Subwoofer Array Designer.

Both arrangements steer low-frequency energy forwards and cancel it behind the array, but they do it differently. An end-fire array places subs in a line front to back, all with normal polarity, and delays each one so the wavefronts add towards the audience. A cardioid (reverse-stack) array faces one sub backwards, reverses its polarity and delays it, which is quicker to deploy and gives strong rear rejection from a smaller footprint.

A single block of subs radiates bass almost equally in all directions, so you get muddy low end on stage, spill behind the speakers and complaints from neighbours. Steering the array sends the energy where the crowd is and cancels it where you do not want it, typically giving a useful reduction behind the array. That cleans up the stage for the band, tightens vocal intelligibility and helps you meet noise limits.

As a teaching rule, ideal spacing for an end-fire array is about a quarter of the wavelength at your target frequency, which the tool works out for you. At a typical dance-music target of around 60 Hz the wavelength is roughly 5.7 m, so a quarter wave is around 1.4 m centre to centre. Tune the spacing to the frequency you most want to control, because the array only cancels cleanly across a band around that target.

Choose the frequency you most want to keep off the stage or away from the neighbours, since the cancellation is strongest around that point and tapers off above and below it. For club and DJ work people often steer around 50 to 63 Hz where the energy and the complaints both sit, while bands with more upper-bass content may aim a little higher. The array still works either side of the target, just with less rejection.

Yes. Every steered array relies on delaying one or more subs by a precise number of milliseconds, and the cardioid mode also needs a polarity invert on the rear-facing box. You set these on a DSP, a digital console's matrix or the subs' onboard processing using the per-sub figures the tool gives you. Without accurate delay and polarity control the cancellation will not line up and you lose the benefit.