P1242 - JBL Car Audio User Guide / Operation Manual. Page 3

03

JBL GTp subwoofers are available
in two different configurations: 
single 4-ohm voice coil and dual 
4-ohm voice coils. Depending on
the amplifier 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
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, consider the 
following rules:

1. Don’t mix different subwoofer 

or enclosure types in the same
system (use all single-coil
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
impedance, 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 
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 impedance 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.

POS ( + )

NEG ( – )

RED
STRIPE
POS ( + )

BLACK
STRIPE
NEG ( – )

POS ( + )

NEG ( – )

RED
STRIPE
POS ( + )

BLACK
STRIPE
NEG ( – )

Connecting Your Subwoofer to Your Amplifier 

JBL Pro Power GTp Series