Sound Systems

Introduction

A bare-bones sound system consists of only a few main parts. You have a bunch of sound sources (microphones, CD players, etc.) fed into a mixing board (a device which combines a bunch of inputs into a couple of outputs). The “mixer” is fed into one or more amplifiers, which take the sound and gives it enough power to drive the speakers. We'll start by looking at the speakers, which I feel should be your first consideration.

Speakers

Speakers are the last part of the sound system chain, and have a huge effect on the sound quality the audience hears. The speaker is more or less an electromagnet and one or more cones (the circle you think of when you think speaker... usually made out of cardboard, foam, or aluminum) inside a wooden “cabinet”. It's pretty important not to overdrive the speakers- i.e. try and turn them louder than they should go. The sound will be pretty distorted (imagine a classical guitar... and now imagine Nirvana. That's what distortion is. Sometimes you want it, but most of the time you don't). Even worse, you run the risk of “blowing” the speaker... when you turn it too loud or try and reproduce frequencies which are too low (turn up the bass), the speaker will try to move the cone farther than it's designed to go and end up ripping it. You can't fix the speaker when this happens usually, so you'll end up having to buy new ones.

The first thing you need to consider when buying speakers is what frequencies you want the audience to hear. You have low frequencies (imagine a bass rumble) that start down near 20 hertz or so, up to really, really high frequencies (imagine a whistle, or a fire alarm) up to about 20,000 hertz. Most of the time, a good choice is to get speakers which are full-range, meaning they can reproduce sounds (reasonably) across the frequency spectrum. Inside a full-range speaker cabinet, you'll often have tweeters (small speakers to take care of high frequency sounds) and woofers (bigger speakers for mid-range and low frequency sounds).

Alternately, you'll sometimes want some real low frequency rumbles. For example, we did a production of Rhinoceros where we wanted the sounds of rhinoceroses. If you want to do that, either rent or buy subwoofers. Those are speakers (usually really large) that are designed to reproduce low frequency sounds. Generally, you'll need to use a crossover with your subwoofers. A crossover only lets frequencies of a certain range through. So you can set your crossover to only send the bass frequencies to the subwoofer and only the treble (high) frequencies to the other speakers.

The Amplifier

The amplifier takes the sound you put into it, and makes it powerful enough to drive the speakers. You plug some sort of sound source (through a mixer or not) into the amplifier, and it amplifies it. Amplifiers are generally really heavy, so keep that in mind when mail-ordering them (AKA wait for free shipping offers). \Amplifiers are generally two channels. That means you plug, say, the left and right channels from your CD up to the two channels on the amplifier. The sound then goes to two different speakers, which are playing slightly different sounds. If you need to get more power out and are only going into one speaker, look into “bridged mono”. You basically plug one terminal into one channel and one into the other channel, and thus double the power. More on that later (in the connectors section).
  • Power considerations in matching amps and speakers are really a pain to deal with. Some people will recommend that you buy a speaker which is rated for more power than your amp, so that it's difficult to send more power to the speaker than it can handle (which will blow out the speaker). More people will suggest though that you should buy an amplifier that is rated for more power than the speaker can handle... when an amp is turned up to the max, the signal starts to clip, creating square waves (distortion) that blow out the speaker. So basically in either case, you're blowing out the speaker. \The way I like to deal with this is to buy speakers and an amp which is rated for a bit more (like 1.5x or 2x) and never turn them up all the way. In either case, turning the amp to 10 will destroy your speakers, so don't do it! Of course, this is more expensive than trying to skimp on one component or the other, but it will be worth it when your system lasts a lot longer. \As a note, when I talked about the power rating for speakers above, I was speaking of the “program” rating, which is the average power it can handle over a long time. They also have a “peak” rating, usually about 2-4x the program rating. Make sure the amp power doesn't go above the peak rating.
  • Impedance considerations. So you also have to deal with calculating the total resistance of a set of speakers when you're plugging more than one into an amp. Basically, think back to high school physics and think of them as resistors wired in parallel. So if you have 2 speakers which are 8 ohms and can handle 250 watts each, the amp will see it as 4 ohms. (1/8 + 1/8 = ¼). Make sure the amp can then put out at least 500 watts (250 + 250).

