GT Series Owners Manual

5/14/99

9:49 AM

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A U T O M O T I V E

S U B W O O F E R S

SERIES

Grand Touring Series
GT1041, GT1041D, GT1081, GT1241, GT1241D, GT1281 Owners Manual

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Thank you for purchasing a new
JBL GT Series subwoofer. Subwoofer installation often requires woodworking skills and some experience disassembling and reassembling automotive interiors. If you lack the tools or necessary skills, have your subwoofer installed by an authorized JBL dealer. Warning: Playing loud music in an automobile can permanently damage your hearing as well as hinder your ability to hear trafc. 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.
Choosing an Enclosure GT Series subwoofers are optimized to perform best in small sealed, vented and prefabricated bandpass enclosures. While innite-bafe mounting of GT Series subs is possible, power handling is greatly compromised because theres no enclosed volume of air to prevent the speakers cone from moving past its limit. For this reason, we do not recommend innite-bafe mounting for GT Series subwoofers. You should choose the enclosure you will use based on the type of music you listen to, how much amplier 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 woofers movement, 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 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 efciency in the 40Hz 50Hz range, but this efciency 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 amplier, 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 specic relationship with the characteristics of the woofer, the enclosure must be built exactly to the specications provided. While there are some prefabricated vented boxes available, matching a prefabricated box to a particular woofer is difcult. 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 amplier-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 Specications 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.

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Connecting Your Subwoofer to Your Amplier JBL GT Series subwoofers are available in three different congurations: single 4-ohm voice coil, single 8-ohm voice coil and dual 4-ohm voice coils. Depending on the amplier you are using, you may use either single- or dual-voice-coil subwoofers in singles or multiples to maximize the power available from your amplier. To achieve the maximum amplier output possible, you should design a speaker system that provides the lowest impedance that your amplier is rated to drive safely. When designing a subwoofer system, abide by the following rules: 1. Dont mix different subwoofer or enclosure types in the same system (use all single-coil 4-ohm woofers, all singlecoil 8-ohm woofers, or all dual-coil woofers).
2. You may connect the coils of a dualvoice-coil woofer in series, but NEVER connect separate woofers in series. Because the amplier-damping factor (the ampliers ability to control the motion of the woofer) is expressed as a ratio of terminal impedance (the sum of speaker impedance, wire resistance and the D.C. resistance of any crossover coil connected to the woofer) to amplier-output impedance, connecting woofers in series reduces the damping factor of the amplier to a value less than 1. This will result in poor transient response. 3. You must use both coils of a dualvoice-coil woofer either in series or in parallel. 4. Most ampliers 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 amplier power, keep the following rules in mind: 1. The total system impedance of woofers in parallel = 1/(1/w1 + 1/w2 + 1/w3.) where w is the nominal impedance of the woofer. 2. The total system impedance of voice coils (or woofers) in series = w1 + w2 + w3. The diagrams below and at right show parallel and series speaker connections. Figure 1. Parallel connection
Figure 2. Series connection

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Specications

GT1041

Conguration Recommended Amplier Power Range Impedance Sensitivity Frequency Response Mounting Depth Cut-Out Diameter 10" subwoofer 18W 275W 4 ohms 90dB 20Hz 500Hz 5-3/8" (137mm) 9-1/4" (235mm)

GT1041D

10" subwoofer 18W 275W dual 4 ohms 90dB 20Hz 500Hz 5-3/8" (137mm) 9-1/4" (235mm)

GT1081

10" subwoofer 18W 275W 8 ohms 90dB 20Hz 500Hz 5-3/8" (137mm) 9-1/4" (235mm)

GT1241

12" subwoofer 18W 300W 4 ohms 93dB 18Hz 500Hz 6" (153mm) 11-1/8" (283mm)

GT1241D

12" subwoofer 18W 300W dual 4 ohms 93dB 18Hz 500Hz 6" (153mm) 11-1/8" (283mm)

GT1281

12" subwoofer 18W 300W 8 ohms 93dB 18Hz 500Hz 6" (153mm) 11-1/8" (283mm)
Declaration of Conformity
We, JBL Europe A/S Kongevejen 194B DK-3460 Birkerod DENMARK declare in own responsibility, that the products described in this owners manual are in compliance with technical standards: EN 50081-1:1992 EN 50082-1:1992
JBL Consumer Products, 250 Crossways Park Drive, Woodbury, NY 11797 800-336-4JBL (4525) www.jbl.com Part No. GTSUBOM Made in USA
Steen Michaelsen JBL Europe A/S Birkerod. DENMARK. 5/99