ThePicMix

White PaperA Surround Sound Primer

by Michael Tapes

TM

Acknowledgements

PicMix products are designed and manufactured by TG Systems, Inc.

PicMix is a trademark of TG Systems, Inc.Concept I, Status, Premiere, and DISKMIX are trademarks of Otari Inc.Dolby is a trademark of Dolby Laboratories Licensing CorporationDTS is a trademark of Digital Theater SystemsSDDS is a trademark of Sony Cinema Products CorporationAll other trademarks belong to their rightful owners

The PicMix White Paper was written by Michael Tapes for Otari CorporationCopyright ©1995-6 TG Systems, Inc. Tel: 516-933-1945 Fax: 516-932-8091 Email: mtapes@aol.comAll Rights ReservedFirst Printing October, 1995Revised Printing January, 1996

A note from the author…I wish to thank the many people who over the years have given so freely of their time and knowledge so that I could bebetter equipped to do my job. PicMix would not have been possible without you. To those listed below and to the somany more not listed, my sincere thanks…Paul Galburt, Doc Goldstein, Michael Minkler, Wylie Stateman, Greg Lan-daker, Steve Maslow, Barry Ross, Kim Aubrey, Larry Goga, Oliver Stone, Roy Segal, Mark Berger, Steve Boze, JimAustin, Tom Davis, Ben Rizzi, Jim Corbett, Leslie Shatz, Howard Schwartz, Scott Gershin, Rick Larson, Steve Potter,Gary Fradkin, Tom Scott, Bobby Mackston, Peter Cole, and all of the others.

Otari, Inc.4-33-3 Kokuryo-cho,Chofu-shi, Tokyo 182 JapanPhone: (81) 4-2481-8626Fax: (81) 4-2481-8633Telex: J26604 OTRDENKI

Otari Corporation378 Vintage Park DriveFoster City, CA 94404 USAPhone: (415) 341-5900Fax: (415) 341-7200L.A. Sales: (818) 972-3687S.E. Sales: (615) 255-6080

PicMix Products are sold and serviced worldwide by

Otari Deutschland GmbH.Sales and Marketing EuropeRudolf-Diesel-Strasse 12D-40670 Meerbusch(Osterath) GermanyPhone: (49) 2159-50861/62/63Fax: (49) 2159-1778Telex: 8531638 otel d

Otari Singapore Pte., Ltd.40 MacTaggart RoadSingapore 368085Phone: (65) 284-7211Fax: (65) 284-4727Telex: RS36935 OTARI

IntroductionThis document is designed to provide an overview to the use of thePicMix™ Monitor and Panning systems in the audio post production en-vironment. For the audio professional who is proficient in surroundsound audio techniques and technologies, it will explain how PicMixprovides cost effective solutions to the day to day problems encounteredin this work. For the audio professional who is new to surround soundaudio post production, it will summarize the process and provide a ba-sic understanding of the solutions that PicMix provides.

The PicMix product line currently consists of 2 products…the PicMixMonitor and the PicMix Panner. Both are modular systems offering a va-riety of system configurations as well as the ability to expand the sys-tems in the field.

With the addition of PicMix, standard multi-bus audio consoles are nowable to provide the features and functionality that are necessary in orderto post audio to picture in a surround sound environment. Dedicatedand expensive re-recording , dubbing, or “post” style consoles are nolonger necessary to provide mix-to-picture services using film style tech-niques. It is our sincere hope that this white paper will give you an un-derstanding of how the PicMix products can help to integrate surroundsound audio post production into your facility or working environment.

The PicMix Monitor and Panner are sold and serviced worldwide byOtari Corporation, which has served the professional audio market withexceptional and innovative products for over 25 years. They were devel-oped and are manufactured by TG Systems, Inc., whose principals,Michael Tapes and Paul Galburt, have a long involvement with success-ful audio product designs including API consoles, Sound Workshopconsoles, ARMS, JH-50 and DISKMIX automation systems, and Otari’sCONCEPT I, Status, and Premiere audio consoles.

In this paper we will focus on the film style mixing techniques that havebeen developed in Hollywood studios and facilities over the last severaldecades. While you may not have the need to mix feature length motionpictures, these techniques are directly applicable to whatever type ofsurround sound work you will be doing, whether it be television, film,commercials, or multimedia.

The Surround Sound ExplosionAudio material containing surround sound channels is all around us!Virtually all US made major motion pictures are released with surroundsound audio channels. Broadcast and cable television programming isloaded with surround sound from episodic drama and comedy series, tosports and special programming. The majority of home video rentalshave surround encoded soundtracks. All of the future video deliveryformats now under discussion include surround sound capability as a

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specific part of their design specifications. Even future audio only for-mats (Super CD, etc.) are being discussed in terms of multiple channels(more than 2) including surround sound channels.

What the above paragraph points out so vividly, is that if a commercialaudio facility cannot handle multi-channel multi-format audio, it willnot be competitive in the marketplace. And handling these formats isnot enough. They must be able to be dealt with as quickly and easily ascurrent stereo formats are handled.

What is Multi-Channel Multi-Format Audio?Since the 1960’s, stereophonic (2 channels, Left and Right) sound hasdominated the music recording industry. Television, until recently, hasbeen monophonic. And the film industry, until the early 80’s, was alsoprimarily monophonic, except for an important distinction. Special pro-jects were released using various multi-channel formats, breaking themonophonic barrier, as early as 1941, when Walt Disney’s Fantasia wasreleased. The film industry has been and still remains the leader in inno-vations in multi-channel audio formats. Even the term “stereophonic”was first used by the film industry and actually referred to multi channelaudio with a surround (or effects) channel. Only years later, after the hi-fi industry, came out with it’s left/right 2 channel multi-channel formatdid the term stereo become associated with 2 channel sound. (When I re-fer to “stereo” in this paper I mean the hi-fi 2 channel stereo, as com-monly used. Note, however, that Dolby™ Stereo refers to the 4 channelencoded system as described below).

Surround Sound Formats

Over the years Hollywood studios have pioneered numerous multi-channel formats. Not all of them used the same number of audio chan-nels and even those that did, placed the audio in different locations fromeach other. The listing and history of these formats are beyond thescope of this paper, but let me list the formats that are in current usagein film and television.

