Subwoofers
Shake your foundations with subwoofers in your home
Subwoofers, or subs as they're affectionately known, are the speakers in any sound system responsible for reproducing the deepest bass tones around 150Hz and lower. Subwoofers are the one speaker with an added dimension of pure fun, since the lowest frequencies in any soundtrack transcend mere hearing and should also be felt. For Home Theater applications you'll want an extremely powerful subwoofer to recreate loud noises and rumbling sound effects the audience can actually feel in their chest. A good sub should be able to shake the walls and rattle glass in your house. But choosing a subwoofer isn't as simple as just picking the biggest and baddest you can find, for most music you'll want to be a little more nuanced in your decision.
Subwoofers for home audio systems come in two basic types: powered and passive or unpowered. Powered subs are by far the most popular, and generally the best option for most Home Theater applications. However the powered sub doesn't necessarily mean better sound quality. A powered sub is easier to integrate into existing systems without overextending amps that are powering the speakers. Passive subs with a dedicated power amp is a perfect option and many passive sub designs come complete with external amplifiers already specially designed for them.
The other biggest consideration with a subwoofer is the size of the driver or cone built into the sub's enclosure. Sub drivers have the largest diameter of all speakers because they are responsible for moving the most air to create the lowest frequencies. Subs can create a load on an amplifier that is far in excess of many normal speaker systems, including speaker systems with multiple drivers. Usually a dedicated amp for a sub or a built in amp for a powered sub will be rated higher than 100 Watts per channel. Extremely powerful subwoofers often go into the hundreds and even thousands of Watts.
The diameter of a smaller sub would be 8" inches, any smaller and it might not be considered a legitimate subwoofer. The most popular sizes are 8", 10", 12" to 15". A 15" subwoofer is extremely large and will produce the lowest frequency bass at the highest volumes or decibels, making them the monsters among subs. However, large driver size doesn't necessarily make for the absolute best subs as many might automatically assume. The larger the driver, the slower the response to subtle changes in bass frequencies- the paradigm that exists in nature also exists with subs.
Large subs create more boom but since they're slower moving they aren't going to produce the tight bass response needed for most musical applications. For example, many overzealous fans of thick and heavy bass will invest in the most powerful 15" sub they can find. It will create earth shaking bass that will sound impressive for a narrow range of musical tastes. The large, powerful subs also sound impressive when recreating explosions and artillery fire in Home Theater movies. But when switching over to jazz or high tempo rock and roll where the subwoofer may be called upon to reproduce several sounds at once in a quick rhythm, it may sound muddied due to slow response.
Choosing a subwoofer is a balancing act that should be dictated by the size of the room you plan to fill with bass. Smaller rooms can get away with a smaller driver because it should be able to fill the room with enough bass. Larger rooms will require larger drivers to feel the bass, but even in extremely large rooms many fans of music other than electronica or hip-hop might be hesitant to add a 15" sub to their kit. Many are opting for one or more smaller subs to strategically balance the volume of tight-fast bass through the room.