The AD-S28Tw, part of the AcousticDesign series from QSC, is a professional-quality surface mount subwoofer designed to provide low frequency enhancement to ceiling or surface mount AD-series speakers. The subwoofer has a marine-grade plywood cabinet that houses a pair of 8" polypropylene woofers. The cabinet has a dual chamber ported bandpass design with a large port to extend low frequency response.

The subwoofer has a defeatable passive 120Hz low-pass filter with impedance compensation and a 70/100V multi-tap transformer that can also be bypassed for use with 8 ohm speaker systems, making it extremely versatile. The subwoofer can be mounted in a number of ways; freestanding with the included rubber feet, or suspended via forged-shoulder eyebolts or the included steel yoke.