Live Sound Buyer's Guide

Introduction

Why learn about live sound?
Learning the basics of live sound reinforcement is an important aspect of becoming a successful live performer. Whether you are a singer/songwriter, member of a band, or venue owner/employee, understanding the basics, and learning some troubleshooting can make a big difference in the impact of your performance, and might even save the show. Becoming more self-reliant will also help you hone your sound.
In this guide we cover the basics in between your voice or instrument, and the audience’s ears. From the different options available for a live sound setup, to some beginner tips, you’ll find everything you need to know to get you started in the world of live sound.

Microphones

The world of microphones can be a daunting one as there are literally hundreds of options to choose from. While they all capture sound, they are not created equal. Each microphone is tailored to a specific application and is designed to pick up sound from a specific direction. There are also different technologies involved which make some more sensitive to sound than others. That being said, there are also similarities between each type of mic. For one, they all convert the sound of instruments and vocals into an electrical signal so that it can be amplified. Let’s first take a look at some of the more popular types of microphones.

Sennheiser e935 Dynamic Vocal Microphone

Dynamic mics are most often found in live performances. They are known for being durable with the ability to handle abuse, within reason. Another key trait is being able to withstand high SPLs (sound pressure levels). This means they can capture really loud sounds without being damaged. On the contrary, they don’t handle instruments with a wide dynamic range as well as condenser mics, which are known to be more sensitive and authentic in projecting the finer details of a sound.

Sennheiser MK4 Studio Condenser Microphone

Condenser mics more faithfully capture the transients and nuances of instruments and vocals. They aren’t as durable as dynamic mics but some can still be used in a live setting, although more care must be taken. The increased sensitivity requires careful placement and gain control so that the signal does not distort. They also require Phantom Power, which is a power source transmitted from a microphone preamp to the mic through an XLR cable. Practically all live sound mixers have Phantom Power, which is sometimes referred to as +48 volts.

Shure PGX Digital Wireless System

Wireless mics are a great option for live performers. Freeing the musician from cables allows them to concentrate on performance, without worrying about tripping or being confined to a limited space. Some wireless systems are analog, whereas others are digital. Digital wireless systems tend to have higher quality audio as far as dynamic response and frequency response are concerned. They are also usually less noisy at the end of range since like most things digital, they are either on or off. Note, some high-tier analog wireless systems have been designed with comparable, high-quality audio.

Analog systems experience no latency, whereas digital systems may have a few milliseconds of delay, depending on the system and application. In addition, digital wireless systems that operate in the 900MHz or 2.4GHz range can usually handle about 4-5 compatible systems in total, much less than analog.

Each has its benefits but to understand more about analog versus digital, check out the AMS Shure Wireless Buyer’s Guide (https://www.americanmusical.com/content--name-Shure-Wireless-Buyers-Guide). Regardless of analog or digital, wireless systems must be setup before the performance to avoid interference, and if you’re purchasing multiple units, make sure they are each operating on different frequencies.

Polar pattern diagram

Polar Patterns
A polar pattern represents how the mic is designed to pick up sound. It’s important to understand them for stage use since you’ll want each microphone to properly capture your vocals and instruments. This is especially true when multi-miking drums as you may want certain mics to pick up the sound of the entire kit, and others to focus on one particular drum or cymbal.

  • Cardioid: This pattern picks up best from the front and sides while completely rejecting from the rear. These are best for vocalists that are using monitors placed directly behind the mic stand.
  • Hyper Cardioid: This pattern’s sensitivity is primarily in the front, but allows a certain degree of sound from the rear. It rejects sound best from the sides. Hyper Cardioid are better for vocalists that place their monitors to the left and right front of them, usually at 45 degree angles.
  • Super Cardioid: This pattern also picks up well from the front and rejects from the sides but is a little less sensitive at the back of the microphone.
  • Omnidirectional: Omni mics pick up well from all sides.
  • Unidirectional: This pattern only picks up from one direction, typically the front.
  • Figure 8: Picks up well from both the front and rear, rejecting anything coming from the sides.

Microphone Placement
The closer a mic is placed to the sound source, the louder it will be. However, this might not produce the sound you desire. For example, placing a microphone directly in front of the cone of a guitar amp may produce a harsh sound, whereas off-axis (when a mic is placed or used at an angle rather than straight on) may soften the sound. A boom stand can be used or the mic can be draped over the front of the cabinet, hanging from the cable.

The most important rule of thumb when miking on the stage or in the studio, is don’t be afraid to experiment. A guitar amp is not going to move throughout a performance but movement by a vocalist is sometimes unavoidable. Account for both when placing your mics.

