Everything You Ever Wanted to Know About Live Sound
From an empty arena to a full blown show. We're at an empty sports arena. Normally a place where the athlete rules supreme. Tomorrow will be a whole different ball game. Athletes won't be running around the arena nor will there be any cheering for victory. The only cheering that will be going on is the loud roar of an audience screaming for more of their favorite band. Tomorrow this arena will be packed with people looking at a huge stage filled with amplifiers and instruments. Hundred watt P.A. speakers will be pumping out rock music at ear splitting levels while the crowd jumps up and down in sync with the pulsating bass coming out of the subwoofers. But today, this arena is empty. Nothing except a few roadies surveying the situation, deciding on the best way to put up the show of a lifetime.
How are shows like this put on? How do you transform an empty sports arena into a full blown concert venue in a day? In the following Premium tutorial we will be looking at all the aspects of setting up a concert. From the roadies putting up the stage to the front of house engineer mixing the show, there are many factors that we have to consider and be knowledgeable about when it comes to organizing a concert.
Setting Up the Stage
Normally, when you are starting out in live sound, they put you in the most challenging and hard job there is. Lugging stage equipment and putting a stage together is not for the faint hearted since it's a lot of hard work. Putting together a stage was probably not the job you were thinking about when you joined a sound reinforcement company, thinking you would be working with bands and music and all that jazz. Unfortunately for the newcomer, setting up the stage and lugging in all the equipment is usually what you start doing. But just like every company, do your initial job well and you will most probably be allowed to work your way up the live sound ladder. That said, many roadies stick to the grunt work, never wanting to be anything but a live sound private. But we want to be generals here, so a thorough understanding of all aspects of this gig is crucial so you can seamlessly move from one task to another.
Flying Up the System
Depending on the size of the show, we are either working with smaller P.A. speakers, or big line array systems. The difference between a line array speaker system and normal P.A. speakers is that a line array system is flown up in the air and each speaker box is calculated so that it has the best distribution of sound from the speakers covering the length of the arena. That way someone who is listening in front of the speaker gets the same sonic information as the one that's listening at the back of the venue.
Regular speaker boxes that are not flown up in a line array must therefore be positioned so that it has the best distribution of sound to the whole venue. We need to elevate them to a certain so that the speakers project sound over the crowd. If we don't elevate the speakers in that way the higher frequencies get absorbed by the first row, resulting in poor frequency distribution to the rest of the crowd.
Active or Passive Speakers
Speaker systems can be either passive or active. It's the same situation like your studio monitors. You can buy passive monitor speakers that need an amplifier to work, or you can buy an active monitor that has its built-in amp. Passive speakers are much more lightweight and easier to carry since the heaviest component of the speaker is the amplifier itself. So when an amplifier comes separate, the speakers get significantly more manageable in weight. Lifting heavy active speakers around can get tiring pretty soon. It's much easier to carry around passive speakers that you can plug into an amplifier that just sits by the side of the stage.
Advantages of passive speakers
- Customizable by tweaking the amplifier settings
Disadvantages of passive speakers
- Extra amplifiers needed to lug around
- More cables and links in the chain
Let's compare two separate systems that I am familiar with and have worked with on occasion. One one hand we have the Meyer MSL-4 active speakers, and on the other we have the JBL VRX passive line array system. You could easily use both systems for the same show, with similar results. But due to the difference in design of these two PA systems, the effort in setting them up is miles apart. The MSL system is an active, self-powered speaker system that needs at least three strong men to lift, while the VRX is a passive line array system that you can pick up with one hand. You will be needing to fly the line array up into the air, but since we usually do that with a lift anyway, we could almost put up the whole sound system by ourselves, instead of needing all the extra manpower.
Power-wise, I can just plug the MSL straight into electrical power and into the mixer and I'm good to go, but the VRX needs to be plugged into an amplifier that needs to be calibrated correctly for the speaker before we can plug it into the mixer. So you can see the drawbacks of a heavy self powered speaker system compared to a lightweight, passive line array system that's fed into an amplifier. The MSL can also be flown in a line array but the difference in weight and size is a good indicator of the difference two speaker systems can have. Which would you like: a small and compact but powerful line array system that you can carry by yourself or a heavy and cumbersome speaker system that although very powerful and loud is an enormous hassle to set up by yourself?
Line arrays come in a few shapes and sizes. If we continue using JBL as an example, their VRX system isn't actually their flagship line array system. Their Vertec line array is the big brother that gets all the biggest gigs. You see, when we have bigger shows and larger arenas we have more sound area to fill. Therefore we need a large line array that we can fly high up into the air, covering all the space of the arena, from the front row to the back bleachers. High tech line array and speakers systems like this use complicated computer programs to calculate how we should position all the speakers in a line array in such a way that it covers every square foot of the arena. By calibrating and calculating correct angles from one speaker to the next we can accomplish the same sonic and frequency distribution across the whole venue, giving each member of the audience the same enjoyable sound.
