This document defines many issues relating to working with, and operating a PA system. I've tried to focus on the major issues, however, each of these areas tend to open up more questions. In order to keep this down to a reasonable size, I've tried to stay on the topic as much as possible. I plan to provide further articles on specific individual topics that focus on things like speaker cabinet design, soldering, building cables, testing cables, equalization, and a multitude of other topics. Please feel free to contact me if you have any questions or suggestions. I'll try to answer what I can, update my writings, or possibly write an article on the topic.
Last updated: 12/31/97
Note: There is alot of information here. You might not agree with all of it - thats ok, you don't have to. This information is based on my experiences and is offered as insights and experience. If it helps you, thats what I had in mind.
Your worst enemy is bad sound. If you are mixed poorly and what comes out the the PA system sounds like crap, well, rest assured peoples opinions of you will be that you stink. The problem can often be traced to how the PA is being run. Are there great Sound people? You bet! Are there terrible Sound people? Plenty of those too. Did you cause the problem sound? Possibly. Is it possible to find or help create good Sound People? Yes!
Just what is the problem? The people who run your Sound need to be familiar with what you do and how you do it. They need to be able to understand hand signals to adjust floor monitors and they really need to be highly aware of how your sound relates to the audience and room that you are playing in.
Playing indoors is greatly different than playing outdoors - Your Sound person needs to be able to compensate for any situation that arises. If you are running sound for a variety of acts, you have to adapt to each of them as they play and you have to have the Sound crew out front and hearing what things sound like.
Sound Crews (be it one person or many) have a tough job because they are:
A common problem arises when the person running sound is the friend of someone who owns the PA, or, a really good Sound person disappears for 'a little while' and leaves someone who has never really ever used the PA system before in charge. Sometimes you have no control over who runs your sound, other times you do. Whatever you do, you need to make sure that you get the sound you need and not just any sound that the Sound person might be happy with.
The Sound person is not always at fault when there is a problem - Egos are always going to get in the way of quality sound, however, if you go to a concert, the people tend to have great Sound people. These people know what it takes to run a Sound System and what things are supposed to sound like.
Keep this in mind if you casually let a friend of yours 'Run The Sound' some evening. If the person has never seen your system, and has no idea what they need to do to compensate for anything that comes up, you might as well let your cat do it - obviously it is not important to you. The problem is that they will sit back and smile all the while telling you 'It sounds great', when it might not sound very good at all.
If you have never seen the Sound Person that you will be working with before, spend some time and draw them a stage diagram and let them know who will be where and what to expect - you have that responsibility since your sound will most likely suffer if you don't let the Sound Crew know what to expect. Try to work as a team - they really want you to sound good and they may be very capable - but they also may not have any idea what to expect until after it happens. If you can give them a set list that indicates the type of song, who will be highlighted and when, as well as any expected volume levels will change dramatically, it will help both of you. This is a lot of work, but you only have to write this stuff up once and make copies of it for the Sound people. Don't expect the Sound Crew to be psychic.
Work out hand signals to deal with sound issues. A frequent command will be to adjust the volume level of your floor monitors. Some PAs can adjust these per monitor, some can't. You also may want to alter the tone quality of your sound. If you use hand signals, don't expect the Sound person to have any clue as to what you are trying to tell them unless you tell them in advance what you are trying to say - maybe documenting these signals is not a bad idea either - then the rest of the band members and stage crew can be consistent.
I can't tell you how many times I've wanted to strangle the Sound Crew - sometimes it was truly my own fault (of course we never like to accept the blame for things like this, but in reality, it was sometimes really my fault). I play guitar and I find it nice to have a Wireless unit instead of a cord so I can hear for myself what things sound like 'out front'. I know what I want to sound like - you probably do too. You should probably get a wireless unit as well (I use NADY wireless units for my guitar work). You may want to send a band member 'out front', while playing a song and using a wireless rig on their instrument to verify the sound once a set, just to be sure that you sound like your are supposed to. I recall an instance where the midrange horns weren't plugged in on one side during an outdoor concert - the sound person was having a beer and it sounded 'great' to him - we had lots of comments that the vocals couldn't be heard - nice work!