The Mixing Board

The mixing board lets you take a bunch of sound sources and combine them into a smaller number of outputs. As an example, you might take 8 different microphones and then combine them into 2 outputs (a left and a right). The mixing board may seem intimidating- there are a lot of buttons- but there's a bunch of repetition, so it's actually not bad at all! \The main parts of a mixing board are a) a bunch of channels, b) a master output section, and c) Auxiliary Buses (on nicer boards).
  • Channels: \Each board has a number of channels, usually in multiples of 8. A small board will have something like 8 channels, while large boards will have something ridiculous like 128! The number of channels you need is basically the number of sound sources you have. \Each channel will usually have the following buttons/meters/plugs: (Start with them all turned down except for the EQ knobs in the middle)
    1. Inputs: On the back/top of each channel, you'll usually have a microphone input that is an XLR plug (see the section on connectors) and a line level input that is a 1/4” plug. Generally, microphones should be plugged into the microphone input and everything else (i.e. CD players) should be plugged into the line input. Sometimes there'll be only one input and a button to choose whether it's mic or line level, so use those same guidelines in selecting.
    2. The topmost button is usually GAIN. What the gain button does is control how much signal goes into that channel from the sound source. The general rule of thumb is to start off with the gain all the way down. Then either turn a CD on or start talking/singing into the microphone that's plugged into the channel. Somewhere on the channel, there are LED's- usually a green one that indicates signal and a red one that indicates clipping. Sometimes they're combined in one that is usually green and turns red when the signal is clipping. Slowly start turning the gain up. So what do you want? You want the signal to be green most of the time and occasionally flashing red. Turn up the gain 'til it does that.
    3. There should be a FADER FOR THE VOLUME. On cheaper mixers, sometimes you'll only have a knob. Sorry. If you turn it up right now, you probably won't hear anything. That's because the master is down. So don't worry about that right now.
    4. [Not on smaller boards] Nicer boards generally also have a bunch of random buttons labeled “L-R” “1-2” “3-4”, etc. What these do is choose what outputs you're sending this signal to. So if you have a ton of different outputs and want to send the signal to all of them, make sure all the buttons are pressed. If you only want it to go to the master, choose “L-R”.
    5. [Not on smaller boards] You also might find a bunch of knobs labeled “1” “2” “3” “4”... sometimes with the words “Aux” in front of them. These choose how much of the signal to send to each Auxiliary Bus (see section on Aux buses).
    6. Phantom Power/+48V. This button should be off except when you have a condenser microphone or another piece of audio equipment that explicitly asks for phantom power explicitly. See the section on mics for more info.
    7. The PAN button chooses between left/right or Aux buses. Remember when you pressed down the “L-R” “1-2” and “3-4” buttons? If pan is in the center, the signal goes to all of those channels. If you turn it to the left, the signal goes only to L, 1, and 3. Turn it to the right, it only goes to R, 2, and 4. When you have a bunch of aux buses, you sometimes have to think about the even/odd configuration of your aux buses in advance.
    8. The EQ section allows you to change the quality of the sound. You can add or subtract treble (high sounds), mids, or bass (low sounds). If the sound is kind of “muddy” or “undefined”, you generally want to add more treble and turn down the bass. If the sound is grating or kind of tinny, you want to add more bass or turn down the treble. A lot of boards have a variable mid so that you can fine-tune your sound. For the most part, this usually ends up in confusion. I like to leave them both in the middle first. Now, try and listen and figure out what you need more/less of in the mix. The variable mid has 2 knobs, one is called “level” and one is called “frequency”. Turn the “level” up a lot and move the frequency knob around slowly until you hear what you want to add more of. Basically, it'll sound ridiculous, but it'll let you hear what you're actually modifying at that frequency. Now, when you hear a sound that you want to raise/lower, leave the frequency there and turn the level to a point where it sounds good.
    9. The MUTE button turns the channel off. Not all boards have them. They're great when dealing with wireless microphones, though.
    10. The Master Section - Here, you'll control the volume for the whole board. If the MASTER VOLUME is down, well, that kind of sucks. You won't hear anything. The way I like to deal with this is to turn up one of the louder channels like 2/3rds of the way, and then turn up the master until it's a reasonable level. This isn't at all scientific or best practices or anything, it's just the way I roll.
    11. The Aux Buses (Submasters) - So we haven't yet defined what the aux buses are for, even though we talked about them in the channel section. There are two good uses for them, generally- grouping together channels that you generally want to move together, and adding more outputs beyond what is contained in the master. \First use- grouping channels together. Imagine mic-ing a drum with 5 different mics. In this case, don't “patch” the channel to the master (i.e. Don't press down the “L-R” buttons). Only patch them to an Aux Bus. Use each individual channel's volume fader to set the relative volumes. \Now, you have to patch the Aux Bus to the master (choose it to output to “L-R”). So now if the drums are too loud, you just have to turn down the fader for that Aux Bus rather than for each mic. \Second use- adding more channels. Aux buses will usually have an output (Aux 1 out, etc.). If you want surround sound speakers, or you want to have, say, a subwoofer, connect those speakers to the aux outputs. Now, everything you want to go through those speakers... patch those channels into the aux. \When connecting all of this, plug all of the sound sources to the board, then plug the outputs of the board into the amplifier and then into the speakers. Don't turn anything on yet and keep the volume all the way down! Turn on the board first. THEN turn on the amplifiers. (You don't want to amplify the noise of turning on a sound board... it'll mess up the speakers since there's a big pop). At the end of the night, turn off the amps first, then turn off and unplug everything else!

