Heinrich's H18-S is a sub-woofer designed to provide high-power bass when used with external power amplifiers, frequency crossovers, and controllers. The H18-S uses back loaded dual port technology, a design already established and proven in the professional audio field. This technology delivers more precise bass reproduction through controlled transient response and an extremely deep cabinet tuning, which provides benefits over simple bass reflex contractions. The H18-S features a powerful 18" loudspeaker with high efficiency and a very linear cone excursion, resulting in high-quality and high-performance sound.