Subwoofers for Home Theater Digital Surround Sound Systems
When choosing subwoofers you must understand that subs are very important to the overall effect and impact of your home theater digital surround sound system. They reproduce the LFE (low frequency effects) information that are "seat of the pants" bass effects. Those LFE effects are the ".1" part of 5.1, 6.1 or 7.1 digital surround audio system. That ".1" LFE information is routed to your receiver's subwoofer out connector. The sub bass effects greatly help to create the feeling of being immersed in the action when watching a movie.
Your powered sub-woofer should have the most power of any of your speakers due to the fact that low frequencies take the largest amount of power to create. I am stressing the previous sentence because for you to be fully satisfied with your home theater surround system you will need a good and powerful sub speaker unit. Low frequencies are long wavelengths and as such take a far greater amount of power to produce than a mid-range or high frequency which are relatively shorter wavelengths. The larger your room is the more power you will need to fill it of course. You may also find it acoustically advantageous to add "bass traps" to your room to help prevent low-frequency build-up of those long wavelengths in your listening environment. Bass traps can either be purchased manufactured models or you may simply place large fluffy throw-pillows in the corners of your room to absorb the sound waves and reduce build-up.
Home theater system subwoofers (or as some call them sub woofers or subs) do not have to be extremely expensive to provide the impact of thunder.
Sub-woofers are not dogs that bark at underwater vessels...
Pardon the pun but here's a bit of historical perspective on subs -- My first recollection of sub-woofers was long ago in the 1974 blockbuster movie "Earthquake". That movie was presented in a format dubbed "Sensurround" wherein - as a gimmick - large Cerwin-Vega bass speakers were placed in theaters to provide the bone-shaking bass effects of an Earthquake ravaging Los Angeles. Nowadays subwoofers come integrated into the HTiB units and can reach ridiculous levels in standalone audiophile component systems. Today's modern home theater digital audio system's powered sub-woofers can produce nearly the same earthshaking seat-of-the-pants low frequency results and usually without the Hollywood blockbuster subwoofer speaker price-tag.
Some of the major manufacturers of sub-woofers are Polk Audio, JBL, Bose and the aforementioned Cerwin Vega.
Most subs you find are the powered models. There are also audiophile varieties that are very large bass speaker enclosures and are externally powered by one's choice of esoteric amplifiers. There are even many plans available for do it yourself enclosures if you are so inclined and handy with power tools. Such DIY subs range from simple sealed or ported types and can include the infinite baffle variety which are often ported into the attic of a home for some real low, low, bass effects.
Whatever your particular needs - there should be a good and powerful sub at the "bottom-end" of the audio spectrum in your home theater.
Once you acquire a decent sub you may be interested in the correct placement of it within your room for the best effect. If so check out --
What is the best subwoofer placement? That section from answers to our FAQ will point you in the right direction (and hopefully point your subwoofers in the right direction too).