A subwoofer is a woofer, or a complete loudspeaker dedicated to the reproduction of bass audio frequencies, from perhaps 150 Hz down as far as 20 Hz, or in rare cases lower.
The subwoofer wiring diagram application discuss in this site (crutchfield.com) includes diagrams for Single Voice Coil (SVC) and Dual Voice Coil (DVC) speakers. A SVC speaker has one voice coil and one set of terminals, one positive (+) and one negative (-). A DVC speaker has two voice coils, each with its own set of terminals. Because of this, DVC speakers (typically subwoofers) offer more wiring options than SVC speakers.
Here is the detail Subwoofer Wiring Diagram Configuration:
Mono Amplifier Configurations:
Two Subwoofers, Mono Amplifier
Three Subwoofers, Mono Amplifier
Four Subwoofers, Mono Amplifier
2-Channel Amplifier Configurations:
Two Subwoofers, 2-Channel Amplifier
Four Subwoofers, 2-Channel Amplifier
4-Channel Amplifier Configurations:
Three Subwoofers, 4-Channel Amplifier
Four Subwoofers, 4-Channel Amplifier