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Dolby™ Stereo (also known as Dolby™ Surround)4 channels - Left, Center, Right, SurroundThis is the most common surround sound format used today. Almost allmajor shows and films produced for theatrical release, broadcast televi-sion, and direct to video are presented in Dolby™ Stereo audio. Thissystem uses the Dolby process of MP (motion picture) encoding to createa stereo (2 channel) release that may be decoded into its 4 playbackchannels. If no decoder is used then the show will play back properly instereo or mono. This compatibility between mono, stereo and full 4channel playback (all on a single release print or video) is one of themain reasons for the popularity of this format. There are other encodingsystems that are compatible with Dolby Stereo and maintain almostidentical technical characteristics. Two of these systems are Ultra-Stereo™ and DTS™ Stereo.

Note: Dolby Stereo format can also be decoded for television without the centerspeaker. This becomes a Left/Right/Surround system, having the Left and Rightspeakers create a phantom center channel.

5.1 Format6 Channels - Left, Center, Right, Left Surround, Right Surround, Sub-wooferThis is the format used in several new digital release formats for motionpictures. It was also the most common format used in recent 70mm re-leases. This differs from the Dolby Stereo format in that the surroundchannel is stereo (2 channel) rather than mono, and there is also a sub-woofer channel. The “5.1” designation is based on the fact that the 5front and rear audio channels are full bandwidth, but the sub-wooferchannel has limited bandwidth, carrying only extremely low frequencies(generally those frequencies below 80 or 120 Hertz, depending on whosedelivery system is used). The two most popular motion picture systemsusing 5.1 are Dolby Digital (SR-D) and DTS Digital (DTS). These areboth digital audio systems in which the 6 channels of audio are stored asa digital bit stream (although SR-D is stored optically on the film print,while DTS is stored on a separate “laserdisc” which is time code linkedto the film print). The current proposal for HDTV (High Definition Tele-vision) includes 5.1 audio, as does DVD (Digital Versatile Disk), the newstandard 5” CD size video/computer disk format.

SDDS (Sony Digital Dynamic Sound)8 Channels - Left, Left Center, Center, Right Center, Right, Left Surround,

Right Surround, Sub-wooferThis format is similar to the digital formats mentioned above except that8 channels of audio are handled, adding the left center and right centerfront speaker positions. Although it is not designated as such, this sys-tem could be thought of as 7.1 with 7 channels of full band audio and 1channel (sub-woofer) of limited bandwidth. The SDDS “player” has ad-ditional output modes so that the 8 channel format may be played backon 5.1 and other smaller format (less than 8 channels) playback systems.

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SURROUND

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What’s a Mother to Do?

The reality for audio facilities is that all three of the above formats (inaddition to mono, stereo, multimedia, and others) will be with us for thenext several years, at which time perhaps some of the formats mightdrop out of usage. In order for an audio facility to prosper, it must beable to handle surround formats of all types. Surround sound formatswill be a permanent part of all future audio delivery formats.

As you can see from the above list (which does not include stereo, multi-media, IMAX and other multi-channel formats), they all deal with multi-ple channels of audio yet each one has a different format. As discussedlater, it is the duality of multi-channels and multi-formats that precludea simple monitor system in a standard console from being applicable tothis type of work.

Until now, in order to handle multi-channel formats properly and effi-ciently it was necessary to use a specialized console or to build custommonitor facilities that could be added to a standard audio console.These specialized consoles (such as Otari’s Premiere™ dubbing console)are large in scope and therefore relatively extensive and expensive.While they serve the dedicated dubbing stage extremely well, they areunsuitable to the many facilities that cannot justify the expense or thededicated features sets that these consoles embody.

Introducing the PicMix MonitorThe PicMix Monitor has been designed to break the big-bucks-consolebarrier and allow surround sound formats to be handled with ease inconjunction with almost any multi-bus audio console. For a studio firstdelving into the world of surround sound, this allows their existing con-sole to be retained, or the purchase of a new, more generalized console,that can better serve the facility.

The PicMix Monitor and its options provides the following functional-ity:

• Up to 32 dual input channels (64 audio inputs)

• Each Channel is assignable to one of 8 speaker buses

• Precision calibrated output monitor level can be set in 1 dB stepsfrom 20 to 105 dB SPL

• Compatible with all surround sound formats including DolbyStereo, Dolby Digital (SR-D), DTS Digital, Sony SDDS, and multi-media

• Serial and parallel machine transport control

• Serial and parallel recorder track arming

• Up to 4 monitor controller remote panels may be used

• Compatible with almost any multi-bus audio console

• All audio I/O is electronically balanced at +4 dB nominal level

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Note: The section on surroundsound panning and the PicMixPanning System begins onPage 30.

• 36 presets available for instant setting of monitor formats

• Hardwire bypass for normal stereo console operation

• LED matrix display shows current speaker assignments

• Alphanumeric display shows SPL level and system messages

• Fully buffered switchable meter outputs

• GPIO connector for simple logic interface with console

• User Preference System allows user customization

PicMix Monitor ComponentsThe PicMix Monitor is a modular system that is comprised of the follow-ing components

Monitor Master

This 2U rack unit is the core of the PicMix Monitor. All basic functional-ity (excluding machine control) is available. All audio connections inter-face to the Master rack. Eight dual input channels allow for 8 tracks ofaudio with Direct/Playback switching, or 16 tracks without Direct/Play-back switching which are each assignable to one of the 8 speaker busesavailable.

Monitor Slave

This 2U rack unit serves to expand the input capability of the Monitorsystem. Each Slave provides an additional 8 dual input channels to thesystem. Up to 3 Slaves may be added for a total of 32 dual input chan-nels (64 audio inputs).

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This 8.8w X 10.5h (inches) panel is designed to mount in or on your con-sole in a blank panel or in an available desktop box. The Monitor Con-troller adds extensive remote control capability to the PicMix Monitor.Multiple Controllers may be utilized for multi-section console operation.Each Controller has 8 control strips that can be assigned in a virtualfashion to any of the (up to 32) input channels in the system.

Machine Control Interface (MCI)

The MCI is a hardware/software “black box” (it’s actually silver incolor) that allows the PicMix Monitor to control track arming (record en-able) and basic motion control for a variety of recorder models. The

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MCI is able to control up to 4 serially controlled machines and up to 2parallel controlled machines. (At least 1 Monitor Controller must be in-stalled in the system in order to use the MCI).

