A Concise Article on Cardioid Subwoofer Arrays – by Steve Bush — Bob McCarthy
How to correctly position multiple Subwoofers for Cardioid Deployment - Live Sound
File:Cardioid Subwoofer Array.png - Wikipedia
Martin Audio Ltd - On #SubwooferSunday, here's 16 DSX in a broadside cardioid sub array for the recent socially distanced Gaia Summer Nights festival in Portugal with LVT Audiovisuais and MLA Compact.
QSC Introduces K Cardioid Single-Box Powered Cardioid Subwoofer | audioXpress