Sound Sources

Microphones

For stage, there are 4 main types of microphones you'll use:
  1. Border microphones are used at the edge of the stage/playing area to pick up the general sound. If you were doing a straight play in a large theater, you'd consider putting some mics on the edge of the stage. Crown PCC-160 floor microphones work well for this, but they pick up a lot of walking noises (i.e. Actors sound like buffaloes, for better or for worse). You might also consider putting a microphone on a table if, say, you're doing 12 Angry Men. Look up border microphones on eBay or in a music catalog in that case. Border mics really only work if people are talking pretty loudly on stage, and for the most part you won't end up using them, even on the mainstage. Tell the actors to get a voice coach before you use border mics, to be perfectly honest. Border mics usually need phantom power.
  2. Choir microphones hang above the actors. These are actually best left to picking up choirs since they tend to feed back or randomly make actors near them really loud. Some people swear by them. I'm not a fan except for a few uses. Always make sure they're facing upstage (away from the audience) unless you really like feedback. These usually need phantom power.
  3. Dynamic microphones are what you normally think of when you hear the word microphone. If someone needs to walk up to a microphone and talk, use these. Shure Beta-58a's are great- they go really loud before feedback and are wonderful vocal mics, but are like $150. Shure SM-58s are also good vocal mics, and are $100 or so. SM-57s are sort of a catch-all choice for instruments, and they also run about $100. 57's can mic everything from a guitar amp to a trombone to a snare drum effectively, so people buy a lot of them usually. If you need a microphone to pick up bass frequencies (a bass amplifier or a kick drum), look at AKG D-112's for about $200. Don't phantom power these, you'll mess them up.
  4. Wireless lavalier microphones. These are what you usually see in musicals when you want to hear a singer above a really loud orchestra. They're very useful but also a huge pain to control. When you're buying a wireless set, look for a) UHF rather than VHF... UHF is the radio frequency range used by the cool kid microphones (AKA the newer ones). b) you can change the channel they transmit on. Most nicer microphones let you choose the channel you transmit on, which is good when you're interfering with microwaves and such. c) That it comes with a subminiature mic that you can hide well. The mic at the left is one of the cylindrical types, and it will show up pretty obviously. It's also tough to hide. The one on the right is a Shure WL93. It's flat and rectangular and is generally pretty easy to disappear. \A wireless mic set will contain the lavalier microphone, the beltpack it's attached to, and a receiver. In terms of dealing with the microphones themselves, make sure not to break them or lose the clips they come with since both of those are extremely expensive. In terms of where to put the microphone on a person, you've usually seen presenters at conferences and such clipping the wireless mics to their shirt collar. BZZZT, wrong. Never do that in the theater since you'll hear every time their shirt rustles, the mic will be far away from their mouth, it'll get in the way during costume changes, and any time they turn their head and talk, you won't hear them. As to the proper place to put a lavalier mic, there are 2 reasonable places: either sticking out of the hair or taped to the cheek. A lot of people prefer to have the cord come up the back of the actor's head, weave through their hair, and then magically pop out right above their forehead, sticking out about ½ to 3/4” of inch and pointing down towards their mouth. Bobby-pin the mic to the hair in a bunch of places. The advantage to this approach is that the mic is hidden pretty well, but the disadvantage is that it's pretty far from the person's mouth. I personally prefer to take the microphone to the cheek with clear medical tape. Of course, make sure the mic isn't right up against the cheek- it should crane out a fair bit so that it has direct line of sight with the actor's mouth. Clear medical tape is pretty invisible if a coat of makeup is applied over it. As a final note, if the actor has glasses they never take off, the side of the glasses where the lens and the part that goes behind the ear meet is a fantastic place to put a mic. You get better sound than on the forehead, and it's tough to see. \Now, the beltpack can either be clipped to the actor's pants or worn in a pack. A lot of professional sound engineers have made their own mic pack sized “fanny packs”, but instruct the actor to wear the pack backwards. The pack is thus in the actor's lower back. With either approach, make sure the antenna is pretty free or else the sound will be terrible. An additional concern is if the actor is dancing a lot or gets really sweaty on stage. The sweat will destroy the mic pack, so what a lot of engineers do is buy XL condoms and put the mic packs in there. Seriously. Someone ends up looking pretty funny walking into the store and buying like a 100 pack of them. Also, keep in mind the battery requirements of wireless mics, especially the extra expense. Most require 9V batteries. Duracell ProCells or other industrial strength batteries are often preferred for this application. You'll usually get 2 or 3 nights of rehearsals out of each battery, but put in a fresh set for each performance!

