Just like a Submarine is a boat that goes under (sub) the water (marine) the Subwoofer was intended to go to frequencies below (sub) what the woofer is producing and should reproduce frequencies down to 20Hz or below. Most good speakers have a woofer that goes down below 35Hz. When a listed subwoofer only goes down to 35Hz you in essence only have a powered woofer. Just thinking out loud and would love to hear other opinions.