JBL W15GTi, W10GTi, W12GTi, MkII automotive User Manual

GTi SERIES

W10GTi MkII W12GTi MkII W15GTi MkII

automotive subwoofer owner’s manual

THANK YOU

for choosing a JBL®GTi Series subwoofer. GTi subwoofers are designed to provide maximum sound output in a variety of enclosure types while maintaining the superb sound quality associated with JBL. To ensure the best subwoofer performance, we strongly recommend that installation be entrusted to a qualiﬁed professional. Although these instructions explain how to install a GTi Series subwoofer in a general sense, they don’t show the speciﬁc installation procedures that may be required for your particular vehicle. If you feel you don’t have the necessary tools or experience, don’t attempt the installation yourself; rather, ask your authorized JBL dealer about professional-installation options.

INSTALLATION WARNINGS AND TIPS

WARNING

Playing loud music in an automobile can hinder your ability to hear trafﬁc, as well as permanently damage your hearing. 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.

YOUR CAR AND BASS REPRODUCTION

Depending on the size of the vehicle’s interior listening space, reproduced frequencies below 80Hz may be boosted by nearly 12dB per octave as frequency decreases. This effect, commonly known as transfer function, or cabin gain, plays an important role in deﬁning the in-car frequency response of your subwoofer. It is displayed graphically, along with freespace response, on the enclosed data sheet for your GTi subwoofer.

POWER-HANDLING LIMITATIONS

The power-handling capacity of any subwoofer is related to the excursion limit of its suspension and its ability to dissipate heat. A speaker reaches its excursion-limited power-handling capacity when its suspension is stretched to its limit. The excursion curve shown on the Enclosure Design Sheet (included with your woofer) displays cone excursion at the input power level required to drive the woofer to maximum linear excursion (X The input power shown may be used

max

as instantaneous input only.

Thermal power handling is determined by the amount of heat that may be dissipated by the driver’s voice coil. The power-handling rating assigned to your GTi Series subwoofer is its thermal-power-handling rating. This rating assumes a clean (unclipped) signal. A clipped waveform has much higher average power, due to the longer duty cycle at the top and bottom of the waveform; it will heat the woofer’s voice coil faster than a clean signal and may damage the voice coil. A square wave has a 100% duty cycle and is extremely dangerous for any speaker. Audible distortion in the output of your woofer is an indication that your ampliﬁer may be clipping, which could damage your speakers over time.

CHOOSING AN ENCLOSURE

GTi Series subwoofers are optimized to perform best in small sealed, vented and bandpass enclosures. While inﬁnitebafﬂe mounting of GTi Series subs is possible, power handling will be compromised since there will be no enclosed volume of air to help the speaker’s suspension control the motion of the woofer’s cone. For this reason, we do not recommend inﬁnite-bafﬂe mounting for high-power applications.

You should choose the enclosure you’ll use based on the type of music you listen to, how much ampliﬁer power you’ll use to drive the subwoofer, and how much space inside the vehicle you can devote to a subwoofer enclosure. If you’ll be using your GTi Series subwoofer for SPL competition, please see the document titled “GTi as SPL Competition Subwoofers” (included with your woofer).

Because a sealed enclosure provides the most control over the woofer’s movement, a woofer mounted in a sealed enclosure will handle more power at low frequencies 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. An optimum sealed enclosure is always smaller than other types of enclosures that are optimized for a particular speaker, so they require the least space inside the vehicle.

Vented enclosures provide better efﬁciency in the 40Hz – 60Hz range, but this efﬁciency comes at the expense of sound output in the lowest octave (below 40Hz) and at the expense of some control and power handling below box tuning. 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 characteristics of the woofer, the enclosure must be built exactly to the speciﬁcations provided. 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 can provide the greatest 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 vented or bandpass enclosure. Bandpass enclosure design is very tricky and the aid of a computer and enclosure design software is necessary if you wish to design the enclosure yourself. Like a vented enclosure, a bandpass enclosure must be built exactly to the speciﬁcations provided. Bandpass enclosures can be quite large and may require a lot of space inside your vehicle.

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