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Powered speakers, also known as self-powered speakers and active speakers, are loudspeakers that have built-in amplifiers. They can be connected directly to a mixing console or other low-level audio signal source without the need for an external amplifier. Active speakers may have greater fidelity, less intermodulation distortion (IMD), higher dynamic range and greater output sound pressure level (SPL) with fewer blown drivers. Disadvantages include heavier loudspeaker enclosures, reduced reliability due to active electronic components within, and the need of a source of electrical power (other than the audio signal). Powered speakers are available with passive or active crossovers built into them. Active speakers with internal active crossovers are widely seen in sound reinforcement applications and in studio monitors. Home theater and add-on domestic/automotive subwoofers have used active powered speaker technology since the late 1980s. == Differences between passive, powered and active speakers == The terms "powered" and "active" have been used interchangeably in regard to loudspeaker designs, however, a differentiation may be made between the terms: *In a passive loudspeaker system the low-level audio signal is first amplified by an external power amplifier before being sent to the loudspeaker where the signal is split by a passive crossover into the appropriate frequency ranges before being sent to the individual drivers. This design is common in home audio as well as professional concert audio. *A powered loudspeaker works the same way as a passive speaker but the power amplifier is built into the loudspeaker enclosure. This design is common in compact personal speakers such as those used to amplify portable digital music devices. *In a fully active loudspeaker system each driver has its own dedicated power amplifier. The low-level audio signal is first sent through an active crossover to split the audio signal into the appropriate frequency ranges before being sent to the power amplifiers and then on to the drivers. This design is commonly seen in studio monitors and professional concert audio. Hybrid active designs exist such as having three drivers powered by two internal amplifiers. In this case, an active 2-way crossover splits the audio signal, usually into low frequencies and mid-high frequencies. The low-frequency driver is driven by its own amplifier channel while the mid- and high-frequency drivers share an amplifier channel the output of which is split by a passive 2-way crossover. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「powered speakers」の詳細全文を読む スポンサード リンク
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