Model 737 Soundtrack Loudness Meter
Contents
1. z vzozv A SV 2h Uld ASL 8 Uld ZZ01L LOI SALON ng el Ll i 2 pems Soe S rans MS MS one ele SH o 9 S ZMS gout i mn t Ax 84 L say o SE 3 DIES S71 s7 D azms SDE J da m oly gt 87 m fo d 2 o di a DEL pms lt S gems 1H o o EY gH x N o 9 ES c o o 9 49 4 d DiEL OLMS cxt 7 2 Ries ZH i ey 4 41 x SAE iM r PEMS by Z 1M N uoQ y Lyr1 er L i412 dnr p MS AO 4 Be ne 1dO E Irsa or Lzoa ASI d4 30 nyo 62 i M 0 219 EN SrlyNL dd30l 1o asz La zu as p o q ews MO an9 Bis iv coi p o g egws wy BEME euejdyoeg xxd9 ldo gt l gt f y one OG ON 39 wouy p n il qzol z l pras 6LY Vol Figure 3 4 Cat No 448B Interface Adapter Schematic Model 737 Soundtrack Loudness Meter Leq m Chapter 4 Specifications Temperature and Humidity Operating 10 C to 35 C natural convection cooling Non Operating Storage 0 C to 70 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 Dimensions 19 x 7 8 x 1 75 inches 43 x 20 x 4 5 cm Net Weight 6 lb 3 kg Power Requirements 24 VAC 500 mA wall transformer provided Power Consumption 10 WAC max Model 737 Soundtrack Loud2. Dolby Model 737 Soundtrack Loudness Meter Leq m Users Manual Issue 3 Part No 91533 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 DISCLAIMER OF WARRANTIES Equipment manufactured by Dolby Laboratories is warranted against defects in materials and workmanship for a period 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 It is understood and agreed that Dolby Laboratories liability whether in contract in tort under any warranty in negligence 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 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 Dolby and the double D symb
3. Isolate the mains power to the processor and remove the existing dubbing in terface Cat No 448 leave all connections to it in place 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 Determine whether Lt Rt default to studio record monitor buses 2 amp 3 or 1 amp 3 If Lt Rt default to 2 amp 3 place the links LK1 4 in the lower position If 1 amp 3 place LK1 4 in the upper position Make the following connections before mounting the Cat No 448B see Table 3 3 and Table 3 4 for pin conventions Cat No 448B CP65 CP55 From Cat No 150 Lt J7 pinL J12 pin 10 From Cat No 150 Rt J7 pin J J12 pin 7 15 V J2 pin 5 J15 pin 5 15 V J2 pin 13 J15 pin 13 OV J2 pin 9 J15 pin 9 Mount the Cat No 448B to the CP65 back panel using the spacers provided and then make the following connections Cat No 448B Cat No 448 DS4 E UK MAT logic line MAT logic line OPT logic line OPT logic line SR logic line SR logic line From DA20 Mon Bus tags Balanced six track inputs To DS4 E Lt Rt tags Lt Rt OPT OUT 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 Model 737 Soundtrack Loudness Meter Leq m Cat No 448B Input Adapter Board 3 5 1 Alignment 1 2 Set the DS4 E into Discrete mode one green LED S
4. 120 110 100 3 90 3 ru 80 70 60 50 40 30 20 10 31 5 63 125 250 500 1k 2k 4k 8k 16k Hz Academy mono Dolby A type Dolby SR Dolby Digital Figure A 1 Peak levels of photographic soundtrack formats Because the 85 dBc calibration technique has been maintained throughout these format changes additional headroom is available on the newer soundtracks Feature films have one consistent subjective mix reference for dialogue record level known as associative loudness When the dubbing mixer sees an actor on the screen and there is no fight with music or effects the dialogue level in a moderate close up is set to be plausible for the visual Within reasonable limits this holds true to within 2 or 3 dB This natural dialogue level does not hold true for narration as there is no corresponding visual reference Music and effects have no direct visual associative loudness Most people are not familiar with the actual sound pressure levels of a Concorde take off or a 50 mm howitzer The music score level is equally uncalibrated As the headroom capability of the recording medium has been extended it has certainly been used the non associative loudness of effects and music has risen to fill the available space The discretionary use of this increased headroom would be justified and desirable on some feature films such as ride and action movies Model 737 Soundtrack Lo
5. YR REV PN RN 2 7 2 3 7 Automated Input Adapter Board Cat No 448B 2 8 22 Mans POWE cinaran n cane oe 2 9 23 Interface peenar i a R R E A 2 9 2 0 Block di ra iinei te nisser P enaar e ua TERMI aS UE 2 10 Chapter 3 Cat No 448B Input Adapter Board 3 1 Del onu c 3 1 3 TC WI deseo Un S Rune D Ult MM ee 3 1 3 3 Component and Connector Layout eee 3 2 3 4 Preview Theatte issenensis FUA VEND UE E E SEES 3 2 EE MENO eicere eere eere D 3 2 3 4 2 Installati n nenei iaa EE RR E RAAR 3 2 343 VGA 11 0 0 eee ene eee ree e a ee a a Ea oe 3 3 3 3 UVTI SN 3 4 Chapter 4 Specifications 1 sees 4 1 Appendix A Background 1 1 7 7 sse retten A 1 Ad MAO UGC Im A 1 A 2 How Loud Is a Movie d A 3 A 3 Standardizing a Measurement Technique for Soundtrack Loudness A 4 A 4 Analysis of the Dalla sei taie oio Potes a dieeusteiiedeanicipeeesaedenet ahead A 6 i 2 2 23 2 4 2 5 2 6 3 1 List of Figures Model 737 front panel 429i rb HDD e mt M UI ei nu M Ic M UNE 2 1 Det il of tront Py AN LOS seo eder btc Re n Rot eda E Ret E 2 1 Mod l 737 Bag panel iusto iet die opui dee vee eed sce eke 2 3 Audio input connectors detail of rear panel sese 2 3 Mon and DC Out and power control connector eee 2 4 Mo
