Sound Advice – Active and Powered speakers

“Amps? Where we’re going, we don’t need amps”

by Ed Selley Aug 10, 2017 at 7:51 AM


  • Hi-Fi Article

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    Sound Advice – Active and Powered speakers
    In the overwhelming majority of separates-based audio systems, the amplifier and the speakers are completely different components. Your amplifier – be it an integrated type or a pre-power unit – will collate signals, amplify them and send them to your speakers.
    From the moment that practical solid state amplifiers have existed though, a selection of people have felt that a more practical division of responsibilities was to place the power amplification in the same cabinet as the drivers. The result is an active or powered loudspeaker and they exist in various forms from a few hundred pounds all the way through to the sort of costs you might associate with buying a very smart car. There are (as ever) some differentiations between the different types so this piece aims to cover those differences and variations before turning its attention to good applications for these speakers and what might work best for you.

    Active vs Powered – what’s the difference?
    Viewed alongside one another an active and powered speaker can look very similar. Both can mount the amplifier inside the cabinet and be controlled from elsewhere. The key difference between the two is the relationship of the amplifier to the crossover of the speaker. A powered speaker is effectively a normal speaker with the amplifier mounted in one or both of the cabinets. This sends a signal to the crossover which then sends the correct signal to the drivers of the speaker. If you scooped the supplied amplifier out of a powered speaker and gained access to the crossover, you could power it with any other amplifier.

    An active speaker is different in that it places the crossover in front of the amplifiers. The speaker receives a signal from a pre-amp and applies crossover frequencies to it before sending it on to amplifiers that act directly on the drivers. This means that an active speaker must have an amplifier for each driver fitted to the cabinet and that it is effectively self-contained. You can’t easily ‘open up’ an active speaker and substitute an alternative component for example.
    The other key difference between the two designs is one that is not strictly required as a function of how they operate but is frequently observed for simplicity. Powered speakers frequently take the form of a powered ‘master’ and passive ‘slave.’ The powered speaker will contain a stereo amp that will power both the speaker it is mounted in and also power the passive unit via a speaker cable connection. This means you will only need to find a single mains socket to run them and your inputs will go to a single speaker.

    As an active speaker must contain the amplifiers to run it, the cabinet will generally require mains power (designs that connect to one another via an umbilical cable to share power exist but are relatively rare) and each will usually require a signal to be sent to it. A final subset of active speaker designs blur this slightly. Some companies will mount the crossover in a separate, powered chassis. This receives the signal and splits it to be sent to power amps which then connect to speakers via speaker cables. These are still active systems – the crossover is mounted in front of the amplification but they offer greater flexibility in setup like being able to choose your amps for example – and there’s no need to get power to the speakers, just the amplified signal.

    Powered Speakers – Advantages and disadvantages
    Advantages
    Powered speakers are often very cost effective. Even a compact standmount type speaker can find the space for a modern class D amplifier to be added to the rear panel. We’ve seen some very capable designs from as little as £200 on this very site and even less expensive designs exist.

    Powered speakers are frequently very convenient with just a single mains input and facilities like Bluetooth, which means a modern powered speaker can be a self-contained audio system that has the considerable advantage of having a level of stereo width – thanks to there being two separate speakers – that a conventional all-in-one simply can’t rival. Many models also have a useful spread of inputs that will support a decent selection of additional devices.

    Generally, powered speakers are easy to setup. There’s little in the way of additional requirements to make them go and they require little in the way of adaptation to any existing equipment you use with them.

    Disadvantages
    A powered speaker will generally have been voiced to work with the amplifier built into the cabinet but the nature of the design means it can’t enjoy some of the engineering benefits that a true active speaker can.

    The ability to upgrade a system using powered speakers is not terribly easy. As they contain the preamp and input functionality as well as the amplification and speakers, they are effectively the same as an all-in-one system and roughly as hard to upgrade.
    Truly high performance powered speakers are fairly rare. This might be best viewed as a convenience item rather than the means of getting optimal performance.

    Active Speakers – Advantages and Disadvantages
    Advantages
    Implemented correctly, an active speaker should demonstrate a performance advantage over a rival passive speaker with an amplifier of the same given measurements. Moving the crossover to a point where it acts on an unamplified signal via powered components should produce more effective results than a passive design. The amplifiers can be designed and selected to perfectly complement the drivers the speaker uses so, theoretically (and that word is going to get used a lot here), it should not be possible to damage an active speaker in normal use due to this relationship between amp and driver.

    The choice of active speakers is very large and runs from cost effective, studio derived designs through to some enormously expensive models that are truly representative of the high-end in its absolute form. Companies like ATC in particular are specialists in the field of active speaker design and produce some fearsomely capable high-end products

    The nature of their design also means that features like room correction and optimisation can be worked in more easily than would be the case in a system with passive speakers. The Linn Exakt system is a key example of this.

    In the case of a ‘classic’ active speaker that accepts a signal from a preamp, you have much more flexibility over the rest of your system. You can choose your source, decoding and preamp to better suit your personal requirements.

    Disadvantages
    Almost every active speaker will need you to have a mains feed available at the point where the speaker sits. This can make them considerably different in terms of their positioning requirements, particularly in older buildings with fewer mains outlets. It is important to take into account that while active speakers are potentially more compact and efficient than a separate amp and speaker combination, they still need to be wired up in much the same way.

    Although they allow for more flexibility in component choices over a powered speaker, an active speaker is still something you should demo thoroughly before purchase as there is little in the way of adjustment that can be made to the overall sonic performance in the manner that can be done by changing the amp running into speakers or vice versa.

    Many pro-audio derived active speakers can deliver excellent performance but it would be a stretch to call them pretty. Some designs are also seriously expensive.

    When are they right for me?
    Both active and powered speakers are easiest to introduce when starting with a clean sheet. Powered speakers in particular make a compelling alternative to an all-in-one system or soundbar that can be used to support a limited number of inputs but still provide decent sized speakers that can be placed a meaningful distance apart. Compared to a soundbar, a pair of powered speakers can generate a superior stereo signal while still sounding extremely good with film and broadcast material.

    Active speakers can be added to an existing system without too much difficulty. If you are replacing amp and speakers, you can look to use a preamp and active speakers instead but their real strength comes in when you consider how many digital sources are now equipped as excellent preamps. In the immediate run up to writing this piece, the Chord Hugo2 and Oppo Sonica have both demonstrated superb performance as digital sources and both are also extremely talented preamps. If you are really only looking for a digital front-end to your system, attaching active speakers to a digital preamp is the most elegant way of completing a system.

    There are some caveats to this though. If you find yourself wanting to add an analogue source to such a system later on, you may struggle without a fairly thorough redesign. It’s also worth checking that the pre-amp functionality of the source device will match correctly with the speakers – this is not so much a gain issue as checking that the useable volume portion is large enough and allows for enough fine adjustment.

    Ultimately, the changing nature of how we are assembling audio systems means that active and powered speakers are both a logical and potentially very exciting choice in how we listen to music and film. Choose the right design and the correct implementation and you can find yourself in possession of a compact but extremely capable system.

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