Cardioid subwoofer arrays can be used to direct the output of an array of subwoofers in order to limit excessive amounts of bass in undesired locations. Cardioid arrays can be used to keep bass off of a stage, stop destructive reflections, or just keep the bass aimed toward the intended audience and not the surrounding area. This paper details the setup and use of DSP settings which Electro-Voice has created for use with the XCS312 and the Xsub loudspeakers.
In general, cardioid loudspeaker arrays use a combination of forward-firing and rear-firing (cancellation) loudspeakers to create a desired polar pattern. This can be done using several methods; however, the method used for the settings discussed here is the traditional cardioid approach. In this approach, the cancellation loudspeaker(s) has the appropriate DSP applied to it in order to match the response of the forward-firing loudspeaker(s) at the back of the array. The cancellation speaker is then inverted in polarity, which interacts with the response of the forward-firing loudspeakers, resulting in drastically reduced output at the back of the array. Additionally, the response from the cancellation woofer wrapping around the front of the array will sum with a small positive gain. When used appropriately, up to 25 to 35 dB of cancellation can be achieved.
By adjusting the setup of the cancellation loudspeaker, the maximum attenuation can be achieved at different locations on the backside of the array. Although this is essentially variable, we have provided several common options. These common options are: cardioid, where maximum cancellation happens at 180; super cardiod, where maximum cancellation happens at ~1308; or dipole, which achieves maximum cancellation at ~908.