Ask any Pro about touring and they will all have horror stories about the Sound system and at least one Sound Crew. You don't have to have these problems and you don't want to contribute to problem sound. Work with your Sound People - they are probably much better than you give them credit for, but what ever you do, never compromise your sound - its why you are playing in the first place. If the sound is bad, so are you.
Whine mode on - When ever you get a band of musicians together, odds are good that no one owns a reasonable PA system. If they are not purely vocalists, why should they? Musicians figure that someone will have one, and there is no reason to buy a system that is used by everyone else, when they would rather have more toys for their instrument. This is a reality of life. Many vocalists show up with their microphone and cable and expect the rest of the band to have provided for them. The rest of the band members look at the vocalist and wonder why they haven't invested in their equipment (ie. at least some of a PA system). As a musician, I tend to be frustrated by any vocalist who thinks that all they need is a microphone to start singing. If I showed up for practice or a paying job with just a guitar, I'd be unprepared. Its a moot point, but vocalists need to invest in themselves and not expect others to do it for them. - Whine mode off.
So, then what is a reasonable PA system? Its definitely not one where the vocals are run thru the Guitar players amplifier (although, I'll be the first to admit, I've done this before - yuck - it was not very good, but it beat the tar out of nothing). This is a hard question to answer. It all depends on what you are planning on doing.
I'm a great believer in matching the PA system to the needs of the music. If you are playing an acoustic guitar in a small club on weekends, your needs won't be the same as a 14 piece Motown influenced band with 'horns', 'keyboards', 'backup vocalists', 'guitars' and 'lots of drums' band. While the person playing their acoustic guitar could easily use the larger PA system, they probably don't have the semi-truck needed to haul it all around.
Where do you start? This is actually a lot easier than it appears; go out and see what other people are using. A lot of people have modular PA systems so that they can bring the parts that make sense for the type of work they will be doing. If you live in a place where you can't find many people doing the same sort of work you plan to do, use the Internet and meet some people who are doing it - they are out there.
I've played in large multi-piece bands, 3 and 4 piece ensembles, as a duo and occasionally as a single act. I've played indoors and outdoors and to massive (over 1000 people) audiences and in intimate settings with just a few people. Here are some of my thoughts.
There are many ways to build a PA system. If you have a large range of places to play, I personally feel that it is in your best interest in having a modular system. Doing so allows you to bring the best match for the need where-ever you decide to play. Every system you use will be some combination of (but maybe not including all):
If you are not following this, the point is that you will need to have a system that allows you to work with either high or low impedance inputs. Try as you might to enforce one or the other, you will always be in a situation where you need to adapt one to the other. It's not as painful as it sounds, it just tends to get expensive. Radio Shack sells an inexpensive low to high impedance transformer based adapter - not perfect, but easily available. Buy at least one or 2 of these - you'll be thankful you did when you desperately need one.
The classic Pre-Amp has either High or Low impedance inputs (occasionally both, but you might only be able to use one or the other), a volume control for each Input, a treble control for each input and a bass control for each input. Sometimes there is a master volume control. This is good enough for most work, but the classic Mixer often doesn't have separate controls for floor monitors - this can be quite a disadvantage. A minimum of 4 channels is required - try for at least 6 channels. Some sort of Reverb is good to have.
A slightly better Pre-Amp will include everything that the classic Pre-Amp has, but it will include a graphic Equalizer.
A more functional Pre-Amp/Mixer will have outs for effect loops and as separate mix level for floor monitors. Having floor monitors implies having a separate power amplifier for them, or buying 'powered' floor monitors.
From here on up, the Pre-Amp stage may have quite a few features that you may or may not use. The cost goes up accordingly. The features that you need should relate to your musical needs, as well as a consideration that the Pre-Amp/Mixer might be used for professional recording sessions. If you plan on using your gear for recording, get a system with very low noise (Mackie makes some nice units that allow for this dual use, as do other high end Pre-Amp/Mixer manufacturers).
I personally like Stereo mixes; where the sound out of the left side of the PA is somewhat different than the sound of the right side. It depends very much on how you mix it. Often this gets mixed very poorly - many Sound people have had bad experiences trying to do this and frown on trying to get a Stereo mix, preferring monophonic all the way. I feel that it can work if you know what you are doing, but thats another topic to discuss.
