AP25 Installation and Operating Guide
Page 87
AP25 Installation & Operating Guide
Document # 9301H79500 Ver. 1.00
channel name will now appear in the field and in the Home Screen (in yellow text just below the
channel numbers).
When a Vu button is highlighted green, that channel will display Vu bars on the Home screen.
To turn off the VU meter in the Home Screen simply touch the green VU symbol next to the
channel name. It will change to grey color and will no longer be displayed on the Home Screen.
4.3.8.4
Routing Crossovers
Crossover use can be attributed to the inability of most drivers to reproduce the entire audio
spectrum smoothly and efficiently. Because of this, most speaker systems are comprised of
several drivers, each of which is dedicated to the reproduction of a specific range of frequencies.
These frequencies are routed to the appropriate driver by a crossover network. This device
divides the audio spectrum into two or more frequency bands. By doing this, each driver will
receive only the frequencies that it can reproduce properly. The crossover network also prevents
potentially damaging low-frequency energy from reaching the midrange or tweeter drivers.
This frequency division process is accomplished by using high-pass and low-pass filters. A high-
pass filter passes frequencies above a pre-determined frequency and attenuates those below. This
pre-determined frequency is called the crossover point. Conversely, a low-pass filter passes
frequencies below the crossover point and attenuates those above. By cascading high-pass and
low-pass filters, a band-pass filter can be realized. Filters of this type attenuate all frequencies
outside of the pass-band created by the high and low-pass filters.
The rate at which the attenuating process takes place is dependent upon the slope of the
crossover. A typical slope for cinema sound systems is 24dB/octave. Higher numbers indicate a
much steeper cutoff rate while the lower numbers indicate a more gradual roll-off.
4.3.8.4.1.
Signal flow
When implementing crossovers or implementing different internal routing on the AP25, the
input channel numbers do not match the output channel numbers. The following explanation
clarifies how the menus operate regarding the channel numbers.
1.
From a user perspective, the channel mapping occurs near the last stage of the signal
processing. Only high pass and low pass filters are applied after the signal routing occurs.
This is illustrated in the diagram below.
Figure 66. Signal Processing Flow Diagram
2.
VU meters on the Home page show the input channel name while showing the VU level of
the sum of the outputs for that crossover channel.
