F18 is our largest single driver sealed subwoofer to meet the needs for a high power home theater solution that retains the dynamic, accurate, and deep bass that we have become known for. Its max output at 20hz is at least 8db higher than that of our 12″ sealed model F12 and more than 11db higher than our competitior’s 12″ model SB** measured by data-bass.com. The amplifier is based on Hypex audiophile class-D module. With the combination of the servo feedback and stiff aluminum cone, we have achieved lower distortion than competitor’s 18″ servo subwoofers (DD18+) with the same or even higher maximum SPL output from 10hz to 100hz , as tested at data-bass.com. In fact, F18 has recorded the lowest THD numbers at the maximum SPL output than any other subs tested. Our servo technology is scalable to all subwoofer designs as well as driver sizes.