Sunshine's n00b Guide to PA Systems
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    Default Sunshine's n00b Guide to PA Systems

    Sunshine’s n00b Guide To PA Systems


    Seeing an influx of questions related to PA gear and how to build a system, in addition to many requests about how to plug in X gear to Y gear, I feel it might be helpful to consolidate all this information into one spot. Mods feel free to sticky this if you feel it’s good enough, but hopefully it will simply help lessen the number of “How do I hook up my Mixtrack in a club” questions and the like. As a DJ, it is important to know at least something about PA sound systems. Doing so can be the difference between showing up for a gig and rocking it or packing up and going home because your controller lost sound somewhere and you don’t knows how to fix it. This is information that I have gathered mainly from personal experience working with various aspects of sound equipment over the years, and I’m not really going to be going incredibly in-depth into the nitty-gritty technological aspects of each topic. This is simply aimed at helping someone with little to no PA/sound reinforcement experience get started and to keep them from doing anything that would be catastrophic to their beloved equipment. This deals with Junior-grade sound systems, not the big concert-level sound reinforcement. If you’re looking to build a festival sound system with hundreds of thousands of watts of power, I’d look at getting some help or further researching each of these aspects in much more detail. If you are curious about any particular topic further, I’ve found that the pro audio threads at Sweetwater.com and the Amp/Speaker thread on DJForums have been very helpful, and the guys really know their stuff. There is a plethora of other information available on the web as well, I’m mainly consolidating it and putting this here for convenience. If I make an error somewhere or you feel I have left out something critical, PM me with the details rather than flaming the living bejesus outta me! I'm sure I haven't covered every base, so if people would like to add to this or help me clarify what I'm trying to say, please feel free. Now here we go:

    Disclaimer: This guide is simply that: a guide. It is not the be-all end-all rules of running live sound; it is simply a basic walkthrough of the core individual pieces of equipment an average PA system utilizes. If unsure about something involving your system, always consult your owner’s manual(s).

    Before we even begin looking at amps/speakers/mixers/etc., we need to understand a bit about the cables that hook everything together and the proper functions that each fulfills. We will look at the main types of audio cables that you are most likely to run into AS A DJ. Optical audio, HDMI, etc. will not be covered. So until the DJM-5000 comes out rocking full optical and HDMI, you probably do not have to worry about encountering either of these. I am including a Wikipedia link to each in case more information is needed. So let’s start at the beginning:

    RCA

    This is the standard red and white jack you see on just about every DJ mixer and the outputs on most controllers. This cable sends a stereo signal from one component to another. Red is for the right channel, white or black is for the left channel.

    http://en.wikipedia.org/wiki/RCA_jack

    XLR

    The cables you see connecting to microphones, these cables carry a balanced audio signal between audio components. They are also used to control various aspects of lighting equipment (called DMX). They vary between 3 and 7 pins, however you will most likely only encounter the 3-pin version, as it tends to be the most common.

    http://en.wikipedia.org/wiki/XLR_connector#Three_pin

    TS/TRS Cable

    The more common name of this is the 1/4in. cable, however this can be misleading, as there are two types. The first, a TS 1/4in. cable, sends one side of an audio signal or a summed mono signal between audio components. If you have a background with electric guitars, you might be aware that this is the same cable you would use to plug a guitar into your amplifier. The second type is the TRS 1/4in. cable. This is a stereo cable of the same size and dimensions, however you will notice that there is an extra ring around the male end of the plug. There is a smaller version of the TRS cable that is found on your average headphone earbuds/cans. This is the 3.5mm 1/8in. jack.

    http://en.wikipedia.org/wiki/TRS_connector#Audio

    SPEAKON

    Speakon cables are relatively new and very similar to XLR cables. However, the main benefit of speakon cables is their locking mechanism that prevents them from being yanked out of a power amplifier/speaker by accident. Speakon cables are designed to handle voltage-level (speaker-level) signals.

    http://en.wikipedia.org/wiki/Speakon_connector

    MIDI

    Not considered an audio cable, but digital DJs will most likely encounter these at some point along the line, so they’re worth mentioning. MIDI cables send data values to allow two pieces of equipment to communicate with each other. Things such as digital controllers, drum samplers, and other digital gear typically communicate via USB over MIDI. This is but one of a few different ways these work. MIDI is complicated and this was an incredibly brief summary of MIDI functionality, and so further reading is advised.

    http://en.wikipedia.org/wiki/MIDI


    Now that we know a bit about our connectors, let us look at the equipment they will be used in. PA systems at their core consist of three main parts: The signal, the power, and finally the speakers.

    MIXERS

    Mixers are defined as any device that is capable of taking one or more audio signals and having the ability to combine them, change the timbre (color) of the signals, or add effects to them and combine the output into a single combined output. The 2-channel DJ mixer is one such style of mixer, however these are modified specifically for DJ use. The general components remain more or less the same, however.