Microphone Technique
The microphone is the instrument of the vocalist. An experienced singer will manipulate the mic based on how loud they are singing and how close they are to the mic. When close they can sing relatively softly for a deep, rich tone. This is known as the Proximity Effect which states that there is an increase in bass when a sound source is very close to a microphone. Experienced vocalists will increase their volume as they move further from the mic. Although their voice seems to be getting louder, it’s really just a greater intensity and the listener is not deafened by the words. When singing close, be careful about plosives, the popping sound that happens on words beginning with B or P.

Direct Boxes

Whirlwind Imp 2 Transformer Direct Box

A direct box, also called a DI (for direct injection), changes the impedance (resistance to the flow of electric current) of the instrument or device plugged into its input. They are useful for plugging Hi-Z instruments such as guitars and bass guitars into a mixer. Unless a mixer has a Hi-Z input, the signal from a guitar without a direct box will not be strong enough.

Mixing Consoles

Allen & Heath QU16 Digital Mixer

The mixer is the brain of the sound reinforcement system. A variety of sound sources connect to the inputs of a mixer. Vocal and instrument microphones, instruments such as guitars and keyboards, media players, etc. can each connect to the mixer at the same time (depending on the number of available channels). The mixer then processes and balances all of the inputs into one unified mix to send through the outputs to the audience. Although some seem daunting due to the amount of knobs and faders, the mixer is mostly made up of what are known as “channel strips.” Once you understand one channel strip you know them all. They each have identical controls used for each input.

Input Types
Each input corresponds with a channel on the mixer so individual adjustments can be made to each sound. Most mixers will have XLR, quarter inch, or combo-jacks (both quarter inch and XLR).

Effects
Mixers are used to process sound and this includes audio effects. Some mixers come with effects and dynamics processors built in, whereas for others you can use standalone, dedicated effect units.

There are two methods for connecting an external processor to a mixer. The first is into an individual channel via an “insert point” (a two way connection). Insert points are useful for devices designed for use on one channel at a time, like a compressor. The second is into a circuit called an auxiliary bus (a special piece of wiring in a mixer than can be tapped into by other channels or controls), which allows for any channel to make use of the effect. This method is useful for effects such as reverb.

Output Types
All mixers have at least one set of master outputs that carry the mixed signal to your amplification system. Usually, they’ll also have a second set of outputs called a Monitor Mix which allows you to send a different mix to an amplification system for the musicians or performers on stage so that can hear themselves playing.

Channel Strips
The channel strip will tell you a lot about the mixer such as what sort of equalizer it has and the flexibility it has in terms of monitoring and patching effects. At the top is the input section, the point at which the sound source enters the mixer. The strength of the signal is governed by the gain control, sometimes referred as a trim pot (trim, as in adjust the incoming signal; pot, as in potentiometer; a smooth running level control). Some mixers also have a pad switch, an instant attenuation that reduces signal level by a fixed amount.

Gain Structure
Learning proper gain structure will ensure the signal entering the mixer is clean and not distorted. It is ideal to end up with all sound sources having equal signal strength. If enough signal doesn’t get into the mixer, the signal won’t be strong enough and increasing the output level of the channel (using the fader) will add noise. Conversely, if too much signal is coming in, the sound will be distorted and no amount of fader attenuation will be able to help it. Use the meters on the channel as a visual guide (some mixers will have a red “clip” light) and of course, your ears as well.

EQ (equalization)
Most mixers feature some sort of tonal adjustment controls. It may be high, mid and low, cut and boost like on a home stereo, or a more sophisticated system where specific frequencies can be isolated and adjusted. Cutting (reducing) the level of certain frequencies can be just as powerful as boosting frequencies when it comes to improving a sound or fixing a problem. If a sound doesn’t need tonal adjustment, don’t make any changes. Boosting frequencies adds noise to the signal chain, and should be avoided whenever possible.

High Pass Filter
Some mixers employ a high-pass filter that will automatically filter out low frequency noise. This switch comes in handy when wanting to reduce wind noise from microphones. It can also protect the speaker from damage if someone accidentally drops the mic.

Auxiliaries (Aux)
Many mixers have auxiliary signal buses to add effects to the sound or deliver a mix to on-stage monitors. An aux knob on a mixer is really just another level control. It adjusts the amount of signal from that channel to that particular aux bus.

