Car audio
Encyclopedia
Car audio/video, auto radio, mobile audio, 12-volt and other terms are used to describe the sound or video system fitted in an automobile
. While 12-volt audio and video systems are also used, marketed, or manufactured for marine, aviation, and buses, this article focuses on cars as the most common application. From the earliest days of radio, enthusiasts had adapted domestic equipment to use in their cars. In the 1960s, tape players using reel-to-reel
equipment, Compact Cassette
s, and then 8-track cartridges were introduced for in-car use. Cassette players were invented before 8-tracks, therefore put in cars before 8-tracks.
A stock car audio system refers to the original equipment manufacturer
(OEM) application that the vehicle's manufacturer specified to be installed when the car was built. The hi-fi systems of specialists such as Bang & Olufsen
, Bose, and Harman International Industries
(which encompasses brands such as Harman Kardon
, JBL
, and Mark Levinson
) are available in several luxury car marques. A large after market industry exists where the consumer can at their desire replace many or all components of the stock system.
In modern cars, the primary control device for an audio system is commonly referred to as a head unit
, and is installed in the center of the dash panel between the driver and the passenger. In older vehicles that had audio components as an option, such devices were mounted externally to the top of or underneath the dash. Car speaker
s often use space-saving designs such as mounting a tweeter directly over a woofer or using non-circular cone shapes. Subwoofers are a specific type of loudspeaker for low frequency reproduction.
Motorcycles have been utilized with similar equipment since they also have the so-called "car audio" experience. Even pedal bicycles, as well as homemade boomboxes have utilized sealed lead-acid batteries (or 12V power supplies) for applications outside of motor vehicle use, likewise the store displays which mount in demo models prior to aftermarket purchases for installation.
Extremely loud sound systems in automobiles, which have been nicknamed "boom cars", may violate the noise ordinance of some municipalities.
came in the 1930s from the Galvin Manufacturing Corporation. Galvin Manufacturing was owned and operated by Paul V. Galvin and his brother Joseph E. Galvin. The Galvin brothers purchased a battery eliminator
business in 1928 and the corporation's first product was a battery eliminator that allowed vacuum tube battery-powered radios to run on standard household electric current (see also Rogers Majestic Batteryless Radio
). In 1930, the Galvin Corporation introduced one of the first commercial car radios, the Motorola model 5T71, which sold for between $110 and $130 (2009: $) and could be installed in most popular automobiles. Founders Paul Galvin
and Joe Galvin came up with the name 'Motorola
' when his company started manufacturing car radios. A number of early companies making phonograph
s, radio
s, and other audio equipment in the early 20th century used the suffix "-ola," the most famous being Victrola
; RCA
made a "radiola"; there was also a company that made jukeboxes called Rock-Ola
, and a film-editing
device called a Moviola
. The Motorola prefix "motor-" was chosen because the company's initial focus was in automotive
electronics.
In Germany Blaupunkt
fitted their first radio to a Studebaker
in 1932 and in the United Kingdom Crossley
offered a factory fitted wireless in their 10 hp models from 1933. The early car radio receivers used the battery voltage (6.3 volts at the time) to run the vacuum tube filaments, and generated the required high voltage for the plate supply using a vibrator
to drive a step-up transformer
. The receivers required more stages than the typical home receiver in order to ensure that enough gain was available to allow the AGC
to mask signal fading as the car was driven. When cars switched to 12-volt batteries, the same arrangement was used, with tubes with 12-volt heaters. In 1952 Blaupunkt became the first maker to offer FM
receivers.
is located on modern cars would reactivate the Seek at whatever sensitivity was last selected.
