Subwoofers:
It is an audio speaker which is specially designed to reproduce low frequency sound, generally from 200 Hz down to around 20 Hz. Two types of Subwoofers:
Active or
Powered Subwoofers are driven by their own dedicated amplifier while
Passive Subwoofers must be driven by the same amplifier that powers the other speakers in the system.
Additional subwoofer design variations include Front-firing , and Down-firing, and the use of Ports or Passive Radiators!
Woofer: A typical universal term for a loudspeaker which reproduces "Bass" effect (/wwooff/)!
Woofer is the term commonly used for a loudspeaker driver designed to produce low frequency sounds, typically from around 40 hertz up to about a kilohertz or higher.
Dual SubWoofers:
See, A Dual Subwoofer is nothing but one speaker system featuring and two 7-21 inch woofers with 2.5-inch and high temperature voice coils and a better 2-way passive bass reflex design.
Remember, a typical dual subwoofer packs more punch, weight, power and response! Not to mention the massive enclosures with insane dimensions!!
Ok, remember all those Bryan Adam/Pink Floyd/Sting/MJ's concerts?? Yeah, all the credit to those massive sound reproductions goes to these things.
So, now you know.