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English

www.jbl.com

THANK YOU

 for choosing a JBL

®

 GT

®

 Series subwoofer tube. This 

product has been designed to deliver great bass performance from a 
compact, easily installed subwoofer tube. To get the best performance 
from your subwoofer tube, it is strongly recommended that installation 
be entrusted to a qualified professional. Although these instructions 
explain how to install your product in a general sense, they do not show 
specific installation methods that may be required for your particular 
vehicle. If you do not have the necessary tools or experience, do not 
attempt the installation yourself. Instead, please ask your authorized 
JBL car audio dealer about professional installation. In order that you 
may be better served should you require warranty service, please retain 
your original sales receipt and serial number.

GENERAL CARE

Do not use any cleaners or solvents on the speaker cone.

INSTALLATION WARNINGS AND TIPS

WARNING:

 Playing loud music in an automobile can permanently 

damage your hearing as well as hinder your ability to hear traffic. 
Listening at low levels while driving is recommended. HARMAN accepts 
no liability for hearing loss, bodily injury or property damage resulting 
from use or misuse of this product.

INSTALLATION TIPS

Always wear protective eyewear when using tools.

• 

Turn off all audio components and other electrical devices before you 

• 

start. Disconnect the negative (–) lead from your vehicle’s battery.
Check clearances on both sides of a planned mounting surface. Be 

• 

sure that screws or wires will not puncture brake lines, fuel lines or 
wiring harnesses, and that wire routing will not interfere with the safe 
operation of the vehicle.
When making electrical connections, make sure they are secure and 

• 

properly insulated.
Before drilling or cutting holes, use a utility knife to remove unwanted 

• 

fabric or vinyl to keep it from snagging in a drill bit or saw.
Do not mount speakers where they will get wet.

• 

CHOOSING A MOUNTING LOCATION FOR THE SUBWOOFER TUBE

Choose a mounting location that doesn’t interfere with cargo, the fold-
down rear seat or the trunk lid. The best location is usually a corner of 
the trunk or cargo area.

CONNECTIONS

Connect the “+” and “–” terminals on the subwoofer tube to the 
amplifier’s outputs, observing proper polarity. Use at least 0.5mm

2

 

speaker wire for the connections to the subwoofer tube.

L Speaker Out

R Speaker Out

Stereo   Bridged

Bridged Power Amplifier

Subwoofer Tube

Note: We recommend a JBL amplifier to power your GT-X1250T. Set  
the amplifier’s crossover to LPF (Low-Pass Filter) and set the crossover 
frequency to a value within the range marked in gray in the drawing 
below (50Hz – 100Hz). For details regarding the installation of your 
amplifier or other amplifier settings, please consult the installation 
manual for your amplifier.

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