About Time Alignment; About Crossover - Eclipse CD7100 Owner's Manual

About time alignment

With vehicle audio systems, the installation position of the speakers and the position of the listener
mean that the distances from the listener to the left and right speakers are almost always different.
These differences in the distance from the listener to each speaker in turn means that the time taken
for the sound to reach the listener is different for each speaker. The result of this is that the phases
of each speaker (biases) become mismatched and the sound becomes unnatural, as though the
sound stage is not wide enough. The "time alignment" function corrects the time taken for the sound
waves to reach the listener in order to set the optimum phase for the listening position so that the
sound becomes more expansive as though it is being listened to on a sound stage.
The basic adjustment method involves measuring the actual distances to each speaker and
calculating the differences in distance relative to the most distant speaker in order to derive the
delay time for the sound from each speaker.

About crossover

The frequency band that is stored by audio media such as CDs is a fairly wide range from 20 Hz to
20 kHz, and it is difficult for a single speaker to be able to play back all frequencies in such a wide
range.
Because of this, several speakers can be used, with different frequency bands (such as treble,
medium and bass) allotted to each speaker so that wide frequency ranges can be played back. The
"Crossover" function is used to allot the frequency ranges that are to be played back by each
speaker in accordance to the installed speaker units and the layout of the speakers, in order to
obtain the maximum level of performance from the speakers and to provide the most stable
frequency characteristics.
The crossover function includes a high-pass filter (HPF) for playing back treble sounds, and a low-
pass filter (LPF) for playing back bass sounds. In addition, the HPF and LPF are used in
combination in order to play back sounds in the mid range.
-3dB
20Hz
For example, when adjusting the HPF, frequencies that are lower than the specified frequency are
progressively dampened, rather than simply not being played back at all. The "slope" adjustment
function is the function that is used to adjust these dampening characteristics.
The slope characteristics of a filter are such that with larger slope values (for example 12 dB/oct),
the slope becomes steeper, and so the amount of sound mixing in with neighboring bands becomes
less so that only the target band is played back. However, it also causes the merging of sound
between speakers to become poorer and can result in greater distortion.
Bass range Medium range
fc1(LPF) fc2(HPF)
How to operate the Sound Adjustment Mode
Treble range
fc3(LPF) fc4(HPF)
fc*: Cutoff frequency
-3dB
20kHz
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