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C
Capacitor
A device made up of two metallic plates separated by a dielectric (insulating material). Used to store electrical energy in the electrostatic field between the plates. It produces an impedance to an AC current.
Casa
A multi-source/multi-room audio control system, that can be controlled from a hand held IR (infra red) remote, or through an in-wall keypad. It is designed to offer a high quality permanent audio installation, reliably and independently serving many rooms in one home through a simple yet powerful user-interface.
Cascading Crossovers
Two crossovers used in series on the same signal in the same frequency range causing greater attenuation of the out-of-band signal. For example, using the crossover in a receiver's bass management setting and the one in a subwoofer simultaneously will create an exaggerated loss of signal.
CD
Also known as Compact Disc. An optical disc storage media that is designed to store audio, video, and computer data in a digital format. CD's have a capacity to store 700 Mb (megabytes) of data. The digital information in a standard audio CD is encoded in the PCM format. (See also
PCM)
Center Channel
The center speaker in a home theater setup. Ideally placed within one or two feet above or below the horizontal plane of the left and right speakers and above or below the display device, unless placed behind a perforated screen. Placement is important, as voices and many effects in a multichannel mix come from this speaker.
Channel
In components and systems, a channel is a separate signal path. A four-channel amplifier has at least four separate inputs and four separate outputs.
Channel Balance
In a stereo system, the level balance between left and right channels. Properly balanced, the image should be centered between the left-right speakers. In a home-theater system, refers to achieving correct balance between all the channels of the system.
Chassis
Frame or basket that houses the midrange or bass driver components.
Chrominance (C)
The color portion of a video signal.
Circuit Breaker
An electrical switch that automatically breaks a circuit if the current through it is too high, then can be manually reset. Performs the same function as a fuse, without the need for replacement after it is activated.
Classes, Amplifier
Basically, amplifying the audio signal means using the wall-current (usually either 120 or 240 volts) to increase the amplitude of the audio signal from milliwatts(mW) to watts (W). Different classes of amplifiers accomplish this in different ways. Turning a vacuum tube on or off with current demand increases the efficiency of the amplifier but may add switching distortion. A Class A amplifier is relatively inefficient, converting much energy to heat, but has no switching distortion. (See also
Amplifier Classes)
Clipping
Audible distortion occurring when the peaks of an amplifier's output are flattened (or clipped). When the input is too high, an amplifier has insufficient power to accurately reproduce the output waveform.
Cms
Mechanical suspension compliance of a driver, consisting of the spider and surround.
Coaxial
1) A speaker typically with one driver in the middle of, and on the same axis as, another driver. 2) An audio or video cable with a single center pin that acts as the hot lead and an outer shield that acts as a ground.
Coaxial Driver
A speaker composed of two individual voice coils and cones; used for reproduction of sounds in two segments of the sound spectrum.
Codec
Mathematical algorithms used to compress large data signals into small spaces with minimal perceived loss of information.
Coloration
Any shift away from the natural rendition of music. Coloration is undesirable - boomy bass, a nasal midband or a splashy treble, for instance. All colorations tend to get in the way of the music.
Compliance
The relative stiffness of a speaker suspension, specified as Vas.
Component Video
A signal that's recorded or transmitted in its separate components. Typically refers to Y/Pb/Pr, which consists of three 75-ohm channels: one for luminance information, and two for color. Compared with an S-video signal, a Y/Pb/Pr signal carries more color detail. HDTV, DVD, and DBS are component video sources, though most DBS material is transcoded to component from composite signals.
Composite Video
A signal that contains both chrominance and luminance on the same 75-ohm cable. Used in nearly all consumer video devices. Chrominance is carried in a 3.58-mHz sideband and filtered out by the TV's notch or comb filter. Poor filtering can result in dot crawl, hanging dots, or other image artifacts.
Compression (Audio)
Compression is when the amplitude is squashed to reduce the level difference between the loud and soft parts of the music (the peaks and troughs on the wave form). This is often used by radio stations to improve the sound of cheap radios with limited output capability when played loud. It is usually avoided in Hi-Fi, because it restricts dynamics. However, with powered subwoofers, a form of compression called soft clipping can be useful to avoid the harsh sound of transistors clipping when the amplifier is used near its limit. It's similar to the way valves (tubes) limit their output.
Conductor
Materials along which electrons will flow, making them suitable for use as connecting links in electrical circuits.
Contrast
Relative difference between the brightest and darkest parts of an image. A contrast control adjusts the peak white level of a display device.
Conventional Current
The representation of current as flowing from positive to negative potential when describing the behaviour of electricity, despite the reality that the actual electrons constituting that flow move from negative to positive potentials.
Crossover
A frequency divider. Crossovers are used in speakers to route the various frequency ranges to the appropriate drivers. Additionally, many crossovers contain various filters to stabilize the impedance load of the speaker and or shape the frequency response. Some crossovers contain levels controls to attenuate various parts of the signal. A passive crossover uses capacitors, coils and resistors, usually at speaker level.A passive crossover is load dependent (the transition may not be very smooth or accurate if a different speaker is substituted for the one the crossover was designed for). An active crossover is based on integrated circuits (ICs), discreet transistors or tubes. An active crossover is impedance buffered and gives a consistent and accurate transition regardless of load.
Crossover Frequency
The frequency at which an audio signal is divided. 80 Hz is a typical subwoofer crossover point and is the recommended crossover point in theatrical and home THX systems. Frequencies below 80 Hz are sent to the subwoofer; signals above 80 Hz are sent to the main speakers.
Crossover Slope
High and low pass filters used for speakers do not cut-off frequencies like brick walls. The rolloff occurs over a number of octaves. Common filter slopes for speakers are 1st through 4th order corresponding to 6db/oct to 24db/oct. For example, a 1st. order, 6db/oct high pass filter at 100hz will pass 6db less energy at 50Hz and 12db less energy at 25Hz. Within the common 1st through 4th filters there is an endless variety of types including Butterworth, Linkwitz-Riley, Bessel, Chebychev, etc. Salesmen and product literature will sometimes make claims of clear superiority for the filter used in the product they are trying to sell. Since the subject fills books, suffice it to say that there is no one best filter, it depends on application and intended outcome. Good designers use the filters required to get the optimum performance from the system.
Crosstalk
Unwanted breakthrough of one channel into another. Also refers to the distortion that occurs when some signal from a music source that you are not listening to leaks into the circuit of the source that you are listening to.
CRT
Cathode Ray Tube. Analog display device that generates an image on a layer of phosphors that are driven by an electron gun.
Current
The flow of electrons along a conductor.
Current (I)
The flow of electrical charge measured in amperes
Cycles Per Second
The unit of measure denoting frequency. (See also Hertz - Hz) (See also Frequency) |
