PA systems are key to live performance. While microphones pick up the sound, PA systems play back and amplify those signals. We’ve covered microphones and the performance-capturing side of live performance quite extensively on our blog, but we’ve not yet taken a technical look at the step after that.
If you’re struggling to find a suitable PA system for your event, it can help to know how they work and the differences between the various options out there. You might be asking the questions, “How do I get heard?”, “What are modern PA systems capable of?”, “How do PA systems work?”, and most importantly, “What is a PA system?” Here’s everything you need to know.
Key takeaways
- PA systems are transducers; they take electrical signals captured by microphones, processed by mixers and outboard processing, and convert them back into acoustic energy – i.e. audible sound waves
- They’re used in live music venues, party venues, bars, conference halls, houses of worship, and more
- PA systems are a combination of amplifier and speaker, and they’re far more advanced than typical speakers
- PA systems come with a range of different amplification types, usually class AB or class D
- They may also have modern features like in-built mixers, audio effects, Bluetooth streaming, speaker pairing, battery power, and app control
- DSP, or Digital Signal Processing, is common and can let speakers have more advanced features
What is a PA system?
PA stands for ‘public address’, which refers to how these systems make sounds audible to large groups of people, i.e., how they address the public. Many of the earliest PA systems were used more for speeches and safety announcements, hence the name.
PA systems consist of a combination of inputs, an amplifier, and typically two speaker drivers. The electrical signal from the microphone is sent through the inputs to the amplifier, which makes the signal stronger. The amplifier then pushes the speaker cones, converting the electrical signal from the microphone back to a perfect recreation of the sound that was originally captured.
Instead of merely inputs, many modern or portable PA systems tend to opt for built-in mixers, allowing performers to directly plug in their instruments and forgo the need for external mixers.
These mixers will often have two channels and a stereo Bluetooth streaming channel. Some more advanced ones will go up to six or eight channels and have built-in effects like EQ, reverb, or delay, and perhaps even app-controllable mixing, but these are optional extras some models won’t include.
At the very least, PA systems will offer two inputs; this lets you directly connect either a vocal microphone and a backing track or a guitar. Alternatively, you can connect external mixers by using their master stereo output, which is why you’ll almost always find these two inputs at a minimum.
No matter how many instruments you’re working with, and how many performers are playing at once, having two inputs gives the flexibility to capture individual sources or complete bands – provided there’s a mixer with enough inputs to hand.
How do they work?
PA systems are what’s known as transducers. If you’ve read our articles about microphones, you might be familiar with the term, as microphones and PA systems technically serve the same function in different directions.
Transducers are designed to convert one form of energy into another. Microphones take an acoustic signal and convert it into an electrical one. PA systems take an electrical signal, amplify it, and turn it back into a louder acoustic signal to be heard by multiple people across a wider area.
So, let’s follow the flow of sound to better understand how PA systems work. First, sounds are generated by performers. This can be speech, singing, or an instrument. This signal will either be picked up by a microphone or, for instruments with built-in electronics like electric guitars or keyboards, sent as a line-level DI signal.
From here, these signals either go into a mixer to be balanced and processed or go directly into the inputs of the chosen PA system. Whether the PA system has a mixer built into it, or the signals have been run to an external mixer, the PA system then receives the sound as a combined stereo signal. The PA amplifies this stereo signal, and the amplification moves the speaker drivers so that they can then be heard.
PA systems can be used in a variety of contexts. For example, they can be used for monitoring purposes, which is how performers and any engineers mixing the show can listen back to it, improving both performance and the overall mix.
In a traditional system, monitoring is usually in the form of monitor wedges on stage directed back towards performers, but there are also in-ear monitor systems that allow engineers and musicians to hear these signals in earphones to protect their hearing.
Front-of-house (FOH) systems are the main speakers in venues, sitting at the front of the stage and facing the audience so that they can hear the show. They tend to comprise multiple PA speakers at once, sometimes just a pair mounted on stands, sometimes a massive stack of them in a line array with multiple subwoofers by the front of the stage – it just depends on the scale of the area they need to cover.
Different types of PA systems and who they’re suited to
Full-range PA systems
Full-range PA systems are the most common form you can find and will typically have at least two speakers. These full-range systems use two-way or three-way drivers.
