Alpine CDA-9811 - Manual (Page 19)

17
-EN
About Time Correction
The distance between the listener and the speakers in a car vary
widely due to the complex speaker placement. 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-9815/CDA-9813/CDA-9811 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 0.1 ms steps.
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.
* 1 Subwoofer speaker.
CDA-9811 only
You cannot change the Time Correction value for the subwoofer,
but you can set the subwoofer's apparent position to the front by
adjusting the Time Correction value of the front and rear speakers.
For details, refer to the “ *
1 ” on page 18.
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").
Here we calculate the time correction value for the front left
speaker in the diagram on the above.
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 ч 343*
2 Ч 1000 = 5.1 (ms)
* 2 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 its distance from the
listener is the same as the distance to the farthest speaker.
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.
2.25m
0.5m
5.1ms
* 1
* 1