The measurement indicates frequency response, not usable frequency range. In order to have a usable frequency range there must also be a range above and below that frequency where the driver will respond. However, if you note the signal loss it's easy to comprehend that the driver was not designed or meant for use at those extreme frequencies. I run both 718s with 2268s and other subs using 2242H drivers. The 2242, used in the SRX replacement line, will respond to lower frequencies (>35hz) better than the 2268, yet the 2268 has a slightly stiffer low mid range (75-90hz). Used together they compliment each other and provide good response from 30-100hz where they were designed to be used.