Aux buses come in two varieties, pre or post-fader. Sometimes they have a switch to determine the operating mode (pre or post). If the aux bus is pre-fader, the sound is sent to the aux bus before it comes under the control of the channel’s fader. This means that adjusting the channel fader will not disturb the amount of signal going to the aux bus. This will prevent a monitor mix from changing just because the engineer is changing the levels in the mix. Post-fader is used when wanting to adjust the level of the channel, while also adjusting the level sent to the effect unit. For example, as the volume is adjusted, the level of delay on a singer’s voice is also adjusted.

Pan (panorama)
Pan controls send the signal to the left, right, dead-center, or somewhere in between the stereo field.

PFL (Pre Fader Listen)
The PFL allows the sound of the channel in headphones to be heard regardless of the channel fader being up or down. PFL can be a lifesaver during a show since the engineer can check an individual channel without disturbing the sound coming out of the main outputs. It’s also helpful when setting initial input levels since it can be done without the sound coming out the main outputs.

Fader
The fader is the vertically sliding cap that increases or decreases the channel’s output. Some mixers use knobs for channel level but the result is the same.

Groups
Mixers that contain groups will have a button on each individual channel that allows the signal to be sent to that particular group fader. Grouping like-minded sounds together can minimize drastic changes to individual sounds. For example; if the drums are a bit low, moving up the group fader would increase all of the drum sounds (provided they were assigned to the same group).

Master Controls and Monitoring
In the master section of the mixer, the Aux Send can control the overall level of the entire mix being fed to the monitor amplifier and speakers. With more than one aux, the monitor mix can be sent to an effect, and can adjust the amount of effect that is applied by tweaking the Aux Return control. On individual channels, the amount of effect routed to that particular channel can also be controlled. There is also a control that adjusts how much of the auxes are applied to the main mix. Finally, the main fader adjusts the overall level of the main output mix.

Types of Mixers
In addition to the standard analog mixer, there are two other topologies to be aware of. Powered mixers have a built-in amplifier and will typically allow control over how much power is used for the monitor mix vs. the main speakers. If a monitor mix is not being used, all the power can be harnessed for the main speakers. These types of systems are good for small outfits like two or three people with guitars and microphones.

Digital mixers have greater control and flexibility over their analog counterparts. They can be programmed so that settings are stored and recalled later. This is helpful for bands since the engineer doesn’t have to remember the settings for a singer’s mic, or channel fader positions for a certain song. Many have on-screen controls and work with proprietary software. They can also easily be integrated into computer setups. Routing is often flexible which means the performer can plug into channel one and route the signal to any desired channel. Check out the AMS Digital Mixer Buyer’s Guide for more info.

Snakes

In Line Audio 16 Channel Audio Snake

A snake is a series of cables bound together as one. On one end of the snake is the input box, which allows for performers on stage to send their signal. At the end of the snake, the cable is unbound and fans out to individual connections for input into several mixer channels. They provide a convenient way of sending signals to and from the console without having lots of cables over long distance to worry about.

Power Amplifiers

QSC GX Power Amplifiers

Amplifiers make sound louder. A quality power amplifier will keep sound clear and help it come alive. An inexpensive amplifier, or one that’s not compatible with the rest of a system, will make the sound weak and dull, or completely fail to operate. A typical two-channel amp will have attenuators for each of the amp’s channels, along with LEDs to monitor signal level and clipping (a term used to describe when a signal is momentarily exceeding safe levels). By properly matching the amplifier to the loudspeakers, overheating issues can be avoided.

Watts and Ohms
The key parameter of an amplifier is its power output rating (how loud it is) Power rating is measured in watts, but wattage is only part of the equation. 200 watts may be twice the electrical power of 100 watts, but this is not the case in terms of loudness or acoustic power, which follows a logarithmic scale. Every time the volume is doubled, a 10x increase in electrical power is required. To double the volume level of 100 watts, 1000 watts would be needed.

The delivery of power is one thing, but how loudspeakers receive and handle the power must be considered. Impedance, or resistance the loudspeaker presents to the amplifier, is measured in units called Ohms. The relationship between watts and ohms not only determines how loud the system will be, but also whether or not the amplifier’s heating will be manageable. Higher impedance translates to lower wattage. Lower impedance means higher wattage. A lot of amplifier advertisements have power ratings shown at very low impedance, which makes the amp look good on paper but is actually misleading in regards to useable power.

2-channel amps can be used in a few different ways:

  • Stereo mode - This powers a left/right system, or as individual mono amps, like one for main speakers and one for a monitor system.
  • Parallel - One input signal is fed to both amplifier channels so the same signal can be fed to two different speaker systems. Each channel’s attenuator can be used to control the level of each set of speakers.
  • Bridge - Each channel’s output is combined into one, giant, mono output. This doubles the power offered by a single set of outputs. This mode is generally used for subwoofers and large speaker systems.

