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Entries found for search: mag

anti-imaging filter : See reconstruction filter.

commag : A technical term for composite magnetic print.

electro-magnetic (EM) : The name for interactions between electrical and magnetic phenomena. The science of electromagnetics deals with the application of electrical principles and apparatus to magnetic phenomena. Transformers, antennŠ, and phonograph cartridges are electromagneticelectro-magnetic devices. Longer explanation: There are four known forces operating in the universe: strong and weak nuclear forces, gravity, and electromagnetism, the latter two being the two manifestations of electromagneticelectro-magnetic force. These are mutually affective, i.e., a magnetic field can influence an electric field and vice versa as an electromagneticelectro-magnetic wave consists of both an electric field and a related perpendicular magnetic field. The electromagneticelectro-magnetic spectrum consists of (in order of increasing frequency) radio waves, microwaves, infrared light (heat), visible light, UV light, X-rays and gamma rays. All electromagneticelectro-magnetic waves propagate at the same speed, the speed of light.

electro-magnetic compatibility : Audio equipment that is designed to be immune to EMI is said to be electro-magnetically compatible. Shielding is one EMI technique, as is line-filtering, etc.

electro-magnetic pick-up : See piezo pick-up, DI.

magnetometer : A device for measuring magnetism and magnetic fields. Useful for testing whether or not tape heads need to be degaussed, and also for verifying the magnetic fields generated by unshielded speakers.

image : (1) The apparent relative placement of individual sound sources, as imagined by a listener of recorded audio, created during the recording and mixing processes, as well as by the final format of the media, e.g., stereo, surround-sound. See imaging(1), Haas effect. (2) See imaging(2).

image shift : In multichannelstereo sound reproduction, a change in the apparent left-to-right position from which a particular soundvoice seems to emanate.

imaging : (1) The ability to localize the individual instruments, voices, or other sound sources when listening to a stereophonic recording is called imaging. Accurate imaging with two channels is almost impossible, requiring both channels to have identical gain and frequency response, the two loudspeakers to be within 1dB of each other in frequency response and the phase must be identical. In addition, the listener must be precisely between the two speakers. The lack of accurate imaging with traditional, two-channel stereo has lead to three-channel (LCR) and higher-channel audio recording and reproduction in an attempt to improve the listening experience. Contrast with stereo spread. (2) The resulting output of a D/A converter is a stair-step waveform which contains a great deal of high-frequency distortion. To reconstruct a smooth replica of the original signal, the stair-step is passed through a steep lowpass filter called an anti-imaging, or reconstruction filter. See quantization error.

mag : Shorthand for sprocketed magnetic film. Film that contains only sound, but no picture.

mag dubber : A type of sprocketed tape recorder/playback machine device that reproduces one or more audio tracks onto the magnetic area of magnetic film which has a magnetic stripe. A playback-only machine for sprocketed magnetic film, reproducing one or more tracks of sound onto the magnetic area on the film stock. Some mag dubbers which are equipped with dual sets of sprockets can reproduce more than one size of magnetic film, e.g., 16mm and 35mm. See mag-optical print.

Magnasync/Magnatech : Two brands of mag dubber sprocketed tape recorders or playback machines. They can be used to transfer a sound source onto magnetic film. These brand names are also used generically to indicate any sprocketed tape recorder or playback unit. See dubberr.

magnetic distortion : A type of distortion in dynamic loudspeakers caused by nonlinearities in the interaction between the magnetic field in the gap and the voice coil.

magnetic film : AudioVideo recording tape manufactured using a base of the same physical film stocks, e.g., 16mm, 35mm, etc., and which contains a magnetic area running longitudinally down the film for the recording of an audio track or tracks. Magnetic film is 3-5 mils thick, so that the same length of film and magnetic film will be of equal diameters when wound on reels. Full-coat magnetic film has magnetic oxide applied across its entire width. Striped magnetic film can have one or more thin stripes of oxide applied longitudinally on the film base. There is usually one (wide) stripe containing a single track of audio (in the same size and location as track-one of a 3-track), while another (smaller) stripe is placed on the opposite side to make the film pack evenly when wound together, usually known as a balance stripe. The balance stripe is sometimes used to record timecode from 1/4 inch or DAT timecoded production masters. Also called mag. Not used since the advent of synchronized audio multitrack recording. See film soundtrack.

magnetic recording tape : Most magnetic tapes have a mylar or polyester base with a thin coat of magnetic material, usually gamma ferric oxide or chromium dioxide, but newer tapes are double-layered which combine the good low-frequency response of ferric oxide and good high-frequency response and low noise of chromium dioxide; the oxide is cured onto the base and the tape is calandered. The metal particles have a random orientation in unmagnetized tape, but they are aligned into definite magnetic patterns by the magnetic field produced by the recording head. If all other factors are the same, the wider the track, the greater the S/N ratio: doubling the track width improves the S/N ratio by 3dB. Professional analog tape recorders are available with tape widths up to 2" and up to 24 tracks. There is a thin guardband of uncoated base tape between the tracks to yield improved channel separation, reducing crosstalk, and providing some tolerance for differences in head/track alignment among machines. See Barkhausen effect, back coating, MOL, bias, domain, extinction frequency, scrape-flutter filter. Magnetic tape has historically come in a number of widths and formats (all denominated in inches):

magneto-optical disk : See MO.

magnitude : The portion of the frequency response or impedance of a device that represents the amplitude is called the magnitude, as distinguished from the phase, which is the other part. Precisely, the term magnitude only applies to complex quantities, i.e., quantities characterized by both a magnitude and a phase. For noncomplex quantities, the term amplitude is used.

mag-optical print : A motion picture film that has both an optical sound track and magnetic soundtracksound tracks so it can be reproduced in conventional theaters with optical sound equipment and also in houses equipped with stereo magnetic sound.

mag stripe print : A 35mm or 70mm print with magnetic oxide stripes painted lengthwise down both sides of film, on either side of the perforations. These formats are now obsolete. See print master.

sep mag : Separate magnetic film. Terminology for a print whose audio track is on a separate roll of mag film to be run in interlock with the picture; the same as double-system.

residual magnetization : Similar to remanence, but generalized to designate the magnetism remaining in any magnetic material once the applied magnetic field is removed.

phantom image : A monophonic sound panned equally to both speakers.



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