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CHAPTER 4: ADDING SUBWOOFERS TO A JM-1P LOUDSPEAKER SYSTEM
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USING DIGITAL SIGNAL PROCESSORS
Full-range signals can be connected directly to Meyer
Sound self-powered loudspeakers because the loudspeak-
ers have built-in active crossovers. External crossovers and
digital signal processors are optional and should be used
with caution as they can introduce phase shifts that cause
destructive cancellations.
If a digital signal processor is used, both the JM-1P loud-
speakers and subwoofer should be driven from the same
processor to keep their delay times the same. Otherwise a
phase shift between the JM-1Ps and subwoofer may be
encountered. In addition, you should verify the delay time
between channels: some digital signal processors may incur
channel-to-channel delays when the processor is near max-
imum throughput, which becomes more likely as the number
of filters in use by the processor is increased.
Third-order filters (and higher) are not recommended. If they
must be used, they should be used cautiously, since they
may cause phase shifts that deteriorate the impulse
response; in addition, their higher roll-off may also interfere
with crossover interaction.
TIP: To address the collective concerns of sys-
tem design verification, subwoofer integration,
digital signal processors, delay systems, and acousti-
cal conditions, a measurement system like Meyer
Sound’s SIM 3 is strongly recommended.