Ashly 24.24M Spécifications télécharger pdf (Page 16)

Operating Manual - 24.24M Matrix Processor

ter 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. The Ashly default crossover filter is 24dB/octave Linkwitz-Riley, 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. 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 the 24.24M crossovers.

Butterworth

Butterworth filters individually are always -3dB at the displayed crossover frequency and are used because they

have a "maximally flat" passband and sharpest transition to the stopband. When a Butterworth HPF and LPF of the same

crossover frequency are summed, the combined response is always +3dB. With 12dB per octave Butterworth crossover

filters, one of the outputs must be inverted or else the combined response will result in a large notch at the crossover

frequency.

Bessel

These filters, as implemented on the 24.24M, are always -3dB at the displayed crossover frequency. Bessel filters

are used because they have a maximally flat group delay. Stated another way, Bessel filters have the most linear phase

response. When a Bessel HPF and LPF of the same crossover frequency are summed, the combined response is +3dB

for 12dB/oct, 18dB/oct, and 48dB/oct Bessel filters, and -2dB for 24dB/oct Bessel filters. One of the outputs must be

inverted when using either 12dB/oct or 18dB/oct Bessel crossover filters or else the combined response will have a large

notch.

Linkwitz-Riley

The 12 dB/oct, 24dB/oct, an 48dB/oct Linkwitz-Riley filters individually are always -6dB at the displayed cross-

over frequency, however the 18dB/oct Linkwitz filters individually are always -3dB at the displayed crossover fre-

quency. The reason for this is that Linkwitz-Riley filters are defined in terms of performance criterion on the summing

of two adjacent crossover HPF and LPF filters, rather than defined in terms of the pole-zero characteristics of individual

filters. The 18dB/oct Linkwitz-Riley individually are 18dB/oct Butterworth filters in that they have Butterworth pole-

zero characteristics and also satisfy the criterion for Linkwitz-Riley filters.

When a Linkwitz-Riley HPF and LPF of the same crossover frequency are summed, the combined response is

always flat. With 12dB/oct Linkwitz-Riley crossover filters, one of the outputs must be inverted or else the combined

response will have a large notch at the crossover frequency.

9.2c Output Delay

Output delay can be used to time align discrete drivers within a cabinet or

cluster using short delay times, or align multiple drivers in different locations

using longer delay times. For a thorough long-delay explanation, see section

9.1e. The following example illustrates a use of short delay to time align speak-

ers within a group: A typical three way speaker cluster has 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 the same sig-

nals (at the crossover points) arriving at the cluster "wavefront" at different times,

creating undesirable wave interaction such as frequency peaks or cancellation.

The solution in this case, rather than fixing the frequency anomalies with EQ, is

to slightly delay the signal to the drivers closest to the cluster front.

High - No Delay

Midrange Delay

12 Inches = 0.9mS

Low Delay

8 Inches = 0.6mS

Example: 12 Inches

Example: 8 Inches

Short Time Delay

For Driver Alignment

1 2 ... 11 12 13 14 15 16 17 18 19 20 21 ... 27 28

Commentaires sur ces manuels

Pas de commentaire

Ashly 24.24M Spécifications Page 16

Commentaires sur ces manuels

Produits connexes et manuels pour Processeurs Ashly 24.24M