Capacitance

The property of an electric nonconductor that permits the storage of energy as a result of electric displacement when opposite surfaces of the nonconductor are maintained at a difference of potential. In a capacitor, capacitance is the measure of the property (the amount of charge that can be stored) equal to the ratio of the charge on either surface to the potential difference between the surfaces.

Capacitor

An electronic device which stores energy and releases it when needed. Also used to direct high frequency energy to tweeters. Rated in Farads.

Cathode

A negative (-) electrode. The point of entry of electrons into a device from an external circuit. The negative electrode of a semiconductor diode.

CD

Compact Disk - The most popular format for conveying music and data currently available. It is among the first digital media to take over from the analog formats of phonograph records and tapes; coming to the market in the early 1980's. Developed by Phillips, Sony, and Pioneer, it records information on the now familiar shiny discs by deforming the inner metal foil on the disc with tiny micro pits burned in by a laser. These pits taken together, form a binary digital code, which when converted to bits, then bytes, can recreate the original information, such as audio. It's superiority as a format, consists of the fact that the process gets around the such problems as: noise, hiss, pops, transducer irregularities, and other audible problems that made analog carriers a less than fully high fidelity mode. Dynamic range exceeds 100 decibels, a sufficient soft/loud difference to make the reproduction very lifelike. Frequency response is at the theoretical limits of human hearing and unwanted aural artifacts are generally below the threshold of perception. The only significant improvement is the DVD borne addition of multiple channels, to recreate the original sonic environment.

CD-MD Control

The ability of a component (device) to operate a CD or MD (mini disk) disc changer.

CD-RW

(CD-Rewritable) allows you to make your own compilation CDs and play them back on CD players. But conventional CD players have difficulties playing them back because CD-RW's reflectivity. The amount of light reflected off from the disc is extremely low.

CD Changer

Separate units that may allow the user to hear any of 3 to 120 discs, or more in whatever order they wish to program them, or to skip from one track to another, or from one disc to another. Many of these come with separate controller units that allow for user operation and programming. Some are built to take advantage of controller systems built in to many receivers expressly for that model. Many also have a device called an FM modulator that permits connection to any standard FM stereo radio. The signal can be heard on whatever unused frequency the radio is tuned to. Most changers also permit direct audio outputs to any standard RCA high impedance, line level, input. This is the preferred input to avoid noise and distortion that may occur with radio usage.

CD Text

A compact disc and player feature utilizing disc, track, and artist information encoded directly on the CD media. Both playback and media components must have CD Text compatibility.

CEA

Consumer Electronics Association - A division of the EIA (Electronics Industries Alliance). Virginia based EIA oversees electronics manufacture, repair, service and sales throughout the U.S.

Cell

A single unit for producing DC electricity by electromechanical or biomechanical action. A common vehicle battery is composed of a number of individual cells connected together. Each cell is typically rated at 2.11 Volts each, and a common 12VDC automotive battery is composed of 6 separate, 2 Volt cells.

Cellular Telephone

A device consisting of a control unit, a transceiver, and an antenna which processes calls to be sent to or received from the cellular system.

Cell Site

The middleman of the cellular system that communicates directly with the cellular telephone and relays all of the control parameters from the MTSO to the cellular telephone, as well as all requests for service from the cellular telephone to the cellular system.

Center-run Wire Path

(Center Path Wiring) A method of running wires to the midrange/tweeter bridge in a coaxial speaker. Actual copper wire (instead of tinsel leads) are run through a hole drilled in the magnet. This offers better signal transfer and efficiency.

Ceramic Composite Tweeters

Extremely strong and lightweight making it ideal for use as a tweeter material. This material improves power handling while maintaining excellent efficiency.

Channel

Common name for a complete amplifying stage in any audio amplifier. Most amplifiers are denominated as 1, 2, 4, 5, or 6 channel units. Each of these is a discrete audio amp on its own, capable of taking a small line signal input and amplifying it sufficiently to be heard on an appropriate speaker. Some amplifiers are capable of bridging two channels together, to form one channel of double the power of each separately. The manufacturer's instructions differ widely on how to accomplish this, and each must be followed exactly.

