Not surprisingly, for an item that can vary so dramatically in price, subwoofers are complex bits of audio equipment capable of very different levels of performance between models.
Power Creating bass is a power-hungry business, and a subwoofer will need a higher capacity than your other speakers. Much of it depends on the size of the space it will be working in. A home cinema subwoofer in a large room will need more power than car subwoofers, for example.
What are you going to use it for? Like the size of a room, the main use of your subwoofer is well worth considering. For a home cinema subwoofer, you should aim for something more powerful than something you will be mostly playing music through. This is because most music lacks the extreme bass notes that you get in movies, though there are exceptions. Because they are used in much smaller confined spaces, car subwoofers should be less powerful.
Passive/Active Passive subwoofers are powered by a separate amplifier like any other speakers. That means that the ability of your subwoofer to produce realistic, deep bass must be matched by the subwoofer amplifier. An active subwoofer contains the amp as well as the subwoofer and will be optimally configured for great delivery. Because there is no power-hungry subwoofer draining the amplifier’s power, an active subwoofer also leads to superior performance from your other speakers. For the best experience, a home cinema subwoofer should be active.
Direction Front-firing subwoofers push sound out into a room while a down-firing subwoofer focuses it into the floor. There is little difference in sound quality but latter setup protects the expensive and sensitive equipment better, making it an excellent choice for people with children and pets, though they can disturb people living below you more than the former.
Crossover Crossover sets the frequency below which the subwoofer will produce sound. An average level is around 100Hz, with higher frequencies routed to the other speakers. Systems approved by THX – a standard for cinema audio reproduction – tend to set this filter at 80Hz, and a home cinema subwoofer will have a lower crossover. If a home cinema subwoofer has a crossover that is too high, it can reproduce too much of the sound, worsening the overall quality. This goes for all uses, and models with adjustable crossover are the best.