One word of warning. Kareoke style Mixers have RIAA equalized inputs for Record Players, CD Players and Cassette Decks, along with one or more inputs for vocals. These are not designed for use as a Band mixer and you really can't use one in place of the other. You may need to invest in both a regular Pre-Amp mixer board and a Kareoke mixer board if you need both capabilities.
For vocals, a compressor/limiter is an excellent addition. The compressor part boosts your volume a little when you are not singing as loud, and the limiter part restricts peaks that might cause distortion. You don't want much compression - 2:1 is all you really ever need. You will need a separate compressor/limiter for each microphone you plan to use this function with.
Reverb is a nice touch - it gives ambiance to vocals and some instruments. This can take on a highly expressive dimension if done in stereo. A single Reverb unit tends to cover all PA needs. You can get separate Reverb units for people if you need them.
Equalizer - Allows you to adapt to the room (or lack thereof if outdoors) that you are playing in. Always start with the sliders at 0 (zero) and add/subtract only what you need to. Never slide the controls all the way Plus or Minus - it will give you some odd sounds if you do. You really want the best sound and this rarely requires excessive boosting or cutting of frequency levels. The lone exception to this might be in the area of cutting feedback - however, like everything else, feedback can be caused by a multitude of things. Usually microphone placement, or just how a vocalist holds their microphone can cause feedback - solve the problem, don't put band-aids on it, then adjust the equalization.
Vocal Harmonizers - These are a one person effect. You need a separate one for each person that wants to use the capability. I like them to a point, but overuse or extream settings really detract from the performance.
If you are just starting up and don't think that you will be playing any large places, you might want to start with a small Power-Amp. I consider it a serious mistake to buy a Power-Amp that cannot put out at least 100 watts per channel (ie . if its monophonic - 100 watts, if its stereo - 100 watts per channel). Why is this? Because low frequency transients are what require the power. Realize also that your hearing is not linear - in order for something to sound twice as loud, it takes 10 times the power. You could get by on less power, but I'm positive that you will be sorry that you bought less than 100 watts worth of Power-Amp. You'll also find that it is much better to turn down the volume and maintain excellent tone, rather than turn up and get crackly garbage out of your PA system.
Even up to medium sized rooms (50 feet by 50 feet) a Power-Amp with 100 watts per channel will suit you quite well. If you plan to use Sub-Woofers in a medium sized room, you will be right at the very edge of a 100 watt amplifiers capabilities. In these cases, it may be to your advantage to look at getting a separate amplifier to drive your Sub-Woofers, as the midrange and above don't really need any more power.
Once you start playing rooms that are large (100 feet by 50 feet or larger), you need to be able to deal with the power required to drive the low frequencies that your PA system will be pushing. Now, if your system is a 'vocals only' system, your 100 watt per channel system will still work quite well for you, even in this much larger room. You will benefit from adding more speakers and providing proper placement to keep the general volume levels consistent everywhere within the room.
Once you move to playing outdoors, you lose the reflected sound that normally bounces back at everyone off of the walls. Everything sounds very different because of this and you make up for this by putting up walls of PA speaker systems. If your PA system deals with sounds mostly in the vocal ranges and above, you can get by with a 200 watt per channel system, but 400 watts will definitely give you more head-room. If you expect to have much in the way of low frequency signal, you need to consider that 1000 watts will probably be just barely enough, and that many large outdoor systems use upwards of 12,000 watts to handle the frequencies below 500 Hz. Things have just gotten very expensive.
In the case of floor monitors, a 100 watt per channel amplifier will probably be all you ever need, no matter where you are playing. You might need more power - it is possible, but you'll probably become deaf as a result (thus requiring even more power).
Get yourself a cable box and establish some procedures about how people are to wind them up and how to keep the different cable types separated so that you can find what you need, when you need it. Some people use large plastic bins, others keep their cables in canvas bags that they put into a larger box for travel. These are your life blood. Treat them well, you can't make music without them. I have lots of pet peeves in this area, probably because I have $300 to $400 worth of cabling and I don't fancy replacing anything I don't need to.
