Sunday, March 27, 2011

Electronic Terms ........ 7

Imaging - it is the speaker’s ability to localize different instruments playing simultaneously.
Impedance - dependent on frequency, it is the AC equivalent of resistance in a DC circuit.
Inductance (L) - the capability of a coil to store energy in a magnetic field surrounding it. It produces impedance to an AC current (jwL) and acts as a short circuit to DC. Inductors are commonly used in audio as low pass crossovers.
Infinite Baffle - a flat surface that completely isolates the back wave of a driver from the front.
Infrasonic (Subsonic) Filter - a filter designed to remove extremely low frequency usually between 8-25Hz or lower, noise from the audio signal. Useful for Ported box designs.
Input - connection from signal source.
Isobarik Enclosure - enclosure where one woofer is buried in the enclosure and a second is mounted up against the first and wired in reverse polarity (there are other variations for Isobarik designs), but this one works best. This allows the effective Vas of both drivers working in this push-pull configuration to be half that of a single identical driver mounted normally. Very small enclosures may be constructed as a result, with increased power handling. Less efficient than other designs, but the push pull configuration greatly reduces second order harmonic distortion. The name Isobarik comes from a term that means "constant pressure".
Keystoning - The process by which a projector optically or digitally racks an image onto the screen in order to compensate for sub-optimal placement with relation to the projection screen. Vertical keystoning is often necessary and recommended for business projectors which are table-mounted, but is always avoided in home theater use due to the fact that even a minimum amount causes pixel blurring and loss of detail.
Lens Shift - The ability of a projector (typically LCD or LCoS, but now DLP as well) to move the entire optical system such that the image can be adjusted/centered, without keystoning, onto the screen from a less-than-ideal projector placement.
Letterbox - This typically refers to the presence of black bars on the top and bottom of a film when displayed on a 4:3 or 16:9 displays.
Low-Pass Filter - an electric circuit designed to pass only low frequencies and act as high impedance to frequencies out of the filters pass band.

Wednesday, March 23, 2011

Electronic Terms ........ 6

Ground - refers to a point of zero voltage or potential.
Ground Loop - An unwanted current in a conductor connecting two points which supposed to be at the same potential, i.e. ground, but are actually at different potentials. This causes noise (typically at 60Hz) within an audio or video system.
Group Delay - The group delay of a filter is a measurement of the average delay of the filter as a function of frequency. It is the negative first derivative of a filter's phase response. It also can refer to the delay of a speaker from the listening position.
Harmonic - the multiple frequencies of a given sound, created by the interaction of signal waveforms.
Harmonic Distortion - harmonics artificially added by an electrical circuit or speaker, and are generally undesirable. It is expressed as a percentage of the original signal.
HDMI - A digital audio connection which is capable of carrying DRM-protected lossless 7.1 audio and HD video over a single jacketed cable. While it provides some strain relief, this now-dominant format isn't exactly the cat's meow in terms of the perfect connector, but it looks to be here to stay. HDMI 1.3a is the latest iteration as of mid-2007 and supports Dolby Digital Plus, Dolby TrueHD, DTS-HD and DTS-HD Master Audio, as well as all legacy digital audio formats. 1080p over HDMI can currently be sent about ~30-40 feet before requiring a DC-powered cable EQ or relay.
Hertz (Hz) - a measurement of the frequency of sound vibration. One hertz is equal to one cycle per second. The hertz is named for H.R. Hertz, a German physicist.
High-pass Filter - an electric circuit that passes high frequencies but blocks low ones by acting as a large impedance to those frequencies.
Hiss - background audio noise that sounds like a Rattler snake.
Home Theater - an audio system designed to reproduce the theater sound experience while viewing movies in the home. A basic system usually consists of a Dolby Prologic Decoder, 5 speakers and a subwoofer. More advanced systems incorporate Dolby Digital/DTS and other discrete 5.1 channel surround formats.
Horn - a speaker design using its own funnel shaped conduit to amplify, disperse, or modify the sounds generated by the internal diaphragm of the speaker.
HQV (Hollywood Quality Video) - Refers to a video processing technology by Silicon Optix which provides scaling, de-interlacing and noise reduction (among other things) to standard and high definition video sources. Silicon Optix also puts out a handy HQV Benchmark DVD (now available in HD DVD and BD formats) to test displays and source components.
Hum - audio noise that has a steady low frequency pitch, often caused by ground loops.

Wednesday, March 16, 2011

Electronic Terms ........ 5

Efficiency Rating - the loudspeaker parameter that shows the level of sound output when measured at a prescribed distance with a standard level of electrical energy fed into the speaker. Usually recorded as XdB @ 2.83V input signal from 1 meter of distance. However, a driver with a high efficiency rating needs a larger box to play a lower frequency than a driver with a lower efficiency rating.
Electronic Crossover - uses active circuitry in addition to passive to filter unwanted signals for each driver. Usually active filters are employed as LPF (Low Pass Filters) for subwoofers or for the sub out of a preamp / receiver.
Enclosure - a box that contains the driver(s).
Equalizer - electronic device that acts as active filters used to boost or attenuate certain frequencies. Farad - the basic unit of capacitance. A capacitor has a value of one farad when it can store one coulomb of charge with one volt across it.
Filter - any electrical circuit or mechanical device that removes or attenuates energy at certain frequencies.
Flat Response - the faithful reproduction of an audio signal; specifically, the variations in output level of less than ±1 dB which is the threshold of human hearing sensitivity.
Free Air Resonance - the natural resonant frequency of a driver when operating outside an enclosure.
Frequency - the number of waves (or cycles) arriving at or passing a point in one second, expressed in hertz (Hz).
Frequency Response - the frequency range to which a system, or any part of it, can respond.
Fundamental Tone - the tone produced by the lowest frequency component of an audio signal.
Full-range - a speaker designed to reproduce all or most of the sound spectrum within human hearing (20Hz - 20KHz).