" tubes that only required 12 volts on their plates without a high voltage plate power supply (typical example was the 6GM8/ECC86). Advances in electronics allowed additions to the basic radio and Motorola offered 16 2/3 rpm disc players fitted to some Chrysler
s known as Highway Hi-Fi
from as early as 1956 and ran through 1958. Records were produced under license by Columbia
"Special Products" division and sold exclusively through Chrysler dealers. The 45 rpm record player was introduced in 1959 and ran through the early 60"s under the RCA and ARC brand. Earl "Madman" Muntz introduced the "4-track
" tape player in the early '60s using a continuous loop cartidge and was the first commercially available "car stereo". Tape players using reel to reel
equipment followed, but their bulk ensured limited popularity. This changed in 1964 when Philips
launched the Compact Cassette
. During the '60s Lear invented and introduced the 8track cartridge in competition with the cassette system. Other early manufacturers and enthusiasts began building extra audio amplifier
s to run on 12 volts (the standard voltage in automotive electrical systems). Jim Fosgate, later to become the founder of Rockford Fosgate
, was one such pioneer. The company a/d/s also brought an amplifier to market in 1978.
and professional markets were simply installed into vehicles. However, they were not well suited to the extremes of temperature and vibration which are a normal part of the environment of an automobile. Different manufacturing techniques, and different component materials were used in construction to adapt to these conditions.
Car audio competitions started in the early 1980s
The first known occurred in 1981 in Bakersfield, CA and evolved into an annual event. It was called The Summertime Car Show and Sound Off Competition, which at its height drew upwards of 300 contestants and continued into the 1990s. The Summertime Car Show and Sound Off Competition began as a promotional event for Cars on Camera, a magazine founded by owners Steve Silver and Scott Burud. Since the magazine derived a large part of its advertising revenue from local car stereo shops (TransLex, AutoSounds and others) it made sense to hold a sound off competition in order to create higher demand for magazine ad space. The original event took place in the parking lot of the local Zody's chain store on Ming Avenue, in Bakersfield, CA. However, the following year it was moved to the Kern County fairgrounds in order to accommodate the thousands of participants. By the second year, the event added a men's great legs contest and a bikini contest that attracted contestants from all over California. Cars on Camera changed its name to Camera Ads, which was then sold to Buck Owens Productions.
The most important of these were CAN (formed by Alpine) and NACA (supported by shop owners and amp manufacturers). Both organizations sanctioned countrywide regional events and hosted National Championship events in the late 1980s. They merged to form IASCA
in 1990. Despite the move to "quality" based judging, volume was still a significant portion of most early 1990s competitions. Since then, the two styles—SPL vs. sound quality—have become almost mutually exclusive. The loudness competitions have become known as dB drag racing
. Currently, Mobile Electronics Australia, an independent organisation conducts Sound Quality Competitions (MEASQ) and SPL Competitions (Bass Battle) nationally in Australia. These formats were developed by enthusiast Marc Rushton, the founder of one of the largest enthusiast organizations known as Mobile Electronics Australia.
application that the vehicle's manufacturer specified to be installed when the car was built and nowadays at least includes a CD-radio, with MP3
player and an aux-in. A large after market industry exists where the consumer can at their desire replace or complement many or all components of the stock system (i.e. kits to include a USB port and A2DP bluetooth
to the stock radio-CD). Nowadays, the most valued port (40% of the users) is the USB.
In modern cars, the primary control device for an audio system is commonly referred to as a head unit
, and is installed in the center of the dash panel between the driver and the passenger. In older vehicles that had audio components as an option, such devices were mounted externally to the top of or underneath the dash.
The headunit itself is usually a multi-purpose device that houses multiple types of components in its housing. The most common components are a radio receiver/tuner
usually with AM and FM bands, and a small amplifier for driving an audio signal to speakers. Other possible components include various media devices, such as (in older vehicles) a tape player (either 8-track or cassette
), CD player, DVD player
, USB flash memory
, and even a portable hard disk drive typically used in notebook computing. Many head units also feature a DSP
component, and equalization
component (such as bass and treble
controls), or a control interface for another feature on the car (such as a back-up/parking camera, navigation system, trip odometer, etc.).
