Certified to THX ULTRA2 and THX SELECT2 standards, the Ci200QSb-THX in-wall subwoofer delivers deep bass and theatre-level output, capturing the drama and emotional intensity of full theatre sound. Engineered with KEF's dedication to acoustic excellence, this speaker features a powerful 200mm (8in.) sub-bass driver. In passive mode, it supplements KEF's Ci series speakers. In active mode, powered by KEF KASA500 amplifiers, it meets THX Select2 and Ultra2 specifications depending on configuration. Installation is streamlined by KEF's patented tension legs for a secure, one-handed fit. Design highlights include a paintable ultra-thin bezel and magnetic grille for discreet integration, and versatility via internal crossover or active amplifier use. Sold in pairs, it suits diverse application and installation needs. Explore this exceptional offering to elevate your audio experience. Specific warranty terms and details for KEF products can be found here.