Dolby Model 737 Soundtrack Loudness Meter – Leq(m) Users’ Manual Issue 3 MAIN Part No.
Dolby Laboratories Inc 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.
Table of Contents List of Figures .........................................................................................................................v List of Tables ..........................................................................................................................vi Chapter 1 Introduction ............................................................................................... 1-1 Chapter 2 Operation and Features ........................................................
Chapter 3 Chapter 4 Cat. No. 448B Input Adapter Board .............................................. 3-1 3.1 Introduction.............................................................................................. 3-1 3.2 Logic map ................................................................................................ 3-1 3.3 Component and Connector Layout .......................................................... 3-2 3.4 Preview Theatre ..................................................
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) ...............................................
List of Tables 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 ...........................................................
Model 737 Soundtrack Loudness Meter - Leq(m) Chapter 1 Introduction 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.
Model 737 Soundtrack Loudness Meter - Leq(m) Chapter 2 Operation and Features 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.
Model 737 Soundtrack Loudness Meter - Leq(m) 2.1.1 Operation and Features 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.
Model 737 Soundtrack Loudness Meter - Leq(m) 2.2 Operation and Features Back Panel Connectors Ch 1 Lt Ch 3 Ch 2 Rt Ch 4 Dolby and the double-D symbol are trademarks of Dolby Laboratories. Ch 5 Dolby Laboratories Inc.
Model 737 Soundtrack Loudness Meter - Leq(m) AC In ~ AC In ~ 24Vac 500mA Gnd DC Out Ref Mon Out Gnd Trip Out Mon Out Start / Stop 2.2.2 Operation and Features Model 737 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.
Model 737 Soundtrack Loudness Meter - Leq(m) 2.2.
Model 737 Soundtrack Loudness Meter - Leq(m) 2.3.2 Operation and Features Connecting to a Dolby Cinema Processor The method for connecting a Dolby cinema processor with the Model 737 depends on the application. For a cinema processor used in a studio or dubbing stage, the matrixencoded Lt and Rt signals are found on the Cat. No. 150E card. If the connection for measurement is occasional, use the red and green test points, respectively.
Model 737 Soundtrack Loudness Meter - Leq(m) 2.3.4 Operation and Features Connecting to Non-Dolby Digital Adapters With the digital adapter connected to the Dolby cinema processor, make a parallel connection 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. 2.3.5 Connecting to the SDU4 Surround Decoder The Model 737 can interface with the SDU4 either before or after decoding.
Model 737 Soundtrack Loudness Meter - Leq(m) Operation and Features 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. Since the null points are only at 82 and 85, to align to 88, reduce the test tone level to exactly 3 dB below Dolby Level and align to a null point at 85.
Model 737 Soundtrack Loudness Meter - Leq(m) 2.4 Operation and Features 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. The transformer should not be operated with the 24 V leads shorted. Transformer units are available for 200–240 VAC input and 100–125 VAC input. Please ensure that the correct transformer is ordered for your local mains voltage.
Model 737 Soundtrack Loudness Meter - Leq(m) 2.
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.
Model 737 Soundtrack Loudness Meter - Leq(m) Chapter 3 Cat. No. 448B Input Adapter Board 3.1 Introduction The Cat. No. 448B is an input adapter board that mounts to the rear of a CP65. The card will suitably switch and adapt signals from a two- or six-track source following logic control from the 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.
Model 737 Soundtrack Loudness Meter - Leq(m) 3.3 Cat. No.
Model 737 Soundtrack Loudness Meter - Leq(m) Cat. No. 448B Input Adapter Board Table 3-2 Connecting the Cat. No. 448B to the CP65 and CP55 Cat. No. 448B CP65 CP55 From Cat. No. 150 Lt J7 pin L J12 pin 10 From Cat. No.
Model 737 Soundtrack Loudness Meter - Leq(m) 3.5 Cat. No. 448B Input Adapter Board 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. The following examples are two common configurations. Example 1 A typical UK setup uses the DA20 or dubbing interface (Cat. No.
Model 737 Soundtrack Loudness Meter - Leq(m) Cat. No. 448B Input Adapter Board Follow these steps to install the devices used in this example: 1. Isolate the mains power to the processor and remove the existing dubbing interface (Cat. No. 448); leave all connections to it in place. 2. Completely remove and discard the Cat. No. 448-MS and re-route the OPT logic line back to the OPT tag of the Cat. No. 448. 3. Determine whether Lt/Rt default to studio record/monitor buses 2&3 or 1&3.
Model 737 Soundtrack Loudness Meter - Leq(m) 3.5.1 Cat. No. 448B Input Adapter Board 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. 3. Set the DS4-E into Matrix Monitor mode with the SR/A or Proc 2 switch not illuminated. 4.
Model 737 Soundtrack Loudness Meter - Leq(m) Cat. No. 448B Input Adapter Board Figure 3-4 Cat. No.
Model 737 Soundtrack Loudness Meter - Leq(m) Chapter 4 Specifications Temperature and Humidity Operating 10o C to 35o C, natural convection cooling Non-Operating (Storage) 0o C to 70o C Humidity Up to 90% relative humidity, non-condensing EMC Limits AC power line conducted Per EN 55022 Radiated Per EN 55022 Immunity Per EN 50082-1 General Dimensions 19 x 7.8 x 1.75 inches (43 x 20 x 4.
Model 737 Soundtrack Loudness Meter - Leq(m) Appendix A Background This Appendix is an edited version of a paper published in the January 1998 SMPTE Journal (Volume 107, Number 1) entitled “Are Movies Too Loud” by Ioan Allen. The complete paper is available from the Dolby website at www.dolby.com/movies. Reprints of the paper are available by sending email to info@dolby.com (include the article title) or by calling 415-558-0200.
Model 737 Soundtrack Loudness Meter - Leq(m) Background 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 technology has been significantly enhanced since Dolby Stereo. Dolby SR extended the headroom by 3 dB at midrange frequencies, and more at low and high frequencies.
Model 737 Soundtrack Loudness Meter - Leq(m) Background 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. • Theatres are playing films substantially below the calibrated level.
Model 737 Soundtrack Loudness Meter - Leq(m) Background None of the existing criteria for loudness can be directly applied to a soundtrack. Fundamental loudness is defined by the relationship between frequency and level. A regular VU or PPM meter does not account for the ear’s varying sensitivity with respect to frequency. Sound level meters account for some frequency/level factors and are typically switchable to different weightings.
Model 737 Soundtrack Loudness Meter - Leq(m) A.3.1 Background 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.
Model 737 Soundtrack Loudness Meter - Leq(m) Background Leq CCIR-w eighted Leq m Leq A-w eighted Leq a 5.6 dB offset w a tch 85 d ea th w ater d um m ie s RAF L evis S an yo 80 S m irn off 75 Figure A-3 CCIR-weighting (Leq(m)) shows influence of 2–6 kHz region. A.4 Analysis of the Data Figure A-4 shows the relationship between un-weighted (Leq) and CCIR-weighted (Leq(m)) samples. The hierarchy on the right of the figure (un-weighted) differs from that on the left (weighted).
Model 737 Soundtrack Loudness Meter - Leq(m) Background Leq m C C IR -w eighted Leq U nw eighted 5.
Model 737 Soundtrack Loudness Meter - Leq(m) Background Leq m C C IR -w eighted Peak Level C -w eighted, fast 110 5.
Model 737 Soundtrack Loudness Meter - Leq(m) Background 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. Leq m CCIR-w eighted Peak Level C-w eighted, fast 95 5.