Due to auto manufacturing differences over the years, aftermarket headunit products are manufactured in multiple form factors. The primarily used size is mostly referred to by its legacy name of DIN, which refers to ISO 7736
. DIN headunits come as single DIN or double DIN. A third less common standard is used mostly by Chrysler group and for a time Mitsubishi in their OEM devices.
Car speaker
s are largely functionally identical to any other loudspeaker design with key components specialized for use in mobile environments, and generally serve an identical purpose. One major key design difference is mult-axial mounting of different types of loudspeakers in the same footprint, such as a tweeter directly mounted over a woofer. Another key difference is non-circular cone shapes, such as square, oval, or even triangular. Both of these features reflect a significant reduction in space and size that a speaker may occupy in a vehicle cabin.
Material construction may also include more exotic and hearty components more suitable to mobile use. Marine speakers may have plating for corrosion resistance. Cones may be coated with a substance to resist expansion and contraction under high vehicle cabin temperatures, known to reach 140 °F (60 °C) in the sun. Subwoofers may also be found in mobile audio applications where a cabin speaker may lack the desired low frequency response on its own.
Before stereo
radio was introduced, the most common speaker location was in the middle of the dashboard
pointing through perforations towards the front windshield
. In most modern applications, speakers are mounted certain common locations including the front deck (or dash), the rear deck (or parcel shelf), the kick panel (located in the footwell below the A-pillar,) or the doors. In the case of subwoofers, mountings are usually under the seat or in the trunk. Each position has certain strengths and limitations from both a quality of sound, and a vehicle manufacturing perspective.
Automobile
An automobile, autocar, motor car or car is a wheeled motor vehicle used for transporting passengers, which also carries its own engine or motor...
. While 12-volt audio and video systems are also used, marketed, or manufactured for marine, aviation, and buses, this article focuses on cars as the most common application. From the earliest days of radio, enthusiasts had adapted domestic equipment to use in their cars. In the 1960s, tape players using reel-to-reel
Reel-to-reel audio tape recording
Reel-to-reel, open reel tape recording is the form of magnetic tape audio recording in which the recording medium is held on a reel, rather than being securely contained within a cassette....
equipment, Compact Cassette
Compact Cassette
The Compact Cassette, often referred to as audio cassette, cassette tape, cassette, or simply tape, is a magnetic tape sound recording format. It was designed originally for dictation, but improvements in fidelity led the Compact Cassette to supplant the Stereo 8-track cartridge and reel-to-reel...
s, and then 8-track cartridges were introduced for in-car use. Cassette players were invented before 8-tracks, therefore put in cars before 8-tracks.
A stock car audio system refers to the original equipment manufacturer
Original Equipment Manufacturer
An original equipment manufacturer, or OEM, manufactures products or components that are purchased by a company and retailed under that purchasing company's brand name. OEM refers to the company that originally manufactured the product. When referring to automotive parts, OEM designates a...
(OEM) application that the vehicle's manufacturer specified to be installed when the car was built. The hi-fi systems of specialists such as Bang & Olufsen
Bang & Olufsen
Bang & Olufsen is a Danish company that designs and manufactures audio products, television sets and telephones. It was founded in 1925 by Peter Bang and Svend Olufsen, whose first significant product was a radio that worked with alternating current, when most radios were run from batteries...
, Bose, and Harman International Industries
Harman International Industries
Harman International Industries is an American-based international audio and infotainment equipment company. The company designs, manufactures and markets audio and infotainment products for the car, the home, theatres and venues, as well as electronics for audio professionals...
(which encompasses brands such as Harman Kardon
Harman Kardon
harman/kardon is a division of Harman International Industries and manufactures home and car audio equipment.Founded in 1953 by Dr. Sidney Harman and Bernard Kardon — two men with a deep interest in music and the arts — the company helped create the high-fidelity audio industry. Their first product...
, JBL
JBL
JBL is an American audio electronics company currently owned by Harman International. It was founded in 1946 by James Bullough Lansing. Their primary products are loudspeakers and associated electronics. There are two independent divisions within the company — JBL Consumer and JBL Professional...