Note: More detailed information about all of the components that make up thePicMix Monitor can be found in the Color Brochure and Technical InformationFoldout Sheet, both available from Otari or your Otari dealer.

Information about surround sound panning and the PicMix Panning Systemcan be found in this paper starting on Page 30.

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January 1996 7

Mix to Picture and Film Style MixingThe PicMix Systems are designed to facilitate fast, efficient, and creativeaudio post production that is or will be associated with a moving pic-ture, whether that be film, video, or multi-media. PicMix draws from along tradition in the Hollywood film community of how this audio postproduction process is accomplished. Even if your work does not involvefilm, or is small in scope, there is much to learn from these pioneers.

The film studios have always been the leaders in sound production.They have always been faced with the most difficult tasks due to thesheer number of audio tracks that have been associated with large bud-get movies, as well as the desire to draw people into theaters with largerthan life sound and picture. While the Hollywood studios are still facedwith the largest projects, shows produced for television are and havebeen catching up.

Movies of the week have become more ambitious and are really minitheatrical release features. Even episodic television dramas have takenon the aura of weekly mini-features. As the track count and demand forsophisticated television audio have increased, so have the demandsplaced on the sound editors and mixers. Over time they have looked tothe people who have done this before, the Hollywood editors and mix-ers. Whether a show is being produced for television or the movies,more and more audio post production for picture is being done usingthe film style mixing techniques that have been developed and perfectedin Hollywood.

Film Style Mixing is a generic term that has come about to describe theprocess that these Hollywood mixers and editors go through in theprocess of creating and molding the sound for a motion picture destinedfor theatrical release. This process can be thought of as an assemblyprocess. The following is a rough summary of the process…

Location Sound AcquisitionProduction dialog and some production location sounds arerecorded during the picture shoot.

Dialog EditingProduction dialog is edited, matched, and tied to selected picturetakes.

Automatic Dialog Replacement RecordingADR is a post production process (formerly known as looping), thatrecords the actors and actresses performing dialog while they arewatching themselves on screen. They perform their lines, attemptingto match their on-screen lip movements, so that better performancescan be obtained, script changes can be inserted, or sections can be re-placed that were poorly recorded due to equipment failure or loca-tion noises.

Sound Effects DesignSounds from live recordings, sound effects libraries, and electronicsynthesis are edited, layered and mixed to create sound effects ele-ments that match on screen events.

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PicMix White Paper

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Foley RecordingFoley artists perform using props, in a specially designed Foley pit(recording area with different floor surfaces) to create sounds whichare recorded live to picture. These sounds include footsteps, cloth-ing noises, paper noises, fight noises, leaf rustles, water noises, etc.

Original Music RecordingThe original music score is recorded. Some or all may be recordedagainst edited sections of the picture.

Sound EditingAll of the above types of audio tracks (plus others such as sourcemusic, licensed music, etc.) are edited and timed so that they matchthe picture edits.

Predub RecordingGroups of audio tracks of similar type (music, effect, dialog, Foley,ADR, etc.) are mixed on the dubbing stage (mix theater) into sub orpre mixes known as Predubs. There may be several predubs mixedfor each type (Music A, B & C, Effects A-F, etc.).

Final MixAll of the predubs are mixed on the dubbing stage to form the finalmix which is broken down into the final music, dialog, and effectsmixes which are referred to as stems.

Print MasterThe final stems are mixed at unity gain to create the actual physicaltape, film or disk that will be transferred to the picture master.

The above list is a generalized and simplified summary and takes licensewith the various processes. In some cases there may be many more stepsthat have not been listed, and in other cases many steps may be mergedinto one. The above procedures are not necessarily done sequentially be-cause some of the processes can be worked in parallel.

While many of the early procedures can occur without regard to sur-round sound, proper surround sound monitoring is essential during thethe predub, final and print master mixes. In some circumstances soundeffects design and music scoring may also be done with full surroundmonitoring to better prepare for the work that will eventually be doneon the dubbing stage.

Note: The final mix, which theoretically is a unity gain mix of the predubs, isactually a very complex mix where all of the audio elements (as well as all of thepicture elements) are brought together for the first time. This is also the firsttime that the show’s director hears the audio in context, which may cause manychanges to be made. It is the last time for the director to make audio choices,such as which music to use, or which ADR lines to use, or even if there shouldbe music or effects in this scene or that. And this does not take into account anylast minute picture changes that might send all of the sound editors scramblingand get all of the mixers growling.

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What is a stem?…A final mix for film or video mayconsist of more then 1 “item”.For an LCRS show, their might bean LCRS music mix, plus an LCRSeffects mix, and perhaps 4 tracksof dialog meant for the centerspeaker. Each of these compo-nents of the final mix is known asa stem. When these stems aremixed together at unity gain, thisrepresents the complete final mix.These stems may exist on sepa-rate tapes (or disks) or may existas separate tracks within a multi-track tape or disk. Some peoplewould also refer to any Predub(group of similar type pre-mixedtracks) as a stem.

What About Me?

Many of you reading this may never be involved in a big budget theatri-cal release, but I guarantee that if you are ever involved in any part ofthe mix to picture process, these techniques (or modifications of them)will be part of your audio toolkit. That is why it is so important to have afirm understanding of the large scale film style mixing procedures.

Now that PicMix is available, it is possible for many more audio facili-ties to become proficient at mix-to-picture audio post production for sur-round sound formats. Of course, any professional will understand thatlike a microphone or a console, PicMix is just a tool. In the proper handsit can help to create artistic audio that will enhance the story being toldby the picture, and in the wrong, inexperienced hands it can help in pro-ducing distracting noise. The purpose of this paper is to inform you ofthe availability of an incredible new audio tool, PicMix…and to hope-fully wet your appetite to pursue the proper education and people thatwill allow you to become proficient and profitable in this exciting area ofaudio.

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Why is PicMix Neededfor Multi-Channel Multi-Format Audio?

In order to understand the need for specialized monitoring facilitieswhen dealing with surround sound, please compare the following draw-ings in which an 8-track tape in various formats needs to be played backthrough the console monitor system. Unlike a stereo tape in which track1 always represents the left channel audio and track 2 always representsthe right channel audio, you can see that each of the following tapeshave different playback channels (speakers) associated with each track.The monitor system must be able to feed each track of each tape intoany one of the 4, 6, or 8 playback speakers.

