Powered speakers, also known as self-powered speakers and active speakers, are loudspeakers that have built-in amplifiers. Powered speakers are used in a range of settings, including in sound reinforcement systems (used at live music concerts), both for the main speakers facing the audience and the monitor speakers facing the performers; by DJs performing at dance events and raves; in private homes as part of hi-fi or home cinema audio systems and as computer speakers. They can be connected directly to a mixing console or other low-level audio signal source without the need for an external amplifier. Some active speakers designed for sound reinforcement system use have an onboard mixing console and microphone preamplifier, which enables microphones to be connected directly to the speaker. Active speakers have several advantages, the most obvious being their compactness and simplicity. Additionally the amplifier(s) can be designed to closely match the optimal requirements of the speaker it will power; and the speaker designer is not required to include a passive crossover, decreasing production cost and possibly sound quality. Some also claim that the shorter distances between components can decrease external interference and increase fidelity; although this is highly dubious, and the reciprocal argument can also be made. Disadvantages include heavier loudspeaker enclosures; reduced reliability due to active electronic components within; and the need to supply both the audio signal and power to every unit separately, typically requiring two cables to be run to each speaker (as opposed to the single cable required with passive speakers and an external amplifier). Powered speakers are available with passive or active crossovers built into them. Since the early 2000s, powered speakers with active crossovers and other DSP have become common 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
The terms "powered" and "active" have been used interchangeably in 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. A powered loudspeaker usually used AC power or AC adapter; A passive loudspeaker usually had no power input or use low power input (such as USB power). Hybrid active designs exist such as having three drivers powered by two internal amplifiers. In this case, an active two-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 two-way crossover.
Integrated active systems The term "active speakers" can also refer to an integrated "active system" in which passive loudspeakers are mated to an external system of multiple amplifiers fed by an active crossover. These active loudspeaker systems may be built for professional concert touring such as the pioneering JM-3 system designed in 1971 by Harry McCune Sound Service, or they may be built for high-end home use such as various systems from Naim Audio and Linn Products.
History Some of the first powered loudspeakers were JBL monitor speakers. With the addition of the SE401 Stereo Energizer, introduced in 1964, any pair of monitor speakers could be converted to self-powered operation with the second speaker powered by the first. The first studio monitor with an active crossover was the OY invented 1967 by Klein + Hummel. It was a hybrid three-way design with two internal amplifier channels. An early example of a bi-amplified powered studio monitor is the Altec 9846B, introduced in 1971, which combined the passive 9846-8A speaker with the new 771B Bi-amplifier with 60 watts for the woofer and 30 watts for the high frequency compression driver. In the late 1970s, Paramount Pictures contracted with AB Systems to design a powered speaker system. In 1980, Meyer Sound Laboratories produced an integrated active 2-way system, the passive UPA-1, which incorporated lessons John Meyer learned on the McCune JM-3. It used active electronics mounted outside of the loudspeaker enclosure, including Meyer's integrated active crossover with feedback comparator circuits determining the level of limiting, often connected to third-party customer-specified amplifiers. In 1990, Meyer produced its first powered speaker: the HD-1, a 2-way studio monitor with all internal electronics. In the early '90s, after years of dealing with the disadvantages of passive systems, especially varying gain settings on third-party amplifiers, John Meyer decided to stop making passive speakers and devote his company to active designs. Meyer said he "hired an ad agency to research how people felt about powered speakers for sound reinforcement, and they came back after a survey and said that nobody wanted them." Sound reinforcement system operators said they did not want loudspeakers in which they could not see the amplifier meters to determine whether the loudspeakers were working properly during a concert. Nevertheless, Meyer kept to his decision and produced the MSL-4 in 1994, the first powered loudspeaker intended for concert touring. The UPA-1 was converted to a self-powered configuration in 1996 and the rest of Meyer's product line followed suit.
Advantages and disadvantages
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