, and Mark Levinson
Mark Levinson
The company Mark Levinson, now owned by Madrigal Audio Laboratories specializes in high-end digital audio processors, integrated amplifiers, power amplifiers, pre amplifiers, and CD players...
) are available in several luxury car marques. A large after market industry exists where the consumer can at their desire replace many or all components of the stock system.
In modern cars, the primary control device for an audio system is commonly referred to as a head unit
Head unit
A head unit, sometimes referred to as a "deck", is a component of a stereo system either in a vehicle or home cinema system which provides a unified hardware interface for the various components of an electronic media system. An antiquated name for a head unit is a receiver; this article focuses...
, and is installed in the center of the dash panel between the driver and the passenger. In older vehicles that had audio components as an option, such devices were mounted externally to the top of or underneath the dash. Car speaker
Loudspeaker
A loudspeaker is an electroacoustic transducer that produces sound in response to an electrical audio signal input. Non-electrical loudspeakers were developed as accessories to telephone systems, but electronic amplification by vacuum tube made loudspeakers more generally useful...
s often use space-saving designs such as mounting a tweeter directly over a woofer or using non-circular cone shapes. Subwoofers are a specific type of loudspeaker for low frequency reproduction.
Motorcycles have been utilized with similar equipment since they also have the so-called "car audio" experience. Even pedal bicycles, as well as homemade boomboxes have utilized sealed lead-acid batteries (or 12V power supplies) for applications outside of motor vehicle use, likewise the store displays which mount in demo models prior to aftermarket purchases for installation.
Extremely loud sound systems in automobiles, which have been nicknamed "boom cars", may violate the noise ordinance of some municipalities.
History
1930s
From the earliest days of radio, enthusiasts had adapted domestic equipment to use in their cars. The commercial introduction of the fitted car radioCar radio
Car radio may refer to:*a radio in a car. See car audio and in car entertainment*"Car Radio", a song by Spoon from their 1998 album A Series of Sneaks...
came in the 1930s from the Galvin Manufacturing Corporation. Galvin Manufacturing was owned and operated by Paul V. Galvin and his brother Joseph E. Galvin. The Galvin brothers purchased a battery eliminator
Battery eliminator
A battery eliminator is a device powered by an electrical source other than a battery, which then converts the source to a suitable DC voltage that may be used by a second device designed to be powered by batteries....
business in 1928 and the corporation's first product was a battery eliminator that allowed vacuum tube battery-powered radios to run on standard household electric current (see also Rogers Majestic Batteryless Radio
Rogers Vacuum Tube Company
Rogers Vacuum Tube Company was founded as "Standard Radio Manufacturing" in 1925 by Edward S. Rogers, Sr. to sell Rogers "Batteryless" radio using vacuum tube technology. It was later renamed Rogers Majestic Corporation Limited when Rogers merged his company with Majestic Corporation of Chicago...
). In 1930, the Galvin Corporation introduced one of the first commercial car radios, the Motorola model 5T71, which sold for between $110 and $130 (2009: $) and could be installed in most popular automobiles. Founders Paul Galvin
Paul Galvin
Paul Vincent Galvin was one of the two founders of telecommunications company Motorola. Founded as Galvin Manufacturing Corporation on September 25, 1928, Motorola is now a leader in communications equipment.-Biography:...
and Joe Galvin came up with the name 'Motorola
Motorola
Motorola, Inc. was an American multinational telecommunications company based in Schaumburg, Illinois, which was eventually divided into two independent public companies, Motorola Mobility and Motorola Solutions on January 4, 2011, after losing $4.3 billion from 2007 to 2009...