6. dB below Full Scale digital e The calibration for each input must be performed with only that input connected When that input is calibrated unplug it and plug in the next input to calibrate All inputs are connected after the calibration in preparation for the actual measurement The calibration procedure is discussed in section 2 3 6 The following sections discuss how to interface the Model 737 to the most commonly used signal sources Connecting to an Audio Console 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 Model 737 Soundtrack Loudness Meter Leq m Operation and Features 2 3 2 2 3 3 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 matrix encoded 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 For more permanent installations connect to pins L and J on the rear panel of the cinema processor For a cinema processor used in a theatre the Lt and Rt signals are found on the red and green test points ground
7. is black respectively on the Cat No 150E or Cat No 150F The Cat No 150D does not have test points Thread up and play a length of Cat No 69T test film at Dolby Level as the signal source Set the unit to Format 04 for the calibration steps that follow in section Section 2 3 6 Calibration Procedure Note Alignment in Format 05 or mono will result in incorrect levels Connecting to a DA10 20 Digital Adapter When checking levels in a theatre or print checking facility the Model 737 derives its input signals directly from the J8 connectors on the back of the DA 10 20 The following table lists the CP Audio Out Conn J8 pin number signal assignments and the nearest ground pin Table 2 5 DA10 20 Audio Out Conn J8 Signal Assignments m fefe For each channel the active pin of the output is wired to pin 2 and the ground to pin 3 of that channel s XLR connector If the units are in the same rack there should be a connection between the metal parts of the 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 When used in a theatre to check released prints thread up and play a length of Cat No 69T US SR D test film at Dolby Level as the signal source Cat No 1012 is still available but seldom used Model 737 So
8. of Cat Nace 3 1 Connecting the Cat No 448B to the CP65 and CP55 sese 3 3 laukvencconde M 3 3 Pin convention continued etr 3 3 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 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 The Dol by 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 measure ment time Since the measurement time is a critical factor in arriving at an accurate re sult 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 measure ment For example a ten second spot requires about two frame accuracy whereas a two minute thirty second trailer needs o
9. of the analog or digital film itself peak levels were checked periodically with a sound pressure level meter in an auditorium The lines indicating Dolby A type and SR show the maximum theoretical levels of these formats The data shows the maximum recorded levels are slightly higher than these theoretical numbers This is not surprising and is due to the slight excessive dimensional modulation consistent with contemporary practice A Q
10. valid measurement technique frequency weighting determining the frequency ranges that most closely correlate to loudness annoyance e long term averaging measurement definitions such as Leq 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 The selected samples used for testing included contemporary digital trailers sections of recent digital releases maximum level Dolby SR and A type releases typical dialogue only recordings in various formats including Academy mono and UK commercials Model 737 Soundtrack Loudness Meter Leq m Background 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 Research at Dolby has revealed that placing heavier emphasis on the 2 6 kHz region better matches how people react to soundtrack loudness It was also discovered that the CCIR weighting curve used to measure low level recording medium noise more closely matched the subj
11. 2 5 to connect the DA10 20 to the positive tags on the Cat No 448B and ground all the negative tags to a O V tag on the Cat No 448B 5 Connect the Cat No 448B output to the Model 737 3 4 3 Alignment 1 Thread up and play a length of Cat No 69T US or Cat No 1012 with the cinema processor placed in Format 10 Dolby Digital Connect each channel to the Model 737 in turn and align the Model 737 in calibration mode for a null point at 85 dB L C R Sw and 82 dB Ls Rs for each channel 2 Thread up and play a length of Cat No 69T with the cinema processor in Format 01 Mono and check that the calibration of the optical pre amp card is normal 3 Select Format 04 Dolby Stereo Connect each channel to the Model 737 in turn 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 Checkthat the Model 737 reads 3 dB higher when in Format 05 than in Format 04 for each channel Model 737 Soundtrack Loudness Meter Leq m Cat No 448B Input Adapter Board 3 5 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 dubb