Unless you like getting your lips welded to a microphone, you need to have all the power for your entire band coming off the same power circuit. I carry over 250 feet of extension cords in my cord case (and I've run out of power cable more than once). I also have made up my own power strip with 8 standard electrical outlets on the end, so I can control where my power comes from. When you play outdoors, the nearest power may be 500 to 1000 feet away. Get a 10 or 12 gauge extension cord for this sort of distance. Avoid power from a generator at all costs - you have no idea what types of power transients it will have and how it might damage thousands of dollars worth of gear. Make sure that your contract includes City Power!!!
Like you did with your PA cables, mark your extension cords - otherwise, you will lose them.
Before you run out and buy anything, keep in mind that the audience will absorb some of the sounds, depending on where the source of the sound is. In the case of very low frequencies, you don't really need to worry too much about the placement of the cabinets - they can be almost anywhere, as long as they are not too far from the audience itself. Typically, you see woofers (and any other cabinets with large speakers in them) on the bottom, where the woofers sit on the floor. The opposite is true for the high end tweeters - these are up as high as you can get them so the sound can travel aimed as close as possible at where peoples ear level is. The midrange speakers should be higher up also.
What this says is that unless you can put your mid to high frequency transducers up at or above ear level, you will have a `muddy' sound. This is undesirable (since you probably want people to be able to hear the vocals). If you'll notice, there are an abundance of PA speaker poles that bring the entire speaker cabinets up in the air to a reasonable height. Moving the low frequency speakers up higher won't hurt anything at all. In modular systems, you'll notice that the low frequency cabinets are at the bottom, the midrange speakers/horns are on top of these, and any high frequency tweeters/horns are on top of all the other speakers. This pile of speakers are normally sitting on a stage, or risers that are above ground level, and as such perform the same function as putting PA cabinets up in the air on stands.
With this in mind, you can now start working out what you really need. If your PA system will be starting small, then definitely look into something that can be put on a stand that is 6 to 8 feet above floor (where the midrange and high frequency transducers are 1 to 2 feet above the audiences heads). I stop at 8 feet for a good reason. There are a great many places to play with only 8 foot ceilings - most houses have this restriction.
|A common starting setup includes a 12 inch woofer and a small exponential horn (midrange and highs). With one for each side of the stage, you can do fairly well provided that you are not playing a large room. the big advantage is that you can go out and buy another set of 2 of these and now you can play much larger rooms. When the time comes, you can can continue to grow these to as many as your PA system can drive. The only problem with these is that they don't always have the most even sound characteristics, so, while they may really be good for vocals and maybe keyboards thru the PA system, they will not be the best choice for people who need a full range sound system (Kareoke, or a MIDI Sequenced band).|
They can be excellent building blocks that can be added to with other types of cabinets at a later time. As long as you have a graphic equalizer, you can also usually compensate for any uneven sound quality (these are quite versatile). These are often not overly heavy - something to consider if you have to heft them up a pole a few feet off the ground.
Another variation is a 15 inch woofer and a larger exponential horn. These have their place as well, but are more trouble to carry around. A 12 inch speaker tends to have better midrange response than a 15 inch speaker, however a 15 tends to have better low range. Its a close call and before you decide, compare speaker systems to each other and make sure it sounds the way you need it to.
|Up until this point, we spoke of 2 way (Woofer + Midrange) systems. The next thing to consider is a 3 way (Woofer + Midrange + Tweeter). There are numerous systems that have a small midrange speaker in conjunction with the Woofer and Horn. This allows the horn to be designated for the upper midrange and highs (which is more optimal for its voice coil) and the woofer to focus on the low range. The midrange speaker need not be large - 6 to 8 inches in diameter is plenty. A system of this nature is similar to what you would find in a mid to high end home speaker system. Far more even sound response, and more usable if a wide range of musical instruments are to be pushed thru the PA system. A set of 2 of these, with a 200 to 500 watt amplifier system can cover a great many situations indoors and outdoors.|
If playing outdoors, you may need more than 2 speaker cabinets to play to a large audience or area; again, you have to determine what you think you will be doing, then plan for it. Its often better to have too many cabinets and turn your volume levels down, than to strain your speakers to the point where your have to replace them.
Other cabinets might include a dual set of Woofers (tuned for low
to midrange frequencies) and a small exponential horn. The variation
here is quite endless - the more speakers you get, the more air you
can move (especially for low frequencies). For outdoor events, or
large auditoriums, you need more speakers to move more air at
low to midrange frequencies.
