PA System Basics By John C. Lind This is a short guide to PA, aka Public Address or Sound Reinforcement, systems. For brevity, I’ll use PA system as a generic term. While nearly anyone who’s played in a band has used one, a musician who hasn’t played in a band, or is starting to play with other musicians, may not have had the opportunity. However, it’s very likely nearly anyone at all interested in music has at least seen one, whether at a live event, on a music video or in a picture. If you’ve seen someone using a microphone during a live performance, then you’ve seen at least one part of a PA system. Types of PA Systems While there are more, most musicians will probably come into contact with two types of systems. They are known by different names, but the main difference is in their size. For simplicity, small systems will refer to those that are self-contained, while large systems will denote those with many separate components. This is somewhat analogous to the difference between a “boom box” and a component stereo system, or a combo guitar amp and a separate head and speaker cabinets. The small (aka portable) system typically consists of a powered mixer, at least one microphone and one or two speakers. A mixer is a device that can accept inputs from a number of sources, usually microphones, but may also include keyboards, portable music playback devices, etc. The amplifier is contained within the unit. When you flip the power switch, it’s ready to go. PA with Powered Mixer For example, let’s say a band has a singer, guitar and bass players, a keyboardist and drummer and practice in a rehearsal studio. The singer will need something to amplify his/her voice, while the keyboardist will also need something to amplify his/her instrument, unless it’s plugged into its own amp. The microphone and keyboard will be connected to the mixer with cables and dials on the front will allow the user to set the levels of the vocals and keyboard so that they can be heard. The primary use is so that the band members can hear themselves, while avoiding one instrument overpowering the others. Another device worth mentioning is the direct box. This allows the player to plug directly into a mixer. It is often used to connect acoustic guitars and other instruments with attached pick-ups to the mixer instead of plugging them into their own amp. These systems are also used in small venues, such as meeting rooms, where a speaker may need to be heard by everyone present, or where music can be played while the guests dance, eat dinner, etc. I once used such a system to amplify a performance of flamenco dancers. They had a few acoustic guitars, some singers that accompanied the dancers. All that was necessary was that the singers and guitars could be heard over the dancers, who stomped around the stage in the flamenco style. There were maybe 50 people present, so a lot of power was not needed. They range in size from quite small to fairly sizeable, but for most bands are only useful for rehearsal. REALLY Small PA Large PA Systems If you’re going to play at a live venue, from a small club to a stadium, you’ll encounter a large system, which also may go by a number of names (e.g. sound reinforcement). The most notable feature is the mixer, which is arguably the heart of the whole beast. 24 Channel Mixer When compared to the previous example, the most obvious difference is the number of channels, 24 as opposed to the 4 with the one above. The reason is that in a larger venue, many more instruments will need to be amplified. There may be a number of singers, a keyboardist with multiple devices, drums, horns, acoustic guitars, etc. In a stadium setting nearly everything will need to go through the PA including the guitar amps, even if there are 4 Marshall stacks. Really Large PA Getting from Point A to Point B So how does the sound get from the stage to the mixer and out of the speakers so that everyone can hear it? The microphones (mikes) are plugged into a snake such as this: A Snake! A Snake! The cables from the mikes (and other devices) are plugged into numbered sockets in the box that sits on the stage. There is a large, heave cable that takes all the inputs (24 in this case) and breaks out into separate, numbered plugs that go into the back of the mixer. The cable itself may be 100’ in length, and is usually quite heavy. Now what happens? Each input plugs into the corresponding channel in the mixer and is then adjusted by the various knobs and other controls to create a mix that will assure that everyone in the venue will be able to hear the singer/s, drums, keyboards, horns or whatever else may be on stage (at least in theory – you know how we guitar players always want to crank up our amps!). The art/science of mixing is a whole subject unto itself, so if you’re really interested, look up some of the many books and magazines around today. (Allow me to don my old-timer hat and say you’re lucky as there was very little around back in the days (daze) when I had to figure most of this stuff out on my own.) Another way to look at the mixer is that it serves the role of the pre-amp. As in a guitar amp, this is the part that contains the tone, volume, reverb, etc., controls. To the mixer are also connected outboard devices, the most common being digital delays and reverbs, vocal compression (helps make the vocals more audible over the rest of the band) and equalizers (or EQ). EQ is particularly important in that it helps to adjust the sound to the acoustics of the room, which may be anywhere from great to abysmal, and helps reduce the highly annoying feedback that comes from the mikes (not the good kind from a guitar amp). All of these various devices are mounted in a rack. If the system is not a permanent installation, it would most likely be in some sort of road case that can be closed up to protect the devices during transit. Please allow me to offer a word of advice, get one, even if it’s