Live Sound 101: Event Sound System Design and Setup

If you have been tasked with setting up a sound system for a 300- to 500-person event, there are various elements, both strategic and technological, to consider. Audio tech people have never had such a broad range of sound reinforcement equipment and techniques at their disposal. The choices of technology and products available can be overwhelming, so let’s talk about some of the options.

Speaker Selection

Your choice of speakers should be based on coverage requirements and the size of the venue. There are some things to consider regarding the shape of the room and how the speakers will interact with boundaries, such as the walls, the ceiling, and the floor.

You want to get the best speakers your budget will allow. Start by figuring out what you can afford and then determine what sounds best to you within that price range. Always listen to the speakers before buying, as not all of them are made equal. When choosing a speaker, you’ll want to consult the specification sheet, which should be readily available from most reputable manufacturers. The most important specs to know are the frequency response, SPL output, and dispersion. If you are using passive speakers, then you’ll need to know the wattage and impedance (ohms resistance).

A full-range speaker with a frequency response of 60 Hz to 18 kHz may be fine for many genres of music, such as country, folk, or folk-rock, where the kick drum and bass don’t need additional punch. For rock, metal, pop, hip hop, EDM, etc., you will want a subwoofer. A subwoofer extends the frequency response down to 45 Hz or lower and will allow the full-range speakers additional headroom and increased output. 

The sound pressure level of a speaker will determine how loud a speaker is at a given distance (typically 1 meter). Most spec sheets will show Peak and Continuous outputs. The peak is how loud the speaker is on loud transients, while continuous output is the average loudness. This is a good indication of how the speaker performs, dynamically. Sound pressure levels (SPL) will attenuate by 6 dB with the doubling of the distance. If a speaker were capable of 135 dB at 1m, then 2m would have an SPL of 129 dB. By doubling the distance to 4m, the speaker would output 123 dB and so on. Another consideration is that doubling up on the speakers will result in a +3 dB increase. If a speaker has a peak output of 135, by adding another speaker the output would increase to 138 dB.

Dispersion is the way the sound is projected horizontally and vertically from the speaker. This is incredibly useful for determining the placement of speakers, as you can direct the sound away from boundaries, such as walls and ceilings. For instance, a speaker with a 60-degree horizontal dispersion might work well for a narrow room, while adding an additional speaker could increase the dispersion to 120. The goal is to offer coverage to the entire audience, while directing the sound off the walls. Many speakers are designed to couple by utilizing a trapezoidal enclosure, versus a square or rectangular enclosure. The trapezoidal design allows for easy placement of the speakers, as they can be placed together in tight-knit group or array, which allows for coupling with reduced interference between speakers.

The vertical dispersion will determine how high the full-range tops will need to be to provide proper sound coverage for the audience. There are many ways to configure a system, in terms of height and whether ground-stacking, speaker stands, scaffolding, or trussing should be implemented as a way to get the speaker high enough to offer extended coverage. The higher the speaker, the farther the sound will travel. If it is too high, there will be a loss of impact in the front. Not high enough may result in the sound being uncomfortably loud for the front row.

For our purposes, I suggest setting the tops at shoulder to head level, about 5 to 6 feet from the floor. If you are utilizing subwoofers, you might try ground-stacking the tops on top of the subs. Many speakers offer pole mounts for use with speaker stands. This is the simplest way to get proper height, especially if you don’t have multiple subs to create a ground stack. At the very least, you want your high-frequency driver above the heads of the people in the audience.

Active versus Passive

There are pros and cons to both active and passive speaker designs. Active speakers are the easiest to deploy with built-in amplifiers that are matched to the speaker components (woofers, mid-range, and tweeters—typically compression drivers). They also feature crossovers, which isolate and route frequency ranges to each component, and built-in limiters for protecting the drivers. A three-way active speaker will have two or more built-in crossovers, which isolate the high, mid, and low frequencies. The advantage of active speakers is the ease of setup and operation. They only require a line level input and you won’t have to use separate amplifiers to power them.

Passive speakers require amplification, speaker cables, and may require an outboard crossover and other signal processing. Some passive speakers will utilize an internal crossover network, which functions much like the active speakers. Other speakers are designed to be bi-amped or tri-amped, which can be a benefit, as this allows greater control over the speaker components, but also requires a separate amplifier for each component of the speaker. If you decide to go with a passive speaker design, you’ll need to look at the specification sheet provided by the manufacturer to determine the correct amplifier(s).

The input range of a speaker is typically given in continuous, program, and peak wattage measurements. You will most likely see the continuous output and either program or peak. The general rule is a doubling of the continuous results in program, while doubling the program will give the peak performance. For instance, let’s say we have a 4-ohm speaker that requires 600 watts of continuous output, a program output of 1,200 watts, and a peak output of 2,400 watts.

