Specifications

5.1-Channel Production Guidelines Production Environment
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3.5.1 Surround Delay for Dolby Digital
Determining channel delays for Dolby Digital is similar in concept to those for Dolby
Surround Pro Logic, with important additional considerations. Since Dolby Digital
delivers discrete signals for each channel, there is no leakage or crosstalk between
channels. There is, therefore, no need to delay the Surround channels to take advantage
of the Haas effect (precedence effect, which states that if two similar sounds arrive at
our ears at slightly different times, the brain tends to focus on the sound arriving first
and ignore the second). Dolby Surround takes advantage of this effect to reduce the
perceived crosstalk between the front and rear channels. A signal arrival difference of
10–20 ms is adequate to make the Haas effect work. The Surround and front channel
signals should arrive at the listening position at the same time (coincident arrival).
Consequently, the Dolby Digital mode uses approximately 15 ms less delay than the
Dolby Surround Pro Logic mode for the same speaker/seating arrangement.
To calculate the Surround delay for Dolby Digital, measure the distance from the
listening position to each of the three speakers:
• Left speaker (L) or Right speaker (R)
• Center speaker (C)
• Nearest Surround speaker (LS or RS)
All of these measurements must be made in feet. If measuring in meters, multiply the
metric measurements by three to get the approximate equivalent in feet. Once these