Ashly Protea 4.8SP Manual de instrucciones - Página 8
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Operating Manual - PROTEA 4.8SP and 3.6SP System Processors
Input (Long) Time Delay
For Remote Speakers
Speaker on
Main Stage
Secondary Speaker
200 ft from Main Stage
Same sound arrives at
two different times.
Fix by delaying secondary
speakers 177mS.
4.6d Crossover (Xover)
Crossover functions are avail-
able only on the output channels.
Every channel's crossover consists of
a high pass filter (HPF) and a low pass
filter (LPF), along with the frequen-
cies 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 frequency 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 11 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 applica-
tion.
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. 24dB/
oct Linkwitz-Riley filters are the industry standard, the easiest to use, and the filter type recommended by Ashly. Other
filter types are available, but may require polarity switching or other adjustments for proper results. The following
paragraphs offer a summary of the three filter types as used in 4.8SP and 3.6SP crossovers:
8
Output channels have time delay as well. 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 fre-
quency band are not necessarily the same physi-
cal depth with respect to the front of the loud-
speaker 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 SP is adjusted only by
time, the corresponding distance in both feet
and meters is always shown as well.
Output (Short) Time Delay
CROSSOVER 1
19.7Hz
24dB-Lnkwtz
For Driver Alignment
Example: 12 Inches
High - No Delay
Midrange Delay
12 Inches = 0.9mS
Low Delay
8 Inches = 0.6mS
Example: 8 Inches
HPF