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LEFT RIGHT

2-RIGHT3-LEFT4-RIGHT5-LEFT6-RIGHT7-LEFT8-RIGHT

1-LEFT

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Monitor System

Stereo FormatA basic stereo console monitoringsystem is all that is needed toplay back this 8 track tape whichconsists of 4 stereo stems.

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Dolby Stereo (LCRS)Here the monitor section must beable to route these two 4 trackstems into the LCRS speakers.This is beyond the scope of stan-dard audio console monitor sec-tions.

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LEFT RIGHT

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5.1 FormatThis 8 track tape consists of a 6track stem (5.1), plus two addi-tional tracks of material thatwere kept separate so theycould be handled separately inthe final mix. Only a dedicateddubbing console would be ableto handle this without PicMix.

SDDS FormatThis 8 track tape consists of an8 track SDDS stem. Only somededicated dubbing consoleswould be able to handle thiswithout PicMix.

Even Within One Format, Monitor Requirements Vary

It is easy to see from the above drawings that working in different for-mats will require different monitor setups. However, even within a spe-cific format (let’s say LCRS to keep this example simple), a series of 8-track predubs will usually contain several combinations of track layouts.Each of these will therefore require a different monitor setup

The 3 examples on these 2 pages show the mixing of a set of Predubsthat might be used in one Dolby Stereo (LCRS ) format show…

The predubs in all 3 examples are part of a single LCRS show, but to cre-ate any of them requires a monitor system that can be completely re-as-signed at any time.

While each of the above predubs was being mixed, the monitor systemwas configured to match the recorder track layout which matched theconsole record bus track assignments. The monitor system is in effect amini-console used for listening which establishes the relationship ofmonitor speakers➔recorder tracks➔console buses.

Of course to produce the final mix, the above predubs are fed into alarge mixing console during the Final Mix. The monitor would then beconfigured to match the final recorder track layouts as required, whichin this case would be LCRS. However, if the final mix created 3 LCRSstems (music, effect, and dialog), those might be recorded to 2 or three 8-track tapes, or 12 tracks of a 24-track tape recorder, or three 4-track filmrecorders, or two 6 track film recorders, or 12 tracks of a hard diskrecorder. So, here too, the monitor must be flexible enough to handleany of these possibilities.

PicMix White Paper

January 199614

PicMix Monitor

1-LEFT2-CENTER3-RIGHT4-SURROUND5-LEFT6-CENTER7-RIGHT8-SURROUND

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Example 1This monitor setup of 2LCRS stems might beused to create musicand effects predubswhere all of the sur-round components arein place. These types ofpredubs would be di-rectly routed to their re-spective LCRS tracksduring the Final Mix.

The PicMix Monitor is, in fact, a mini-console that is able to assign eachof its inputs to one of the 4, 6 or 8 speaker outputs. When a set of assign-ments is created, as in any of the examples above, it can be saved as oneof 36 Presets within PicMix. When this format is later needed again, thePreset is simply recalled, eliminating the need to assign all of the inputsindividually.

PicMix White Paper

January 1996 15

PicMix Monitor

1-CENTER2-CENTER3-CENTER4-CENTER5-CENTER6-CENTER7-CENTER8-CENTER

Effects B PredubDialog A Predub

8 Track RecorderMulti-Bus Audio Console

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Example 3Dialog consists of monotracks. This predub con-figuration would allowdifferent characters tobe split onto individualtracks, as well as sometracks having alternateproduction or ADRtracks for the directorto choose from duringthe final mix.

A mono Effects B predubmight contain effectsthat the SupervisingSound Editor was notsure the director wouldlike. Because they arenot “married” (mixedinto) to the Effects ALCRS predub, decisionsof whether or not to usethem can be made lateron the dubbing stage.

PicMix Monitor

1-LEFT2-RIGHT3-LEFT4-RIGHT5-CENTER6-CENTER7-CENTER8-CENTER

Music B Predub

8 Track RecorderMulti-Bus Audio Console

LEFT RIGHTCENTER

SURROUND

L C

S

R

Example 2This monitor configura-tion allows the creationof an additional musicpredub B, which con-tains 2 stereo stems andfour mono tracks. Thesemight be solo instru-ments or sections thatcould be used to seg-ment the basic LCRSmixes in Music PredubA. Alternately, theymight represent sub-mixes of the completescore which would allowthe LCRS mix to be es-tablished on the dub-bing stage.

PicMix White Paper

January 199616

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32313029282625From the Assign Matrix sectionof the PicMix Master (left) andSlave (right), inputs can be as-signed to speakers. Assignmentsare always displayed on the LEDassignment grid.

More than Just Assigning SpeakersThe ability to assign inputs to speaker buses is the most obvious andcritical aspect of a surround sound monitor system. But the needs gomuch further. PicMix has a host of additional features that are critical tothe efficient implementation of surround sound mixing techniques.Some of these facilities are listed below.

Precision Calibrated Level Adjustment

In a stereo console, a very important specification is the tracking preci-sion of Control Room Level Control. The Left and Right channels mustbe maintained in perfect balance throughout the range of the control. Ifthe control is out of spec, the mix engineer will compensate which willproduce an out of balance mix. (The out of spec pot can be corrected bychanging the relative power amplifier input gain settings, but this willnot work if the control varies it balance at different level settings).

In a multi-channel monitoring environment this problem is further com-plicated because there are 4, 6 or 8 channels to keep in perfect balance.This cannot easily be accomplished with a conventional level control.

The PicMix Monitor has a sophisticated digitally controlled, calibratedlevel control system. This assures that all 8 speaker outputs (actuallyamplifier feeds) track accurately. In addition, once the system is cali-brated to your amplifiers and speakers, absolute SPL levels can be setfrom the Master panel or from any Controller. This is important becausewhen mixing shows for theatrical release, Dolby specifications requirethat they be mixed at specific Sound Pressure Levels (usually 85 dB SPLat each speaker). The PicMix Monitor allows SPL levels to be adjusted in1 dB increments and also has 3 user stored SPL presets that can be re-called to instantly set a specific SPL level. A rotary monitor level controlcan also be optionally added.