a cheap one! The cost of a repair for one broken knob can easily exceed that of a case strong enough to have prevented the damage to begin with. I speak from experience on this subject. Outboard Devices in Road Case There are various ways to integrate these devices into the system, which I won’t go into here. The box is usually placed in a convenient spot for the soundman (or woman) or engineer to access them. Now that the sound is mixed, EQ’d, sent through the reverb, digital delay, compression, etc, it’s time to get the signal to the power amps. These are usually placed near the speakers and are also mounted in some sort of road case: Stack of Power Amps How do we get the sound to the amps? You got it – through the snake! It contains connectors to get the sound from the stage to the mixer and outboard devices and then returns it to the amps for distribution to the speakers. Another term you’ll run into is house. No, not that kind of house, but house in the sense of venue, room, auditorium, arena, etc. – the place where the band is playing. The house mix is what the audience hears. As you’ve probably already guessed, this sound comes out of the various large speakers that are stacked perhaps at the sides of the stage, or on scaffolding, depending on how large the place is. In order to more efficiently process the house mix, it’s usually split into 3 or more parts using crossovers. Those of you who’ve been around large automotive sound systems are probably already somewhat familiar with crossovers. In this application, they’re used to divide the signal into various frequency ranges, which are then fed into the power amps and finally their respective speakers. For this example, in a 3-way or tri-amp, system, the lowest frequencies are filtered out and sent to one amp that is connected to the subwoofer. The same happens with the mid and high frequencies. There are various types of crossovers. In a large arena or outdoor venue, there may be 6 or more crossover points. Do an Internet search for more information. High End (or Tweeter), Mid-Range, Subwoofer (from top to bottom) Stage Monitors Another important function of a PA system is to provide foldback, meaning helping the performers on the stage to hear what their fellow band members are playing. When you’re on a stage using amps, you’re most likely not going to be able to hear the bass, keyboards, horns or whatever else you need to hear to keep from getting lost and blowing a cue. Or you may just need to be able to hear yourself sing over the drums. The solution is to send some of the sound back to the stage and out through monitors, usually placed on the floor. Floor Monitor The monitor mix may pass through a separate power amp, or the floor monitor itself may be powered, i.e. contains its own amp. In large arenas there may even be a separate mixer just for the monitor mix. Putting it all together Here’s a diagram of where all the pieces go. While it doesn’t show it, everything would get from the stage to the mixer and back via a snake: Lost in the Mix Just to review, the PA provides a way for performers to make their instruments or voices heard by the audience, as well as a way for them to hear each other. If you’re in a gigging band and playing a lot of clubs and halls, you may not be lucky enough to have your own system and will have to depend on whatever the place may have to offer. This brings us to an important point. Having worked both sides of the stage, as a band member and as an engineer (ok, just the sound guy, but engineer sounds loftier), I’ve come across a few suggestions along the way that I can pass on. The first and foremost, is never assume the place has whatever you need. I can’t tell you how many times someone in a band has expressed emotions ranging from disappointment to vociferous indignation (like, they were really pissed) that there were only 9 mikes and not 12, just to name one real life example. The drummer in my band had a PA that we rented out on the side, and I got us a long term job in one of the larger rock clubs in San Francisco. He had 8 mikes, plus I had a vocal mike of my own, making a total of 9. Sure enough, at least once every weekend someone would get all worked up because there weren’t more. I frequently had to instruct him or her that if it was so important that we have 12 mikes, someone should have called and asked beforehand. While we may not have been able to put our hands on enough extra mikes, perhaps the band could borrow a few. The same goes for whatever else it is you need. If you really love a bit of delay or reverb on your vocals, snare, etc, then ask when you book the gig if it’s available. Even better, if it’s an integral part of your sound, get whatever effect you need yourself. You’ve probably run into soundmen/women who are not the easiest to get along with. I used to use a tape delay on my vocals that had a feature I wanted to turn on and off with a footswitch. I had numerous “discussions” with the sound guys about not hooking it through the mixer, and occasionally had to give up because we were cutting into the time we had to perform. Being a musician really helped when I was the sound guy. It gave me a better understanding of the band’s needs as well as skills for dealing with all the different egos. Some people were really agreeable and easy to work with, while others were not (although I may have used other words to describe them). There is a common belief that sound people are really just frustrated musicians who were never good enough to get into a band. I’m sure it’s true in some cases, but never assume it’s always true. There are just as many types of sound people as there are musicians, or anyone else. If you have your own sound person, s/he’ll get a lot further by showing at least an awareness that the equipment does not belong to them and should treat it with respect. On the other hand, if you’re working sound, don’t totally dismiss a band’s