JBL GT1241D, GT1041D, GT1281, GT1081 owner manual Choosing an Enclosure

Thank you for purchasing a new JBL GT Series subwoofer. Subwoofer installation often requires woodworking skills and some experience disassem- bling and reassembling automotive inte- riors. If you lack the tools or necessary skills, have your subwoofer installed by an authorized JBL dealer.

Warning: Playing loud music in an auto- mobile can permanently damage your hearing as well as hinder your ability to hear traffic. We recommend listening at low levels while driving. JBL accepts no liability for hearing loss, bodily injury or property damage resulting from use or misuse of this product.

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Choosing an Enclosure

GT Series subwoofers are optimized to perform best in small sealed, vented and prefabricated bandpass enclosures. While infinite-baffle mounting of

GT Series subs is possible, power handling is 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 GT Series 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 move- ment, a woofer mounted in a sealed enclosure can handle more power than a woofer mounted in another enclosure type. 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 enclo- sures available. An optimum sealed enclosure is always smaller than other types of enclosures optimized for a par- ticular speaker, so they require the small- est amount of space inside the vehicle.

Vented enclosures provide better effi- ciency 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. 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 character- istics of the woofer, the enclosure must be built exactly to the specifications provided. While there are some prefabri- cated 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 verify that your design is correct if you wish to build it yourself. An optimum vented enclosure is always larger than the optimum sealed box for the same woofer, and will require more space inside the vehicle.

Bandpass enclosures often provide the most output available from any amplifier-and-subwoofer combination at the expense of sonic accuracy. If sheer SPL (sound-pressure level) is what you desire most, choose a bandpass enclosure. Bandpass-enclosure design is very tricky; using a computer and enclosure-design software is necessary. If you are an experienced installer or have some woodworking experience, you may wish to build the enclosure described in the Specifications chart in this manual. Fortunately, there are many prefabricated bandpass boxes available, and they are all optimized to extract the most output possible from any woofer. Bandpass enclosures can be quite large and may require a lot of space inside your vehicle.