While active speakers have an internal amplifier, a separate power input and audio inputs, and often a built-in mixer, passive speakers only have a single input and output that handles both the power and the audio signal. This makes passive speakers a lot cheaper than active speakers and, compared to 100% active systems, can be used to build a potentially extensive and more efficient system by connecting multiple passive speakers up to one amplifier that only needs one power socket and one audio input.
The Big to the Small: 8 inch, 10 inch, 12 inch or 15 inch Passive Speakers
In the pro-audio world, most passive speakers will be 8 inch, 10 inch, 12 inch or 15 inch models. Smaller speakers are often used as part of fixed installation in public spaces, like in cafes and pubs, shops and so on. The size of a passive speaker doesn't refer to the size of the cabinet, or box, but to the size of the woofer it has. The bigger the woofer, the deeper and more full the bass reproduction, and the bigger the space you're working in, the bigger the woofers need to be. Otherwise the bass frequencies will have too far to travel and will end up sounding weak and thin rather than big and beefy. The size of the tweeter (the smaller speaker that comes built in) isn't so important, because higher frequencies have much less trouble travelling long distances. Another thing to think about when considering the woofer size you'll need is the kind of music you'll be pumping through it. Electronic music, for example, has really deep and heavy bass to it, so if you know you'll be playing a lot of it, you'll need some big woofers. Larger venues will usually set themselves up with 12 inch or 15 inch speakers to take care of that extra bass (and space), while smaller venues usually go for 8 to 10 inch speakers. To give the bass a really body-shaking punch, you could also add one or more subwoofers to the system.
Hooking Passive Full-Range Speakers Up to a Good Amplifier
Passive speakers can be connected to an amplifier via various methods. Some models have wire-terminals (like home stereo speakers), while some have Euroblock ports, locking speaker ports or standard 6.3mm TS jack ports.
What's the Difference Between Wire-Terminals, Euroblocks, Speaker Ports & Jack Ports?
So, why is it better to opt for a model with locking speaker ports (like the SpeakOn sockets made by Neutrik) instead of a model with jack ports? Basically, SpeakOn sockets and plugs are the safest and most reliable choice because they can literally be twisted and locked in to make sure it can never accidentally come loose. While wire-terminals and Euroblocks clamp the connecting cable in place and are a little safer than jacks, they're just not as secure as SpeakOns. You can also connect bare speaker cables, without plugs, up to wire-terminals and Euroblocks, which you really can't with SpeakOn and jack ports.
How Much Power Will Your Amplifier Need?
As a rule of thumb, we recommend picking out an amplifier that's able to deliver 150% of the RMS-power output of the passive full-range speaker per channel. For a passive subwoofer, we recommend 200%. What's the RMS-power of a speaker? This is the level of power that a speaker is able to produce continuously. It's important not to get RMS-power confused with peak power. The peak power of a speaker refers to the limit of really short peaks of power that the model can withstand without suffering damage. Then, you need to check the impedance of the speakers and amplifier.
In Practice:
Say you have a speaker with an RMS-power rating of 200 Watts at an 8 Ohm impedance. We recommend hooking it up to an amplifier that can deliver 150% of the RMS-power rating. 150% of 200 Watts is 300 Watts, so you need an amplifier that's able to deliver 300 Watts per channel at 8 Ohms.
Passive Speaker Systems
Passive speakers can be connected either in parallel or in series. A parallel connection is the most common, but series switching is used in situations where a parallel connection could potentially damage the speakers or amplifier.
Setting Up in Parallel
With a parallel setup, a set of passive speakers are chained from one to the other before being connected to one channel of an amplifier. All passive speakers have both an input and an output, so if you want to connect two passive speakers up to a single amplifier channel, this is what you do: connect one channel of the amplifier up to the input of your first speaker, then connect the output of the first speaker to the input of your second speaker. That's it! You've connected two passive speakers up in parallel. Now you can do the same for the second channel of your amplifier to complete a four-speaker system.
The higher the impedance of the speakers, the more you can connect to one amplifier channel in parallel. The minimum impedance of an amplifier is usually 4 Ohms (but can sometimes be 2 Ohms), so normally, you could connect up a maximum of one 4 Ohm speaker, two 8 Ohm speakers, or four 16 Ohm speakers up to one channel in parallel. When setting up the system, you need to note that the power demand is also being doubled, and that, at some point, you might be demanding too much power from the amplifier and since the resistance can get too low as you add more speakers, it may cause damage.
Setting Up in Series
You can connect more speakers with a lower resistance up to a single amplifier in series than you can in parallel. In series, you make a loop of the negative and positive amplifier channels through the speakers. It's easier to understand with a two-speaker system: first, connect the '+' of the amplifier channel to the '-' of the first speaker, then connect the '+' of the first speaker to the '-' of the second speaker, then the '+' of the second speaker to the '-' of the amplifier. You've just completed a parallel loop.
Although the power demand in a serial setup increases just like a parallel setup, the resistance of each speaker is increased instead of decreased. Two speakers with an impedance of 4 Ohms have a combined impedance of 8 Ohms. Two speakers with an impedance of 8 Ohms have a combined impedance of 16 Ohms.
What Other Gear Do You Need?
When setting up a passive speaker system, you'll definitely need an external amplifier to power the speakers and feed them an audio signal, but what other gear might you need?
Crossovers
You might want to combine a set of passive speakers with one or more passive subwoofers, but it's not actually possible to connect passive speakers and a passive subwoofer up to the same amplifier, because the amp will feed the sub a full-range signal, which might actually end up damaging the subwoofer as it tries to reproduce frequencies that it's not designed to handle. For this reason, the higher and lower frequencies need to separated via an external crossover before sending them to the speaker amplifier and the subwoofer amplifier.
Equalizers
The tone controls of an external amplifier are often limited and passive speakers don't have any tone controls at all. So, to gain more in-depth control over the tone, you might want to add an external equalizer to your sound system.
Speaker Management System
A system built out of multiple amplifiers, crossovers and equalizers can get pretty complex pretty quickly. Using a management system you can set up and control different groups of speakers and subwoofers with more ease.
Frequently Asked Questions About Passive Speakers
What's the difference between passive and active speakers?
Active speakers have an integrated amplifier and an independent power input, audio inputs and sometimes a mixer will come built-in. Passive speakers only have a combined power and audio input and output, so they need to be connected to an external amplifier to be fed power and an audio signal. For more info, see our blog The Difference Between Passive & Active Speakers.
What are the best speakers?
If you need help finding the right speakers for your setup, then feel free to reach out to our Helpdesk so they can put you in touch with one of our PA specialists.
What does a passive speaker system look like?
If you know what you're doing, you can use passive speakers to build an efficient and extensive sound system. Passive speaker systems need the support of one or more external amplifiers, and if you're using passive subwoofers, then you'll also need at least one crossover. On top of that, you might need equalizers and speaker management systems to complete the setup.
What does passive speaker mean?
A passive speaker doesn't have a built-in amplifier, so it needs to take both power and an audio signal from an external amplifier.
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