    POWER AMPLIFIERS

    A power amplifier takes a line-level signal (such as an instrument, microphone input, iPod, etc.) and converts it to a voltage-level signal and sends it to the speakers. Technical jargon aside; it is what makes your system loud. If building a PA system, you will need at least one of these. Power amplifiers can be bought standalone or built into speakers and mixers (more on this below). Standalone power amplifiers have power ratings based on the resistance the amp is presented. In general though, the higher the numbers are, the more powerful/loud the amp will be. When powering up a system, turn the power amp on last. When powering the system down, bring the knobs all the way down then turn it off first. This will prevent your speakers from doing a nasty “thump” sound that could possibly damage them.

    SPEAKERS/SUBWOOFERS

    We have sent our signal through the mixer, into the power amplifier, and now it has reached the speakers. The forcing of air back and forth by the speakers inside their cabinet is what projects the sound out into the audience’s ears. Speakers come in two different types: Active and Passive. Remember reading above about how power amplifiers could be built into speakers? Such a design is called an active speaker, and features a built-in power amplifier that drives the speakers. This allows the engineer to simply plug the main outputs of their mixer straight into the individual speakers and to generate sound. Passive speakers are simply speakers with input connection terminals, but no amplifier. They require an amplifier or mixer with a built-in power amplifier to output sound.
    Slightly different from your average speaker is the subwoofer. Subwoofers are designed to handle the low and sub-bass frequencies put out by the signal, such as kick drums. Subwoofers are the reason you feel your chest vibrate at a loud concert. Like regular speakers, subwoofers also come in both active and passive models.
    Speakers typically are categorized by the wattage they are able to handle (called Peak Power rating) and how much is ideal to run them (called RMS rating). When selecting a power amplifier and speakers, you ideally want an amp that puts out double the RMS rating of the speakers (i.e. if my 8-ohm speakers handle 400W RMS, I want an amp that would put out 800W of power at 8 ohms). Overpowering a speaker is much better than underpowering it.

    CROSSOVERS

    The crossover is specifically designed to take a full audio spectrum sound input (such as a song) and split it, designating which frequencies will go to the speakers and which will go to the subwoofers. The crossover is convenient for many reasons, one being that it will prevent your main speakers from attempting to push heavy bass frequencies once you have subwoofers connected.
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    Now that we have a general idea of how all of this awesome equipment you have (or will have) is connected and the purposes of each component, let us look at some of the terms used to describe the various aspects of a PA system. These terms get thrown around a lot (often in incorrect context) and so it is important to define them so that everyone is on the same page.


    IMPEDANCE/RESISTANCE

    Impedance refers to the resistance being placed upon an amplifier by a speaker. Speakers are rated based on their impedance, with most modern speakers having an impedance of 4 or 8 ohms (Ω). The more speakers you run in parallel (daisy chain) together, the lower the impedance gets. Impedance becomes important when we need to know how many speakers we can connect to an amplifier (more on this later).

    “For components connected in parallel, the voltage across each circuit element is the same; the ratio of currents through any two elements is the inverse ratio of their impedances.”
    —Wikipedia

    This means that if I connect two 8-ohm speakers in parallel (daisy-chained), I end up with a 4-ohm total impedance. With a few exceptions, running a system with an impedance of lower than 4 ohms is not advisable, and if your equipment is not rated for it, it can be damaged.

    WATTAGE

    Wattage refers to the total amount of power being generated by either a power amplifier or powered speaker. A general rule of thumb is that the more watts being produced, the louder the system will be. Unfortunately, many companies rate their amps/speakers as having the ability to produce much more wattage than they actually do, so further research into a product is important. An amplifier’s power will change based on the total resistance/impedance being placed upon it. Most amps are able to achieve higher output when presented with a lower impedance.



    DO’S AND DON’TS OF PA SYSTEMS:

    DO: Run subwoofers. Subwoofers take a lot of strain off of your main speakers. It will also make your system sound worlds better. As a DJ, a subwoofer is just about mandatory. If your initial budget will not allow for one, it should be the first thing purchased when upgrading the system.

    DON’T: Use signal level cables as speaker cables. When connecting speakers to your amp, USE SPEAKER CABLES!!!!!! Using a standard instrument cable (XLR, TRS cable, etc.) will work in practice, but it will eventually destroy the cable and possibly cause damage to the amp. Speaker cables are designed especially to handle the power that comes out of an amp, instrument cables are not.

    DON’T: Run your system at a lower impedance level than your amp can handle. Doing so will most likely fry your amplifier, thus costing you a lot of money for a stupid mistake. Make sure you know your resistance levels!