What is a Surround Encoder?

When a show is done in the Dolby Stereo format (or compatible formatsuch as DTS Stereo or Ultra-Stereo) the final mix is made up of 4 discreteLCRS tracks or several sets of LCRS tracks (stems for music, dialog, andeffects, for example). However, the delivery medium, in almost all caseshas only a stereo (left/right) pair of tracks. The beauty of the DolbyStereo format is that the discrete 4 channel LCRS mix can be “encoded”into just 2 tracks which can be “decoded” or expanded into the original 4LCRS channels upon playback (and the stereo tracks can be played in“stereo” without decoding, as well). In a theater, a professional Dolbydecoder system is used, while in a home theater a Dolby Pro Logic de-coder is used. In either case the original 4 tracks of the final studio mixare extracted from the stereo (LT/RT, or Left Total/Right Total) tracksthat exist as a stereo optical soundtrack on a movie or a stereo magneticsoundtrack on a video. However, the 4➔2➔4 encode/decode process is

PicMix White Paper

January 1996 17

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The absolute monitor level is al-ways displayed on the PicMix Mon-itor Master. Using the SPL Adjust,A, B, and C buttons, monitor levelscan be instantly set to 1 of 3 storedlevels, or adjusted in 1dB incre-ments. These same adjustmentsare also available on all MonitorControllers.

not perfect. In order to make the stereo tracks compatible with playbackin stereo or mono (with no decoder), compromises were made in the de-sign of the encode/decode process.

When producing the original 4-track mixes in the studio, it is misleadingto monitor them discretely because this will not take into account thechanges that will occur due to the encode/decode process. It is thereforedesirable to monitor through an encoder plugged into a decoder so thatthe anomalies of the encode/decode process can be heard while mixing.In this way the mix engineer can preview what the viewer will hearwhen the Dolby Stereo mix is decoded back into 4 channels of soundduring viewing. Adjustments in placement and level can be made dur-ing the mixing process to minimize any undesirable effects of the en-code/decode process, so that the desired sonic results can be achieved.

The PicMix Monitor allows you to insert a Dolby DS-4 encode/decodeprocessor (or similar device) into the monitor loop at precisely the cor-rect point in the signal path, so that the processor receives the exact cali-brated levels that it requires. The processor device may be taken in orout of the signal path at the push of a button on either the Master Rackor the Controller Panel. You do not need to listen through a surroundprocessor if the format maintains true discrete tracks upon playback, asit is the case with SDDS and most 5.1 formats.

So What is PEC/Direct, Anyway?

Whenever surround monitoring is discussed, the term “PEC/Direct”switching comes up. While the actual definition is now outdated, itsfunction is not. Allow me to explain some more of the film style mixprocess which will lead us to a complete understanding of the mysteri-ous PEC/Direct.

PicMix White Paper

January 199618

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Surround encode/decodeprocessors (such as the DolbyDS-4) can be punched in andout of the monitor signal pathfrom the Monitor Master(shown) or the Monitor Con-troller.

Simplified (and partial) PicMix MonitorBlock Diagram shows monitoring througha surround encode/decode processor.

Because of the complexity of mixing to picture, the mix proceeds in a 3steps forward, 1 step backward kind of way. In many cases each picturecut on the screen represents a new sound perspective, so the mixerneeds to change the settings of the EQs, reverbs, and faders for eachchange in perspective. Tie this in with the large number of inputs in-volved with mix to picture projects and you end up with a very complexmix that has many starts and stops. Of course these starts and stopsmean that the recorder must be punched in and out repeatedly duringthe course of a mix.

This constant punching in and out puts great demands on the recorderbeing used. It (or they) must be able to seamlessly punch in and outquickly and with no audible artifacts. The other great demand is put onthe mix engineer. He or she must ensure that at the time of the punch in,the signal coming from the console exactly matches (in every way) whatis already on the recorder. If the punch represents an audio insert, thepunch out must also be matched perfectly or else the viewer (or on thedub stage, the director!) will hear the punch.

In order to facilitate the perfect matching before a punch, surround mon-itor systems have provisions to listen to the output of the console or theplayback of the recorder. This creates an additional great demand. Themonitor must be able to switch between these 2 input sources with noaudible glitch. While the glitch would not be recorded (since this is just amonitor function), it would distract the mix engineer from discerningwhether or not the console output perfectly matched the audio alreadyon the recorder. Since this matching process occurs hundreds of timeduring a mix, the crossover between console and recorder must besmooth and perfectly timed so that there is no click, no gap, and no au-dio buildup during the switch.

So what does PEC/Direct switching mean, anyway? When the recordersused on the dub stage were optical recorders (before my time), listeningto a playback meant listening to the output of the Photo Electric Cell, orthe PEC input to the monitor. Listening to the console directly meant lis-tening to the DIRECT input to the monitor. Switching between themcame to be called PEC/Direct switching. Now it is referred to as Di-rect/Playback switching.

PicMix has superb facilities for handling Direct/Playback switching. Ofcourse each input channel of the PicMix monitor has two audio in-puts…1 for the console output and 1 for the playback output of therecorder. Proprietary circuitry has been developed to ensure a smooth,click free, gapless crossover during switching with minimal audiobuildup and optimal timing. Each channel is factory calibrated for glitchfree switching. While each input can be switched at the Monitor Master,in practice this occurs from 1 or more of the monitor controllers whichare mounted in or on the console.

The purpose for all of this matching between the console and the previ-ously recorded mix, is to allow seamless punch ins and outs. PicMix hasfull provisions for actually performing the punches on a variety of audiorecorders. When the PicMix Machine Control Interface (MCI) is in-stalled, the monitor controller Record On and Record Off buttons now

PicMix White Paper

January 1996 19

“speak” directly to your recorder. Since the Direct/Playback buttons areadjacent to the Record On/Off buttons this allows the mix engineer topunch as soon as possible after the audio match is confirmed.

The MCI can control up to 4 serially controlled machines and 2 parallelcontrolled machines at one time. One of these ports can also be set up toperform basic motion control functions (Play, Stop, Fast Forward, FastRewind, and Reverse Play on some machines) from the motion controlbuttons which are also located on the Monitor Controller panel.

