Crown Audio I-Tech 4x3500HD - Manual (Page 65)

I-Tech HD DriveCore Series Power Amplifiers
Operation Manual page 65
Fig. 16.8 Measured individual driver responses (left ) and overall
summed on-axis response (right) of the two-way system of Fig. 5
driven with 3.67 ms latency 3 kHz FIR crossover filter generated by an
I-Tech HD amplifier. Fig. 16.9 Reversed-polarity on-axis response (left) and ±25° off-axis
response of the two-way system of Fig. 5 driven with 3.67 ms latency 3
kHz FIR crossover filter generated by an I-Tech HD amplifier.
16 Application of FIR Filters to Loudspeaker Crossovers
Figure 16.8 shows the measured individual driver responses of the
same two-way system driven by the FIR crossover as produced by the
Crown I-Tech HD amplifier and the resultant summed 1m on-axis
response. Note the extremely sharp filter rolloffs in the left magnitude
graph. Note also that the right on-axis response is essentially identical
to the previous LR on-axis response.
The final two graphs, shown in Fig. 17.9, illustrate the reversed-
polarity on-axis response and the ±25° off axis response for the FIR
crossed-over system. Note the extremely narrow crossover regions due
to the rapid filter rolloff of the FIR filter. Psycho acoustic tests reveal
that these narrow high-Q dips in the response are much less audible
than low-Q wider dips. 16.14 Conclusions
Crown’s powerful DSP processing power in the latest I-Tech HD Series
amplifiers allow sophisticated crossovers to be implemented using
Finite Impulse Response (FIR) filters. FIR filters offer a number of very
strong advantages when used to implement DSP electronic
loudspeaker crossovers.
16.15 Refereces
For those who want a more in depth treatment of the topics in this white
paper, here are three good reverences.
[1.] A.V. Oppenheim, R. W. Schafer, Digital Signal Processing,
(Prentice Hall, Englewood Cliffes, NJ, 1975).
[2] E.C. Ifeachor, B.W. Jervis, Digital Signal Processing, A Practical
Approach (Addison-Wesley Publishers, Reading, MA, 1996).
[3] g. J. Krauss, “Advantages of FIR Filters in Digital Loudspeaker
Controllers,” Presented at the 120
th convention of the Aud. Eng. Soc.,
Convention Paper 6779. (May 2006, Paris)
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