Georgia Hilton MPE CAS MPSE Prod/Dir/Editor

Film Services Professional ( Producing / Editing / Delivery )


Dolby Facility Requirements

Posted on February 28, 2010 at 12:52 AM

Dolby requirements post.. too go to not put up here. Jacobfarron posted this and its a great post of some of the Dolby requirements:

Theatrical Sound Production Facility Requirements

1. Introduction

Dolby Production Services contracts services and encoding equipment to content owners and

distributors wishing to release their theatrical program in a Dolby format. To ensure the highest

quality and reliability, Dolby requires that these services take place in an audio production facility that

meets the minimum requirements outlined below.

Facilities wishing to be considered for Dolby approval should contact Dolby Production Services.

2. Room Design

2.1. The room must be large enough to accommodate at least “Mid Field” monitoring. The minimum

acceptable room dimensions are 20’ long (Screen to Rear Wall) by 13’ wide with a 9’ ceiling

height. The optimum mix position is located 2/3 the length of the room away from the screen. In

the minimum sized 20’x13’ room, this position is 13’-4” from the screen.

Refer to chart below for acceptable room dimensioning ratios. The shaded area represents

acceptable conditions, whereas the straight line represents the optimum ratio.

3. Speakers

3.1. The screen speakers (Left, Center, and Right) must be the same make and model and must be

behind a perforated projection screen. The screen speakers should be able to reproduce

frequencies +/-3dB from 40 Hz to 16 kHz without assistance (satellite systems utilizing a

subwoofer to achieve full range are not acceptable for use as the screen speakers). The screen

speakers must be able to produce “clean” sound pressure levels (peaking) up to 105dBC SPL.

The location of the Left and Right speakers should not subtend an angle greater than 45

degrees from the mix position. The speaker cabinets should also be mounted at the same

vertical height, which should be mid-screen, for all screen channels.

Rev 20080213 Page 1 of 3

3.2. There must be at least (2) pairs of surround speakers mounted along the sidewalls to create an

effective surround “array”. Larger mixing rooms will have several surround pairs that cover

listening areas in front of and behind the mix position. In smaller rooms, the first pair of

surrounds must be slightly in front of the mix position. The second surround pair should be

slightly behind the mix position.

Mix stages that are to be equipped for Dolby Digital Surround EX must also have at least (1)

pair of surround speakers mounted on the rear wall. A separate two-channel amplifier must also

power the rear surround speakers to allow proper Surround EX monitoring.

For smaller mix rooms, surround speakers should never be directly “on axis” with the mix

position. The surround speaker array must be able to produce “clean” sound pressure levels

(peaking) up to 105dB SPL.

3.3. There must be a separate subwoofer capable of producing an equalized response of 25Hz-

120Hz +/- 3dB. The subwoofer must also be able to produce “clean” sound pressure levels

(peaking) up to 115dBC SPL.

4. Equalization & Delay

4.1. The speaker system must be equalized to the ISO 2969 “X” curve. There must be 1/3 octave or

parametric equalization inserted before the screen channel amplification to accomplish this

equalization. For the surround channels, single octave EQ is acceptable but not recommended.

4.2. If the distance from the mixer to the screen is more than 1.5 times the distance from the mixer to

the surrounds, a suitable delay line should be inserted (Pre-EQ) into each surround channel

monitoring path. It is recommended that the delay line is patchable so that it can be inserted in

the recording chain should a separate picture and track screening master be required.

4.3. A parametric EQ of at least one but preferably more bands and a 120 Hz low pass filter (Pre-EQ)

should be inserted in the LFE (subwoofer) monitor path. The LFE filter should be a 3rd order

Butterworth filter set with a crossover point at 120 Hz. Higher order filters are acceptable, but

lower order filters can cause incorrect perception of the LFE channel. Also, it is recommended

that the 120 Hz low pass filter is patchable so that it can be inserted in the recording chain

should a separate picture and track screening master be required.

5. Level

5.1. After proper equalization, the monitor levels need to be calibrated to 85 dBC SPL for each

screen channel (L,C,R), 82 dBC for each surround channel, and +10 dB in-band gain (RTA

method) referenced from the center channel for the subwoofer. A compliance check of EQ and

levels by a Dolby engineer must be performed prior to commencement of each contracted mix.

5.2. The sound system must be designed to provide a minimum headroom specification of +20dB

above normal reference level for each channel.

