Operating Manual - PROTEA SYSTEM II 3.24CL Crossover / System Processor
8
Output channels have time delay as well, but much less than the inputs. This
is because output delay is best used to align discrete drivers within a speaker cabinet or
cluster, normally quite close together. For example, a typical three way speaker cluster
would have low end, midrange, and high frequency drivers all located near one another.
The different drivers for each frequency band are not necessarily the same physical
depth with respect to the front of the loudspeaker cluster, so there exists the problem of
same signals (at the crossover points) arriving
at the cluster "front" at different times, creating
undesirable wave interaction and frequency
cancellation. The solution, again, is to slightly
delay the signal to the drivers closest to the
cluster front. Using the location of the driver
diaphragm farthest back as a reference point,
measure the distance to other drivers in the clus-
ter, and set the output delay for each accord-
ingly, with the driver diaphragm closest to the
front getting the longest delay and the driver at
the very back getting no output delay. Note:
Although delay in the 3.24CL is adjusted only
by time, the corresponding distance in both feet
and meters is always shown as well.
Sam e sound arrives at
two different times.
Fix by delaying secondary
speakers 177m S.
Speaker on
M ain Stage
Secondary Speaker
200 ft from M ain Stage
Input (Long) Time Delay
For Remote Speakers
High - No Delay
M idrange Dela y
12 Inches = 0 . 9mS
Low Delay
8 Inches = 0. 6 mS
Example: 12 Inches
Example: 8 Inches
Output (Short) Time Delay
For Driver Alignment
Crossover
Channel 1-6
HPF or LPF
Frequency
Crossover LCD Display
Select
Slope and
Response
HPF and LPF
CROSSOVER 1
19.7Hz
HPF
24dB-Lnkwtz
4.6d Crossover (Xover)
Crossover functions on the
Protea 3.24CL are available only on the
six output channels. Every channel's
crossover consists of a high pass filter
(HPF) and a low pass filter (LPF), along
with the frequencies and filter types
used. Each output's crossover section is essentially a bandpass filter, making it necessary for the user to map out ahead
of time which outputs will be used for the various frequency bands, and set the overlapping filter frequencies and types
accordingly.
Note: The HPF determines the lower frequendy limit of the signal, while the LPF determines the upper
frequency limit.
The frequency range for the high pass filter (HPF) is from 19.7Hz to 21.9kHz, with an option to turn the filter off at
the low end of the frequency selection. The low pass filter (LPF) offers the same frequency range, with the "off" option
at the high end of the frequency selection.
There are eleven types of filters available in the crossover section, each suited to a specific preference or
purpose. The slope of each filter type is defined by the first characters in the filter type, 12dB, 18dB, 24dB, or 48dB per
octave. The steeper the slope, the more abruptly the "edges" of the pass band will drop off. There is no best filter slope
for every application, so experiment to see which one sounds most pleasing in a specific system. Ashly factory default
presets use all 24dB/octave Linkwitz-Riley filters in the crossover section, but of course they can be changed to suit the
application.
In addition to the frequency and slope, crossover filters can be selected as having Butterworth, Bessel, or
Linkwitz-Riley response. These refer to the shape of a filter's slope at the cut-off frequency, affecting the way two
adjacent pass bands interact at the crossover point. 24db/octave Linkwitz-Riley filters produce a flat transition through
the crossover region, assuming both overlapping filters are set to the same frequency, slope, and response type.