The question that many people ask, is how much power do I need? Do I really need a 2,400-watt amplifier to power this speaker? The answer depends on your total required SPL output. Looking at the speaker’s specifications. We see it offers a continuous SPL output value of 128 dB and a peak SPL output of 134 dB. Let’s say you want an SPL output of 105 dB at 50' from the speaker. Remember every doubling of the distance, lowers the SPL by 6 dB. The speaker’s program output requirement is 131 dB at 1m. 16 meters or 52.8 feet would offer an SPL of 107 dB, therefore you can safely use a 1,200W power amplifier to achieve your target. If we doubled the program output of 1,200 watts to 2,400 watts, you would gain an additional 3 dB. My opinion would be to purchase more power than needed to maintain headroom. This, of course, comes down to budget, because some speakers may require up to 11,000 watts peak output, which would push you into another class of amplification with a much higher price tag.

Another consideration is the impedance or ohms resistance for the speaker. You will need to consult the amplifier specifications to determine how much power an amplifier is able to produce at a given impedance. Most manufacturers will boast the highest output of both channels at the lowest resistance. When matching your amplifier to your speaker, it’s important to consider the ohms rating and wattage. For instance, an amplifier that is rated at 4,000 watts (2,000 watts per channel) at 2 ohms will realistically deliver 1,400 watts at 4 ohms and 850 watts at 8 ohms. Our example speaker has a 4 ohm impedance, which can easily be powered by our 4,000-watt amplifier.

Some amplifier manufacturers will indicate power draws as 1/8 power, 1/3 power, and full power. 1/8 power delivers the amplified signal below the built-in clip limiters, while 1/3 power will have the clip limiters occasionally flashing. Full power will have the limiters in constant activity. When engaging the clip limiters, you are actually rounding off the audio signal to prevent distortion, but the signal of the audio will be compromised. I prefer to run the amplifiers at 1/8 power, which will give plenty of headroom without squaring off the waveforms. You may also use a higher-rated amplifier at 1/8 power without fear of damaging your speakers. Remember, the quickest way to blow a speaker is to underpower it.

Subwoofers also come in active and passive options with the same pros and cons. There are many different designs that can offer outstanding results. The best bang-for-the-buck I recommend is a Yorkville ES18P. It is a self-powered, single 18" rear-horn loaded design with a tremendous output, rivaling or surpassing most double 18" designs.

Depending on your setup and how many subs you have, you will have more consistent results by placing all the subs together. Placing two subs together will yield a 3 dB gain in SPL and they will couple without interference. A stereo sub configuration may create null points in the room where certain frequencies cancel each other out. Other tricks to maximize bass are to place the subs near a wall or corner, as each of the boundaries will reinforce the sound and help load the room. My favorite configuration is to center-cluster four subs together (2 wide x 2 tall).

Speaker Processors

Regardless of whether you are using active speakers or passive speakers with an amplifier, you should invest in a speaker processor. In my opinion, it is the most important piece of gear and will save you time, money, and headaches. A speaker processor combines a number of processors into a rackmount signal processor. You will find gain, EQ, delay, crossovers, and limiting for both input and output. A typical processor might have a stereo input and six outputs. The inputs will feature a 6- to 8-band parametric EQ and/or a graphic EQ, as well as a system delay. Each output on your processor will offer gain, a 4-band parametric EQ, a delay for time-aligning speaker components in a bi-amp or tri-amp application, or a full-range speaker and a subwoofer.

You will also find digital crossovers featuring Bessel, Butterworth, and Linkwitz-Riley band-pass filters. Each crossover offers a high-frequency and low-frequency setting with selectable filter types. For tops, I typically set the HPF to 96 Hz on a 24 dB per octave Linkwitz-Riley filter and the LPF to off. For subs, I set the LPF to 96 Hz on a 24 dB per octave Link-Riley filter and the HPF to 30 Hz on a 48 dB Butterworth filter. The major focus is the crossover between the LPF of the sub and the HPF of the top. A 24-dB-per-octave Link-Riley filter keeps the frequency response flat where both the subwoofer and top are crossing over.

Note: A speaker processor delay is not a digital delay effect, as it is intended to literally delay a signal by a set amount and does not offer a “wet/dry” setting. If a manufacturer offers time delay settings for your speakers, you can use those to time align the tops and subs. For example, if a subwoofer has a 3 ms delay, then adjusting the tops to match the inherent delay of the subs will provide a coherent and phase-accurate wave front. If you don’t have the specs, you can invest in a measurement system like SMAART. For those on a budget (and in possession of an iPhone or iPad), you can purchase the AudioTools app by Studio Six Digital, which can help you measure and calibrate your sound system.