12. 7 Figure 2 6 Model 737 block diagram The six input channels each have a balanced to unbalanced stage buffering the input sig nal Trimpots on the front panel set each channel s input level The unbalanced signals then pass to the metering CCIR filters and make up gain stages The signals on the wipers of the selector switch controlled by the Mon trimpot are buffered and sent to Mon Out on the rear panel 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 The analog long term averaged DC signal is sent to the DC Out connector on the rear panel for optional connection to a chart recorder or moving coil meter The short term average DC voltage is converted to12 bit binary and sent to a 6805 processor that also averages but over a much longer time span The samples are taken at 850 msec intervals summed divided by the time since the Start button was pressed and then converted to a square root value This value is then converted to a dB log scale scaled to a reference level of 85 and sent to the front panel LED display When the Stop button is pressed the averaging circuit and a
13. Rt matrix encoded 85 Rt matrix encoded 88 85 L matrix decoded 85 L matrix decoded 88 85 C matrix decoded 85 C matrix decoded 88 Ls 82 R matrix decoded 85 R matrix decoded 88 Rs 82 S matrix decoded 85 S matrix decoded 88 Sw 85 1 Press the Cal button 2 Sendthe appropriate test signal at Dolby Level to the first input only Connect only one input at a time when calibrating 3 Adjust the input trimpot associated with that input until the and LEDs beside the trims are of approximately equal brightness null point and the Leq m value displayed is correct according to Table 2 6 Model 737 Soundtrack Loudness Meter Leq m Operation and Features 2 3 7 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 The window of equal illumination is designed to be extremely narrow which yields an accurate level setting when both LEDs are on albeit dimly the gain error is less than 0 1 dB 4 Unplug the calibrated input and repeat the calibration procedure for all other input channels one at a time 5 Asa final check plug in all inputs and send the appropriate tone to all applicable channels The meter should reg
14. 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 Pushbuttons e 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 e Start Push to begin a measurement e Stop Push to stop a measurement and display the final level of the measurement Model 737 Soundtrack Loudness Meter Leq m Operation and Features 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 r Analog Audio Inputs CE Left Right Left Surround Right Surround EL 00000 KO Rt orien 4 e Dolby Laboratories Inc San Francisco USA Wootton Bassett UK Model 737 Ch1 Lt Ch2 Dolby and the double D symbol are trademarks of Dolby Figure 2 3 Model 737 back panel 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 LURt measurements of two channel encoded material The Right Surround and Subwoofer channels share a co
15. and pass this auxiliary signal to the DS4 E UK auxiliary meter input normalized for Dolby Level This increases the versatility of the board to cope with varying installation requirements from the studio through preview and optical transfer facilities Note Refer to Figure 3 4 Cat No 448B Interface Adapter schematic on page 3 7 Logic map Table 3 1 shows the logic map of the Cat No 448B X switch closed O switch open Table 3 1 Logic map of Cat No 448B 3 dB 6 trk in Format No Dolby SR Aux in Dolby A Aux in No Dolby SR 6 trk in Dolby A 6 trk in Dolby Digital Dolby Digital 0 dB Model 737 Soundtrack Loudness Meter Leq m Cat No 448B Input Adapter Board 3 3 Component and Connector Layout C2C5 D1 Sw a IU e es JH L L C C Rs Rs Sw Sw NL emere eme to MODEL a R26 C1 C4 RIR3R2 R4 R5 j gt EIE 75 s A u m DTI mene no B RI RY RY RI not nig E Moon L1 R15 DET 000000 Ti Fe SIG FROM Cok see ME DA MON Era m Ds GND CAT 7 3 LK1 4 CAT NO 448B INTERFACE ADAPTOR FOR MODEL 737 A2A7463 REV A Figure 3 1 Cat No 448B Interface Adapter 3 4 Preview Theatre 3 4 1 Concept The DA 10 or DA20 feeds six Dolby Digital channels the Cat No 150 supplies two Since the DA 10 20 output is unbalanced the posi
