About The Time Correction - Alpine CDA-7892E Owner's Manual

NOTES
• If no buttons are pressed within 5 seconds, the setup menu
returns to the normal audio display.
• These functions are inoperative when an external, Ai-NET
processor is connected.
• If HPF, LPF, Bass Control and Treble Control are all set to
ON, depending on the Bass Control and Treble Control
settings, you may not be able to reinforce the sound effect.
• Except when the HPF and LPF is turned OFF, the subwoofer
is in monaural mode.
• When the subwoofer is set to OFF, LPF mode and change of
phase does not work.

About the 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-7892E 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.
0.5m
2.25m
∗
Tips
* Subwoofer speaker.
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 "Tips" on page 8.
5.1ms
∗
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.
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.
7
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