    DON’T: Attempt to use an amplifier to run a powered speaker. Hopefully basic common sense would indicate this. Some speakers may have an amp bypass function on them, and then in which case it would be acceptable. But be prepared for sparks and smoke if you plug in an amp to a powered speaker and turn em both on.

    DO: Turn your system down if you hear it distorting. If you turn your system up and begin to hear a crackling sound, turn it down. Your system is distorting because it is too loud. If you push it any further, you run the risk of blowing something.

    DON’T: Connect any external components other than speakers after your amplifier. You can hook mixers into mixers into mixers, but never go from the output of a power amplifier to anything other than speakers. Doing so is a good way to fry your component.

    The final word: DO LISTEN TO THESE FEW TIPS. These should help you put together and run a system that you will get enjoyment out of for a considerable amount of time.

    Sunshine is a PA enthusiast and up-and-coming mobile DJ. Most of his equipment is crap, but he has gotten to play around with a lot of expensive stuff, with varying levels of success. Most of this guide was built on lessons he learned the hard (and expensive) way, and would like to help guide people so they do not make the same mistakes his dumbass self did.
    Last edited by DJ Sunshine; 04-17-2012 at 11:33 PM.
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    Quote Originally Posted by DJ Sunshine View Post
    DOíS AND DONíTS OF PA SYSTEMS:

    DONíT: Use signal level cables as speaker cables. When connecting speakers to your amp, USE SPECIALIZED SPEAKER CABLES!!!!!! Using a standard instrument cable (XLR, TRS cable, etc.) will cause damage to both the cable and the amp. Speaker cables are designed especially to handle the power that comes out of an amp, instrument cables are not.
    Wait, what?
    Last edited by ellgieff; 04-17-2012 at 06:41 PM.
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    Edited, thanks.
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    Quote Originally Posted by DJ Sunshine View Post
    Edited, thanks.
    yw. Although I must apologise for not being clear - it wasn't the failure of markup I was referring to, it was the content of the paragraph.

    Could you expand on this a little more for me? How does a specialised speaker cable differ from a "signal level" cable?
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    Quote Originally Posted by ellgieff View Post
    yw. Although I must apologise for not being clear - it wasn't the failure of markup I was referring to, it was the content of the paragraph.

    Could you expand on this a little more for me? How does a specialised speaker cable differ from a "signal level" cable?
    From Fender's website:

    http://www.fender.com/news/index.php...ay_article=458

    Your instrument cable is low power and high impedance. It's built to convey a weak unamplified signal from your guitar (in our case, the mixer) to your amp, where it's boosted up to a useable level. Since it doesn't need to carry a lot of juice—a small DC current with a small voltage—it consists of a single small-diameter "positive" inner wire (usually 24 gauge) running through a braided shield conductor that works as the ground connection, plus various insulators and the outer jacket. Its small, lightweight wire size is good for cable flexibility (it needs to follow you around onstage, remember), and the shielding prevents much of the noisy external electromagnetic interference that low-power signals are susceptible to.

    Your speaker cable, on the other hand, is just the opposite—high power and low impedance. It's built to carry a strong signal from your amp to your speakers—a relatively high AC current and voltage. Unlike the instrument cable, it has not one but two wire conductors, both with a relatively large diameter in order to allow greater signal flow from amp to speakers.

    If you use an instrument cable as a speaker cable, you're probably OK at low signal levels. At high signal levels, though, trouble brews—all that amp power attempts to flow through the instrument cable's too-small conductor. The unhappy result is that a lot of amp power is converted to heat and never even reaches the speakers. You get reduced speaker output, some probable distortion and, in extreme situations, heat-induced cable or cable connector failure. And you definitely don't want your amp overheating.
    I know many a guitar player that disregard this rule and use short instrument patch cables between their amp head and their speaker cabinets, and it does work. However, this is usually with a relatively low amount of wattage (no more than 50-100 watts in an average guitar amp head) and as such, the damage to the cable can take a bit longer. When dealing with multiple thousands of watts however, it is not advisable and certainly puts a lot of undue stress and abuse on the cable as stated in the article.

    Hope this helps
    Last edited by DJ Sunshine; 04-17-2012 at 08:41 PM.
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    Quote Originally Posted by DJ Sunshine View Post
    Hope this helps
    It does, it helps a whole lot. Thanks!
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    Can anyone link to "Specialized Speaker cables" ???

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    Quote Originally Posted by kamjongill View Post
    Can anyone link to "Specialized Speaker cables" ???
    Sorry, they're magic

    I meant to emphasize the importance of the difference between regular instrument cables and speaker cables. For serious though, they're super special.
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    Quote Originally Posted by DJ Sunshine View Post
    Sorry, they're magic

    I meant to emphasize the importance of the difference between regular instrument cables and speaker cables. For serious though, they're super special.
    LoL, forreal though, my packages say "microphone" cable, it's 1/4in to XLR, is that bad?

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