16. ctive loudness than a peak measurement Leq Peak Level CCIR weighted C weighted fast 5 6 dB offset poe AClip watch death 5 water dummies RAF Levis 80 Sanyo Smirnoff 175 Figure A 7 Comparison of Leq m with peak levels for UK commercials Figure A 7 shows that some of the UK commercials are pushing at the maximum available loudness of the media format Even these Dolby A type soundtracks show a loudness far greater than a constraint on maximum peaks would control Attempts have been made in Europe to restrict loudness of commercials by defining a maximum level with respect to 100 of the medium s clipping level For example a 50 limit would mean that no peaks would be permitted to exceed a level 6 dB below the maximum excursion of a Dolby A type stereo optical release This constraint however would have the effect of restricting dynamic range and not necessarily of controlling the subjective loudness of the material US created digital trailers typically have an Leq m level up to 15 or even 20 dB above the feature they advertise It must be emphasized however that the higher Leq m values of trailers is caused in part by the selection of only the loudest most exciting segments of the movie packed into the 90 second or two minute sample When the entire movie is averaged the Leq m value is normally much lower Verification of the Data Although the prime measurements for the data were direct electrical sums
17. del 737 DIGG KO ae PAN iiic eese crease acs etes te b xp esiti Sassi usn tela Dr bastuu ict ia eniinn reaa 2 10 Cat No 448B Interface Adapter E 3 2 Installation of Cat No 448B iei eet ima e dedi lup NOM IU 3 2 Typical E dii I 3 4 Cat No 448B Interface Adapter schematic 1e eio irte ste diner rese cia Geert 3 7 Peak levels of photographic soundtrack formats eene A 2 A weighting vs CCIR weighting curve offset by 5 6 dB sess A 5 CCIR weighting Leq m shows influence of 2 6 kHz region eese A 6 Comparison of weighted and un weighted Leq eee A 7 Comparison of Leq m and peak levels esee A 8 Peak levels in reel 4 of Shine iouis Ett t tb e PER n duda Um Med Es A 8 Comparison of Leq m with peak levels for UK commercials sesssss A 9 2 1 2 2 2 3 2 4 2 5 2 6 3 1 3 2 3 3 3 4 List of Tables XLR input wiring convention for channels 1 6 sese 2 3 Non tut wiring GOBVEDLUOH qddscdoqusteriqiadti drip o dr I Ries MB pM e Mer T 2 4 DC Out Winne convention MR c n 2 4 Power and control connector wiring convention serene 2 5 DA10 20 Audio Out Conn J8 Signal Assignments see 2 6 Calibration levels for Dolby Dolby SR and Dolby Digital soundtracks 2 7 eee map
18. dness Meter Leq m Operation and Features 2 1 1 2 1 2 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 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 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 See Section 2 3 Connection and Calibration for a complete discussion of how to connect and calibrate the Model 737 to different signal sources 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 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
19. ective annoyance criteria Figure A 2 dB 20 10 A weighting TAS 10 CCIR weighting i 20 30 P2 40 Hz 10 100 1k 10k 100k Figure A 2 A weighting vs CCIR weighting curve offset by 5 6 dB Although there is no technical parallel between high level soundtrack loudness and low level recording medium noise the CCIR curve provided a convenient weighting filter for the tests and a better subjective match than Leq a The CCIR curve can be further adapted to represent soundtrack loudness by offsetting the level by 5 6 dB with a 2 kHz reference point Loudness values derived from this characteristic are referred to in this document as Leq m Figure A 3 shows the relationship between Leq m and Leq a for UK commercials Although the average values for Leq m and Leq a are the same higher relative Leq m values show a signal content with greater emphasis in the 2 6 kHz region Model 737 Soundtrack Loudness Meter Leq m Background Leq CCIR weighted Leq A weighted Leq Leq 5 6 dB offset watch death 85 water dummies RAF Levis Sanyo i Smirnoff 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 hiera
20. end 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 amp C input trimpots on the Model 737 will be reversed 10 Set the DS4 E into Matrix Monitor mode with the SR A or Proc 2 switch not illuminated Ensure the DS4 E meter is in direct mode rear toggle switch up and the red rotary switch on the Cat No 291 of the DS4 E is set to Lt Rt position Send tone at Dolby Level to Lt Rt 6 dB on DS4 E meter and check Model 737 for 85 per channel Select SR on the DS4 E SR A or Proc 2 switch illuminated and check Model 737 for 88 per channel Place the DS4 E meter to Monitor position rear toggle switch in down position and adjust the rear trim pots on the meter for 6 dB per channel the DS4 E must be in SR mode Thread up and play a length of Cat No 69T and insure alignment of Cat No 240A Set the DS4 E in Matrix A and Optical mode and adjust RV1 L and RV2 R for a null point of 85 per channel on the Model 737 Set the DS4 E in Matrix SR and Optical mode and check that the Model 737 reads 3 dB higher on each channel Cat No 448B Input Adapter Board Model 737 Soundtrack Loudness Meter Leq m A 0 G Uld A Sb Uld A GL EL Uld ZL Uld LLZOG EMS ZMS LMS AO Vb Uld 8 Uld A SL 1 Uld AN6PO SOWO ZII