Crossover

Behringer Super-X Pro CX3400 Crossover

A crossover is a series of filters that splits a full range signal into frequency bands. Most loudspeakers have a passive crossover that distributes the signals to the low and high frequency drivers, respectively. For a multiple speaker setup (subwoofer included), separate amplification is needed for each. An active crossover gives control of the frequency ranges being sent to each component. The subwoofer just gets the lows; the mains get the mids and highs. If you are using a powered speaker system, crossovers are usually built into the subwoofer. The Sub plays the low frequencies and sends the mid and high level frequencies to the full-range powered speaker.

Signal Processors and Effects

Signal processors and effects are tools that alter signals. They can either be built into the mixer or standalone units. Here are a few examples of signal processing:

  • Compressor - A compressor reduces the dynamic range of a performance. The threshold on a compressor controls the levels automatically. Whenever any sound exceeds the threshold, it is automatically pulled down in volume.
  • Noise Gate - While a compressor attenuates the level of any signal that exceeds the threshold, a gate can attenuate or remove any signal that is below the threshold. Its purpose is to remove unwanted, low-level noise such as wind or the squeak from a kick drum.
  • Reverb - Reverb is an ambiance created from a sound reflected off a surface. Reverb units simulate the effect of sound coming from a different physical or virtual space.

PA Speakers

Yamaha DXR15 15 Inch Powered PA Speaker

Passive Loudspeakers
Loudspeakers turn electric energy into acoustic energy. In order to get the most from a sound reinforcement system, you must use appropriate loudspeakers for the amount of power being sent from the amplifier. Power ratings and impedance play a critical role so make sure you’re properly matching them. The following terms are ways loudspeakers are rated and marketed:

  • Noise - The noise rating signifies the amount of power the loudspeaker can handle if pure white noise is applied continuously for a period of 8 hours with desired results. It’s basically a speaker torture test.
  • Program - Program is a real-world measurement rating. It’s used to determine the acceptable output of the power amplifier needed to use with the speaker.
  • Peak - The highest power the loudspeaker can handle, momentarily. Continuous operation at this level will damage the speaker system but it can occasionally accept this power level.
  • Impedance - A loudspeaker’s impedance is quoted as “load” or input impedance. Under powering, or using an amplifier with insufficient power, damages more loudspeakers than an amplifier with too much power.

Active Loudspeakers
Powered speakers offer many advantages over their passive counterparts, whether used on the road or in permanent installations. Separate amplifiers and cables aren’t necessary so setup is fast and easy, and reliability is significantly improved. The ability to plug directly into speaker inputs saves space, and your back if you gig a lot.

Loudspeaker Build
Speaker cabinets (both passive and active) are made out of a range of materials and each has benefits. The most common material for passive speaker cabinets is wood.

  • For optimized performance, wood is the preferred cabinet material. Due to the very rigid nature of the plywood used in cabinet construction, more energy from the loudspeaker drivers is directed towards your audience, resulting in significantly greater SPL output and better control of low frequency performance than an equivalently rated plastic cabinet. Wood cabinets are naturally heavier than their plastic counterparts, but their increased performance is generally worth the extra weight. The modern Class-D switching power amplifiers found in nearly every currently manufactured powered loudspeaker are extremely light, and add very little overall weight to the cabinet. Modern quality loudspeaker coatings are made of very hard, scuff and scrape resistant material that helps keep the loudspeaker looking good to your audience for much longer.
  • Plastic loudspeaker cabinets offer very good portability due to their reduced weight, and generally smaller size. They also tend to be more economical. The more professional products from brands such as Electro-Voice, RCF, Bose and others maximize the performance of plastic speaker designs by using very high quality drivers.

About the Author - Headsnack

Headsnack has specialized in creating training materials for some of the biggest names in music gear retail, for over 12 years. His Training Snacks brand has produced several pro audio category and product training segments which can be found on YouTube and in written form on AmericanMusical.com.

As a musician, Headsnack is a positive-minded producer, performer, and lyricist who specializes in electronic beat-making and writing hilarious songs that mock humanity. His music, which has been described by fans and reviewers as everything from “conscious hiphop” to “next-level pop”, has been licensed to several artists, labels and films including Public Enemy, Sky Mall, and the Independent Film Channel. His viral-style YouTube videos have garnered over 60,000 views and he has also DJ’d for various clubs and parties for over 15 years.