By looking at the picture above you can see how the different angles of each speaker are calculated in such a way as to direct their sound towards a specific area in the arena. The person that is listening to the first box won't be affected by the last boxes due to how they are angled away, throwing the sound to the far back of the arena.
Front of House
Now that we've flown up the line array system, plugged it into the amplifiers and calculated the correct angles for sonic distribution, we can start setting up the front of house area. The front of house area usually consists of a mixing desk and an effects rack. In today's age, analog is being slowly taken over by the digital revolution, so there are more and more cases of digital mixers being used exclusively, eliminating the need for tedious work patching the effects rack to the mixing desk.
If we are using an analog mixer with an effects rack, we have to individually patch every compressor, every gate and every effect manually into the mixing desk. This can result in some tedious work, especially if we are working with an insane amount of tracks that all need some sort of treatment. We use inserts, just like on our computer program to patch our compressors and gates into an analog mixer. This can be done either with a Y-plug that connects to the processors send and return on one hand and the mixers insert on the other. If a mixer has both an insert send and return then you just plug the send to the return and vice versa.
It's much easier to just go digital and use the mixer's built-in compressors, gates and other effects. I am a huge advocate of using digital mixers, especially in live sound since it cuts the setup time down exponentially. That said, many old school engineers prefer using analog gear and swear by their refrigerator-like effects rack. Just like the example above, with the two different speaker system, I choose things that are compact and easy to use over heavyweight and bulky machinery.
But what do you need to patch when working as a FOH engineer? Live sound mixing isn't that different than normal mixing in the way that all the same instruments needs similar treatments. It's good practice to gate and compress the kick drum and toms just like you do normally. I tend to compress the bass quite heavily since I don't want the low end to be shaky during a live gig, much preferring a steady bass sound than a dynamic all-over-the-place performance. Similarly, I compress vocals just like normal, but try to take into account the character of the singer, backing off the compression for softer genres and compressing harder if it gets all rock 'n' roll. Likewise with EQ, just because we are in a live arena doesn't mean the frequency spectrum has changed. We still need to filter and cut the same frequencies that annoy us in the studio, and we can enhance the players on stage with the same boosts that would use in a studio mixing session. If you are confused about the frequency spectrum, check out my article on How to Recognize Frequencies or Will Walker's EQ guide for some good tips on the EQ spectrum.
Testing Out a System
When you've set up the P.A system and the FOH mixing station it's always good practice to test the system to hear how it sounds in the arena that you are in. By using CDs that you know well you can easily gauge if you think some frequency area is more dominant then others. By using a graphic equalizer over the master bus of your mixer you can easily slide frequencies up and down to hear which ones are causing you problems. If you feel that there is too much muddy bass clouding up the system it is a good idea to cut at 200Hz or 250Hz to reduce boominess in the speakers. A boxy sound can often be an annoying factor when testing a system in an empty arena. By lowering the frequencies around 630Hz or so you can avoid an overabundance of boxy frequencies plaguing your otherwise nice sounding test CD. It's crucial to listen to a high quality CD that you know inside out when testing a system. That way, you will have an easier time equalizing when you have a reference that you know in your head.
Back of House/Monitor Mixing Position
The monitor mixing engineer is the most important person when it comes to making the band feel comfortable on stage. He controls the sound that's coming out of the monitors, sending any instrument the band wishes to hear to their monitors.
There are a few things a monitor mixing engineer should concern himself about when setting up the monitors and preparing his monitor mix.
- Correct Placement. Correctly placing the monitors is crucial to hearing what's coming out of them. Simple? It's amazing how many times bands can't hear themselves because the monitors have been badly positioned and aren't facing the right way. Imagine sound coming out of the speaker in a cone shape. If you are standing outside the cone shape, you can't hear the sound. Make sure the monitors face the right way and are aimed at the ears of the musicians playing. Otherwise, creating a good monitor mix is futile since they won't hear it anyway.
- Feedback Control. By using graphic equalizers before the monitors we can eliminate pesky feedback frequencies by cutting them. That way we can raise the overall volume of the monitors without risking more feedback.
- Don't overpower the monitors. You don't have to add every single element to the monitors. A bass player that is standing behind a 8x10" bass cabinet might not need bass in his monitors because he hears himself fine through his amp. Only add instruments to a monitor mix that the musicians need.
- Make them ask. Don't automatically assume that the singer might want more of this or more of that. If the band isn't asking for something in their monitors, don't add it as a favor. It might catch them off guard and they'll resent you for it. Make them tell you what they want, don't assume to know unless you've been touring with the band and they trust you.
We don't use the faders of a mixing desk when we are monitor mixing, instead we use the auxiliary sends on a mixing board to create separate sub-mixes for all the members of the group on stage. In that aspect, monitor mixing can be a trickier task than FOH mixing. Because you are essentially creating multiple mixes on stage for various musicians and bands, you actually have more on your plate than the FOH engineer that only needs to think about his one stereo mix. Monitor mixing is a challenging but enjoyable task that combines a stressful and adrenaline rushed stage performance with quick thinking-on-your-feet audio engineering. For a more in-depth look at monitor mixing, check out my guide on How Good Monitor Mixing Enhances a Performance.
