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SOUND BYTE

Boom-time in the boot

Subwoofers are larger speaker drivers used to recreate frequencies around and below 100Hz. They are generally eight inches or larger in diameter and require more amplifier power than coaxial or component speakers due to their larger size. Subwoofers also require an enclosure to produce these lower frequencies, which can be as simple as the boot of the car or as complex as a series-tuned dual-reflex bandpass enclosure.

There are several manufacturers that offer non-typical subwoofer kits. Examples are the tube-type subwoofer and the vehicle-specific subwoofer system. Tube subwoofers are cylinders (tubes) with one end containing the subwoofer, the other end being sealed - a good way of adding a subwoofer to a limited space application or a leased vehicle.

Vehicle-specific subwoofer systems are usually built from wood and fibreglass and are designed to fit snugly into a factory void or pocket. Because they are specific to one vehicle, they are more expensive then either a standard box or tube configuration. However, they cannot be beaten for fit and use of space.

A word of advice before purchasing subwoofers - determine how much space you are willing to give up and then decide what subwoofer you want. Be realistic about your goals for the system and the space you are willing to sacrifice to achieve those goals.

Aspects and features to be considered when purchasing a sub:

Type of enclosure

This is the type of box or enclosure your subwoofer will be mounted in. The main types are infinite baffle, sealed, vented (ported), and bandpass.

Power handling ability

This is the amount of power a speaker can withstand before failing after a given amount of time. The most important number is the speaker's continuous or RMS power handling. Remember, PMPO or Peak power handling means virtually nothing.

Sensitivity

This is a reference measure of how loud a speaker will be with a certain amount of power at a certain distance. The standard is one watt at one metre. By halving the distance, an increase of six decibels will be realized and doubling the power will increase the output by another three decibels. This is a trick used by some companies to make their speakers appear more efficient than they are. Most loudspeakers will be in the 90 decibel range. Keep in mind that a difference of three decibels is equivalent to a doubling of the amplifier power. Now go, get that sub!

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