Two-way speakers utilise a singular large speaker driver often called a woofer to reproduce low-end and low-mid frequencies and a smaller speaker driver called a tweeter to reproduce higher frequencies.
Three-way speakers use a similar system but tend to have an extra mid-sized driver to handle the midrange, allowing for a fuller and more precise sound.
Full-range systems will often be set up on stands or on top of subwoofers. They can range from a single pair of two-way speakers on tripod stands to a full system with a full line of subwoofers underneath the stage working with a series of full-range speakers scattered across a venue.
A full-range system can also look like a large suspended line array of flown speakers stacked together.
These systems are great at reproducing the full spectrum of sound and will commonly be seen installed in music venues, bars, clubs, theatres, and hotel entertainment rooms – they can be found just about anywhere. Due to their scalability, they’re often installed in spaces that frequently hold events, whether these are public or for-hire spaces.
Smaller touring acts such as DJs, singer-songwriters, and small bands may also use these as a pair, but the upfront cost and portability may not always be ideal when compared to alternatives. We recommend the Electro-Voice ZLX-12P G2 and the G4M 12″ Active DSP Speaker for this style of PA system.
Column PA systems
Column PA systems are a more recent take on portability that tries to deliver more power and coverage whilst still being easy to take on the go.
Coming as a full-sized subwoofer and a column full of smaller full-range drivers, column PA systems can be bulky once set up.
Most manufacturers account for this by making the column of full-range drivers collapsable into multiple segments, which also offers some flexibility with setup if you don’t need the coverage afforded by the full column.
However, this does make for two bags’ worth of speakers to set up and tear down, though it’s more of an issue of size than being a difficult setup.
Column systems are great for DJs and larger-scale performances like small bands, as well as outdoor entertainment, with a punchier sound courtesy of their included subwoofer unit. Whilst they can be more expensive than some pairs of full-range speakers, the features available make them a good choice.
Plus, many column systems can be linked for stereo pairing either wirelessly over Bluetooth or through a wired connection. We recommend the LD Systems MAUI 28 G2 and the SubZero L48B if column systems are right for you.
Portable PA systems
Portable PA systems are the ideal workhorse for travelling musicians and entertainers who need a light space-saving speaker and don’t have the option of mains power.
They’re a leading choice for buskers, small garden parties, travelling entertainers, singer-songwriters, DJs, and general entertainers playing small spaces like community halls.
Portable PA systems are usually battery-powered, but typically provide the option of receiving mains power as well, giving you flexibility in where and when it’s used.
Due to their smaller size, however, they tend to have fewer inputs and more stripped-back internal mixers. That said, they’ll often make up for the mixer section by offering even more advanced DSP features than many full-range systems.
Many portable systems even offer a full mixing experience via app control, which can give access to far more advanced controls than other onboard mixers. You may see digital parametric EQ, more customisability, and options for effects like reverbs and delays – perhaps even individual effects per channel!
Some portable systems also come with extras like wheels and handles to make transportation and storage easier. They tend to be smaller than full-range speakers, typically with 8 or 10-inch drivers, and may also have useful additions like wireless microphones or general wireless transmitters to cut out the hassle of running cables into a smaller speaker.
Many portable PA systems are also versatile for everyday performers, enabling them to be used as not only FOH speakers but also kicked back for outdoor performances, or placed sideways as personal stage monitors.
Their lighter weight and smaller size are a significant advantage for frequent travelling, but their power isn’t great for bigger shows or venues. Our favourite portable PA systems are the Bose S1 Pro+ and the SubZero P10.
Active vs. passive PA speakers
There are two main types of PA speakers: active and passive. The main difference between them is how the all-important amplification stage is handled.
Active PA speakers have amplifier stages built-in. This means they’re direct all-in-one speakers that can be deployed anywhere for immediate playback.
Using an active speaker is much simpler and more convenient than a passive speaker, and it offers access to those all-important DSP features. However, this makes the speaker much heavier than passive speakers, and they tend to lose some power through inefficiencies like heat loss.
Active speakers are a complete solution, making them better for travelling acts of all kinds, whether this is a large-scale tour or a small local performer. All column and portable PA systems will be active due to their standalone designs.
Passive PA speakers don’t have an amplifier built into the speaker. This means they need to be driven by a separate power amp stage. Passive speakers are lighter and more affordable than active speakers, but they can be more expensive overall when you combine a good power amp with the cost of the speakers.