' when his company started manufacturing car radios. A number of early companies making phonograph
Phonograph
The phonograph record player, or gramophone is a device introduced in 1877 that has had continued common use for reproducing sound recordings, although when first developed, the phonograph was used to both record and reproduce sounds...
s, radio
Radio
Radio is the transmission of signals through free space by modulation of electromagnetic waves with frequencies below those of visible light. Electromagnetic radiation travels by means of oscillating electromagnetic fields that pass through the air and the vacuum of space...
s, and other audio equipment in the early 20th century used the suffix "-ola," the most famous being Victrola
Victor Talking Machine Company
The Victor Talking Machine Company was an American corporation, the leading American producer of phonographs and phonograph records and one of the leading phonograph companies in the world at the time. It was headquartered in Camden, New Jersey....
; RCA
RCA
RCA Corporation, founded as the Radio Corporation of America, was an American electronics company in existence from 1919 to 1986. The RCA trademark is currently owned by the French conglomerate Technicolor SA through RCA Trademark Management S.A., a company owned by Technicolor...
made a "radiola"; there was also a company that made jukeboxes called Rock-Ola
Rock-Ola
The Rock-Ola Manufacturing Corporation was, along with Wurlitzer, a top maker of jukeboxes. The company, which originally made slot machines, scales and pinball machines, was founded in 1927 by Coin-Op pioneer David Cullen Rockola....
, and a film-editing
Film editing
Film editing is part of the creative post-production process of filmmaking. It involves the selection and combining of shots into sequences, and ultimately creating a finished motion picture. It is an art of storytelling...
device called a Moviola
Moviola
A Moviola is a device that allows a film editor to view film while editing. It was the first machine for motion picture editing when it was invented by Iwan Serrurier in 1924.-History:...
. The Motorola prefix "motor-" was chosen because the company's initial focus was in automotive
Automobile
An automobile, autocar, motor car or car is a wheeled motor vehicle used for transporting passengers, which also carries its own engine or motor...
electronics.
In Germany Blaupunkt
Blaupunkt
GmbH is a German manufacturer of electronics equipment, noted for its home and car audio equipment. It was a 100% subsidiary of Robert Bosch GmbH until March 1st, 2009 when its Aftermarket and Accessories branch including the brand name were sold to Aurelius AG of Germany for an undisclosed...
fitted their first radio to a Studebaker
Studebaker
Studebaker Corporation was a United States wagon and automobile manufacturer based in South Bend, Indiana. Founded in 1852 and incorporated in 1868 under the name of the Studebaker Brothers Manufacturing Company, the company was originally a producer of wagons for farmers, miners, and the...
in 1932 and in the United Kingdom Crossley
Crossley Motors
Crossley Motors was a British motor vehicle manufacturer based in Manchester, England. They produced approximately 19,000 high quality cars from 1904 until 1938, 5,500 buses from 1926 until 1958 and 21,000 goods and military vehicles from 1914 to 1945.Crossley Brothers, originally...
offered a factory fitted wireless in their 10 hp models from 1933. The early car radio receivers used the battery voltage (6.3 volts at the time) to run the vacuum tube filaments, and generated the required high voltage for the plate supply using a vibrator
Vibrator (electronic)
In early electronics vibrators were used in inverter circuits to provide an alternating current electric power supply from a direct current source....
to drive a step-up transformer
Transformer
A transformer is a device that transfers electrical energy from one circuit to another through inductively coupled conductors—the transformer's coils. A varying current in the first or primary winding creates a varying magnetic flux in the transformer's core and thus a varying magnetic field...
. The receivers required more stages than the typical home receiver in order to ensure that enough gain was available to allow the AGC
Automatic gain control
Automatic gain control is an adaptive system found in many electronic devices. The average output signal level is fed back to adjust the gain to an appropriate level for a range of input signal levels...
to mask signal fading as the car was driven. When cars switched to 12-volt batteries, the same arrangement was used, with tubes with 12-volt heaters. In 1952 Blaupunkt became the first maker to offer FM
Frequency modulation
In telecommunications and signal processing, frequency modulation conveys information over a carrier wave by varying its instantaneous frequency. This contrasts with amplitude modulation, in which the amplitude of the carrier is varied while its frequency remains constant...
receivers.