sound guy. As many times as I round s/he didn’t know what s/he was doing, I found that s/he knew things I didn’t and I was able to learn things that proved quite useful. The best single word I can offer is cooperation. Look for the avenue of least resistance and you’ll often avoid sound guy beefs. If you have your own sound guy, make sure s/he tries to look at things from the band’s point of view, while at the same time is using someone else’s equipment. Now if the sound guy asks you to “hit your snare”, don’t hit it once and then resume the ”cool” pose you’d been practicing for months in front of your mirror. In the case I have in mind (a “neo-surfer” band, or whatever they called it), I very quickly determined that said drummer was more concerned with looking “cool” than with how his drums sounded. He’d hit the drum once and otherwise look bored, as if he were above talking to mere soundguys. So I figured why have more concern for his sound than he had and adjusted the levels during their first song. More Lost in the Mix Just like the most successful bands are usually those who’ve been fortunate enough to find the right group of people to work with, this spirit of working together extends to the band’s relationship with the support personnel. True, there are people who’d rather die than give up a tiny bit of power, but a lot of potential beefs can be avoided by just showing a little respect of the others’ needs. Here a few Do’s and Don’t’s that I hope will make things easier: Even if you know you’re really good at what you’re doing, show the sound guy the same respect you’d expect for yourself. You never know that s/he may be just as talented. Respect the house PA equipment; e.g. DO NOT swing the mike around your head by the mike cable! If you want to pretend your Robert Plant, or it’s an indispensible part of your onstage persona, then get your own mike and cable and swing it all you want. There were a number of times where if the singer had swung the mike one more time, I was not only going to turn it off, but remove it from the stage altogether. Again, have the same respect for other people’s equipment that you’d expect them to have for yours, if not more so. If you damage a $150 mike and $30 cable, you just might find yourself in small claims court, or worse, if you wind up hitting someone in the audience. If you and/or your band mates have a beef with the club’s management, don’t take it out on the equipment by knocking down mike stands, putting your foot through floor monitors or whatever. Chances are no one will be impressed (at least positively) and you could find yourselves declared persona non grata, or 86’d, from the club. It may very well be the case that the PA doesn’t even belong to the club, but is subcontracted out to someone else, like another band trying to make a few extra bucks (as it was in my case). Thus, you’re not actually causing the club owner any loss at all. It’s true, many club owners are big flakes, but just as many, if not more, are not. The bottom line is throwing a tantrum and trashing the PA is a great way to ensure you’ll never play there again. Word may even get out and other club owners won’t book you. The best single way to deal with any disputes is to try to work it out with the club’s management. It may sound easier in theory than in practice, but it’s better than acting like a bunch of spoiled brats and causing damage to someone else’s equipment. Would you like it if someone came up and started throwing your guitars, amps and drums around? My guess is probably not. How many times have you hooked up your stuff and found that something wasn’t working quite right? Whether it was due to a bad cable, a weak battery or having overlooked this or that knob on an effects box, when you’re using a lot of components, there’s always a chance something won’t work right at some time or another. The same goes for a PA system, only multiplied by at least 10. I once counted the number of connections necessary to set up our moderate size system and stopped when I reached 50. So if you’re onstage and the PA has some sort of glitch, be patient and let the sound crew work it out. If it turns out that every time you play at the same place there are PA problems, then you can conclude the problem is not exactly intermittent, and you may want to rethink about playing there in the future, or at least asking the club management if they have any idea when the problems will be fixed. In Conclusion I could continue with numerous anecdotes from back in the days (daze). If you’re interested, let me know and I’ll entertain you with my wisdom – well, let’s just say there are a number of stories I could pass on that some of you may or may not find interesting. This guide probably has some errors, but its main purpose is to give those of you who haven’t yet had a chance to use PA’s, or would like a better idea of how they work, some information that may prove useful. If there’s something slightly inaccurate, or just plain wrong, feel free to point it out. I’d appreciate it if you could give me a link so that I can check things out and improve my knowledge of the subject. The Scene of the Crime (upstairs, years before). I still have fond memories of this place. Note the Transamerica Pyramid Building in the background. If you’re a musician and have some technical aptitude, a great way to stay involved in live music is to get into running PA systems. If nothing else, you’ll get into shows for free and might even make a few bucks. You can meet a lot of fellow musicians and do the “network” thing. Speaking for myself, I find it hard to attend a show unless I’m somehow involved, and working sound is my second choice to playing on stage. Also, if you’re known as the “sound guy”, you can frequently get into the club for free. You may want to choose lights, photo/videography or playing DJ. All are useful and can often bring in cash when performing can’t. Good luck!