Physical and Virtual Machines

When mixing to a predub or final, it is essential that the mix engineerhas complete control of the recorder where the stem or predub re-sides. But many times the recorder is a multi-track that is beingshared. Two or more stems might be recorded onto a 24-track ma-chine, for example. And perhaps each stem “belongs” to a differentengineer.

In order to allow control of smaller parts of larger recorders, PicMixallows you to you define Physical Machines and Virtual Machines.The physical machines are the actual recorders that reside in your sys-tem. The Virtual Machines are subsets of the Physical Machines, sothat you can have complete control of a smaller number of tracks and

PicMix White Paper

January 199620

1 2 3 4 5 6 7 8

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The PicMix Monitor Controller has complete facilities for seamlessly switch-ing between console outputs (Direct) and the recorder outputs (Playback).When used in conjunction with the PicMix Machine Control Interface,recorder punch ins and outs as well as basic transport functions are alsoavailable.

treat them as if they were part of a completely separate recorder. TheseVirtual Machines, of course, do not really exist, but merely point to theactual tracks of the Physical Machines. PicMix can define up to 8 Physi-cal Machines numbered 1 through 8, and 26 Virtual Machines called Athrough Z.

PicMix White Paper

January 1996 21

Physical Machine 124 Tracks

VirtualMachine E

E1-E8

1-8

9-16

1-4

1-24

VirtualMachine F

F1-F8Virtual

Machine G

G1-G4Virtual

Machine H

H1-H24

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A1-A6

1-6

7-12

13-18

19-24

VirtualMachine B

B1-B6Virtual

Machine C

C1-C6Virtual

Machine D

D1-D6

Physical Machine 28 Tracks

VirtualMachine M

M1-M2

3-4

5-6

7-8

VirtualMachine N

N1-N2Virtual

Machine O

O1-O2

VirtualMachine I

I1-I8

1-8

1-4

5-8

1-2

VirtualMachine J

J1-J4Virtual

Machine K

K1-K4Virtual

Machine L

L1-L2

Through the use of Virtual Ma-chines, the mix engineer does nothave to have knowledge of wherethe actual tracks are beingrecorded. Up to 26 Virtual Ma-chines can be set up to point toany contiguous range of tracks onany 1 of the 8 Physical Machines.

Controlling Tracks

Once the Virtual Machines are set up for the system, they can be as-signed to Monitor Controller strips. Any strip can dial up any track of aVirtual Machine. Each Virtual Machine Track (VMT) points to a track ofa Physical Machine and to a PicMix input channel. Any Controller stripor strips that are assigned to a VMT will control the physical track andinput associated with it. This allows different mix engineers to be able tocontrol the same tracks by dialing up the same VMTs on multiple Moni-tor Controllers. The Controllers are completely virtual and set no limitsas to which tracks can be controlled from which controllers. Anythinggoes.

A Controller strip allows control of the following functions…

• Mute of the PicMix input

• Solo of the PicMix input

• Switch the PicMix input between Direct (console output) and Play-back (Recorder output)

• Punch in or Out of the Recorder Track

• Safe the strip to prevent switching and punches

• Make the strip a Machine Master or a Global Master

Grouping Tracks

When recording a stem (let’s use LCRS for this example) there are manytimes that you will want to control all 4 tracks at once, but there are alsotimes when controlling the Center track alone or the Surround trackalone is more appropriate. PicMix makes it easy to do both. (By control Imean do any of the functions listed above…Mute, Solo, Direct/Playbackswitching, Punch In or Out).

Normally all tracks work independently. Pushing the Master buttonabove any Controller strip, however, makes that strip become a MachineMaster. Asserting a function on a Machine Master activates that functionon all tracks that belong to that same Virtual Machine. By “safeing”some strips using the enable button (set enable to off), Machine Masterscan control subsets of Virtual Machines.

By pushing the Master button above a strip a second time (so that theLED flashes) that strip becomes a Global Master that will control all en-abled strips in the system.

Linking Tracks

To allow the control of more than 8 tracks on each Monitor Controller,PicMix permits the Linking of multiple tracks “beneath” each controlstrip. By using the Setup Link function, up to 8 Virtual Machine Tracksmay be assigned to each Controller strip. That strip then controls allVMTs that are linked to it. A VMT that is linked to a Controller strip canstill be assigned to other Controller strips in the system.

PicMix White Paper

January 199622

Mute

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The PicMix Monitor Controllerhas 8 strips that can be as-signed to any Virtual MachineTracks. Any strip can become aMachine Master or a GlobalMaster by using the Master but-ton.

PicMix Metering

The PicMix Monitor Master has 8 buffered meter outputs along with a 3input switching network. From either the Master panel or the Controllerpanel one of the 3 meter modes can be selected.

• Input Metering - The meter feeds read the PicMix input signalsjust post the Direct/Playback switching. This allows the viewing ofthe console outputs or the recorder outputs. (Each Monitor Slavealso has 8 buffered meter feeds that allow the viewing of it’s 8 au-dio inputs).

• Pre VCA Metering - The meter feeds read the calibrated signal lev-els on the internal speaker buses. This metering point is critical be-cause it allows the checking of the signal levels that are fed to thesurround processor if it is used. An internal jumper selects whetherthis meter feed comes before or after the insert return. If it is set be-fore, then the meters always read the signal going to the processor.If it is set after, then the input or output of the processor can be readby switching it in or out of the circuit.

• Post VCA Metering - The meter feeds read the signal after theVCAs, which control the monitoring output level. This position al-lows the viewing of the signals being fed to the monitor power am-plifiers. Since in a film style mix environment the entire monitorsystem (including power amplifiers and speakers) have been cali-brated, these levels are relevant.

Note: The meters that you use with PicMix should be set at unity gain (+4dBuin = 0 Vu reading).

PicMix White Paper

January 1996 23

Post VCAPre VCAInput

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Speaker Solo and Mutes

While mixing to picture, it is often necessary to listen to only the signalsthat are assigned to a specific speaker…or to mute all signals being fedto a specific speaker. For example, to check if the proper signals are be-ing routed to the surround speaker, you would want to mute all of theaudio assigned elsewhere. The problem is that in muting these signals, itis extremely easy to make a mistake and mute a wrong signal or missone.