When setting up the receivers, put them close to the stage (in the pit, off the side of the stage, etc.) but try to keep a line of sight between them and the actors. Then run a snake to the back of the house. Don't put the receivers in the back of the house unless it's a small house. Radio transmission is good but unreliable. Oh, and when using wireless mics, the rule about how to set the gain no longer applies... good luck. \

When you're recording, however, you often would be best served with different types of mics. Condenser mics are often the top choice for making a nice recording. They come in large diaphragm and small diaphragm varieties. The large diaphragms pick up everything. Seriously. They're good for micing a string bass in a room or a vocalist since they get all of the nuances of the performance. Small diaphragm condensers don't pick up quite as much, and are good for micing acoustic guitars (put the mics up close) or drum sets where you don't actually want every movement on the strings or cymbal rattle to come across. Engineers often use a “matched pair” (2 mics with similar frequency response) of small diaphragm condensers on an acoustic guitar or overhead a drum set to get a nice stereo sound. A good condenser mic will run at least $200. I personally really like the Rode NT-1 and NT-5. Condenser mics almost always require phantom power.

Playing recorded music

These days, CDs, Minidiscs, and Computers are the main ways to play recorded music into a sound system.

CD players can be the kind you see in home stereo systems or the cooler kind that DJs use (rack-mounted). The rack-mounted units a) can be put into a sound rack, which makes them look much cooler b) give you more exact options to see how much time is remaining on a song c) can often be set to stop playing at the end of a particular track (so that the sound operator doesn't have to hit pause) and d) sometimes have pitch shift, which is really fun to play with. As a result, I'd recommend trying to get one of the rack-mount units. Stanton has nice models that sell for pretty cheap.

CDs are nice since recordable CDs are extremely cheap these days. However, if you burn one that is finalized, the CD is kind of dead once you make any changes. Thus, CDs are good once you have everything worked out. CD players almost always have RCA outputs.

Minidiscs came into favor in the theater world about 10 years ago since they had high sound quality, could skip tracks, and could be recorded on multiple times (this is before the era of the CD burner in every living room). They've since fallen out of favor since a lot of editing takes place on the computer and it's easier to burn a CD than transfer to a minidisc. You may still use them as a recording medium for live shows, since the decks are already in place.

Computers are my preferred way of playing back sound. You can edit sound cues on the spot as they change. You also have very fine-grained control over when a sound starts playing if you're using the right programs (don't use iTunes to play back sound!). I like to open files in either a wave editor (more on this later) or WinAmp and play them back that way. There are commercially available sound cueing programs available for PC and Mac, too. Depending on your show's complexity, you might look into those. Computer sound cards usually have an 1/8” output, although some more expensive ones have RCA outputs. Make sure you have a good sound card if you're playing back sound (i.e. The sound card that came with your mother board is probably not the best idea for great sound quality).