Sunday, March 13, 2011

Electronic's Terms .......... Part 4

DAC – Digital to Analogue converter, turning on/off pulses into analogue sound. CD players have DACs built in. Separate DACs can upgrade a CD player or other digital player/ recorder, or can be used with dedicated CD transports.
Damping - the reduction of movement of a speaker cone, due either to the electromechanical characteristics of the speaker driver and suspension, the effects of frictional losses inside a speaker enclosure, and/or by electrical means.
Damping Factor - This is a quantity which defines how quickly the amplifier can stop a reproduced frequency such as a bass note. The higher the damping factor, the better the amp will control the woofer and help reduce overhang distortion. The damping factor of an amplifier is mostly dependent on the quality of the power supply which feeds the power amp.
Damping Material - any material added to the interior of a speaker enclosure to absorb sound and reduce out-of-phase reflection to the driver diaphragm (cone). Usually acoustic fiberglass, polyester batting, or Polyfill is used in speaker enclosures.
Decibel (dB) - (1) a logarithmic scale used to denote a change in the relative strength of an electric signal or acoustic wave. It is a standard unit for expressing the ratio between power and power level. Using the logarithmic relationship for power PdB = 10*log[Pout/Pin] , a doubling of electrical power only yields an increase of +3 dB. Increasing the power tenfold will yield an increase of +10 dB and is a doubling of perceived loudness. The decibel is not an absolute measurement, but indicates the relationship or ratio between two signal levels. (2) SPL (sound pressure level) can be measured in dB. 0 dB represents the threshold of normal human hearing, 130 dB represents the threshold for pain, 140 dB causes irreparable hearing damage, and 150 dB can cause instant deafness, anything greater than about 192 dB can kill you.
De-interlaced video - Most video sources, including DVD, standard-definition TV, and 1080i high-definition TV, transmit interlaced images. Instead of transmitting each video frame in its entirety (what is called progressive scan), most video sources transmit only half of the image in each frame at any given time. Deinterlacing is the process of stitching back together, properly, the individual fields into a solid frame of video.
Diaphragm - the part of a dynamic loudspeaker attached to the voice coil that moves and produces the sound. It usually has the shape of a cone or dome.
Diffusion - The scattering of sound.
Dipole - A speaker design which generates equal amounts of sound both forward and backward, with the two sounds being out of phase. Dipoles are often used as surround speakers.
Direct Current (DC) - current in only one direction.
Diffraction - a change in the direction of a wave that is caused by the wave moving past or hitting an obstacle.
Dispersion - the spreading of sound waves as it leaves a speaker.
Distortion - any undesirable change or error in the reproduction of sound that alters the original signal.
Dome Tweeter - a high frequency speaker driver with a dome-shaped diaphragm usually made of metal or silk.
Driver - a loudspeaker unit, consisting of the electromagnetic components of a speaker, typically a magnet and voice coil.
DRM - a term referring to technologies used to control usage of digital media - including hardware controls to deactivate unauthorized use.
Dynamic range - the range of sound intensity a system can reproduce without compressing or distorting the signal.

Wednesday, March 9, 2011

Electronic's Terms .......... Part 3

Capacitor - a charge storage device made up of two metallic plates separated by a dielectric, with equal but opposite charges. The AC impedance of a Capacitor is (1 / jWL) and acts as an open circuit in DC applications.
Circuit - a complete path that allows electrical current from one terminal of a voltage source to the other terminal.
Class A - transistor amp conducts for the entire cycle of input signal, conduction angle 360 deg. Runs hot, as the transistors in the power amp are on all the time, but has high sound quality.
Class B - positive and negative halves of the signal dealt with by different parts of the circuit, the output devices switching continually. Runs cooler, but the sound is not as pure.
Class AB - biasing the transistor amp at a non-zero DC current much smaller than the peek current of the signal source. Second transistor conducts during negative half cycle of waveform and the currents from the 2 transistors are combined at the load. A compromise between sound quality of Class A and efficiency of Class B. Most amp designs employ this method.
Clipping - a form of distortion caused by cutting off the peaks of audio signals. Clipping usually occurs in the amplifier when it's input signal is too large or when the voltage rails of the power supply cannot deliver the necessary voltage to the power amp.
Coloration - any change in the characteristic of sound that reduces naturalness, such as an overemphasis of certain tones.
Compliance - the relative stiffness of a speaker suspension, specified as Vas.
Cone - the conical diaphragm of a speaker attached to the voice coil which produces pulsation's of air that the ear detects as sound.
Crossover Frequency - the frequency at which the driver's roll off at - usually when response is down -3dB.
Crossover Network (Filter) - an electric circuit or network that splits the audio frequencies into different bands for application to individual speakers.
Current (I) - the flow of electrical charge measured in amperes.