What is a PA system? Loudspeaker systems 101

Public address systems — or PA systems — are specially designed mixer, amplifier, and speaker combinations used to communicate with an audience. Typical speakers like portable Bluetooth® speakers are used to simply play back prerecorded audio, like streaming music. So, what is a PA system, exactly, and how is it different? PA systems are more advanced than regular speakers, as they can enable live sound for multiple audio sources and can blend and amplify these sources to achieve a unified mix.

PA systems come in a wide range of shapes and sizes and are used for amplifying sound in large arenas and clubs as well as in small venues. They’re perfect for live bands, intimate acoustic sets, DJ sets at a party or bar, spoken word or poetry performances, lectures, speeches, and more.

Read on to learn more about PA systems and how they work.

If you want to understand how a PA system works, a large music venue or club PA is a good example to study. These PA systems include a mixing desk with up to 24 channels — sometimes more — to accommodate microphones for lead and backing vocals, mics on guitar, and bass speaker cabinets, plus mics on all the pieces of a drum kit for a live band performance. There may also be direct line-level inputs (DI) for keyboards, bass guitars, or laptops triggering loops, samples, or full backing tracks.

All audio signals are routed from the stage monitor to a mixing desk via cables, where the various low, medium, and high frequencies are combined and equalized. You can even add effects like compression, delay, or reverb. The mixed channels are then amplified and sent back as a stereo signal to drive the front-of-house (FOH) passive speakers facing the audience, projecting the final mix. There are usually multiple FOH speakers, hung from rigging or stacked on either end of the stage, preventing feedback from the audio sources on stage.

These types of larger PA systems usually require an audio engineer to set them up and make adjustments as a band performs. There are also floor-mounted monitor speakers on stage facing the musicians, so they can hear themselves while they play. While live music venues feature the most complex PA systems, all PA systems use the same basic configuration — input sources to mixer, then mono or stereo-mixed signal to a power amplifier, and finally to a speaker.

Technological advances have made it possible to combine input channels, a mixer, and a powered speaker into a compact, powerful portable unit. This changes the parameters of what is a PA system and what isn't, and it brings the separate components together in a single system to provide a much simpler option for smaller-scale performances like at parties, cafes, or bars.

When choosing a portable PA system, first identify how many input sources you need. For example, if you're an acoustic singer-songwriter who plays guitar and sings, you'll need a portable PA system that can receive and mix two separate signals simultaneously and output them loud enough for your audience to hear.

The Bose S1 Pro+ Portable Bluetooth® Speaker System is a great example. You can plug a guitar and vocal microphone into separate inputs with ToneMatch controls designed specifically to enhance the sound of each instrument. There's also volume, EQ controls, and reverb if you need to dial in some ambience to add depth to your sound. You can also stream music from your Bluetooth-enabled device through the third AUX channel while you take a break between sets.

The rechargeable battery in the Bose S1 Pro+ lasts for up to 11 hours. It also adds optional wireless radiofrequency (RF) transmitters for instrument jacks and vocal microphones, which eliminates the need for any cabling. Plus, it's lightweight and easy to carry, ruggedly constructed, and simple to position in four ways (elevated, tilt-back, monitor mode, or mounted on a speaker stand). With a built-in power amplifier to drive the speaker with enough volume, you'll always be heard loud and clear. All of these innovative features make it perfect for cable-free operation in any location, indoors or outdoors.

Not only is the Bose S1 Pro+ our best portable PA system for small venues, intimate gigs, and DJ sets, it can even double as a party or karaoke speaker. Simply plug in a line-level source with backing tracks to the AUX input or use a wireless streaming device via Bluetooth. Then you can add a vocal microphone (or two!) and adjust the signal levels to your satisfaction.

If you find you need more power and reach, a line array system can expand your portable PA capabilities. You can also add an audio mixer for extra input channels if you have other members joining your gig, like a bassist or keyboard player. Even better, whether you're using a single PA system or adding a line array, you can control everything using the Bose Music app through your phone, so you can easily set up and fine-tune your portable PA on the fly.

PA systems may come in many configurations, but all are designed with one purpose: to project sound and forge an unforgettable connection with an audience.