Sound System Design at Concerts and Festivals - 180D-FW-2023/Knowledge-Base-Wiki GitHub Wiki

Introduction

Sound system design is a critical aspect of any live concert or festival, determining how well the audience hears and experiences the performance. This technical yet creative field involves a careful blend of equipment choice, acoustic considerations, and system configuration to deliver clear and impactful sound. In this article, I will go into the essential elements of sound system design, including the components used, the software that aids in system optimization, and the process of designing a system tailored to specific event needs.

Fundamentals of Sound System Design

Sound System design has a couple major components:

Sound Wave Propagation: The basic premise of live sound involves understanding how sound waves propagate through different environments. Sound engineers need to account for factors such as distance, air absorption, wind, and temperature, which can all affect sound quality. For example, the figure below shows how sound moves faster through hot air and slower through cold air and how that can change the propagation of sound depending on the distribution of hot and cold air.

Audience Coverage: A good sound system should distribute audio to the entire audience evenly and with minimal loss of sound quality. To ensure this, sound engineers are constantly experimenting with different technologies and sound coverage patterns.

One example of innovation in sound coverage is the introduction of line array speakers. These speakers allowed sound to be distributed more evenly across a vertical plane. This innovation will be explored further in the hardware section.

Sound Pressure Levels(SPL): Sound pressure level refers to the pressure of sound relative to a reference level and is typically measured in decibels (dB). It is crucial for sound engineers to ensure that these levels are evenly distributed and, more importantly, never pass the human pain threshold of 120 dB. Failure to do so can result in “dead zones” where sound is too quiet, and “hot spots” where the sound is uncomfortably loud. Sound engineers have to do rigorous testing of speaker placement and choice to deal with this issue.

The SPL is typically measured with a sound level meter (shown above), which captures fluctuations in air pressure caused by sound waves and presents them as a decibel value. Professional sound engineers use these meters to ensure consistent and safe sound levels throughout a venue.

Time Alignment: Time alignment refers to the timing of sound emanating from multiple speakers so that the sound from each speaker arrives at a specific listening point at the same time. This is particularly important when using a combination of main speakers and delay towers or when integrating subwoofers with full-range speaker systems. Time alignment can be adjusted by physically moving speakers or by using digital signal processors (DSPs) to delay the signal to certain speakers.

_If two speakers are placed in different locations with respect to the listener as shown in the figure, the time delay must be considered or the listener will hear two different sounds. _

Phase Alignment: Phase alignment ensures that the sound waves from different speakers are in phase, meaning the peaks and troughs of the sound waves match up. When two sound waves are in phase, they reinforce each other; when they are out of phase, they can cancel each other out, especially at low frequencies where the wavelength of sound is significant compared to the distances between speakers.

Feedback Management: Feedback occurs in a sound system when a microphone picks up sound from the speaker it is feeding into and re-amplifies it, creating a loop. The result is often a loud, screeching noise that can be disturbing to the audience and damaging to the sound system. Managing feedback is a critical aspect of sound system design and operation.

Hardware in Sound System Design The hardware in sound systems is a multifaceted field that plays a large role in ensuring sound is efficiently and properly delivered to large crowds. Each piece of hardware has a lot of research and thought put into it.

Microphones come in various forms, each tailored to specific tasks within a sound environment. Dynamic microphones stand robust in high-SPL (Sound Pressure Level) situations typical of live concerts. Condenser microphones, known for their sensitivity and broader frequency response, require an additional power source, commonly phantom power, to operate. For a touch of warmth in the audio, ribbon microphones are occasionally employed, especially in environments where the intricacies of sound are celebrated, like studio recordings.

The mixing console acts as the central hub for channeling and refining audio signals. Analog mixers offer a tangible, hands-on approach with knobs and faders for direct manipulation of sound. Their digital counterparts, on the other hand, bring advanced capabilities such as digital signal processing, memory recall for different setups, and even remote control options which are indispensable in managing the complex soundscapes of modern performances.

Loudspeakers translate electrical signals back into the auditory experience, with point source speakers radiating sound from a singular origin, while line arrays distribute the sound through multiple elements arranged vertically, offering a more even coverage, especially over longer distances. Subwoofers fill the gap in low-frequency reproduction, ensuring that the bass is felt as much as it is heard.

Amplifiers and signal processors form the underpinnings of sound reinforcement. Power amplifiers are the workhorses that boost audio signals to levels capable of driving loudspeakers. Equalizers meticulously adjust frequency components, compressors manage the dynamics, and effects processors embed depth and ambiance through reverb, delay, or modulation effects.

Cables and connectors are the veins and arteries of sound system design, carrying the lifeblood of audio from one component to another. XLR cables are commonly used for balanced audio signals, particularly microphones, due to their ability to minimize noise over long cable runs. SpeakON connectors ensure a secure and robust connection for loudspeakers, while quarter-inch TRS and TS cables cater to line-level and instrument signals.

Monitoring systems like in-ear monitors and stage monitors are essential for performers. In-ear monitors provide a clear mix of the sound directly to the artists' ears, reducing stage volume and the risk of feedback. Stage monitors, although more traditional, serve a similar purpose but are placed strategically on stage to direct sound toward the performers.

Software

The software complements the hardware in a sound system by offering tools for configuration, control, and optimization. Digital Audio Workstations (DAWs) such as Pro Tools, Logic Pro, and Ableton Live, are crucial in music production for recording, mixing, and mastering. Live performance software like MainStage can manipulate sounds in real-time during concerts.

For the acoustic planning and setup of a venue, simulation and modeling software like EASE and MAPP XT are invaluable. They allow designers to anticipate how sound systems will behave in a space before any physical setup begins. Loudspeaker management systems, including Lake Controller or BSS Soundweb London, give audio engineers fine control over speaker processing elements like crossovers, EQ, and dynamic processing.

When tuning and troubleshooting live systems, Real-Time Analysis (RTA) tools are essential for visualizing the audio spectrum and identifying problematic frequencies. Integrated within digital mixers or standalone units, Digital Signal Processing (DSP) platforms are harnessed for sophisticated signal processing tasks, such as feedback suppression and room equalization.

Amplifier control and monitoring software are becoming standard for modern amplifiers, facilitating adjustments and diagnostics over network connections. This capability is particularly useful in large venues or festivals where the sound system is sprawling and complex.

Managing frequencies and monitoring battery levels and gain for wireless microphones and in-ear monitors is also streamlined by specialized software, which is increasingly critical in the age of wireless audio systems. Virtual soundcheck capabilities allow engineers to play back previously recorded material through the live sound system to set up and adjust the system without the performers being present.

Automation and control software systems like Q-SYS and Crestron integrate audio processing, playback, and system control for sophisticated audio setups, essential in large venue and event management.

Software's role in sound system design is vital for the precise control and creative manipulation of audio. With the growing integration of digital technologies in sound equipment, familiarity with these software tools is essential for modern sound system designers to deliver an impeccable auditory experience.