Miking Up the Stage
Just like any recording situation, we'll be using microphones to put the sound of the stage into the sound system. Depending on the scope of the concert there might be more things miked up, like two microphones for the kick drum, a combination of DI signal and miked up sound for the bass as well as two microphones on the snare. However big the concert may be, you can be sure to find all the typical microphones everywhere else, dynamic mics on guitar cabinets, a trusty Shure SM57 on the snare as well as Shure SM58 lining the front for vocals. The ratio of dynamic microphones vs condenser microphones varies significantly when it comes to live shows since the sensitivity of the condenser just isn't viable for the loud environment of a live concert. Therefore, you will probably only come across them for drum overheads, for hi-hats and the occasional acoustic and/or orchestral instrument.
All these microphones are plugged into so-called stage boxes that split the signal to the FOH engineer and the monitor mixing desk. By splitting the signal using these stage boxes, or snakes, both the FOH mixer and the monitor mixer have separate signals they can work with in their respective environment without interfering with each other. Thus, regardless of what the monitor mixing engineer does to the stage sound, the FOH engineer won't have to worry about unpredictable feedback or other annoyances to his side of the system.
All the audio equipment the band uses is called the backline. Usually a backline consists of amplifiers, drum-kits and the occasional keyboard, but normally it doesn't include the instruments themselves. Next time you are asked "What's the backline there?" it usually means this: "What don't I have to bring?" A guitar player needs to know what type of amplifier he is going to be playing through, as his sound may be different according to his amplifier needs. A metal guitarist won't be able to coax the same sound out of a Fender Twin Reverb as he would a Mesa Boogie Dual Rectifier, so if you are put in charge of coordinating the backline for a gig, make sure you supply amps that the musicians can actually need. And when in doubt, you can't really go wrong with a nice Marshall stack. It covers everything from nice cleans to screaming distortion.
Let's imagine for a second that we're putting up a backline for a concert that involves a few different types of bands, and there is no headliner in particular, i.e. no world famous band that always has the same gear supplied. Then we have to know the line-up of each band and take down any special needs and or different instrumentation that these bands have. Most of the bands playing at this make-believe concert have the typical line-up of drums, bass, double guitar and two vocals. It's easy to place the drums in the center, the bass amplifier by the hi-hat side and two guitar amplifiers on opposite sides of the drum kit.
But some have acoustic guitar, electric violin, keyboards and playback that all need to go into the system somehow. We're not going to amp up any of these instruments, so what do we need for "odd-ball" instruments such as these?
Answer: DI Boxes.
We use DI boxes to plug in any instruments that have a line output but aren't usually amplified. I usually line the front of the stage with DI boxes, placing them by the monitors for easy reach of the musicians. Now the acoustic guitar player can easily plug in his acoustic guitar into the DI box, and since the DI box is plugged into the sound system the monitor mixer enables the singer to hear his guitar through his monitor. We do the same thing with all the other instruments that need this sort of treatment. Electric violins, CD playback for singers and keyboards act the same way, we just plug them into the DI boxes, the monitor mixer sends them a little signal back to their monitors and they're good to go.
Dealing With the Artist
Musicians are peculiar creatures. I would know, I kind of border both sides and I think I'm pretty weird, and especially unstable when it comes to my music. Musicians have slaved over their songs, constantly doubting them and making them better, so that when they perform them live they hope somebody other than themselves and their girlfriend will like them. So it's no wonder musicians get all nervous and edgy when it comes time to perform them live, and it's your job to do as much as you can to make them feel better. Many live sound guys have this holier-than-thou attitud e that makes them think that because they set up all the equipment they shouldn't need to do any extra work to make the artist feel comfortable. I think the opposite is true, your job is only over when the artist returns from the stage after a successful show.
Barring the fact that some artists can be primadonnas, most musicians just want to have a good time, hear themselves well on stage and perform their often very personal songs to the audience. It's your job to make their performance as easy and seamless as possible for them. A hack sound engineer, a bad monitor mixer and a rude roadie can all help weaken the performance that could have been great if all of the tech crew would have done their job. Your job isn't over until the musician is done playing, and if he had a bad time playing, review everything you did and ask yourself if you could have done anything better. It doesn't have to be your fault, but it doesn't hurt to be professional and retrospective towards your work.
Now we've gone over all of the biggest factors that have to do with setting up a big live show. Everything from setting up a stage, flying up a system, testing our speakers and lining the stage with monitors and amplifiers for the artist to use. Each of these factors are pieces of the live sound puzzle and by doing one of them wrong, the whole show could fall apart like a house of cards. Badly tested sound systems can result in a muddy sound for the audience while a hack monitor mixer might be fighting with feedback on stage the whole show. Even supplying the right backline, correctly flying up a line array system and using the right microphones on stage are crucial elements to a show's success. Concert promoters and sound reinforcement companies work like a well oiled machine in order for everything to work out well, preventing the things that might go wrong from going wrong. Sure, everything regarding a live show is subject to Murphy's law, but the excitement, hard work and fast paced situations make it totally worth it.