KS21i is a compact reference subwoofer designed to extend the bandwidth of A15i and A10i systems in installation applications. KS21i features one high excursion, direct-radiating 21‘‘ transducer mounted in a bass-reflex tuned enclosure. KS21i couples with A15i and A10i to reinforce contour and extend bandwidth to 29 Hz and 31 Hz respectively. KS21i features L-Vents that substantially reduce turbulence and port noise at high levels while also increasing LF efficiency. The association of modern components and laminar vents greatly improves short-term SPL compared to similar-sized subwoofers.