Channel-Cellular

A frequency or band of frequencies assigned to a station or communications system. Also, a sub-circuit of a larger system, i.e., voice channel, control channel, paging channel.

Channel-Security

The term usually used to describe the number of different functions possible for manipulating the buttons on a remote control transmitter.

Charge

Stored energy in a battery or capacitor that is discharged as electrical energy.

Chebyshev Filter

A filter that has some ripple in the pass-band but has an initial attenuation slope which is steeper than a Butterworth filter.

Circuit

A number of components wired together to perform an electrical function. When voltage is applied, current flows and the function is performed. Mostly used as an confirmation sound.

Circuit Breaker

An electromechanical device designed to quickly break its electrical connection should a short circuit or overload occur. A circuit breaker is similar to a fuse, except it will rest itself or can be manually rest, and will again conduct electricity.

Clamshell

Operating two subwoofers face to face on the same baffle board and electrically out of phase with each other. A type of "compound loading", it allows a subwoofer to operate in a smaller box.

Class-Amplifier

Amplifier Classes - There are different classes of amplifiers, depending on how the biasing of the amplifier circuit is done.

Audio power amplifiers are classified primarily by the design of the output stage. Classification is based on the amount of time the output devices operate during each cycle of signal swing. Also defined in terms of output bias current, (the amount of current flowing in the output devices with no signal).

Clipping

The distortion that occurs when a power amplifier is overdriven. This can be seen visually on an oscilloscope, when the peaks of a waveform are flattened, or "clipped of", at the signal's ceiling.

Closed Loop

A feedback path in a self-regulating control system. Unlike a standard open state trigger that needs to have a connection established to serve as a trigger, a closed loop trigger will act to trigger a security system when its loop (connection) is broken.

Close Circuit

To come together, referring to contacts in a relay or switch. When the circuit is closed, the contacts are touching, completing the circuit.

Closure Wire

Terminology used describe a wire found on some vehicles that, when given a certain duration input, will cause the doors to lock and the windows and or sunroof (if applicable and or installed) to close.

Co-Injection Molded Woofer

A process by which the woofer's cone and surround materials are molecularly bonded together. This bond is much stronger than traditional glue and allows the woofer to reproduce tighter, deeper bass with significantly lower distortion than conventional woofers.

Co-Linear Antenna

An antenna that uses a phasing coil to electrically connect stacked elements in the proper order.

Coaxial Cable

A single copper conductor, surrounded with a layer of insulation, covered by a surrounding copper shield and finally, an insulating jacket. A constant-impedance unbalanced transmission line. In audio, this type is commonly used for low level, line, signals terminated in RCA plugs.

Coaxial Speaker

The coaxial speaker has a large cone for the low range, and a smaller tweeter for the high spectrum. There is a cross-over network which divides and routes the signal to the correct driver (cone).

Code

The aspect of a security system that can be tailored by the manufacturer or the installer to personalize the particular system for a user or group of users. A remote security system that is coded will operate only with those transmitters that are coded to the same matching code.

Coil

A number of turns of wire around an iron core or onto a form made of insulating material. Used as an inductor, a coil offers a great deal of opposition to the passage of AC, but very little to the passage of DC.

Comb Filter Effect

This acoustical and electronic effect occurs when two signals interact in such a way as to produce an irregular spiked and choppy response pattern. When graphed on paper, this pattern looks like the teeth of a comb, hence the name. This effect is frequently the product of overlapping outputs from the various drivers in the system. It can develop in either a single speaker between the individual drivers, or between unmatched sets of speakers. This same effect can also be produced by wall reflections and other room anomalies. The usual remedy for this, if it becomes objectionable, (not every instance is even perceived as such) is to make sure the Crossover set points are appropriate for the drivers being used, or that the crossover is operating correctly. Obviously, one should also use only compatible speaker sets.

