Classification of some audio amplifiers
Below you will find descriptions of individual types of speakers and microphones and their division according to the principle of operation.
Separation of loudspeakers according to the principle of operation.
Magnetoelectric (dynamic) - a conductor (magnetic coil), through which an electric current flows, is placed in the magnetic field of a magnet. The interaction of the magnet and the conductor with current causes the movement of the conductor to which the membrane is attached. The coil is rigidly connected to the diaphragm, and all of this is suspended in such a way as to ensure axial movement of the coil in the magnet gap without friction against the magnet.
electromagnetic – The acoustic frequency current flow creates an alternating magnetic field. It magnetizes a ferromagnetic core connected to the diaphragm, and the attraction and repulsion of the core causes the diaphragm to vibrate.
Electrostatic - an electrified membrane made of thin foil - having a deposited metal layer on one or both sides or being an electret - is affected by two perforated electrodes located on both sides of the foil (at one electrode, the signal phase is turned 180 degrees with respect to the other), as a result of which The film vibrates in time with the signal.
magnetostrictive - the magnetic field causes a change in the dimensions of the ferromagnetic material (magnetostrictive phenomenon). Due to the high natural frequencies of ferromagnetic elements, this type of loudspeaker is used to generate ultrasound.
Piezoelectric – the electric field causes a change in the dimensions of the piezoelectric material; used in tweeters and ultrasonic devices.
Ionic (membraneless) - a type of diaphragmless speaker in which the diaphragm function is performed by an electric arc that produces plasma.
Types of microphones
Acid - a needle connected to the diaphragm moves in dilute acid. Contact (carbon) - the development of an acid microphone in which the acid is replaced by carbon granules that change their resistance under the pressure exerted by the membrane on the granules. Such solutions are commonly used in telephones.
Piezoelectric – a capacitor that converts an acoustic signal into a voltage signal.
Dynamic (magnetoelectric) - air vibrations created by sound waves move a thin flexible diaphragm and an associated coil placed in a strong magnetic field generated by a magnet. As a result, voltage appears on the coil terminals - an electrodynamic force, i.e. vibrations of the magnet of the coil, placed between the poles, induces an electric current in it with a frequency corresponding to the frequency of vibrations of sound waves.
Modern wireless microphone
Capacitive (electrostatic) - This type of microphone consists of two electrodes connected to a constant voltage source. One of them is motionless, and the other is a membrane that is affected by sound waves, causing it to vibrate.
Capacitive electret - a variant of a condenser microphone, in which the diaphragm or fixed lining is made of electret, i.e. dielectric with constant electric polarization.
High frequency capacitive – includes a high-frequency oscillator and a symmetrical modulator and demodulator system. The change in capacitance between the electrodes of the microphone modulates the amplitude of the RF signals, from which, after demodulation, a low-frequency (MW) signal is obtained, corresponding to changes in acoustic pressure on the diaphragm.
Laser - in this design, the laser beam is reflected from the vibrating surface and hits the photosensitive element of the receiver. The value of the signal depends on the location of the beam. Due to the high coherence of the laser beam, the membrane can be placed at a considerable distance from the beam transmitter and receiver.
Optical fiber - the light beam passing through the first optical fiber, after reflection from the center of the membrane, enters the beginning of the second optical fiber. Fluctuations in the diaphragm cause changes in light intensity, which are then converted into an electrical signal.
Microphones for wireless systems - the main difference in the design of a wireless microphone is only in a different way of signal transmission than in a wired system. Instead of a cable, a transmitter is installed in the case, or a separate module attached to the instrument or carried by the musician, and a receiver located next to the mixing console. The most commonly used transmitters operate in the FM frequency modulation system in the UHF (470-950 MHz) or VHF (170-240 MHz) bands. The receiver must be set to the same channel as the microphone.