21. er is 54057 In some countries the primary cable for the module may not have a mains plug fitted These unterminated leads must be properly wired to a mains plug in accordance with the following international code e Brown wire Live or hot e Blue wire Neutral CAUTION If you are uncertain about the wiring of your mains outlet do not use it Consult a qualified electrician Interface The connections for remote start stop control are normally wired to a relay across the projector motor or to a console mounted toggle switch When the contacts close or the Stop button is pressed the display flashes the last measured value When the contacts open again or the Start button is pressed the unit enters measurement mode Pressing the Cal button causes the unit to enter calibration mode regardless of the last function pressed To remotely start a measurement from calibration mode the contacts must close and then open again The contacts should be capable of passing 10 mA and should not have contact with other circuits A simple toggle switch or a pair of uncommitted relay contacts is ideal Grounding There is no connection between the audio common inside the unit and the metalwork For most grounding schemes a link of 16 AWG between pins 4 and 7 of the power control connector provides a satisfactory grounding scheme If this induces hum be cause of a loop via the rack mounting the link can be removed Model 737 Soundtrack L
22. ing interface Cat No 448 output switched to the CP65 S The Cat No 448B should take this unbalanced six track signal as the main input grounding the negative inputs and the two track signal from the Cat No 150 via the auxiliary input OPT and MAT should be fed from either the FA line of the CP65 or the MAT line of the dubbing interface and SR should be grounded Follow the installation steps in Section 3 4 2 on page 2 The six track input is paralleled from the 300 mV input to the CP65 after any switching between the monitor bus and DA20 Cat No 448 No 448 6p2w Switcher 6p2w Switcher lt DA10 20 DA10 20 x6 unbal x6 unbal bh CP65 x6 bal x2 Lt Rt opt Cat No 448B Model 737 Figure 3 3 Typical UK setup Studio monitor bus Example 2 The six track main inputs are balanced and the two track inputs are derived from the main input channels 1 amp 3 or 2 amp 3 OPT MAT and SR lines are fed from the dubbing interface The DA20 output should be routed at the calibrated level to the main monitor buses of the studio before the dubbing interface Cat No 448 CP65 x6 unbal x2 Lt Rt opt x6 bal Cat No 448B 3 Model 737 Studio monitor buss 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
23. 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 Set adjustment sets the level that lights the Trip LED 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 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 trim pots for the six analog inputs and a 6 4 2 channel switch DO bas 64 2 L C R Ls Rs Sw Mon Soundtrack Loudness Meter Leq m T Model 737 Trip 5 Oe e d oo TT Set e Figure 2 1 Model 737 front panel The right side of the front panel is shown in detail below Cal Stop Audio Input Trimpots Calibration LEDs Mon Out Trimpot Cal Start Stop L 4 OE ee T EE _V 64 2 L C R Ls Rs SwMon E em ee USERREUD Set Start Trip Set 6 4 2 channel switch Figure 2 2 Detail of front panel controls Model 737 Soundtrack Lou
24. ister an Leq m value of 88 Dolby LURt 9 Dolby Digital Dolby SR Lt Rt and Dolby LCRS soundtracks 94 Dolby SR LCRS 6 Repeat the calibration if there is a significant discrepancy Note The 3 dB difference between L C R and the surround channels matches the transfer levels for Dolby Digital movie soundtracks Automated Input Adapter Board Cat No 448B An additional input adapter board is available for UK type installations that provides channel switching and level calibration specific to the format under measurement The card follows a logic source from either a Dolby Cinema processor i e CP65 the DSA E mkII UK or a custom control to switch between formats Re calibration and re plugging is then avoided except for normal periodic alignment checks see Chapter 3 Cat No 448B Input Adapter Board Model 737 Soundtrack Loudness Meter Leq m Operation and Features 2 4 2 5 2 5 1 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 V AC input and 100 125 V AC input Please ensure that the correct transformer is ordered for your local mains voltage e For 110 VAC Dolby part number is 54058 e For 230 VAC Dolby part numb
25. mmon filter and rectifier so the Subwoofer input is not normally used except when measuring 5 1 channel material r Analog Audio Left Center 8 Right Left Surround Right Surround Subwoofer 000000 au the um D o are See arm mA 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 Chassis Audio Audio Model 737 Soundtrack Loudness Meter Leq m Operation and Features 2 2 2 Mon Out CE 8 500mA fogs ME e oa o s S amp I 9509J09 OES e me 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 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 Chassis Mon signal out Mon signal common 2 2 3 DC Out DC Out is an unbalanced output to drive an optional moving coil meter chart recorder Usi
