[. . . ] subwoofer owner's manual THANK YOU for purchasing JBL CS Series® automotive speakers. [. . . ] Sealed enclosures provide more accurate sonic reproduction than other enclosure types, so they are well suited to all types of music. Sealed-enclosure construction is straightforward and there are many prefabricated sealed enclosures available. An optimum sealed enclosure is always smaller than other types of enclosures optimized for a particular speaker, so it requires the least amount of space inside the vehicle. Vented enclosures provide better efficiency in the 40Hz ­ 50Hz range but this efficiency comes at the expense of sound in the lowest octave (below 40Hz) and at the expense of some control and power handling. If you are using a small amplifier, a vented box will provide more bass output from less power. Because vented enclosures require the volume of the enclosure and the size of the port to have a specific relationship with the characteristics of the woofer, the enclosure must be built exactly to the specifications provided. While there are some prefabricated vented boxes available, matching a prefabricated box to a particular woofer is difficult. If you wish to use a vented enclosure, we strongly recommend having your authorized JBL dealer build it, or at least verify that your design is correct if you wish to build it yourself. [. . . ] Features, specifications and appearance are subject to change without notice. JBL Consumer Products 250 Crossways Park Drive, Woodbury, NY 11797 USA 1. 800. 336. 4JBL (4525) · FAX 1. 516. 682. 3523 · www. jbl. com © 2003 Harman International Industries, Incorporated JBL is a registered trademark of Harman International Industries, Incorporated. [. . . ]