PicMix eliminates this drudgery by offering complete solo and mute fa-cilities for the speaker signals. On the Master panel, the speaker assign-ment buttons can mute or solo speakers when the panel is in these spe-cial modes. On any Monitor Controller, the panel can be set to SpeakerSolo/Mute mode. In this mode the 8 Controller strips represent the 8speaker buses, and the Solo and Mute buttons act on the speaker busesinstead of the VMTs that the strips is assigned to. All other buttons con-tinue to act on the VMTs.

Using PicMix with Standard Multi-Bus ConsolesPicMix is a monitoring system. It does not have any direct effect on therecord chain. As such, it can work with just about any standard multi-bus console. However, special provisions have been made within PicMixso that normal console operation can occur unimpeded whenever sur-round sound functionality is not needed.

Because PicMix is the final device (except for room EQs, if used) in themonitoring chain, all power amplifiers must be connected to PicMix. Theconsole Control Room outputs that would normally feed the left andright amplifiers are connected to PicMix. When PicMix is not turned on,or is in the PicMix Bypass mode, the console Control Room outputs arerouted, through relays, directly to the left and right power amplifier in-puts. This is a true hardwire bypass because the signal does not gothrough any active circuitry. In addition, to ensure that there is ab-solutely no affect on the console’s sonic integrity, the internal PicMix cir-

PicMix White Paper

January 199624

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L C R S L S R S B X

When the PicMix Monitor Controlleris set to Speaker Solo/Mute mode,the top half of the panel changes toallow the soloing and muting of the8 speaker buses. The alphanumericdisplays change to label the 8 stripswith the speaker bus names.

cuitry that the Control Room signals also feed (for console solo opera-tion through PicMix), are totally lifted via additional relay contacts. Allof the other power amplifier inputs are also shorted to ground duringthese bypass modes, preventing any signal leakage from appearing atthose speakers.

So that PicMix may fully integrate with the console’s solo and communi-cations functions, provisions are made for connection of logic lines fromthe console to the GPIO (General Purpose Input and Output) connectoron the rear of the PicMix Master. When the console drives the solo logicline low (indicating that the console is in AFL or PFL solo mode), PicMixmutes all normal inputs, and feeds the console’s Control Room outputsto the left and right speakers. When the console drives the communica-tions logic line low (indicating that the console is in slate, comm, or talk-back mode), PicMix mutes or dims the monitor level (depending on asetting in the User Preference System). PicMix has several additionallogic inputs and outputs that allow even tighter integration with thehost console system.

In addition to the console Control Room output connections and logiclines, this list summarizes the wiring of a large scale PicMix system…

• The console record bus outputs must be wired to the recorder andalso wired to the Direct inputs on the PicMix Master and Slaves (ifany)

• The outputs of the recorder(s) must be connected to the Playbackinputs on the PicMix Master and Slaves (if any)

• The surround processor (if used) must be connected to the insertsend and returns on the PicMix Master

• The power amplifiers that drive the speakers must be connected tothe main outputs on the PicMix Master

• The audio outputs of the PicMix Slaves (if used) must be connectedto the previous Slave or Master rack (cables provided)

• All components of the PicMix Monitor system being installedshould have their Control Network (PCN) connectors wired in par-allel and connected to the PCN connector on the PicMix Master.This includes Slaves, Controllers, and the Machine Control Inter-face.

• If meters are used, they should be connected to the PicMix Master.If full input metering is desired the additional meters (beyond thefirst 8) should be connected to the PicMix Slave(s).

The drawings on the next two pages outline the interconnections in-volved in a complete PicMix Monitor System. They are meant as anoverview. For details regarding installation, please consult the PicMixOperations Manual and your PicMix dealer.

PicMix White Paper

January 1996 25

PicMix White Paper

January 199626

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I Don’t Mix Film. What’s In It For Me?I have spent a lot of pages outlining the film style mixing process in thecourse of this paper, yet I have also stated that most of you will probablynever mix a big budget motion picture. The reason for this is simple.Our talented friends in Hollywood have been dealing with the complexissues of posting sound to picture longer than anyone else has. All thosethat start to work in surround sound audio eventually come to find thatthese film style techniques or modifications of these techniques, eventu-ally find their way into the process. My hope is that by looking at themost complex applications of PicMix in surround sound posting, it willbe easier to identify the portion or portions that might be applicable toyou and your work.

PicMix was designed not only to handle large scale film dubbing jobs,but also to handle the smaller tasks, down to and including the simple(now that PicMix exists) task of just listening to a surround sound tapeor disk. The modular design of PicMix allows you to create the exact sizesystem that is required for your work. The system can grow as yourneeds expand by simply adding additional components. This is an ex-tremely cost effective and practical way to adapt your business to sur-round sound mix to picture.

The following is a brief list of some of the places and applications wherePicMix can help ease the burden of dealing with surround sound…

• Music Mixing Rooms

• Film and Video Multi-Format Screening Rooms

• Edit Suites

• Sound Design

• Television Broadcast Facilities

• Ad Agencies

• Jingle Houses

• Multimedia Production

• Dubbing Stages

• Remote Recording Trucks

• Remote Broadcast Trucks

The next section of this paper will present a basic explination of the na-ture of surround sound panning and the PicMix Panning System.

PicMix White Paper

January 1996 29

PicMix White Paper

January 199630

Surround Sound Panning BasicsThe previous section of this paper focused on the general aspects of sur-round sound formats, the complexities involved in monitoring them andhow the PicMix Monitor System simplifies these complexities.

In this section we will explore the basics of surround sound panning andthe extraordinary functionality of the PicMix Panning System. While thePicMix Panner is fully compatible with the PicMix Monitor, please notethat it can also be used with almost any multi-bus console and does notneed to be used in conjunction with the PicMix Monitor.

In order to understand the need for panning in the surround sound en-vironment, we will first take a look at the purpose of panning whilerecording or mixing for the standard 2 channel stereo format.

Panning for Stereo

A stereo mix is ultimately played back through 2 speakers, left and right.By assigning audio elements during the mix, to either the left speaker,the right speaker or to both speakers, the listener is led to believe thatthe sounds are emanating from the left speaker, the right speaker, orfrom a phantom center speaker that is located directly between the leftand right speakers. (We are assuming that the room acoustics and theposition of the listener allow this phenomenom to occur. In other wordsthe listener is in the sweet spot of a good room).