26. ness Meter Leq m A 1 A 1 1 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 Over the past few years the film production community has become increasingly concerned that movies are getting louder In addition movie goers often complain that movies are too loud and as a result many theatres now reduce the audio fader below the calibration level used in the dubbing theatre This chapter introduces some of the issues that motivated the creation of the Dolby Model 737 Soundtrack Loudness Meter Leq m e What factors affect soundtrack loudness e How can loudness be quantified e Donewsound formats Dolby SR Dolby SR D Sony SDDS and DTS exacerbate the problem Loudness Those familiar with movie soundtracks won t be surprised at the subjective statement that The Right Stuff 1983 Dolby A type 70 mm and Dolby A type stereo optical was a loud movie The Right Stuff was a subjectively louder movie than Shine 1996 Dolby Digital Since Shine was subjectively louder than Days of Heaven 1978 perhaps a case could be made that movies have been getting both louder and quieter Of c
27. ng 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 Table 2 3 DC Out wiring convention Chassis DC out 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 kQ Model 737 Soundtrack Loudness Meter Leq m Operation and Features 2 2 4 2 3 2 3 1 Power and Control The 8 pin power and control connector uses the following wiring conventions for the control and AC power signals Table 2 4 Power and control connector wiring convention LI NECI NENNEN a x The trip output is a simple open collector buffer that passes current when the trip value is exceeded The voltage on the open trip contacts should not exceed 24 VDC and the current passed when closed should not exceed 20 mA Connection and Calibration The Model 737 may derive its input from a variety of signal sources including an audio console a cinema processor the SDU4 Surround Decoder the DA 10 20 Digital Adapters and non Dolby digital adapters The Model 737 accurately measures both matrix encoded two channel and decoded four and six channel sources The following three important points are independent of the signal source e Dolby Level should be used as the test signal input level In the digital domain Dolby Level correlates to 20 dBFS 20
28. nly two second accuracy for correct measure ment 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 The Model 737 consists of six input channels with setup trims followed by five weight ing 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 Model 737 Soundtrack Loudness Meter Leq m Chapter 2 Operation and Features 2 1 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
29. ol are registered trademarks of Dolby Laboratories 2000 Dolby Laboratories Inc all rights reserved W01 111 Table of Contents LEISEOPPIGUTBS eroe eee nee vere ren ERU ROI E S i tU ud v List of Tables PP vi Chapter i IntFOdUCllOliu eod asd iban can lados Gnade eds 1 1 Chapter 2 Operation and Features esses 2 1 2 1 Pront Panel CODBIPOL uu super ipe ttes es taie Inque a cues ap E REER 2 1 2 1 1 6 4 2 Channel Switch Dm 2 2 21 2 Tnp t TOMPpots eoe eO b iden i aies 2 2 My UTS CU em RS 2 2 214 MM I DET 2 2 423 Back Panel C OHDeOfOES eecesuiee dion aque ei intet niam du dua pn ipn e and His 2 3 2 2 1 Analog Audio Inputs iioc in esnc reete orsa sd vaseeriernsdeseavesnossaes 2 3 AME bem S 2 4 22 DO Ouf rc HQ 2 4 2 24 Power and Control 5 obti ae et vUox Spa b RG 2 5 2 3 Connection and JIDEAU GEL ope repens ipe mature de rio Neb aS Ge 2 5 2 3 Connecting to an Audio Console eese 2 5 2 3 2 Connecting to a Dolby Cinema Processor essss 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 ares misc repone veio ed Reina belge
30. oudness Meter Leq m Operation and Features 2 6 Block diagram o Monitor Out in L Lt gt Rectifier in i CCIR 4 Le o H xX v Filter in 7 T d C a in Y l Rectifier in j CCIR o la ad y ls 73 Filter ad ii in EET ees E in R Rt Rectifier In A CCIR Co o t xX M Filter i in x REAN Sub af in am Rectifier in A o audes CCIR 4 Co o H Rs M Filter in Rectifier A o 2 CCIR L Lo TO c A X bd Filter 7 Rectifier and LED Driver rb IDEAS fine level Y d l1 o DC out Lt Square Display Average Root AID Driver H H Start F Average 3 i Hex L jen Trip Level ET oa Logic Run 7 2 Trip point out ENT 5 Y Hold o Remote Start Stop r o 47
31. ourse this does not lead to an objective assessment selected titles can be used to prove either trend Gone with the Wind 1939 could be used to argue that films have become quieter over the last six decades 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 back of the new stereo optical soundtracks were set up such that an equivalent pink noise signal would generate the same 85 dBc with the playback fader set to the calibrat ed setting This meant that theatres playing films at the calibrated fader setting fader 7 on most cinema processors would reproduce the same volume level selected by the film director and audio engineers in the dubbing theatre 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 tech nology 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 In recent years the new digital formats have further increased the headroom Figure A 1 dB