Power amps will often have DSP features built-in, which can be a benefit or a drawback, depending on whether you’re able to find a unit that has the available processing you want. Passive speakers are easier to suspend over a stage and stacked in flown arrays due to their lighter weight, making them common for use inside fixed venues that want their sound systems installed and fixed in place.
What to look for in a PA system
Wattage
Wattage is a measure of the power of amplification. This can apply to either internal power amps of active speakers or external power amps for driving passive speakers.
Wattage comes in two forms – Peak and RMS. Peak power is the maximum wattage the amplifier can reach when driven to its absolute limit without failing. It’s only really safe for a speaker’s amp to hold at this level for a few seconds, so don’t count on this being the true output level!
RMS, or Root Mean Square, is an average measurement for the wattage of an amplifier. This will give you a better idea of the average power you’re working with, giving you a frame of reference for the volume and sound throw you might be able to get out of the speaker.
However, wattage is not a perfect representation of a speaker’s sound output, which can be affected by factors like efficiency, driver design, and the type of amplifier.
Sound quality
To better understand the sound of a PA system, look at frequency range figures and frequency response graphs when available. Frequency ranges will let you know what frequencies the speaker can recreate. Ideally, you want this to be at least 20 Hz up to 20 kHz as this is the full range of human hearing. Any extension beyond this will result in additional detail.
Full-range speakers may have fewer low frequencies, starting somewhere around 60 to 100 Hz. This is not a big problem as you can pair a subwoofer with the speakers to extend the low frequencies downwards.
If the information is available from the manufacturer, have a look at your chosen PA system’s frequency response graph. This displays a line across the frequency spectrum that shows how well the speaker represents specific frequencies. It will give you a better picture of how the speaker actually sounds.
To understand volume, look at the listed maximum SPL of the speaker. This will give you insight into how loud the speaker is at range with a precise measurement. Exceeding this level will result in distortion, but most PA systems are designed with failsafe features like overload protection to prevent this.
Size and weight
Size and weight affect how easily you can fit the speaker in key venues and how convenient carrying and transporting the system is. This can be easy to overlook, but knowing how much your speaker weighs and how big it is will be very important to the logistics of travelling with this system.
Can you fit it in the boot of your car? Can you comfortably carry it on your own or do you need another person to help? Will you need to lift it? Understanding the physical size and weight of your PA system will help you answer all of these.
Complexity of the mixer
The complexity of your system’s built-in mixer can make all the difference. You might want an in-depth mixing experience that forgoes the need for an external front-of-house mixer, especially if you’re an experienced performer who knows exactly how to run your sound. However, if you’re a beginner or have little interest in running sound, you’ll probably want a simpler PA system that allows for a faster experience.
There are also built-in mixers with stripped-back onboard controls, ones with in-depth wireless mixing, and some with no mixer at all, so what you choose will need to align with your intended workflow and performance style.
Plus, there’s the question of how many inputs it has and if it’s sufficient for the number of instruments you want to run at once. I can’t tell you what’s right for your needs, but whatever PA system you have your eye on, look at how the mixer works and if it fits you.
FAQs
What does a PA system do?
A PA system amplifies sound, ensuring clear and loud audio for large audiences. It consists of microphones, amplifiers, and speakers that work together to project sound across a wide area, making it essential for events, speeches, and performances where audibility is crucial.
Can you play music through a PA system?
Playing music through a PA system is entirely possible and commonly done. PA systems are designed to handle a variety of audio inputs, including music, delivering clear sound at high volumes. They’re often used at concerts, parties, and public events to broadcast music effectively.
What are the three types of PA systems?
The three types of PA systems are personal, medium-sized, and full-scale. Personal systems are portable and suited for small spaces; medium-sized systems are ideal for venues like schools; full-scale systems are used for large concerts or events, providing extensive coverage.
Final thoughts
If you’ve been asking the question, “What is a PA system?“, you’re now better equipped to shop the right one for you. We’ve discussed what different kinds of PA systems there are, how they work, who they’re good for, and where they might be used. If you have your eye on a PA system, you should now know whether or not it’s right for your setup!
For further reading, take a look at our other live sound guides:
The 9 Best PA Speakers for Bands and Solo Performers
The 12 Best Wireless Microphones for Unrestrained Live Vocals
A Comprehensive Guide to Live Sound Mixing
0 Comments