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31-EN
The sound is not balanced because the distance
between the listening position and the various
speakers is different.
The difference in distance between the front left
speaker and the rear right speaker is 1.75 m (68-7/
8").
Time correction eliminates the differences in the time
required for the sound to reach the listening position.
The time of the front left speaker is corrected by 5.1
ms so that its sound reaches the listening position at
the same time as the sound of other speakers.
Example 2. Listening Position: All Seats
Adjust the time correction level of each speaker to
almost the same level.
1 Sit in the listening position (driver’s seat, etc.)
and measure the distance (in meters) between
your head and the various speakers.
2 Calculate the difference between the distance
to the farthest speaker and the other speakers.
L = (distance to farthest speaker) – (distance to
other speakers)
3 Divide the distances calculated for the speakers
by the speed of sound (343 m/s (765 mph) at
20˚C).
These values are the time correction values for
the different speakers.
Time Correction:
The distance between the listener and the speakers
in a car vary widely due to the special conditions of
the mobile environment. This difference in the
distances from the speakers to the listener creates a
shift in the sounds image and frequency
characteristics. This is caused by the time delay
between the sound reaching the listener’s right
versus the left ear.
To correct this, the CDA-7878R is able to delay the
audio signal to the speakers closest to the listener.
This effectively creates a perception of increased
distance for those speakers. The listener can be
placed at an equal distance between the left and
right speakers for optimum staging.
The adjustment will be made for each speaker in a
step of 0.1 mS.
Example 1. Listening Position: Front Left Seat
Adjust the time correction level of the front left
speaker to a high value and the rear right to zero or
a low value.
Here we calculate the time correction value for the
front left speaker in the diagram at the left.
Conditions:
Farthest Speaker – listening position: 2.25 m (88-9/16")
Front left speaker – listening position: 0.5 m (19-11/16")
Calculation: L = 2.25 m – 0.5 m = 1.75 m (68-7/8")
Time correction = 1.75 ÷ 343
*
× 1000 = 5.1 (ms)
*Speed of sound: 343 m/s (765 mph) at 20˚C
In other words, giving the front left speaker a time
correction value of 5.1 ms makes it seem as if the
distance to the front left speaker is the same as the
distance to the farthest speaker.
2.25 m
(88-9/16")
0.5 m
(19-11/16")
5.1 ms