Apogee APL-220, Руководство пользователя

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With both systems in-phase, a low-frequency peak will occur in the region
where the two systems overlap. This is normal and can be dealt with by one
of the following:
(a) The low-frequency peak in the overlap region can be filtered out with an
equalizer. (NOTE: Usually equalizing only the full-range system is sufficient. To
this end Apogee’s powered full-range speakers are equipped with a 80 Hz
high-pass switch, making it easy to adapt them for use with subwoofers).
However, in some situations (such as when a large number of subwoofers
and full-range speakers are deployed), it may be necessary to equalize both
the full-range system and the subwoofer system, to achieve a perfectly flat
response through the overlap region.
(b) The full-range speaker system can be driven from the subwoofer’s high-
pass output (all Apogee Powered Subwoofers and Apogee non-powered
Processor-Based Subwoofers are equipped with a high-pass output). This out-
put effectively attenuates the energy to the full-range speaker system in the
overlap region, eliminating the low-frequency build-up. It behaves similarly to
the 80 Hz high-pass switch supplied on Apogee full-range powered loud-
speakers, but provides a steeper, 24 dB/octave roll-off.
(c) The Subwoofer can be switched out-of-phase with the full-range system.
This will cause a deep cancellation through the overlap region and is not rec-
ommended. It may sound better than the low-frequency accentuation caused
by the overlap, but it can (and will) adversely affect the system’s impulse and
phase response, as well as cause the drivers to work harder for less output
because of the cancellations taking place. It is a far better practice to prop-
erly equalize the system than to take a shortcut by using cancellation to
shape the frequency response of the system.
If the Subwoofer is NOT located directly over or under the full-range sys-
tem, but rather some distance away from it, the proper phase relationship
will need to be determined. This is also true if the Subwoofer is offset in
depth, such as in front of, or behind, the full-range system. See Figure 6.
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Figure 6
An APL-500 full-range speaker offset behind an APL- 1 0 subwoofer