GTO 1204D - JBL Car Audio User Guide / Operation Manual. Page 3

JBL Grand Touring Series 
subwoofers are available in two 
different configurations: as dual 
4-ohm voice coils or as dual 2-ohm
voice coils. Depending on the 
amplifiers you are using, you may
use GTO 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 will drive safely. When
designing a subwoofer system, 
consider the following rules:

1. Do not mix different subwoofers or

enclosure types in the same sys-
tem. Subwoofers being used in the
same enclosure or powered from
the same amplifier should be iden-
tical models. Mismatched woofers
and enclosures can result in poor
performance from your subwoofer
system.

2. You may connect the coils of a

dual-voice coil woofer in series,
but we recommend that you avoid
connecting separate woofers in
series. 

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 can be 
calculated using the formula:  

Impedance =

1

 1 

+

 1 

+

 1  ...

w

1

w

2

w

3

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:

Impedance = w

1

+ w

2

+ w

3

...

The diagrams at right show parallel
and series speaker connections.