1950s
A common feature of modern car radios is the "seek" function which allows tuning from one station to the next at the push of a button. This was a popular option on some Ford products in the 1950s. It was known as the "Town & Country" radio since it used a pair of switches marked "Town" and "Country." Pressing the Town button actuated a motor to rotate the tuning mechanism while the receiver sensitivity was reduced so that only local (stronger) signals would be received. When a station was tuned, the motor stopped. Pressing the Country button had the same effect except that full sensitivity was enabled so that the very next available station would be selected. In addition, for repeated seeking operations, pressing a foot switch on the driver's floor up to the left where the "dead pedal"Dead Pedal
In an automobile, the dead pedal is located to the left of the other pedals. Unlike the throttle, brake or clutch pedal, the dead pedal does not move and is not connected to anything...
is located on modern cars would reactivate the Seek at whatever sensitivity was last selected.
1960s-1970s
The introduction of semiconductors (transistors) allowed the output stage to change to a transistor, which soon lead to the elimination of the vibrator, and the use of "space chargeSpace charge
Space charge is a concept in which excess electric charge is treated as a continuum of charge distributed over a region of space rather than distinct point-like charges...
" tubes that only required 12 volts on their plates without a high voltage plate power supply (typical example was the 6GM8/ECC86). Advances in electronics allowed additions to the basic radio and Motorola offered 16 2/3 rpm disc players fitted to some Chrysler
Chrysler
Chrysler Group LLC is a multinational automaker headquartered in Auburn Hills, Michigan, USA. Chrysler was first organized as the Chrysler Corporation in 1925....
s known as Highway Hi-Fi
Highway Hi-Fi
Highway Hi-Fi was a system of proprietary players and seven-inch phonograph records with standard LP center holes designed for use in automobiles...
from as early as 1956 and ran through 1958. Records were produced under license by Columbia
Columbia Records
Columbia Records is an American record label, owned by Japan's Sony Music Entertainment, operating under the Columbia Music Group with Aware Records. It was founded in 1888, evolving from an earlier enterprise, the American Graphophone Company — successor to the Volta Graphophone Company...
"Special Products" division and sold exclusively through Chrysler dealers. The 45 rpm record player was introduced in 1959 and ran through the early 60"s under the RCA and ARC brand. Earl "Madman" Muntz introduced the "4-track
4-track
4-track or 4-track tape may refer to:* The 4-track cartridge as an analogue music storage format popular from the late 1950s* A 4-track tape used in professional recording studios for multitrack recording...
" tape player in the early '60s using a continuous loop cartidge and was the first commercially available "car stereo". Tape players using reel to reel
Reel-to-reel audio tape recording
Reel-to-reel, open reel tape recording is the form of magnetic tape audio recording in which the recording medium is held on a reel, rather than being securely contained within a cassette....
equipment followed, but their bulk ensured limited popularity. This changed in 1964 when Philips
Philips
Koninklijke Philips Electronics N.V. , more commonly known as Philips, is a multinational Dutch electronics company....
launched the Compact Cassette
Compact Cassette
The Compact Cassette, often referred to as audio cassette, cassette tape, cassette, or simply tape, is a magnetic tape sound recording format. It was designed originally for dictation, but improvements in fidelity led the Compact Cassette to supplant the Stereo 8-track cartridge and reel-to-reel...
. During the '60s Lear invented and introduced the 8track cartridge in competition with the cassette system. Other early manufacturers and enthusiasts began building extra audio amplifier
Audio amplifier
An audio amplifier is an electronic amplifier that amplifies low-power audio signals to a level suitable for driving loudspeakers and is the final stage in a typical audio playback chain.The preceding stages in such a chain are low power audio amplifiers which perform tasks like pre-amplification,...
s to run on 12 volts (the standard voltage in automotive electrical systems). Jim Fosgate, later to become the founder of Rockford Fosgate
Rockford Fosgate
Rockford Fosgate is a manufacturer of aftermarket and OEM car audio and In-Car Entertainment products and accessories, as well as limited Pro Audio, and personal electronics such as earphones. Lightning Audio is a subsidiary brand of the company....