Since music and sounds that occur in nature do not emanate from only 3point sources, a recording with only left, right, and center (phantom)placements would sound unnatural. We need to be able to spread oursounds across the entire listening panorama. For this we use the aptlynamed pan pot or panner. The pan pot not only allows us to assign ouraudio elements fully to each speaker, but also to assign them to bothspeakers in unequal amounts. By varying the amount of signals fed toeach of the 2 speakers, we can place the sound sources at any locationbetween the speakers.

Note: Since I mentioned music and sounds that occur in nature, I should beclear that the use of a multiple pan pots, feeding multiple mono sound sources,to multiple places in the sound field pananora, does not equal great reproduc-tion of natural sounds. Panned mono sources are a way of life in the studio oftoday, and I could write 30 pages on that topic but I won’t (at least not here).Let’s assume that we all understand that panning is used to simulate the ac-tual, natural stereo recording that we all wish we could be doing.

So the main thing that a pan pot allows us to do is to place a monosound source at any location between 2 speakers. The other thing that apan pot can do is to move that signal smoothly over time. A soundsource can be moved in space by operating the pan pot while mixing orrecording. This can be used to provide special effects in a music record-ing (number 9...number 9...number 9) or to match the movement that oc-curs on screen when mixing to picture.

PicMix White Paper

January 1996 31

0dB

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Panning curve for standard 2 channel stereopanner.

Panning for Surround Sound Formats

The reasons to use a panpot when mixing for surround sound are thesame as when mixing for 2 channel stereo…to precisely place a soundsource within the sound field (created by multiple speakers) or to dy-namically move a sound source within the sound field. However, theconventional stereo pan pot is not up to the task. Surround sound for-mats present a host of barriers that must be overcome.

First of all, as we have seen in the previous sections of this paper, thereare several surround sound formats that must be accommodated.

To simplify our discussion I will use just the 5.1 (LCRlSrS) format, realizingthat this discussion should be applied to all surround sound formats, either pre-sent or future.

It is difficult (if not impossible) for analog controls to create the audiocurves necessary for panning into the various surround sound formats.Therefore, it is only practical to implement a multi-channel multi-formatpanner using digital control of the audio electronics. With this approachthe panner is able to accommodate all formats and do tricks that werenot possible in previous generation all analog designs.

Full Divergence

Most of the major surround formats have 3 speakers in the front of thesound field. This fact is what makes the standard “stereo” pan pot inad-equate for the job of surround format panning. When an audio elementis panned across the front (as in our 5.1 example) the signal must appearonly in the left speaker when it is panned to the left, only in the centerspeaker when panned to the center, and only in the right speaker whenpanned to the right. The fact that the sound moves to each speaker sepa-rately in the course of the pan, is known as divergence. The panner issaid to be a divergent panner or to have full divergence.

In order to understand why this necessary, let’s diverge for a moment todiscuss the center channel speaker.

Why a Center Channel Speaker?

In a home hi-fidelity music reproduction system there are only 2 speak-ers, left and right. What is different about film that made “them” add acenter channel speaker? There are several differences. The first is that ina theater, most of the viewers are not sitting in the “sweet spot”, so theirbrains are unable to form a focused center image. Secondly, these samepeople would be distracted if they were sitting near the right speaker,for example, because their eyes are looking to the center of the screen,but their ears are being drawn to the right speaker. In addition, beforemulti-channel film sound was introduced there was only a center chan-nel speaker, so in truth, the left and right (and surround) were added,not the center speaker.

PicMix White Paper

January 199632

Center Left Right

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Panning curves for 3-way fully divergentpanner. This panner is used for the frontspeakers in Dolby Stereo (LCRS) and 5.1(LCRlSrS) formats.

While a home theater system is not the size of a commercial theater (un-less you go to a newly constructed multiplex!), the reality of the smallsweet spot is actually worse than in a large commercial theater. It canonly serve 1 or 2 people at most. Anyone who has made the transitionfrom an original home Dolby Surround (LRS) system to the 4-channelDolby Pro Logic system (LCRS), with the center channel speaker, can at-test to the dramatic improvement this seemingly subtle change makes.

It is also important to remember that the usual purpose of a film (or filmon video) is to convey a story and the most important aspect of tellingthe story is usually the dialog. Having a center speaker helps ensure thatthe dialog (which resides in the center speaker 99% of the time) can be asintelligible and localized as possible.

Back to Divergence

Let’s remember that person sitting on the right side of the theater andsuppose that a car is about to drive across the screen (in the movie) fromthe left to the right. The sound first appears in the left speaker exclu-sively. When the car is center screen, the sound emanates from the cen-ter speaker only (because the panner is fully divergent). If the soundcame from the left and right speakers (forming a phantom center image),or even from all three speakers, the right sitting person would perceivethe sound as coming from the right speaker and the effect of the smoothpan would be destroyed. Since we also defined the job of the panner tostatically place sound elements, it is clear that when an element ispanned (or positioned) for placement in the center, it must also comeonly from the center speaker. But there are exceptions…

A Little Less Divergence

Let’s talk about the person sitting over by the right speaker once again.If a sound element is panned (positioned) full left, then there is a chancethat this person will not hear the element clearly or at all, because it iscoming from only the left speaker. To remedy this, the sound can bepanned slightly to the right so that it appears left of center (to someonesitting in the sweet spot). This will be a perfect solution in many cases.The right sitting person will hear the sound better because some of itsenergy is now also coming from the center speaker which is closer totheir viewing position.

Another remedy would be to keep the element panned full left, but re-duce the divergence of the panner. When the divergence of the panner isreduced (making it less divergent) some of the energy of the sound isfed to the other speakers, allowing the sound to have a presencethroughout the sound field, while still being predominant in a specificspeaker.

In a dynamically panned element, the pan will be smoother, because thesound never completely disappears from the alternate (not panned to)speakers. Rather than jump from speaker to speaker during a fast pan, itwill glide smoothly.

PicMix White Paper

January 1996 33

Decreasing the divergence of a panner also acts to limit the spread of thepan. Instead of panning from full left (of the sound stage) to full right asthe knob (or joystick) goes through its full range, the sound will appearto pan from left-center to right-center. The spread can be varied bychanging the amount of divergence that is applied to the panner.

The drawings later in