Active loudspeakers are speakers that have amplifiers built into them. They are also called powered speakers, as they have their own power source. There are a huge variety of active loudspeakers designed for practically any type of sound system. Conversely, passive loudspeakers are powered only by the signals that produce the sound they output. If passive speakers are only able to handle a low-wattage input signal, too much power from a source will cause them to malfunction; if passive speakers are too large for a sound system, they will not produce enough sound while in use.
Active loudspeakers can be particularly advantageous if used with a low-wattage system. The built-in powered amplifier can take a weak incoming signal and amplify it on its own. Another advantage is size. Unlike passive speakers, which must be very large to handle high-input signals, active loudspeakers can be designed to be much smaller while producing comparable levels of sound.
A very basic design of an active loudspeaker consists of a power source, an amplifier, and a woofer or tweeter for delivering the actual sound. Another common design element is a preamplifier, which electronically processes the incoming signal prior to going through the speaker's main amplifier. More complex designs will contain at least one woofer and one tweeter per speaker, and each can contain their own powered amplifier.
The process of choosing which active loudspeaker is right for a specific purpose depends on the source and for what the speakers will be used. Even though powered speakers are more flexible than the passive variety, it is still possible to choose a set that is too weak and will break when input levels are too high. Specifications between a source and speakers must always be compared prior to buying and connecting them to ensure compatibility.
Active loudspeakers are not just more flexible than their passive counterparts in terms of size. There is also much more leeway involved in their design. This is highly advantageous for people who want to use unique speakers as decor in their home or workspace, rather than just boxes that transmit sound.
Combinations of the passive and active speakers are called crossovers, but still can be considered as types of active loudspeakers since they still must have their own power source. A good example of a crossover speaker contains a passive tweeter with a powered woofer, but the combinations are practically limitless. Another variation of active loudspeakers is wireless speakers. These will definitely need their own power source—batteries to make them truly wireless—and amplifiers since the incoming signal is transmitted through the airwaves.