GT 1081 (serv.man2) - JBL Car Audio User Guide / Operation Manual. Page 3

03

Connecting Your Subwoofer to Your
Amplifier
JBL GT Series subwoofers are available 
in three different configurations: single 
4-ohm voice coil, single 8-ohm voice coil
and dual 4-ohm voice coils. Depending 
on the amplifier you are using, you may
use either single- or dual-voice-coil 
subwoofers in singles or multiples to
maximize the power available from your
amplifier. 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, abide by the 
following rules:

1. Don’t mix different subwoofer or enclo-

sure types in the same system (use all
single-coil 4-ohm woofers, all single-
coil 8-ohm woofers, or all dual-coil
woofers).

2. You may connect the coils of a dual-

voice-coil woofer in series, but NEVER
connect separate woofers in series.
Because 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 imped-
ance, connecting 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 either in series or in
parallel.

4. Most amplifiers 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 amplifier power,
keep the following rules in mind: 

1. The total system impedance of

woofers in parallel = 1/(1/w

1 

+ 1/w

2 

+

1/w

3

...) where w is the nominal imped-

ance of the woofer. 

2. The total system impedance of voice

coils (or woofers) in series = w

1 

+ 

w

2 

+ w

3

...

The diagrams below and at right show
parallel and series speaker connections.

Figure 1. Parallel connection

Figure 2. Series connection

GT Series Owners Manual  5/14/99  9:49 AM  Page 3