User manual JBL GTO1204BP-D

[. . . ] While infinite-baffle mounting of GTO subs is possible, power handling will be greatly compromised because there's no enclosed volume of air to prevent the speaker's cone from moving past its limit. For this reason, we do not recommend infinite-baffle mounting for GTO subwoofers. You should choose the enclosure you will use based on the type of music you listen to, how much amplifier power you will use for the subwoofer and how much space inside the vehicle you can devote to a subwoofer enclosure. [. . . ] Because a sealed enclosure provides the most control over the woofer's movement, a woofer mounted in a sealed enclosure will handle more power than a woofer mounted in another enclosure type. Sealed enclosures provide more accurate sonic reproduction than other enclosure types when mounted inside a vehicle, 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 they require the smallest 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 at the lowest frequencies. If you are using a small amplifier, a vented box will provide more perceived bass output from less power. Vented enclosures are also well-suited to a variety of music types. 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. Mismatched woofers and enclosures can result in poor performance from your subwoofer system. You may connect the coils of a dual-voice coil woofer in series, but we recommend that you avoid connecting separate woofers in series. You must use both coils of a dualvoice coil woofer connected either in series or in parallel. Most amplifiers deliver exactly the same amount of power bridged into a 4-ohm load as they do running a 2-ohm stereo load. To design a subwoofer system that maximizes available amplifier power, keep the following rules in mind: 1. The total system impedance of woofers in parallel can be calculated using the formula: 1 Impedance = 1 1 1 + w + w . . . w1 2 3 where w is the nominal impedance of the woofer. The total system impedance of voice coils (or woofers) in series can be calculated using the formula: Impedance = w1 + w2 + w3 . . . [. . . ] The total system impedance of voice coils (or woofers) in series can be calculated using the formula: Impedance = w1 + w2 + w3 . . . The diagrams at right show parallel and series speaker connections. NOTE: There are two jumpers supplied with the woofers to make connections easier. [. . . ]