c - Propagation velocity of sound at STP, approximately 342 m/s.
Cab - Acoustic compliance of air in the enclosure.
Cabin Gain - Also referred to as the “transfer function,” this is the build up of long pressure waves (bass notes) inside of the vehicle in which the music is playing. At sea level the speed of sound is 1127 ft/ per second, which at 40 Hz means the wave is approximately 28 ft long, since the typical vehicle cabin is near 12 ft in length (give or take depending on the vehicle) than it is possible to gain 12 dB’s simply from this function. The less air space inside of the vehicle cabin occupied by the subwoofers and enclosure will give the vehicle more cabin gain, and vice versa.
CAFE - Refer to Coporate Average Fuel Economy
Capacitance - The property exhibited by two conductors separated by a dielectric, where an electric charge becomes stored between the conductors.
Capacitor - Formerly known as a condenser is a passive two-terminal electrical component used to store energy in an electric field. The most commonly used capacitors are round and consist of a thin layer of insulating film (dielectric) sandwiched between two pieces of conductive foil material which build up an electrical field as energy and then released. Capacitors are used to filter out direct current and allow alternating current to flow through, smoothing out the output of power supplies, in the resonant circuits that tune radios to certain frequencies, temporarily storing and emitting alternating power, and many other ways. They are characterized by a single value, capacitance which can be measured in Farads.
There are two types of Capacitors commonly seen in Car Audio, Polarized and Non-Polarized. Polarized capacitor is an electronic device that stores energy and releases it when needed. Used in power supply applications. Polarized capacitors have specific terminals for positive and negative connections. Non-polarized capacitor is an electronic device that stores energy and releases it when needed based on the frequency of the signal. Used in passive crossover audio filtering applications. Non-polar capacitors do not have specific terminals for positive and negative connections.
California Air Resources Board (CARB) - The agency in California that is responsible for regulation and enforcement of vehicle emissions standards often described as more stringent than Federal EPA guidelines.
CAN - Refer to Controller Area Network
CARB – Refer to California Air Resources Board
Cas - Virtually the acoustical equivalent of Cms.
Cathode - The electrically negative pole of an electronic device such as a semiconductor. A diode, for instance, has a positive and negative pole; these are known as the anode and the cathode.
CCA - Refer to Cold Cranking Amps
CEA - Refer to Consumer Electronics Association
Cell (Energy Storage) - A Single unit for producing DC electricity by electrochemical or biochemical action. A common 12.66V vehicle battery is composed of a number of individual cells connected together. Each cell is typically rated at 2.11 volts; a common automotive battery is composed of six separate two-volt cells.
Cell (Wireless Communications) - The basic geographic unit of wireless coverage. Also, shortened for generic industry term “cellular.” A region is divided into smaller “cells,” each equipped with a low-powered radio transmitter/ receiver. The radio frequencies assigned to one cell can be limited to the boundaries of that cell. As a wireless call moves from one cell to another, a computer at the Mobile Telephone Switching Office (MTSO) monitors the cal and at the proper time, transfers the phone call to the new cell and new radio frequency. The handoff is performed so quickly that it’s not noticeable to the callers.
Cell Site - The location where a wireless antenna and network communications equipment is placed in order to provide wireless service in a geographic area.
Cellular Digital Packet Data (CDPD) - Non-voice two-way communications transmitted in the cellular band.
Center Channel - In home theater, sound decoded from the stereo signal sent to a speaker mounted in front of the listener, specially designed to enhance voices and sound effects from a movie soundtrack. Used in car audio to help offset skewed stereo imaging due to seating positions in the automotive environment.
CDMA - Refer to Code Division Multiple Access
Channel (Audio) - The term used to describe a specific output or input in an audio system, usually as simple as “Left Channel” or “Right Channel” in stereo signals. Depending on the device (such as a signal processor or multi-channel source), there may be further designations of center, rear or low frequency channels.
Channel (Security) - The term used to describe the number of different functions possible for manipulating the buttons on a remote control transmitter.
Channel (Wireless Communication) - 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, etc.).
Chassis - The metal frame of the vehicle often held together by various bolts and pinch welds.
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.
Chirp - The term used to describe the brief sounding of a security system’s siren designed to indicate the state of arm of the system.
Circuit - Is a closed path in which electrons from a current or voltage source flow through, typically within wire or traces through which electrical current can flow. Inline of a circuit maybe found capacitors, resistors, transistors, relays, switches, inductors, diodes, transmission lines and many other components. They may typically conduct alternating and direct currents.
Circuit Breaker - Is an automatically operated electrical switch designed to protect an electrical circuit from damage due to current overload or short circuit. The basic function of the circuit breaker is to automatically break the current when detecting an overload or short in the circuit, which can then be reset to operate and continue the flow of current or voltage. Circuit breakers may vary in size and current capabilities (typically measured in Amperes) to fit any given application. The breaker reset process can be manually or automatic depending on the breakers design and application.
Clipping - Audible distortion that occurs when continuous power-to-peak power capabilities (headroom, ceiling) are exceeded.
