The SL-GSUB is a high-performance cardioid subwoofer specifically developed to support the low-frequency requirements of the d&b SL-Series. Engineered for ground stack use, the SL-GSUB is designed to deliver precise and directional bass reproduction, making it ideal for use in large-scale touring, fixed installations, and demanding sound reinforcement environments. Its cardioid dispersion pattern significantly reduces unwanted low-frequency energy behind the enclosure, enhancing clarity and control in reverberant or acoustically complex spaces. The SL-GSUB is an actively driven, two-way bass-reflex design that incorporates three 21-inch long-excursion neodymium drivers. Two drivers are front-facing while one is rear-facing, each operating in separate bass-reflex chambers and powered by individual amplifier channels. This configuration supports superior low-frequency definition and contributes to a more consistent acoustic experience across the audience area. Constructed with durability in mind, the SL-GSUB features a marine plywood enclosure finished in Polyurea Cabinet Protection to withstand rigorous touring conditions and variable environmental exposure. Though it does not include rigging hardware, the cabinet is equipped with stacking aids and heavy-duty rear wheels to support practical handling and deployment. The SL-GSUB is a reliable and precise solution for professional audio providers seeking robust low-frequency performance as part of the wider d&b SL-Series system configuration.