The 21NLW9601 is a high-performance 21-inch subwoofer designed to deliver exceptional low-end clarity and power. When placed in a Type O Parareflex enclosure, it becomes even more capable, taking advantage of the enclosure's unique design to enhance bass response and minimize distortion. The Type O Parareflex enclosure optimizes airflow and reduces port noise, resulting in smoother, more defined bass frequencies even at high output levels.