|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
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.
3.1. 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.
5.1. 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.
Rev 20080213 Page 2 of 3
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.
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 .
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 .
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.
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. http://jblpro.com/pub/cinema/cinedsgn.pdf __________________
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