June 17, 2016
One of the biggest choices musicians and pro audio enthusiasts make when purchasing speakers is whether they should spring for passive or active speakers. Just like with any equipment, the right choice comes from a combination of understanding the main components of each and finding the one that best suits your application. This basic guide will cover the main differences between active and passive models and help you choose which one is better for your needs.
Understanding the Basics
Before we launch into the passive vs active debate, it is important to understand the basics about passive crossovers, active crossovers, power amps, and AC power sources, so we are using the terms with the same understanding.
A passive crossover is the device (or circuit) consisting of large coils, large capacitors, input jacks, and resistors in a passive speaker. It takes a power output signal from your power amplifier and splits it into separate frequency bands. These separate bands, which often consist of low, mid, and high in a 3 way speaker or low and high in a 2 way speaker, are then directed to the speaker component (usually call a driver) that is designed for that range of frequencies. The passive crossover can be very complicated or it can be very simple. The level of complication usually goes with the cost or “pro level” where the cabinet is to be used.
Note: With Carvin Audio and many other high end manufacturers, the passive crossover is designed for the particular speakers in the cabinet, the placement of the speakers in the cabinet, the protection circuits needed, and the extra EQ and level adjustments needed for the loudspeaker. Rarely does a crossover designed for a particular cabinet work correctly in other cabinets with similar, but different components and placements in the cabinet.
Active crossovers or electronic crossovers, on the other hand, are placed before the power amps using small circuit parts. These can be analog circuits or digital in the form of DSP processing. They can be in power amps, stand alone products placed before the power amp, or in an active speaker. The benefits of active crossovers are increased versatility for the designer, more advanced EQ and limiting, and lower cost to achieve these.
Power amps, and AC power sources are common terms, but we want to make sure you know what we are talking about. A power amp is any amplifier that takes in a low level signal and amplifies it to a high power level able to move the coils in speakers. This can be a stand alone power amplifier, a powered mixer with built in power amplifiers, or a section inside an active speaker. The AC power source is simply the AC socket in the wall. We are not talking about the power supply in the amplifier, just the AC wall power you wanted to put paper clips and flat screw drivers into when you were little. Ouch!
If a speaker is passive, it utilizes a passive crossover, and it requires an external power amplifier to create any sound. For an example outside the PA world, there is the guitar amp head and speaker cabinet, where the cabinet needs the head connected to it to put out any audio.
The advantages of passive cabinets are numerous. They can weigh less and be more compact, but advances in lightweight power amps and power supplies have reduced this advantage for active cabinets. The fact that they only need a speaker cable from the power amp and not an AC power source plus an input signal, allows for more flexible speaker placement. This also cuts down on the total number of power cords running across the stage. Multiple cabinets can be chained together with a single cable between each cabinet as long as the amplifier can handle the load impedance.
The disadvantages of passive models are getting the right amplifiers for the cabinet, less efficient output due to passive crossover components stealing a little power, and less protection preventing damage to the speaker. If you provide active processing before your amplifiers, you can improve the last item. Bi-amping speakers can eliminate the passive crossover losses, but that’s a whole new can of worms outside this article.
Active models come equipped with a built-in amp and active crossover. Think of them as a cousin of a guitar amplifier combo. In the early days of PA gear many of them were modified guitar amplifiers or vice versa. Each cabinet requires an AC power source. They generally reduce the overall time involved in setup compared with a passive system. This is due to the internal processing and more advanced circuits in the active crossover providing a flatter response and more ideal performance.
The advantages are easier setup, because you don’t have to bring or setup power amps and speaker cables, and you can plug them straight into your mixer. Many active models can accept microphone level, line level, instrument level, and phone or playback device level inputs for an all in one unit.
Disadvantages are the need for an AC power source at each cabinet, higher cost for each unit, although you can subtract the cost of a power amp, and two cables to each cabinet when connecting multiple active cabinets together.
Active systems with passive cabinets
Showing up more and more are system level active speakers like the Carvin Audio TRC Systems using the active TRx3018A subwoofer. Here the subwoofer has an extra power amp output with processing to run the special top cabinets which are passive. These are usually considered an active speaker system. Although, the TRx3018A can run any top cabinet down to 4 ohms and has internal crossover to adjust for the external top cabinet.
Which One is Better for You?
The choice between active and passive will depend heavily on the nature of how you intend to use it. If you want a convenient all-in-one package that travels and sets up easily, a high-quality active model like Carvin Audio’s PM15A will fit the bill. Home audio enthusiasts and bands who just want to leave a PA in their practice space will likely find that a set of passive speakers and an amplifier or powered mixer will work just fine.
Bands where a higher number of input channels and monitors than box mixers can provide may find going the active route to be much easier. This reduces space taken on stage for power amps, because the active cabinets and active monitors plug right into the mixer.
When adding subwoofers to any small to mid size system, it is usually easier to add active subs like the Carvin Audio LS1801A. This is especially true with box mixer systems, where the amps are running the passive mains to their minimum loading and extra power amplifiers would not carry well with the box mixer.
In larger systems, running active speakers boils down to preference. Even in the large line array systems some die hard passive users have switched to active. Often times the processing and power amplifiers needed in complicated large bi-amped systems out weight the need to run an AC power source to each speaker.
Neither active nor passive speakers are necessarily better and both have their essential place in the pro audio world.
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