Closed Cell Foam (CCF) - The trapped gas increases the insulation capability of the cured foam. The cured foam must be strong and of a medium density in order to lock in the gas bubbles. The foams strength, coupled with its closed cell nature, enable it to resist liquid water and function as a vapor retarder.
Closed Circuit - A continuous, unbroken circuit in which current can flow without interruption.
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.
Cms - Is any given driver's mechanical compliance (reciprocal of stiffness), in m/N.
Cmes - The electrical capacitive equivalent of Mms.
Coaxial Driver - A speaker composed of larger cone for low range frequencies and a smaller cone or tweeter for higher frequencies aligned on the same axis. A crossover network is necessary to route the proper signals to each driver. These may be passive (usually included). If the speakers are bi-amplified, an active crossover will be used to route the proper range of frequencies to the respective amplifier channels.
Codec - A codec is a method of compressing and decompressing digitized sound. MP3 and WMA are examples of different codec’s. In the standard CD audio format, one minute of music takes up to roughly 10 megabytes. When converted to MP3, that same minute of music takes up only about 1 megabyte.
Code Division Multiple Access (CDMA) – A are interface channel access technology used by many wireless phones and services providers (including its CDMA2000 derivatives- RTT, EV-DO and EV-DV).
Coherence - Referring to sound quality, being aesthetically ordered, integrated and natural to the ear.
Coil - Often referred to as a Voice Coil, the coil itself is the copper former wrapped around the pole of the subwoofer. This coil acts as an electromagnet when electrical current is introduced.
Cold Cranking Amps (CCA) - This is a rating often use in the automotive and battery industries to describe a battery's ability to start in cold weather conditions. The CCA shows the amount of amps a 12-volt battery can deliver at 0°F for 30 seconds while maintaining a voltage of at least 7.2 volts.
Coloration - Any change in the characteristics of sound that reduces naturalness, such as an over emphasis of certain tones or frequencies.
Common Mode Rejection - The ability of the device to reject common-mode signals, i.e., those that appear simultaneously and in-phase on both inputs.
Compliance - The relative stiffness of a speaker suspension, specified as Vas.
Conductivity - Also known as electrical resistivity is a measure of how strongly a given material (conductor) opposes the flow of electrical current. Less electrical resistance through the conducting material means better conductivity of the conductor. The resistance of the conductor is traditionally measured in Ohms.
Constant (12V, B+) - A lead, wire, or connection point that shows positive 12 volts regardless of ignition key position or any other switch.
Consumer Electronics Association (CEA) - Catalyst to the dynamic technology industry, the Consumer Technology Association (CTA) accelerates growth and progress for the fast-paced economy. With leading market research, CTA educates members, and by establishing standards, CTA shapes the industry at large.
Continuity - The condition of being continuous.
Controller Area Network (CAN) - Also known as CAN-bus, is a computer network protocol and bus standard designed to allow microcontrollers and devices to communicate with each other and without a host computer. It was designed specifically for automotive applications but is now also used in other areas. CAN is also supported in the Linux Kernel since the 2.6.25 version. CAN-bus was originally developed in 1988 by Intel Corporation and Robert Bosch GmbH.
Copper (Cu) - Has a shiny reddish-orange color, and is ductile with very high thermal and electrical conductivity. The electrical and thermal conductive properties of copper are exploited in wire, amplifiers, subwoofers, heat sinks, and many other conductors recognized in the car audio industry. Copper maybe mixed with other alloys to provide a cheaper alternative (i. e. CCA grade wire).
Copper Clad Aluminum (CCA) - commonly abbreviated as CCAW or CCA, is an electrical conductor composed of an inner aluminum core and outer copper cladding.
Corporate Average Fuel Economy (CAFE) - The US government standards set requirements on automakers for improving the average fuel economy.
Coulomb - An amount of electrical charge which contains 6.24 X 10^18 (6,240,000,000,000,000,000) electrons. One coulomb per second past a given point is equal to 1 ampere of Current flowing.
Cross Interleave Read-Solomon Code (CIRC) - A combination of codes and interleaved data that make it possible to detect and correct errors in a compact disc system.
Crossover - Is a class of electronic filter that separates levels of signal frequency. Some drivers may not be capable of extending across the spectrum of frequency without increasing distortion, so it is necessary to incorporate an electronic crossover to filter out certain (possibly harmful) frequencies to said driver. The three most common classes of crossovers are passive, active, and mechanical.
Crossover Frequency - Often referred to as Crossover Point, is the frequencies at which a passive or active (electronic) crossover network divides the audio signals, which are then routed to the appropriate speakers.
Crosstalk - Also known as Channel Separation, is the amount of signal that leaks from one stereo channel into the other, or from one tape track into another. It is expressed in decibels, with the higher the value the better. Channel to channel crosstalk should be at least 30 db, with 40 db being very good.
Cu - Refer to Copper
Cutoff Frequency (F3) - In physics and electrical engineering, a cutoff frequency, or break frequency is a boundary in a system’s frequency response at which energy flowing through the system begins to be reduced (attenuated or reflected) rather than passing through.
Current (I) - The rate of flow of electricity, measured in amperes (amps).