As they do running a 2-ohm stereo load | JBL P1240, P1042, P1040

Connecting Your Subwoofer to Your Amplifier J B L Pro Power GTp Series

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/w1 + 1/w2 + 1/w3...), where w is the nominal impedance of the woofer.

2.The total system impedance of voice coils (or woofers) in series = w1 + w2 + w3...

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

Figure 1. Parallel connection

RED	BLACK
STRIPE	STRIPE
POS ( + )	NEG ( – )
POS ( + )
	NEG ( – )

Figure 2. Series connection

RED BLACK

STRIPE STRIPE

POS ( + ) NEG ( – )

POS ( + )

NEG ( – )