiated Immunity General Dimensions Net Weight Power Requirements Power Consumption Specifications C to 35 C, natural convection cooling C to 70...

  • Page 27: Appendix A Background

    A.1.1 The Current Situation In the mid-1970s, Dolby Laboratories introduced a calibration recommendation for monitor levels in movie soundtracks. A pink noise reference signal was used in the record chain to adjust the audio monitor level to 85 dBc. All theatres equipped for play-...
  • Page 28 Model 737 Soundtrack Loudness Meter - Leq(m) This system worked quite well for many years. Dolby Stereo (A-type encoded) films had limited headroom and the resulting constrained dynamic range yielded few audience complaints. Most theatres played films at the calibrated level. Soundtrack format tech- nology has been significantly enhanced since Dolby Stereo.

  • Page 29: How Loud Is A Movie

    Model 737 Soundtrack Loudness Meter - Leq(m) In practice, the following undesirable symptoms have arisen: • There are an increasing number of audience complaints that movies are too loud. Newspaper articles have been written on the subject and respected sound mixers have spoken publicly about the problem.

  • Page 30: Concept

    It would be highly desirable to combine these concepts to produce a single value that accurately represents the loudness of a movie. Dolby Laboratories decided to set up a variety of measurement techniques to evaluate film samples. Obviously, it was impossible to measure a totally comprehensive set of material.
  • Page 31 Model 737 Soundtrack Loudness Meter - Leq(m) A.3.1 Alternative Measurement Indices As might be expected, the samples yielded different loudness values when assessed with different systems. The low-frequency roll-off of A-weighting results in a reduction in Leq when the material has a substantial bass content. Determination of annoyance, however, does not necessarily match the A-weighting curve.

  • Page 32: A-3 Ccir-Weighting (Leq(M)) Shows Influence Of 2–6 Khz Region

    Model 737 Soundtrack Loudness Meter - Leq(m) Leq CCIR-w eighted w a tch d ea th w ater d um m ie s R A F L evis S an yo S m irn off Figure A-3 CCIR-weighting (Leq(m)) shows influence of 2–6 kHz region.

  • Page 33: A-4 Comparison Of Weighted And Un-Weighted Leq

    Model 737 Soundtrack Loudness Meter - Leq(m) Ind ie Tem p le o f D oo m (A ) M a rs A tta cks Traile r (D ) P riso ne rs of the M oun tain Traile r (D )

  • Page 34: A-5 Comparison Of Leq(M) And Peak Levels

    Model 737 Soundtrack Loudness Meter - Leq(m) C C IR -w eighted 5.6 dB offset S tar W ars Tra ile r (D ) Indie Tem ple of D oom (A ) S la yer's R e tu rn (S R )

  • Page 35: A-7 Comparison Of Leq(M) With Peak Levels For Uk Commercials

    Model 737 Soundtrack Loudness Meter - Leq(m) Next, examine Figure A-5 again, then Figure A-6, and compare the peak levels in reel 4 of Shine with the Leq. Although this reel has an extreme dynamic range, audiences do not complain that it is too loud. In this case, the dynamic range is correct for the nature of the material, and the Leq is much more indicative of the subjective loudness than a peak measurement.

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