Dynaudio AIR 15, Справочное руководство

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Appendix: Acoustics
Dynaudio Professional AIR reference manual – 2014-09-28 119
Delaying monitors
ITU 775
When using a 5.x setup with monitors arranged on a
circle (as with ITU 775), the distance from the listener
to each of the main monitors is the same.
If space is limited, the three front monitors can be ar-
ranged on a straight line instead of a circle. To compen-
sate the center monitor being closer to the listener than
the left and right monitor in this setup, the center sig-
nal can be delayed. To obtain coincident arrival of the
sound from all front monitors, a delay between 0 and 3
milliseconds is used for compensation. The speed of
sound is approximately 340 m/s or 1130 ft./s. Accord-
ingly, approximately 1 millisecond delay will be used
to virtually move the monitor 1 foot or 30 centimeters
backwards.
Cinema setup
In a cinema setup, the front monitors are always ar-
ranged on a straight line. Here, the audience is closer
to the surround monitor(s) than to the front monitors. In
order to retain the directional information towards the
screen, the surround monitors are delayed.
Normally the psychoacoustic Haas effect is taken into
account. In the listening position, the sound from the
surround monitors will arrive about 15 to 20 millisec-
onds after the sound from the front monitors. The delay
times involved with cinema processing for the surround
channel is dependent on the size of the mixing facili-
ty, the cinema, or the home theatre/living room. Proper
setup requires calculating the difference in distance be-
tween the front monitors and the closest surround mon-
itor. Then, the time difference is calculated. To this, 15
to 20 milliseconds are added.
Example: From a listening position, the distance to
the front monitors is 20 meters and five meters to the
surround monitors, so the difference is (20 - 5 =) 15
meters. The time difference that needs to be compen-
sated is 15/340 sec, which equals 0,044 seconds or 44
milliseconds. To this value, 15 milliseconds are added.
Accordingly, the surround signal has to be delayed 59
milliseconds (or the closest possible value).