In the past, Shure made a PA system that was a 'vocals only' system, called the 'Vocal Master'. It used a combination of 8 inch and 10 inch speakers. It was optimized for the frequency range of the human voice. If you watch some of the Elvis specials where he was in Las Vegas (around 1971), you'll see 4 of these cabinets in a very large Casino showroom. There were 4 8 inch speakers and 2 10 inch speakers per cabinet. I have used these in the past (I still own one of the 100 watt 6 channel Shure 'Vocal Master' mixers), and they definitely lack low and high end capabilities. They are greatly improved with a set of Woofers and tweeters per side. Many other companies have built similar systems, many newer PA systems don't follow this logic.
|Large exponential horns are often required if you are playing a large venue, or outdoors. These tend be expensive, and if you have them, they should probably have their own separate amplifier such that they are not over-driven outside of their frequency range. Alternately, a cross-over network can be used to restrict the frequency response.|
Because of the size of the voice coils, these have very little low frequency response - they also are sensitive to transients - ie. blasts of high energy outside a valid frequency range. You really don't need these for most clubs, but if you have them, and can get them above the audiences ear level, vocals should have no problem cutting thru.
There are 3 types, floor monitors, 'near field monitors' and remote monitors.
|For floor monitors, you can standardize on an 8, 10 or 12 inch woofer and a midrange horn. The reason to choose a size is relative to how close the person using the monitor will be from it. a common size uses a 12 inch woofer. It is often overkill, but, it never hurts to be over-prepared, unless you have a very small stage to work from. These are usually wedge shaped, so that they sit on the floor aimed at the person who the monitor is for.|
A number of floor monitors have their own built in power amplifiers. These are called 'Powered Monitors'. The output of the mixer (before the signal gets to a power amplifier) is sent to these and they usually have their own volume controls such that you can work them with your hand, and/or your foot. The built in power amplifier is usually in the range of 25 to 100 watts. I personally prefer these to floor monitors that I don't have control over the volume of. You have to make sure that you can get an extra power line to each of these, which contributes to the miles of cables that always seem to be scattered about the stage.
Another type of monitor is called a 'near field monitor' and it is used by people who cannot use a floor monitor because it simply won't work. For example, people playing keyboards have all sorts of 'stuff' in front of them, effectively blocking the sound coming up from the floor. Drummers have a lot of things that can get in the way of a floor monitor. 'Near field monitor' tend to be very small, often containing 2 4 or 5 inch full range speakers, or a 6 inch by 9 inch speaker. They also sit in positions that are fairly close to the musicians face. Some are put on top of stands, others sit on top of equipment and are easily aimed to where they are needed most. These can be powered (I built a number of these for my last musical project - I used 4 to 10 watt power-amp ICs to drive these and found these to be very functional and easy to work with). If they are powered, the Vocalist/Musician can adjust their own volume/tone levels and since they are small, you are not constantly tripping over them. They are not real useful if you tend to move around a lot on the stage.
Remote monitors are small FM receivers that are set to a frequency that is unused in the area and then an earphone is put in the ear of the wearer of the receiver. The main PA system has an FM transmitter that is set to the same FM frequency. The live PA mix is then sent out onto the air-waves. The range is fairly limited (less that the distance of a 100 yard (95 meters) football field), and they can be noisy. These are often used by professionals who move/dance around alot when they sing, along with a headset microphone/transmitter rig. The have a lot of advantages in that any message can be passed on to the band members wearing them without it being heard by other people. These actually don't have to be expensive, since anyone can buy a pocket FM radio & many people (like Radio Shack) sell small low power FM transmitters. There is additional setup since you often need to re-tune these when in playing at different locations, and you need to make sure that everyone has a fresh set of batteries handy. The nice part is that there are no cables to trip over and no feedback caused by this form of monitor (however, there are plenty other sources of feedback). Sound quality may not be very good depending on the FM transmitter used. Some sources of FM transmitters on the Internet - I found these using a using a search engine (I've never used any of these products) - all of these provide for an input source other than a built in microphone:
Questions? Comments? .
© 1997 - Shavano Music Online