An electromagnetic coil is an electrical conductor such as a wire in the shape of a coil. Electromagnetic coils are used in electrical engineering, in applications where electric currents interact with magnetic fields, in devices such as electric motors, generators, inductors, electromagnets, transformers, sensor coils such as in medical MRI imaging machines. Either an electric current is passed through the wire of the coil to generate a magnetic field, or conversely, an external time-varying magnetic field through the interior of the coil generates an EMF (voltage) in the conductor.
A loudspeaker is an electroacoustic transducer that converts an electrical audio signal into a corresponding sound. A speaker system, also often simply referred to as a speaker or loudspeaker, comprises one or more such speaker drivers, an enclosure, and electrical connections possibly including a crossover network. The speaker driver can be viewed as a linear motor attached to a diaphragm which couples that motor's movement to motion of air, that is, sound. An audio signal, typically from a microphone, recording, or radio broadcast, is amplified electronically to a power level capable of driving that motor in order to reproduce the sound corresponding to the original unamplified electronic signal. This is thus the opposite function to the microphone; indeed the dynamic speaker driver, by far the most common type, is a linear motor in the same basic configuration as the dynamic microphone which uses such a motor in reverse, as a generator.
A microphone, colloquially called a mic, or mike, is a transducer that converts sound into an electrical signal. Microphones are used in many applications such as telephones, hearing aids, public address systems for concert halls and public events, motion picture production, live and recorded audio engineering, sound recording, two-way radios, megaphones, and radio and television broadcasting. They are also used in computers and other electronic devices, such as mobile phones, for recording sounds, speech recognition, VoIP, and other purposes, such as ultrasonic sensors or knock sensors.
A tweeter or treble speaker is a special type of loudspeaker that is designed to produce high audio frequencies, typically up to 100 kHz. The name is derived from the high pitched sounds made by some birds (tweets), especially in contrast to the low woofs made by many dogs, after which low-frequency drivers are named (woofers).
Headphones are a pair of small loudspeaker drivers worn on or around the head over a user's ears. They are electroacoustic transducers, which convert an electrical signal to a corresponding sound. Headphones let a single user listen to an audio source privately, in contrast to a loudspeaker, which emits sound into the open air for anyone nearby to hear. Headphones are also known as earphones or, colloquially, cans. Circumaural and supra-aural headphones use a band over the top of the head to hold the drivers in place. Another type, known as earbuds or earpieces, consists of individual units that plug into the user's ear canal. A third type are bone conduction headphones, which typically wrap around the back of the head and rest in front of the ear canal, leaving the ear canal open. In the context of telecommunication, a headset is a combination of a headphone and microphone.
A balun is an electrical device that allows balanced and unbalanced lines to be interfaced without disturbing the impedance arrangement of either line. A balun can take many forms and may include devices that also transform impedances but need not do so. Sometimes, in the case of transformer baluns, they use magnetic coupling but need not do so. Common-mode chokes are also used as baluns and work by eliminating, rather than rejecting, common mode signals.
A spark-gap transmitter is an obsolete type of radio transmitter which generates radio waves by means of an electric spark. Spark-gap transmitters were the first type of radio transmitter, and were the main type used during the wireless telegraphy or "spark" era, the first three decades of radio, from 1887 to the end of World War I. German physicist Heinrich Hertz built the first experimental spark-gap transmitters in 1887, with which he proved the existence of radio waves and studied their properties.
A pickup is a transducer that captures or senses mechanical vibrations produced by musical instruments, particularly stringed instruments such as the electric guitar, and converts these to an electrical signal that is amplified using an instrument amplifier to produce musical sounds through a loudspeaker in a speaker enclosure. The signal from a pickup can also be recorded directly.
The chief electrical characteristic of a dynamic loudspeaker's driver is its electrical impedance as a function of frequency. It can be visualized by plotting it as a graph, called the impedance curve.
Georg Neumann GmbH is a manufacturer of professional recording microphones. It was founded by Georg Neumann and Erich Rickmann in 1928 and is based in Berlin, Germany. Its best-known products are condenser microphones for recording, broadcast, and live music production purposes. For several decades Neumann was also a leading manufacturer of cutting lathes for phonograph disks, and even ventured into the field of mixing desks. Today Neumann also manufactures preamplifiers, studio monitors, headphones, and audio interfaces.
An electret microphone is a microphone whose diaphragm forms a capacitor that incorporates an electret. The electret's permanent electric dipole provides a constant charge Q on the capacitor. Sound waves move the diaphragm, changing the capacitance C, which produces a corresponding voltage change across the capacitor of ΔV = Q/ΔC. The electret's constant charge eliminates the need for the polarizing power supply required for non-electret condenser microphones, though a preamplifier is typically incorporated to boost the audio voltage signal.
The RCA Type 77-DX microphone is a poly-directional ribbon microphone, or pressure-gradient microphone, introduced by the RCA Corporation in 1954. It was preceded by the Type 77-D introduced in 1948. Its popularity and classic design has resulted in the 77-DX becoming an iconic microphone, used by broadcasters and media personalities such as Edward R. Murrow, David Letterman and Larry King.
AKG Acoustics is an acoustics engineering and manufacturing company. It was founded in 1947 by Rudolf Görike and Ernest Plass in Vienna, Austria. It is a part of Harman International Industries, a subsidiary of Samsung Electronics since 2017.
A variety of types of electrical transformer are made for different purposes. Despite their design differences, the various types employ the same basic principle as discovered in 1831 by Michael Faraday, and share several key functional parts.
The proximity effect in audio is an increase in bass or low frequency response when a sound source is close to a directional or cardioid microphone. Proximity effect is a change in the frequency response of a directional pattern microphone that results in an emphasis on lower frequencies. It is caused by the use of ports to create directional polar pickup patterns, so omni-directional microphones do not exhibit the effect
The moving iron speaker was the earliest type of electric loudspeaker. They are still used today in some miniature speakers where small size and low cost are more important than sound quality. A moving iron speaker consists of a ferrous-metal diaphragm or reed, a permanent magnet and a coil of insulated wire. The coil is wound around the permanent magnet to form a solenoid. When an audio signal is applied to the coil, the strength of the magnetic field varies, and the springy diaphragm or reed moves in response to the varying force on it. The moving iron loudspeaker Bell telephone receiver was of this form. Large units had a paper cone attached to a ferrous metal reed.
The BBC-Marconi Type A is a ribbon microphone that was produced by the BBC and Marconi between 1934 and 1959. The microphone has been described as "iconic" and a symbol of the BBC.
A valve microphone is a condenser microphone which uses a valve amplifier rather than a transistor circuit.
The Electro-Voice RE20 is an American professional cardioid dynamic microphone, commonly used in broadcasting applications since 1968. Designed by Electro-Voice using the company's patented Variable-D technology and a large-diaphragm element, it has been described as an industry standard "iconic" microphone for its natural sound and its wide usage in radio, television and recording studios. In 2015, the RE20 was inducted into the TEC Awards Technology Hall of Fame.
The RCA Type 44 microphone is a bi-directional ribbon microphone, or pressure-gradient microphone, first introduced by the RCA Corporation in 1931.
