Setting up an auditorium, whether as part of a new initiative or a remodel, requires considerable planning and conscious design. AV equipment must perfectly match the environment, room, audience, and concept, giving everyone in the room the tools to get the most out of every presentation or performance.
Auditorium design involves understanding your space, what’s in that space, who is in that space, and what the equipment is being used for. The following guide will give you some idea of how to measure and select auditorium equipment, but chances are, you still need help from a professional to get everything right.
Considering the Room and Its Surfaces
Choosing sound and video equipment will heavily depend on the room, its size, and its surfaces. Ideally, sound will comfortably fill the space, maintaining the same volume in every seat. In practice, this can be very difficult, because conditions such as upholstery, curtains, and carpet can absorb sound.
- Fabric or cushioned surfaces such as carpet, drapes, upholstery, etc., which might absorb sound
- Hard surfaces such as cement, wood, and metal, which will likely reflect sound
- Pillars, dividers, and desks which may block sight or sound
A small auditorium with absorbent surfaces, such as a small theater, may require a higher sound output than a larger auditorium with reflective surfaces such as a cement floor and wooden benches.
Audience and their Direction
Most auditoriums use permanent seating, intended to ensure the quality of sound. This means your audience will be seated in a specific pattern and sound must be directed to them, based on where and how they are sitting. In addition, your audience is likely the most significant sound absorber in the room.
- Sound must be directional, coming from the direction of the stage or speaker (no one wants to listen to someone talking from behind them)
- Large groups of people will mute sound, so people in the middle will hear a lower volume. Speakers must be positioned overhead to ensure continuous volume.
Measuring Sound Output
It’s important to measure sound output at every point where someone will sit or stand. Most audio professionals will manage this measurement for you, but you can do so yourself using an SPL meter. For the most part, this is not recommended, as you likely won’t be able to calculate anything out of the measurements that you couldn’t get by choosing a medium sound system for a medium space.
Small amphitheaters, like those managed by most organizations and educational facilities, require small speaker systems with low-mid-high frequency drivers, alongside amplifiers. Larger systems benefit from incorporating component speakers (woofer, subwoofer, tweeter) with amplifiers to better divide a full spectrum of sound across every area of the system.
Speakers use a sensitivity or efficiency rating detailing how much sound they produce per watt of power.
Decibels of sound per watt of power at 1 meter away. The lower the sensitivity, the more power you need. Producing 3 decibels of sound typically requires doubling power usage, meaning that the shift between an 87 sensitivity and 90 sensitivity speaker is a large difference.
Impedance measures resistance, typically in Ohms. 8-16 is standard, 4 is low. A higher Ohm rating means you need more power output for the same sound volume.
Power, measured in watts, directly translates to volume, based on factors including sensitivity and impedance. Driven channels are separately powered, to produce more sound per channel. Receivers vary from 50 to well over 100 watts.
Most small-to-medium amphitheaters benefit from small systems, such as a 50-watt per channel receiver with 90 decibel sensitivity.
Mixing and Equalization and Directions
Any sound system should include a mixer, equalizer, and directional microphones. Auditorium equipment must be chosen to reduce noise disturbances and to account for frequencies and acoustic properties of the room. While it’s ideal if you can re-do a ceiling to reduce acoustics, this often isn’t fully possible. Equalizers reduce feedback, reduce acoustics, and reduce reflective audio, all of which will improve the total sound quality of the auditorium.
Mixing consoles are also critical, because they “mix” sound together, bringing multiple channels into a single output of sound. Choose a mixer that meets peak requirements for device capacity (including speakers, microphones, and headphones, known as monitors) on stage, output devices, etc.
Monitors, Video Walls, and Teleprompters
Monitors and digital screens exist to aid the speaker and to offer visual aids or visual presentations to the audience.
- Teleprompters and monitors facing speakers can be useful
- Tablets may take the place of both, and offer controls for any displays or screens in the room
- Wall-screens and video walls may be a good idea if speakers frequently use visual aids or give presentations
- Screens should be sized to offer an ideal view to the person in the middle of the room, meaning they are slightly too large for people in the front and slightly too small for the people in the back.
Displays are important and necessary for most modern auditoriums, because they take the place of projectors, teleprompters, and offer opportunities for virtual and remote speakers. Should you choose to include them, you must calculate screen size based on optimal viewing distance, light, and screen size.
Hire a Sound Expert
While you could wrestle with calculations like seat sound absorption, early-to-late sound index, and early lateral energy fraction, you probably don’t want to. It’s important to understand how sound works when calculating where to place speakers and why and it’s unlikely you could simply gain the knowledge to do so, as a layman, by reading an article or watching a few videos.
In most cases, your installer will be able to provide an expert who can design solutions around the room, to ensure that sound meets the needs of the room, to calculate projection and screen size, and to ensure that auditorium equipment fits the needs of the room.
Building an auditorium entails calculating how, where, and what sound and video equipment is needed, which often requires significant calculations. You can roughly calculate what you need on your own, but you will need an expert to ensure the system truly fits.