Ashly Protea 4.8SP Manuale operativo - Pagina 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:

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