The KSL-SUB is a high-performance cardioid subwoofer engineered to deliver controlled and accurate low-frequency extension within the d&b audiotechnik SL-Series. Designed for seamless integration with KSL8 and KSL12 loudspeakers, the KSL-SUB supports both flown and ground-stacked configurations, making it suitable for a broad range of touring, installation, and live sound applications. In flown configurations, the KSL-SUB can be arrayed using the KSL-SUB Adapter Frame in combination with KSL-TOP cabinets, allowing system designers to maintain consistent directivity and performance throughout the full frequency range. This actively driven subwoofer employs a 2-way bass-reflex architecture and houses three neodymium 15-inch drivers — two front-facing and one rear-facing — each operating in isolated chambers and powered by independent amplifier channels. The result is a cardioid dispersion pattern that significantly reduces rearward sound radiation, thereby minimising low-frequency build-up behind the system and improving clarity in acoustically sensitive environments. With a frequency response from 36 hertz to 105 hertz, or 33 hertz to 75 hertz in INFRA mode, the KSL-SUB offers flexible performance that meets the requirements of professional sound reinforcement in medium to large-scale venues. Constructed from durable marine plywood and finished with d&b’s Polyurea Cabinet Protection, the KSL-SUB is built to withstand demanding conditions. While the KSL-SUB includes integrated rigging components for suspension, the KSL-GSUB variant is designed specifically for ground-based deployment.