Chapter 2 Mics and Speakers Flashcards
Identify these music technology words.
Amplifier
A device which increases the amplitude of a signal by adding energy to it. In acoustic terms, this means increasing the volume of the sound. Signals must be amplified so that they will have enough energy to move a speaker cone back and forth, creating sound waves from sounds represented varying voltage. Amplifiers can be built into speakers or can be discreet components. A simple example of an amplifier is the tuner unit of most home stereo systems.
Diaphragm
A thin, internal part of a microphone which is moved slightly when sound waves impact it. This is the part of a microphone which actually gathers sound waves from the air. Diaphragms are usually made of a metal alloy such as neodymium in cheaper microphones, while more expensive models use foils made from precious metals such as gold.
Line level
A signal is said to be line level when it is put out at a level of -10 dBu. The outputs you find on the back of your CD player operate at this level, as do most professional synthesizers. Some higher- level pro equipment operates at +4 dBu. Examples of signals which are not line level include the raw output of microphones, electric guitars with passive circuitry, and the outputs of amplifiers. (Amplifiers add so much energy to a signal that their output is typically far above line level.)
Mic Cable
A cord with 3 conductors which has a male XLR connector on one end, and a female XLR connector on the other end. Mic cables are typically used to connect mics to mic preamps, but can be in other places as well.
Microphone
(mic) A transducer which is capable of producing a tiny voltage which changes constantly in response to sound waves which impact its diaphragm. The simplest microphones accomplish this through the use of an inductance coil attached to the diaphragm, while other, more expensive (and sensitive) de- signs utilize a metal diaphragm as a charged capacitance plate. The later design actually requires power from the mixer called phantom power. Phantom power is typically +48 VDC, but many mics can operate from a standard 9 volt battery.
PA system
(Public Address System) A system which includes a microphone, a mic preamp, an amplifier and one or more speakers used to amplify the sound of someone’s voice. PA systems are common at large sporting events, churches, and larger stores.
Preamplifier
(preamp, mic preamp, mic pre) A device used to add energy to the output of a microphone. (Preamps can be used on other devices such as guitars, phonographs, etc., but this chapter deals exclusively with their use with microphones.) Preamplifiers are commonly found integrated into mixers, where their presence can be easily detected by looking for XLR connectors and gain knobs on the mixer’s channels. Preamps are also made as discreet units, usually packaged in rack mountable boxes. While most fall into the $100-500 price range per channel, specialized or esoteric mic pres can easily run into several thousand dollars per channel.
Speaker
A transducer used to convert electronic representations of sound waves into sound waves mov- ing through the air. Simple designs incorporate an electromagnet which moves a paper cone housed in a tuned wooden enclosure to disturb air molecules, thus creating sound waves. Some more sophisticated designs utilize both a moving coil design with a piezo driver element. The moving coil produces lower frequency sounds while the piezo ‘driver’ produces higher frequencies.
XLR Connector
(Exchanging Line Receptacle Connector.) A circular 3-pin connector which carries two copies of a signal, each 180 degrees out of phase. At the receiving end of a cable, a summing stage cancels any noise the cable might have picked up. This balanced system allows much longer cable runs without fear of induced hum or other noise. Almost all microphones have XLR connectors, and many high-end audio devices use them as well.
