The SL-SUB and SL-GSUB are cardioid subwoofers designed to enhance the GSL and KSL Systems. With rigging hardware tailored for the SL-SUB, it's feasible to fly columns of up to 14 cabinets. In contrast, the SL-GSUB is tailored exclusively for ground-level installations. Both these subwoofers boast an active 2-way bass-reflex structure that houses three 21″ high-movement neodymium drivers. Of these, two face forward and one faces backward. Each set of drivers — front and rear — operates in distinct bass reflex compartments and is powered by individual amplifier channels. Their cardioid distribution pattern diminishes unnecessary energy behind the setup, optimizing reverberant field reduction and ensuring precise low-frequency sound. Their frequency range spans from 33–84 Hz to 30–65 Hz.

As for their physical makeup, the SL-SUB comes with both front and rear rigging capabilities, whereas the SL-GSUB, devoid of rigging components, is purely for ground-level setups. Both cabinets are crafted from marine-grade plywood and finished with a durable, weather-resistant PCP (Polyurea Cabinet Protection). Rigid metal grills shield both the front and back of the subwoofers, backed by a sound-permeable, water-resistant fabric. The bottom panel is safeguarded by two runners stretching from the front to the back. The top panel is designed with two corresponding indents that snugly fit the runners, ensuring stability when stacking. Additionally, each side panel features four embedded handles for ease of transport, and the subwoofers' backside is equipped with four robust wheels.