Common Sense Turn-on

The ability of amplifiers or outboard devices to be turned on by an incoming speaker-level signal.

Compliance

The measurement in liters or cubic feet of the volume of air that is equal to the compliance of a speaker's total suspension.

Component Speaker System

Separating the units of a coaxial speaker into a tweeter and a woofer or midrange driver. This allows for better placement in a car environment, improving the stereo image.

Compound

Using two subwoofers coupled together in a small airspace. It allows a woofer to be used in a smaller enclosure. Compound loading can be done by clamshelling or positioning the woofers front to back.

Compression

An increase in density and pressure in a medium, such as air, caused intermittently by the passage of a sound wave. 2. The region in either air or material in which this occurs.

Compression Driver

Compression drivers are usually dynamic; that is, with a magnet and interacting coil arrangement, and a small diaphragm as the main transducer. These are the motor parts, also known as the driver, of a compression horn tweeter or compression horn general-purpose speaker, such as those used for Public Address (PA) purposes. These drivers are usually coupled to the throat of an exponential horn. Such an arrangement enables this type of tweeter to have very high directional characteristics, which allows them to be especially effective in situations requiring a very wide sound field. In typical home and car stereo near-field applications, large horns can be a bit too narrowly directional to be practical. For this reason, compression horn systems are usually found only in special purpose speakers used in mid and wide field applications such as PA systems or the sound systems installed in large theaters. However, some specialized horns have small apertures and very shallow horns, and can be quite suitable for close spaces.

Compression Wave

A wave propagated by means of the compression of a fluid, such as a sound wave in air. To create sound, the opposite state of rarification alternates with the crest of every compression.

Cone

The most common shape for the radiating surface of a loudspeaker. Often used to refer to that part of the speaker that actually moves the air.

Configurable Power Supply

Technology for amplifiers where the power supply configuration can be changed from High Voltage mode, for superior output power driving 4 or 2 ohms, to High Current mode, for superior low impedance stability.

Constant Bass

The ability of an active crossover to maintain a constant bass output regardless of the position of a system fader control.

Constant Directivity Horn

Proprietary horn design that smoothly and accurately reproduces high-frequency sounds throughout a much wider listening area.

Constant Output

An output of a security system that provides a constant or continuous output to drive a device. Often used for sirens and engine interrupts.

Copper Plated Chassis

By bonding copper to a chassis, superior shielding is achieved, providing superior rejection of induced noise.

Copper Polepiece Caps

Reduce magnetic eddy currents and extend high frequency performance.

Counter Firing

A method for reducing harmonic distortion at low frequencies that involves the use of a secondary coil in a woofer or mid bass driver to cancel non-fundamental wave elements not found in the original signal. The signal from the coil is used by the amplifier to refine it's damping control over the cone motion. This proprietary servo-feedback technology was originally developed by Velodyne in the early '90s.

Crossover

A device intended to separate the different frequency bands and redirect them to different components.

Crossover-Electronic

Uses active circuitry to send signals to appropriate drivers. More efficient than passive crossovers.

Crossover-Passive

Uses inductors (coils) and capacitors to direct proper frequencies to appropriate drivers. These crossover systems can be simple (First Order = 1 component @ -6 dB/octave slope) to complex (Fourth Order = 4 components @ -24 dB/octave slope).

Crossover Frequencies

The frequencies at which a passive or electronic crossover network divides the audio signals, which are then routed to the appropriate speakers.

Crossover Network

A unit which divides the audio spectrum into two or more frequency bands.

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

The interference of signal from one channel to another. Crosstalk is measured in DECIBELS as the ratio of desired signal to undesired signal; the higher the number the less the undesired signal.

Current

The rate of electrical or electron flow through a conductor between objects of opposite charge. Symbol I, measured in amperes or amps.

Curvilinear Cone

A cone design pioneered by JBL that allows for better midrange and off-axis performance.

Custom File

A feature package that provides intuitive and safe source management for an audio and A/V system. Examples include Disc Memo, Station Memo, and Memo List.