Finding Sound

This is often one of the most mystifying parts of sound design- where do I get sound? Here are some hints:
  • Music Libraries. Yup, these exist and are awesome. At Harvard, the Morse Music and Media collection at Lamont houses decent collections of jazz, world music, and judaica. The classical collection, though, is pretty strong. CDs circulate for 28 days and DVDs for 7 days. The Loeb Music Library has a much better selection than Lamont, but those recordings circulate only within the library for 4 hours. Their jazz and world music collections are extensive, and the classical work is second to none. However, their staff is very adamant that you do not copy materials and will kick you out of the library if they catch you doing so. I'd recommend you not try.
  • Online. www.Findsounds.com is a vaguely helpful search engine for sound fx, though make sure you set the quality settings to something decent. For music, check out www.archive.org, which has a large collection of free (legal) music, as well as an excellent archive of live music and bootleg recordings. There are also speech recordings and such on archive.org. You might also search for “public domain” and “creative commons” recordings. Public Domain means, in the most basic sense, that the creator has given up copyright on the song. Creative Commons is a new trend where musicians can choose “less restrictive” licenses that are also supposedly easy to understand. They're often not, however, and you'll most often find indie bands trying to be cool releasing material with Creative Commons licenses... ant not much else.
  • Sound FX collection at the ART. Dave, the ART's sound designer, has a pretty good collection of SFX from Sound Ideas. He has a lot of the Sound Ideas 1000,2000,4000,6000 libraries, the BBC SFX collection, and a bunch of random libraries. He doesn't let sound effects leave the sound booth, though, so you must make an appointment with him well in advance and bring in your laptop to rip the effects you will need. He has a lot of the effects in a computer database, which is really helpful when you're trying to find what you need. Also, www.sound-ideas.com has their own database, but it unfortunately doesn't let you listen to the sounds, whereas Dave's does.
  • Friends with good musical taste. A lot of the older sound designers in the community have excellent collections of music. Take advantage of them.

Now, a big question is what kind of music should you look for. I would advise that you stay away from songs people might recognize unless that recognition adds to the moment in the show (i.e. playing Brick House underneath a scene in a serious play about the 70's would distract the audience's attention. If you're doing a comedy version of the Big Bad Wolf story, though, and you want to play Brick House at the appropriate moment in the show, it'd be really funny and probably add to the comedic nature of the scene). Also, keep in mind the effect sound effects will have. Just because the script calls for a doorbell ringing and footsteps doesn't mean you should go find a sound effects CD of doorbells and footsteps. If the audience hears these playing over the sound system, it might distract them since it will clearly not be real. In that case, it's usually better to get a real, physical door bell and make it part of the set to preserve the realism.

  • Editing music on the computer

First off, you need to set up your computer to work well with audio. I mainly use Windows and Linux machines so I'll basically concentrate on those. \To look at how to shut off unnecessary processes that would slow down your computer when playing with audio, check out:

Also make sure you have a quality sound card in your computer. The Sound Blaster Audigy and most of the products by M-Audio would fit this description. If you need to plug microphones into your computer, you generally want to take a microphone preamp and go into an input that's actually meant for this- plugging a nice microphone into the “mic” input on your motherboard generally doesn't sound too good. I use an M-Audio Delta 1010, which gets an excellent noise-free sound. It also has 8 separate inputs and 8 separate outputs.

As far as software, there are 4 categories I usually deal with.

  1. Wave editing software. These programs let you take a sound file, open it up into a graphical view of the sound waves, and then chop it up/add effects to/cut and paste parts of it. When you're “editing” a file, this is what you're most often thinking of. Good software for this is Sonic Foundry's Sound Forge (now bought up by Sony... and also widely pirated). Some software is made specifically to loop songs (take a part and play it over and over again) such as Sony's Acid. Unless you're really into techno, you don't often use these as part of a show, but the ability to match the speed of files is very helpful if you have a little Clint Mansell in you.
  2. Multitrack Software. These programs let you take a number of different audio files and mix them together. You can also add effects track-wide. The main advantage here is that it's easy to adjust the relative volumes on each “track”. This is also the software you'd use if you're trying to record a rock band's CD since you can set each microphone to a different track, and then later tweak each track separately. Cakewalk's Sonar is wonderful (and widely pirated) software for this. Protools and

Digital Performer also fall under this category. N-track and Audacity are free options, but are unfortunately not very good. Most multitrack software also includes basic wave editing capabilities.

  1. MIDI synthesizer software. Ever hear corny computer-synthesized music? Ya, that was MIDI, a system in which “models” of instruments produce the sound. It doesn't sound very good, generally, although it's been getting better in recent years.
  2. Live editing software. Reason and other similar programs are made to be used in the heat of battle (or the middle of a show) to modify sounds and such. These are more helpful for avant-garde and artsy shows.

Note from Nick - If you're a CS concentrator, you can try looking at Max/MSP for live work. However, be warned, it's hard code, and not for the faint of heart.