Alpine CDA-9811 About Time Correction, Example 1. Listening Position Front Left Seat, 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.

5.1ms 0.5m

2.25m

*1 *1

*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 ÷ 343*2 ⋅ 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.

17-EN