Analog Mixers versus Digital Mixers

Analog mixers are the mainstay of any audio system, and range in price and features. There are some diehard analog enthusiasts who will not move to a digital mixing board, as they believe the analog components sound superior to digital. If you are mixing a live band, you will want some additional signal processors to shape the sound of each instrument. Most analog mixing consoles will offer a built-in four band parametric EQ, which helps balance the tonal sound and carves out space for each instrument in the mix. It is rare to find analog consoles with built-in dynamics available on every channel. Therefore, an all-analog setup will require several racks of gear to accommodate the additional signal processing, such as compression and gates for each channel.

Another aspect to consider is the use of wedge monitors or stage monitors. These are speakers that are typically on the floor and angled up toward the performers, offering a dedicated mix, which allows the musicians to hear themselves on stage. Feedback can become a problem, so the use of graphic EQs will be needed to remove the frequencies that are feeding back. Add in additional signal processors like multi-effects, delays, and reverbs and you can see the analog setup may sound better, but will cost more money with the additional signal processing, plus there are additional racks, cabling, troubleshooting, and maintenance involved.

Digital mixers have made some considerable advances in recent years regarding the quality of the sound, and pricing that is comparable to many moderately priced analog consoles. Digital mixers offer the best solution for any event with a large channel count because each channel is packed with a four-band EQ, compression, and gating. Additionally, each output features graphic EQ for ringing out monitors. Many mixers feature internal effects with up to eight insert slots for use with internal sends. You can still use your favorite outboard gear, but the digital platform reduces the amount of gear substantially. Another benefit of the digital mixer is the wireless control options. Many mixers offer iOS and Android control apps.

If the FOH position is in a less than desirable place, the engineer can move about the room to make informed adjustments based on the audience’s perspective. This also allows the engineer to tweak monitors from the stage, while standing next to the musicians. Many mixer platforms will allow multiple device setups in which band members may adjust their own mix in real time, allowing the FOH engineer to focus on the main mix. Other features now incorporated in the digital platform include spectral analysis and a real-time analyzer (RTA) for making adjustments to monitors or to the entire mix. However, I still recommend a dedicated speaker processor for tuning the sound system.

Stage Snakes and Stage Boxes

A stage box or multi-channel snake is highly beneficial for reducing clutter on the stage. Some larger stage setups use a splitter that splits the signal from all the sound sources on stage between FOH and monitors. Most mid-level bands typically don’t have a dedicated monitor engineer, so the FOH engineer will perform both main mixing and monitor duties. With an analog setup, you’d be working with a 16- to 24-channel audio snake with a cable run of 100+ feet. A drum kit may have 8 to 12 microphones set up to capture the sound, so a dedicated sub-snake allows for shorter mic-cable runs and a much cleaner stage setup.

Utilizing stage sub-snakes before going to the main stage snake will keep the cable clutter on stage to a minimum. Many digital mixers offer digital stage boxes that function like an analog stage snake, only instead of a 16- to 24-pair multi-channel cable, the digital snake will use a single CAT5 cable to connect to the mixer in the FOH position. This cuts down considerably on the weight and setup time of the entire system.

Microphones

For musicians to be heard, microphones are used to capture vocals, guitar amplifiers, and drums. The mainstay of live music is the use of dynamic microphones. There are many microphone manufacturers, but the favorite of most clubs is still the Shure SM58 for vocals and SM57 for instruments. They have proven their value over time by sounding good and being incredibly rugged. They can literally take a beating and still function. If there is the budget and desire for wireless microphones, I highly recommend the Shure GLXD24R+ or QLXD series digital microphones. The GLXD is an affordable option with a clean, clear sound without any artifacts, a simple setup, and a built-in charger in the receiver.

In-Ear Monitors

Many bands prefer to forgo the use of stage monitors and opt for in-ear-monitors (IEM). I’ve used the entry-level PSM300 Shure Personal Monitoring System for years and have had excellent results. With a digital mixer, the setup and operation is even simpler, resulting in very happy musicians who are able to set their own monitor mix—and without excessive stage volume.

In Conclusion

As you can see, there are many directions one can choose when setting up a sound system for your band or event: analog mixers versus digital mixers; passive speakers and subs versus active designs. Each has its pros and cons. The most important thing is to use your ears when making decisions. Always listen to speakers before purchasing and, if possible, demo speakers and subs together, especially if you are using different brands. I can’t recommend enough the importance of having a dedicated speaker processor for any system, regardless of size or budget.