Editing Subwoofer (section)

=====Rear delay array=====
[[File:Cardioid Subwoofer Array.png|thumb|CSA: Six subwoofers arranged for less bass energy on stage. Signal going to the reversed enclosures is delayed a few milliseconds.]]

Another cardioid subwoofer array pattern can be used horizontally, one which takes few channels of processing and no change in required physical space. This method is often called "cardioid subwoofer array" or "CSA"<ref name=CSA /> even though the pattern of ''all'' directional subwoofer methods is cardioid. The CSA method reverses the enclosure orientation and inverts the polarity of one out of every three subwoofers across the front of the stage, and delays those enclosures for maximum cancellation of the target frequency on stage. Polarity inversion can be implemented electronically, by reversing the wiring polarity, or by physically positioning the enclosure to face rearward. This method reduces forward output relative to a tight-packed, flat-fronted array of subwoofers, but can solve problems of unwanted low-frequency energy coming into microphones on stage. Compared to the end-fire array, this method has less on-axis energy but more even pattern control throughout the audience, and more predictable cancellation rearward. The effect spans a range of slightly more than one octave.<ref name="CSA"/>

A second method of rear delay array combines end-fire topology with polarity reversal, using two subwoofers positioned front to back, the drivers spaced one-quarter wavelength apart, the rear enclosure inverted in polarity and delayed by a few milliseconds for maximum cancellation on stage of the target frequency.<ref name=Brill /> This method has the least output power directed toward the audience, compared to other directional methods.
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