JBL Speaker GT120D User Manual

GT SERIES  
Automotive Subwoofers Owner’s Manual GT100 GT100D GT120 GT120D GT150 GT150D  
 
Connecting Your Subwoofer to Your Amplifier JBL GT Series  
Figure 1. Parallel connection  
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:  
JBL GT Series subwoofers  
2. You may connect the coils of a  
dual-voice coil woofer in series,  
but we recommend that you  
avoid connecting separate  
are available in two different  
configurations: as a single 4-ohm  
voice coil or as dual 4-ohm voice  
coils. Depending on the amplifiers  
you are using, you may use either  
single-voice coil or dual-voice coil  
subwoofers in singles or multiples  
to maximize the power available  
from your amplifiers. To achieve  
the maximum amplifier output  
possible, you should design a  
speaker system that provides  
the lowest impedance that  
your amplifier is rated to drive  
safely. When designing a  
subwoofer system, consider  
the following rules:  
1. Don’t mix different subwoofer  
or enclosure types in the same  
system (use all single-coil  
BLACK  
RED  
STRIPE  
NEG ( – )  
STRIPE  
POS ( + )  
woofers in series. The amplifier-  
damping factor (the amplifier’s  
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  
amplifier-output impedance.  
Therefore, connecting separate  
woofers in series reduces the  
damping factor of the amplifier  
to a value less than 1. This will  
result in poor transient response.  
3. You must use both coils of a  
dual-voice coil woofer connected  
either in series or in parallel.  
4. Most amplifiers deliver exactly  
the same amount of power  
bridged into a 4-ohm load  
POS ( + )  
NEG ( – )  
1
1
w2  
Impedance=  
1
w1  
1
w3  
. . .  
Figure 2. Series connection  
+
+
BLACK  
RED  
STRIPE  
NEG ( – )  
STRIPE  
POS ( + )  
where w is the nominal  
impedance of the woofer.  
2. The total system impedance  
of voice coils (or woofers) in  
series can be calculated using  
the formula:  
POS ( + )  
NEG ( – )  
Impedance = w1 + w2 + w3 . . .  
The diagrams at right show parallel  
and series speaker connections.  
woofers or all dual-coil woofers).  
as they do running a 2-ohm  
stereo load.  
03  
 
Specifications JBL GT Series  
GT100  
GT100D  
10" Dual-voice coil  
GT120  
12" Automotive  
GT120D  
12" Dual-voice coil  
automotive subwoofer subwoofer  
GT150  
15" Automotive  
GT150D  
15" Dual-voice coil  
automotive subwoofer  
10" Automotive  
subwoofer  
automotive subwoofer subwoofer  
Power handling (RMS) 250 Watts  
Power handling (Peak) 1000 Watts  
250 Watts  
250 Watts  
250 Watts  
250 Watts  
250 Watts  
1000 Watts  
1000 Watts  
1000 Watts  
1000 Watts  
1000 Watts  
Sensitivity (2.83V/1m)  
Frequency response  
90dB  
90dB  
93dB  
93dB  
95dB  
95dB  
28Hz – 500Hz  
28Hz – 500Hz  
23Hz – 450Hz  
23Hz – 450Hz  
20Hz – 400Hz  
20Hz – 400Hz  
Impedance  
4 Ohms  
Dual 4-ohm voice coils 4 Ohms  
Dual 4-ohm voice coils 4 Ohms  
Dual 4-ohm voice coils  
6-3/4" (172mm)  
Mounting depth  
Cut-out diameter  
5-3/4" (147mm)  
9-1/8" (232mm)  
5-3/4" (147mm)  
9-1/8" (232mm)  
6-1/4" (159mm)  
11-1/8" (283mm)  
6-1/4" (159mm)  
11-1/8" (283mm)  
6-3/4" (172mm)  
14-1/4" (362mm)  
14-1/4" (362mm)  
Declaration of Conformity  
We, Harman Consumer International  
2, route de Tours  
72500 Chateau-du-Loir  
FRANCE  
JBL Consumer Products • 250 Crossways Park Drive, Woodbury, NY 11797  
Features, specifications and appearance are subject to change without notice.  
declare in own responsibility, that the products described in this owner’s manual are in  
compliance with technical standards:  
©2002 JBL, Incorporated • JBL is a registered trademark of JBL, Incorporated  
Part No. GTSUBSEROM  
EN 50081-1:1992  
EN 50082-1:1997  
Emmanuel Millot  
Harman Consumer International  
Chateau-du-Loir, FRANCE. 7/02  
 

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