by Pablo Bellinghausen –
When looking for a small or portable PA system, one of the choices you need to make is whether to get passive or active/powered speakers.
Of course, both types need power to be somehow fed into them – the difference between them is whether the amplifiers are in a separate box, which then feeds the power into passive speakers, or built into the back of the speakers themselves, which are at that point called active, or powered.
Active vs Powered: Similar, but Not Identical
Before we go any further, it is important to note that there is technically a difference between active and powered speakers, which while small in practice, does give you quite a bit of extra information about a particular model.
Powered speakers are really just a passive speaker with a single power amp bolted on; the woofer and tweeter are driven by a single amp, with the same passive crossover one would expect inside a passive speaker.
An active model is slightly different (and technically better), since it it has two completely separate amplifiers, one for the tweeter and one for the woofer. The crossover (which, to refresh your memory, separates the treble and bass and sends it to the tweeter and woofer respectively) can in that case be”active”, which means it’s placed before the amp and can use more complex circuitry. It is a lot more difficult to change the sound of a signal once it has power with it, and doing so also wastes a lot of power; about 30% of an amp’s power is lost at the crossover stage inside a passive speaker.
An active crossover therefore allows for less volume loss, as well as much sharper and better-sounding crossover filters. This can even be done in the digital domain, with equalisation very accurately matched to the exact characteristics of the driver and enclosure.
Why go for a powered/active system?
The first thing is, as discussed above, a potential increase in sound quality and a definite one in power efficiency when selecting an active system. Usually, a small active PA system can sound (slightly) louder and better than a similarly-priced passive system with the same specs (although this depends on the quality of the design, so it isn’t a hard-and-fast rule).
The sometimes tricky act of matching amps with speakers, which is confusing to many, is not an issue with active systems. The amps are also carefully matched in terms of power to their respective driver (woofer vs tweeter), with often separate limiters for each. This can add to the durability of the drivers at high volumes, although a carefully-selected speaker should seldom have to be used at anything close to its maximum volume (for more info on this we suggest the following article).
There is, of course, one fewer box to carry. Amplifiers are relatively bulky, and if you aren’t already carrying a rack case (in which case an extra unit or two of rack space is a relatively small increase) this can mean a more convenient setup. In very small systems where you only need couple of inputs, you can even get an active/powered speaker with one or two microphone-level sockets, reducing the need for even a mixer.
Another thing that is remarkably easy to do with active/powered speakers is daisy-chaining. Whilst daisy-chaining on a passive system can strain and actually break a power amp if you don’t know what you are doing due to impedance problems, an active speaker will have a line-level “through” output which can be carried on through dozens of active speakers without noticeable degradation or safety concerns.
And talking about sound fidelity, active systems carry the signal through balanced XLR cable, which is lossless for hundreds of metres with no power loss at all. This is very much unlike standard speaker cable, which becomes noticeably lossy after a few dozens of metres, degrading the audio as well as losing power and volume. In extreme circumstances, the added impedance to the cable can cause problems in the power amp as well – none of this is a consideration with an active/powered system.
One last consideration has to do when using multicore stage-boxes and “snakes” in situations where the stage is far from the mixer; it is generally a terrible idea to send speaker-level signals through multicore cable at the same time as mic and line-level signals. However, using active/powered speakers allows you to use a basic snake for your return signals going into the main speakers, as well as any foldback monitors for the musicians, in the most convenient way and without any signal degradation.
Why go for a passive system instead?
As useful and convenient as active/powered speakers are, there are still many situations in which a passive system is a better choice, and this becomes the case more often than not with larger and more complex systems.
Possibly the most important reason is a larger degree of system control over at the mixing location. On any system large enough for a dedicated sound engineer to be away from the stage, having power amplifiers becomes more convenient, since any volume, tone, or speaker management features can remain in a rack next to the engineer and not at the back of speakers, which will likely be on stands and in an awkward position on stage. In multi-speaker systems in a large venue, managing power quickly becomes impossible for a single sound engineer with an active/powered system, whereas it is easy to have a rack of power amps, crossovers, and EQs to the side of the mixer.
Whereas small and/or portable active/powered systems (2–6 speakers) are usually just as safe as passive ones, providing power to all speakers can prove tricky on larger setups due to the fact that AC power needs to be provided to the speakers separately to the audio signal, meaning two separate cables per box as opposed to one. In addition, power cables will usually have a standard non-locking IEC (kettle plug), whereas passive systems provide both power and audio signal through a single cable terminated with a Speakon plug, which is sturdy, locking, water-resistant. When wall-mounting speakers for installation, the safer option in general is to avoid AC cabling altogether and use passive models instead.
Reliability, and ease of repair, is another consideration that needs to be taken into account on systems that get heavy use. In general, it is good form to have a modular system so that if something fails, it is easier, cheaper and quicker to repair or replace a single part instead of a bigger unit. For example, the “powered mixers” (mixers with a built-in power amp) that were so common in the 90s before the popularisation of active speakers are renowned for being less reliable than a mixer and amp combo, partly due to the heat caused by the power amp components creeping up onto the mixer circuitry, causing long-term problems.
One of the advantages to active speakers, which is the automatic management of crossover and power settings between woofer and tweeter, becomes a hindrance if more control is required, in particular when using subwoofers. A fully modular passive system will have a separate rack crossover, in which the best frequency and filter steepness can be selected depending on the speakers, their position, and the room’s acoustics – this degree of control is seldom possible with the often scant options at the back of a powered sub.
Whereas it is perfectly possible to get the same power and sound quality with either a passive or an active/powered system, there are certain situations where one type will be more convenient than the other. As a rule of thumb, we recommend active speakers with small, portable systems with two speakers (and maybe one or two subwoofers), while for larger set-ups, or permanent installs in general, it is likely better and more convenient to go for passive speakers. As usual, this will depend on your exact requirements and also your personal preference – if you’re at all unsure, do contact your favourite retailer, where someone can help you decide.