32. rchy on the right of the figure un weighted differs from that on the left weighted The slope of the connecting lines denotes the amount of bass content in the program Lines with higher slopes indicate larger amounts of bass while horizontal lines 0 slope or lines with negative slope indicate less bass content Of the samples shown notice that ndiana Jones and the Temple of Doom is raised in the hierarchy due to the lack of bass in the five minute sample This matches the apparent loudness of the sample one of the loudest Dolby A type films Model 737 Soundtrack Loudness Meter Leq m Background Leq CCIR weighted 5 6 dB offset Empire Trailer D Twister Trailer D Star Wars Traile Evita Traile Indie Temple of Doom Slayer s Return S Mars Attacks Trailer Shine Trailer ST Generations Reel 2 D Prisoners of the Mountain Trai a Shine Reel 5 D Gakkou No Kaidan A Shine Dialog D Spencer s Mountain Mono Leq Unweighted 100 Shine Reel 4 70 65 60 Figure A 4 Comparison of weighted and un weighted Leq Figure A 5 compares the maximum peak level reached in each sample with the weighted Leq m value The slope of the line between the values is now proportional to the dynamic range the range between the average level and the loudest peaks on the soundtrack It is important to consider the dialogue level in these samples The concept of associative loudness discussed above is
33. some frequency level factors and are typically switchable to different weightings A weighting for example attempts to account for the ear s decreased sensitivity to low frequencies The length of the sound is another important factor in determining the perceived loudness of a sound It is well known that people attending a loud three hour rock concert may suffer from some temporary hearing loss after the concert A five minute exposure to the concert however does not create the same effect It can be construed that the longer a loud sound lasts the greater the apparent loudness or annoyance Loud sounds of short duration may cause great surprise but little annoyance A sudden gunshot in the middle of an otherwise quiet scene causes few if any complaints Repeated gunshots however can distress an audience One measure of sustained loudness is called Leg loudness equivalent which was originally derived to gauge potential hearing damage from exposure in industrial environments to sustained varying level sounds Leq can be defined as the level of a steady state tone with an equivalent level as the level of a time variant signal The original intent was to define potential hearing damage in industrial noise environments Several different formulae define Leq but all perform averaging of the level of material over time Standardizing a Measurement Technique for Soundtrack Loudness The following factors must be considered to develop a
34. supported by the comparison of dialogue levels of Spencer s Mountain 1963 an Academy mono film with the dialogue level of Shine 1996 a Dolby Digital release The two films show identical Leq levels confirming the supposition that mixers set dialogue levels at a plausible point associative loudness regardless of the format of the release Model 737 Soundtrack Loudness Meter Leq m Background Leq Peak Level CCIR weighted C weighted fast 5 6 dB offset 110 Shine Reel 4 105 Empire Traile D Twister Trailer D c Star Wars Trailer Evita Trailer Indie Temple of Doom Om UO Slayer s Return Mars Attacks Trailer Prisoners of the Mountain Trailer D Shine Traile ST Generations Reel 2 D pages c 80 Shine Reel 5 D Gakkou No Kaidan A pe 70 Shine Dialog D 65 Spencer s Mountain Mono 60 Figure A 5 Comparison of Leq m and peak levels Shine demo 1 Rach Ill I 75 d Figure A 6 Peak levels in reel 4 of Shine Time Model 737 Soundtrack Loudness Meter Leq m Background A 4 1 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 subje
35. tive tags should be used and the negative tags grounded To ensure that the auxiliary two track input is used in matrix mode the MAT and OPT logic lines should be paralleled together and fed from the CP65 logic Additionally the SR logic line should be permanently grounded to disable the 3 dB attenuation on L R of the six track input to ensure sufficient gain 3 4 2 Installation DA10 20 unbalanced x2 Lt Rt opt gt x lt O Cat No 448B Model 737 Figure 3 2 Installation of Cat No 448B 1 Before mounting the Cat No 448B ensure the jumpers LK1 4 are in the upper 1 amp 3 position 2 Connect the Cat No 448B with the cinema processor using Table 3 2 and adhere to the pin conventions in Table 3 3 and Table 3 4 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 150 Rt J7 pin J J12 pin 7 MAT amp OPT logic lines J13 pin W J6 pin W SR logic line 0 V on 448B 0 V on 448B 15 V J2 pin 5 J15 pin 5 15 V J2 pin 13 J15 pin 13 OV J2 pin 9 J15 pin 9 Table 3 3 Pin convention EXER ERESERETESEQESESRA ET EZES ES RAE BEB EHE ECSESIEEE ee Table 3 4 Pin convention continued EJEJEJEJEIUS 3 Mount the Cat No 448 B to the CP65 back plane using the spacers provided 4 Use Table
