Alpine HDS-990 HDS-990 Owners Manual - Page 26

 HPF (High Pass Filter): intercepts lower frequencies and allows higher frequencies to pass.  LPF (low pass filter): intercepts higher frequencies and allows lower frequencies to pass.  Slope: the level change of one-octave frequency change (dB).  The larger the slope value, the steeper the slope.  Do not use tweeters that have not set HPF to on or have been set to low frequencies, otherwise the speakers may be damaged due to low frequency content.  The frequency of the divider cannot be adjusted to be higher than HPF or lower than LPF.  It should be adjusted according to the recommended crossover frequency of the connected speakers. Please determine the recommended crossover frequency of the speaker. Adjusting beyond the recommended frequency range may damage the speakers.  We are not responsible for speaker damage or malfunction caused by using a crossover beyond the recommended value. About Time Correction The distance between the listener and the speakers in the car can vary greatly due to the complex speaker placement. This difference in distance between the speaker and the listener will cause deviations in the sound image and frequency characteristics. This phenomenon is caused by the time delay for the sound to reach the listener's right and left ears. To solve this problem, this unit can delay the audio signal sent to the speaker closest to the listener. This can effectively create a feeling of extended distance for these speakers. The distance between the listener and the left and right speakers can be equal to obtain the best results. Each speaker will be adjusted with 3.4cm as a step difference. Examples of listening positions are as follows: Example 1: Front left seat Adjust the time correction level of the left front speaker to a larger value, and adjust the right rear speaker to zero or a smaller value. he distance between the listening position and each speaker is different, so the sound is unbalanced. The distance difference between the front left speaker and the rear right speaker is 1.75m (68-7/8"). Here we will calculate the time correction value of the left front speaker in the figure above. condition: The farthest speaker-listening position: 2.25m (88-9/16") Left front speaker-listening position: 0.5m (19-11/16") Calculation: L=2.25m-0.5m=1.75m (68-7/8") Time correction=1.75÷343*×1000=5.1(ms) * Speed of sound: 343m/s (765mph) at 20℃ In other words, setting the time correction value of the front left speaker to 5.1ms can make the distance between it and the listener seem to be the same as the distance between the listener and the farthest speaker. Time correction can eliminate the time difference required for the sound to reach the listening position. The time of the left front speaker is corrected by 5.1ms, so that its sound will reach the listening position at the same time as the 23 EN