A comprehensive audio equipment list is essential for event planners and musicians. This article will cover everything from basic home studios to professional sound systems.
Microphones with varying polar patterns, to capture sounds in different directions. Also, acoustic foam to absorb sound waves and tame standing waves. And cables to connect microphones and instruments to your mixing desk.
Speakers
Speakers are electroacoustic transducers that convert an electrical audio signal into acoustic waves to produce sound. They are found in many electronic devices, including radios, televisions, portable audio players and personal computers (computer speakers), headphones, earphones and public address systems. Larger speakers are used for home hi-fi systems (stereos), electronic musical instruments, and sound reinforcement in theaters and concert halls. The term speaker may also be applied to individual drivers, or to complete speaker systems that include an enclosure and one or more drivers.
The most common type of speaker is a dynamic speaker, which uses a linear motor with a diaphragm to translate an electric current into motion of air that produces sound. When a variation in electric current from an amplifier passes through the voice coil, it creates a variable electromagnetic field that interacts with the magnetic system of the driver and causes it to move axially across the diaphragm. This motion causes the air to vibrate in response to the original unamplified audio signal.
Frequency response refers to the range of audio frequencies a speaker can reproduce with low distortion and high accuracy. A speaker may be rated as full range, or specialized for particular audio frequency ranges such as tweeters, mid-range drivers or woofers. In two-way or three-way speaker systems that have drivers for different frequencies, there is a small piece of passive electronics called a crossover to combine and filter the different audio signals to each speaker.
Other measurements of speaker performance include amplitude and phase characteristics over the frequency range; impulse response under one or more conditions (e.g., square waves or sine wave bursts); directivity (horizontal, vertical, spherical, etc.); harmonic and intermodulation distortion vs. frequency; stored energy; and impedance vs. frequency.
Microphones
Whether you’re on set at a movie studio or recording music in the comfort of your home, microphones play a big part in the quality of your audio. Microphones are electroacoustic transducers that convert acoustic sound pressure into an electrical signal.
There are many different types of microphones, but the two most common are dynamic and condenser microphones. Dynamic microphones are robust and able to handle high sound pressure levels, making them perfect for live performances or capturing loud instruments like drums. Condenser microphones are more sensitive and offer a wide frequency response, making them ideal for recording vocals or instruments.
When sound reaches the microphone, it vibrates the diaphragm which in turn creates an electrical signal. This electrical signal is transmitted through the microphone element and sent to an audio amplifier where it is converted into a musical output.
Microphones come in a variety of styles and prices. They can be categorized by their transducer principle, polar patterns, intended use and even the design of their body.
Polar patterns describe how well the microphone responds to sounds coming from different directions. Having the right mic pointed in the right direction can make or break your performance.
A basic microphone consists of a capsule with a diaphragm that is placed in front of a closed chamber. The diaphragm is acoustically coupled to a wire coil, called the voice coil which is suspended over a permanent magnet. When the voice coil vibrates due to acoustic sound pressure, it causes a change in airflow around the microphone and this generates an electric current between the two metal plates that are spaced slightly apart. These metal plates act as capacitors and create an electrical signal when they vibrate.
Amplifiers
An electronic amplifier takes tiny electrical signals that contain musical frequencies and amplitudes and increases their strength. This makes them strong enough to send back and forth through speakers, creating air pressure variations that we hear as music. An amplifier can be a separate piece of equipment, or it may be built into other devices. It can be used for many kinds of signals, not just audio: RF (radio frequency) amplifiers can boost electronic signals that range from radio broadcasts to high-definition TV. The same principles apply to servo amplifiers and instrumentation amplifiers that deal with very low-frequency signals like direct current.
The key thing to remember about an amplifier is that it doesn’t just boost an electric current: it also faithfully reproduces the quality of the input signal. This isn’t easy: electronic signals are constantly changing, with a range of both frequency and amplitude, or in other words the height of the ups and downs. Audio amplifiers amplify frequencies in the sound range that young, keen human ears can hear; RF amplifiers boost a wide variety of signals at different frequencies; and video or servo amps can work with very low-frequency signals up to 300 GHz.
All amplifiers have gain, which is a multiplier that relates the magnitude of some property of the output to the magnitude of the property of the input signal. Amps can be categorized in various ways, according to their circuit configuration and mode of operation: class A amplifiers have a very linear output but low efficiency; class B amplifiers have higher efficiency but less-linear output; and so on. They can also be rated in terms of power, which is how much energy they consume (and hence how loud they can play). Some amplifiers are even more specific in what kind of input signals they will accept.
Mixers
The heart of any PA system, an audio mixer is where many of the most important processing decisions – gain structure, channel EQ and mix – are made. They vary in size from a couple of variable resistors and knobs, up to the huge consoles used at the largest multi-performance events. Digital mixers are now widely available, and offer a number of features that make them a valuable addition to any PA setup.
The channel gain control adjusts the level of the signal arriving at that channel, so that it is suitable for the mixer’s circuitry and the amplifiers and speakers that are attached to it. It is a process that involves compression and distortion, and the goal is to bring the levels up to within a safe working range. If levels are too high, the amplifiers and loudspeakers may be driven into limiting or distortion, with consequences that can range from loss of clarity to sound-baffling and even failure.
A GROUP bus (or Master) allows multiple channels to be combined and controlled by one fader, for example grouping together all the microphones for a drum kit. This is useful because a single raise or lower of the GROUP fader will change the volume for all channels in that group, and allows more precise control than would be possible with individual channel faders.
Most mixers also have AUX sends (or Aux) which can be routed to different locations such as on-stage monitors and external effects units. These ‘auxiliary’ sends often have pre-fade and post-fade options to enable the engineer to select which part of the mix is sent to the headphones or monitor wedges.