5.3. The console monitor section must have a multi-channel assignable fader with at least six inputs

and outputs. The monitor section must also provide a ‘fixed reference level’ mode for proper

listening levels when mixing and print mastering.

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6. Equipment

6.1. Dolby will supply a Digital Mastering Unit (DMU) to approved 5.1 mixing studios IF the length of

the film is 40 minutes or more. For short subjects or trailers, the film must be mastered to a

digital multitrack format and transferred at an approved Dolby Digital transfer facility..

6.2. Studios that are approved to use the Dolby DMU mastering system must also meet certain

business requirements (films per year) to be considered for a permanent installation. For studios

not meeting these business requirements, Dolby supplies a traveling DMU on a “per-mix” basis.

6.3. The “Dolby Surround Tools” plug-in for ProTools can not be used to create an Lt/Rt during the

final film print master. This plug-in does not facilitate the proper metering and processing needed

during mastering. Although the plug-in cannot be used for print mastering, it can be used for pre-

mixing. Also, any analog tape machines being used for the mix should be equipped with Dolby

SR noise reduction

Note: Dolby Laboratories, Inc. Model CP650 is a recommended cinema processor for decoding many

formats such as: Dolby Digital Film Soundtrack, SR/A Optical Film Soundtrack, and Digital 5.1 and

Lt/Rt Studio Masters.

Dolby Multichannel Music Mixing pdf. I do not know if these numberscarry over into TV Post sound. However, in the appendix it seems thatDolby has simply copied these numbers from AES, EBU, and ITUrecommendations. These are also almost identical to THX recommendationsI have seen.

3.1.2 Acoustics

Early Reflections

Any early reflections (within 15 ms) should be at least 10 dB below the level of the

direct sound for all frequencies in the range 1 kHz to 8 kHz [6].

Reverberation Field

Reverberation time is frequency-dependent. The nominal value, Tm, is the average of

the measured reverberation times in the 1/3-octave bands from 200 Hz to 4 kHz and

should lie in the range: 0.2 < Tm < 0.4 s. Tm should increase with the size of the room;

the formula in Table 3-2 is a guide.

Reflective and Absorbent Surfaces

Large flat reflective surfaces should be avoided in the mixing environment.

Placement of doors, control room windows, and equipment should be considered with

speaker placement and aiming in mind. A combination of diffuse reflectors and

absorptive materials should be used to achieve a smooth RT decay time within the

specified range shown in Figure 3-1.

Again, it is recognized that these values may not be achievable in some installations,

but is recommended that the room be measured using a real-time analyzer and that

architectural solutions (wall treatments, bass traps, room reorientation, and so on) be

utilized first to achieve the recommended values. A mixture of diffuse reflective and

absorbent surfaces, applied evenly to the whole room, aids in creating an acceptable

reference listening condition [12].

Only after considerable effort has been made using architectural solutions to smooth

the room response should equalizers be introduced into the monitor chain. See

Section 4.2 for more information on room equalization.

Background Noise

The listening area should ideally achieve an NC rating of 10 or below with the

equipment off, measured at the reference position. A studio with equipment such as

video projectors, video monitors, and other ancillary equipment powered on should

achieve a rating of ? NC 15.

Any background noise should not be perceptibly impulsive, cyclical, or tonal in nature.

NR 10 or NR 15 may be hard to realize in a practical manner in some installations, in

which case, every effort should be made to identify the loudest noise sources and

correct as appropriate. The most common noise sources and possible remedies include:

• HVAC systems: Increase the surface area of the supply air vent. Separate or float

all mechanical connections between high velocity or rumbling motors and ducts

and the listening room.

• Equipment: Contain computers and other equipment with loud fan noise in noise

attenuating, ventilated cabinets.

• Doors and windows: Make sure all the doors and windows are aligned properly

and form a seal when closed. Adding a second window or door, with air space

between it and the original, can reduce unwanted noise considerably.

Other sources of problem noise may need to be addressed. Every effort should be

made to approach the recommended values shown in Figure 3-2.

Once again, THESE ARE NOT REQUIREMENTS FOR APPROVAL. They are the onlyrecommendations I have found Dolby to make. Furthermore, they aregeneral guidelines based on AES, EBU, and ITU recommendations.

If someone knows that these figures are not applicable for Cinema/TV, etc please let me know.

JBL also lists acoustic considerations specifically for Cinema, based on Lucasfilm recommendations. __________________

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