36. ty The resultant distortion from overloaded equipment may well exacerbate the loudness problems of recent soundtracks causing increased incidence of complaints How Loud Is a Movie Loudness is an extremely subjective term and has been defined and measured in many different ways Various definitions have arisen from a desire to quantify loudness in specific situations e How annoying is the background noise level in a working space e How damaging is sustained high level noise exposure e How intrusive is the noise level of a recording or transmission medium e How can the instantaneous loudness of different spectra be compared In attempting to measure the loudness of a movie or trailer soundtrack conventional level meters in the recording chain are of only marginal help A VU meter has slow time constants and is of little use in detecting short term peaks The PPM meter was designed to show short term peak levels that might clip the recording or transmission media Neither system demonstrates an index of what determines the perceived loudness of a film soundtrack Model 737 Soundtrack Loudness Meter Leq m Background A 3 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
37. udness Meter Leq m Background A 2 In practice the following undesirable symptoms have arisen e 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 e Theatres are playing films substantially below the calibrated level A fader level of 5 as opposed to the calibrated level of 7 is not uncommon representing a level reduction of approximately 6 dB Trailers are fighting for competitive loudness Theatre playback levels are often set by complaints generated by the loudest and earliest element of the show If the playback level is set in response to the loudest trailer the feature often plays at the same reduced level The result is that the dialogue level of the feature is lowered by the same level deemed necessary to attenuate the trailer A feature film played 6 dB below the calibrated level may have serious dialogue intelligibility problems e Mix engineers are using ear plugs to avoid the risk of hearing damage e In Europe where commercials are played before the feature competitive loudness has led to the desire for a uniform measurement technique and a self disciplined constraint It is possible that the increased use of headroom from Dolby A type to Dolby SR and digital releases has not been matched by a corresponding increase in power amplifier and loudspeaker capabili
38. undtrack Loudness Meter Leq m Operation and Features 2 3 4 2 3 5 2 3 6 Dolby Format 04 Level 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 Connecting to the SDU4 Surround Decoder The Model 737 can interface with the SDUA either before or after decoding To measure the matrix encoded signal connect the signals intended for the SDU4 s Lt and Rt inputs to the Lt and Rt inputs channels 1 and 3 on the Model 737 To measure the decoded signal connect the four channel L C R S outputs from the SDUA to the Left Center Right and Left Surround inputs on the Model 737 Calibration Procedure To obtain an accurate Leq m measurement the input trimpots must be used to calibrate the inputs to standard levels to account for the differing levels and formats of the various signal sources Use the table below to determine the calibration setting and follow the steps below to calibrate the inputs Table 2 6 Calibration levels for Dolby Dolby SR and Dolby Digital soundtracks Dolby SR Format 05 Level Dolby Digital Format 10 Level Channel dB Lt matrix encoded 85 Lt matrix encoded 88
39. veraging routine are reset while the last value measured is displayed The pushbutton logic is a simple tri stable gate that drives the LEDs in the pushbuttons and also generates processor interrupts to indicate mode changes It is remoted to the back panel via a single start stop line Model 737 Soundtrack Loudness Meter Leq m Chapter 3 Cat No 448B Input Adapter Board 3 1 3 2 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 con trol 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 The Model 737 is then calibrated to compensate for this attenuation with 3 dB more gain on the L and R input trim pots When Format 05 Dolby SR is selected the attenuation is switched out giving the required 3 dB gain on Lt Rt for this format In addition when either matrix formats are selected Format 04 or 05 the C Ls Rs and Sw channels are muted This concept is appropriate for most studio applications assuming that Lt Rt exist on monitor buses 2 3 or 1 3 Input jumpers are available to switch between the two The Cat No 448B can switch an auxiliary two track input i e Optical from Cat No 150 to the Model 737
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