Dynacord CXM15 - Брошура - Сторінка 6

Переглянути онлайн або завантажити pdf Брошура для Спікери Dynacord CXM15 -. Dynacord CXM15 - 8 сторінок. Coaxial floor monitor with optional fir processing

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Fig. 7: Vertical isobar curves of the 60° coaxial system. Discrepancies

between the horizontal and vertical curves are attributable to the

shape of the enclosure

Fig. 9: Controller functions for the passive version (above) with IIR

(blue) and FIR filters (red) as well as for the active 2-way version

(below) with IIR (light blue) and FIR filters (orange)

orange curves representing the FIR variants

are characterized in general by more details

and in the active version considerably grea-

ter steepness.

If you look more closely at the FIR setup in

the IRIS software, you will notice at once

that in the lower frequency range there are

an additional two IIR filters, a bell filter and

a high-pass filter. These minor reinforce-

ments are necessary because the FIR filters

no longer afford sufficient resolution or fre-

quency selectivity in this range.

Depending upon the selected number of

coefficients of the FIR filters, there is an

increase in the total latency of the system,

which otherwise, independent of the num-

ber of signal processing functions, is 1.03

ms at a sample rate of 96 kHz and 2.3 ms at

production partner 12/09_01/10 sonderdruck

Fig. 8: Maximum level at 3 % (blue) and 10 % (red) THD along with

the calculated curve (green) for the maximum supplied power of

900 W referenced to 4 ohms

Fig. 10: Frequency response of the CXM 15 in passive mode without

the controller (green) as well as with the controller and IIR (blue) or

FIR filters (red)

48 kHz. With a sample rate of 48 kHz and

512 coefficients, for example, the increase in

latency attributable to the presence of a FIR

filter in the signal path comes to 5.3 ms

when the filter is designed to be linear pha-

se. This value can be calculated by dividing

the number of coefficients by twice the

sample rate – in this case, then, by dividing

512 by 2 x 48.000 1/s. At this point, it must

be emphasized once again that the latency

is not conditioned inexorably by the princi-

ple of the FIR filter but by the filter function

itself. If the FIR filter is designed with a

minimal phase function, its latency can be

just as long or short as that of an IIR filter.

The latency is only a by-product of the line-

ar phase approach. What is needed, therefo-

re, is to find a good compromise with a suf-

ficiently short linear phase FIR filter combi-

ned with an IIR filter. The IIR filter is then

used where the short FIR filter for want of

frequency selectivity can no longer interve-

ne – i.e. at the bottom end of the frequency

range. This is the thinking here behind the

combination of a 512-tap FIR filter and two

additional IIR filters. These configurations

can be nicely appraised using the IRIS-Net

software (Fig. 15), in which the amplitude

and phase of all the filter elements can be

viewed singly and together – if necessary

in conjunction with the frequency respon-

se of the loudspeakers. At the present time,

as far as we know, the IRIS-Net software is

the only controller software that offers

such possibilities together with the measu-

red values of the loudspeakers (see Fig. 16).