, was one such pioneer. The company a/d/s also brought an amplifier to market in 1978.
1980s-1990s
In 1983, Zed Audio became the first company to build a 2000 watt per channel car amplifier, which was invented by company founder Steven Mantz. At first, speakers from the home audioHome audio
Home audio, essentially, refers to any audio electronics intended for home use, such as shelf stereos and surround sound receivers, which are becoming the most popular piece of home audio equipment...
and professional markets were simply installed into vehicles. However, they were not well suited to the extremes of temperature and vibration which are a normal part of the environment of an automobile. Different manufacturing techniques, and different component materials were used in construction to adapt to these conditions.
Car audio competitions started in the early 1980s
The first known occurred in 1981 in Bakersfield, CA and evolved into an annual event. It was called The Summertime Car Show and Sound Off Competition, which at its height drew upwards of 300 contestants and continued into the 1990s. The Summertime Car Show and Sound Off Competition began as a promotional event for Cars on Camera, a magazine founded by owners Steve Silver and Scott Burud. Since the magazine derived a large part of its advertising revenue from local car stereo shops (TransLex, AutoSounds and others) it made sense to hold a sound off competition in order to create higher demand for magazine ad space. The original event took place in the parking lot of the local Zody's chain store on Ming Avenue, in Bakersfield, CA. However, the following year it was moved to the Kern County fairgrounds in order to accommodate the thousands of participants. By the second year, the event added a men's great legs contest and a bikini contest that attracted contestants from all over California. Cars on Camera changed its name to Camera Ads, which was then sold to Buck Owens Productions.
The most important of these were CAN (formed by Alpine) and NACA (supported by shop owners and amp manufacturers). Both organizations sanctioned countrywide regional events and hosted National Championship events in the late 1980s. They merged to form IASCA
IASCA
International Auto Sound Challenge Association is a worldwide association that promotes car audio championships. These have separate categories for hi-fi sound quality and for maximum dB ....
in 1990. Despite the move to "quality" based judging, volume was still a significant portion of most early 1990s competitions. Since then, the two styles—SPL vs. sound quality—have become almost mutually exclusive. The loudness competitions have become known as dB drag racing
DB drag racing
dB drag racing is a competition rewarding the person who can produce the loudest sound inside a vehicle. The "dB" means decibels of sound pressure level . In these competitions, Sound Pressure Level of 155 dB can be reached, and it is not unheard of to see more than 160 dB as well...
. Currently, Mobile Electronics Australia, an independent organisation conducts Sound Quality Competitions (MEASQ) and SPL Competitions (Bass Battle) nationally in Australia. These formats were developed by enthusiast Marc Rushton, the founder of one of the largest enthusiast organizations known as Mobile Electronics Australia.
Stock unit
A stock car audio system refers to the OEMOEM
OEM means the original manufacturer of a component for a product, which may be resold by another company.OEM may also refer to:-Computing:* OEM font, or OEM-US, the original character set of the IBM PC, circa 1981...
application that the vehicle's manufacturer specified to be installed when the car was built and nowadays at least includes a CD-radio, with MP3
MP3
MPEG-1 or MPEG-2 Audio Layer III, more commonly referred to as MP3, is a patented digital audio encoding format using a form of lossy data compression...
player and an aux-in. A large after market industry exists where the consumer can at their desire replace or complement many or all components of the stock system (i.e. kits to include a USB port and A2DP bluetooth
Bluetooth
Bluetooth is a proprietary open wireless technology standard for exchanging data over short distances from fixed and mobile devices, creating personal area networks with high levels of security...
to the stock radio-CD). Nowadays, the most valued port (40% of the users) is the USB.
Head unit
Head unit
A head unit, sometimes referred to as a "deck", is a component of a stereo system either in a vehicle or home cinema system which provides a unified hardware interface for the various components of an electronic media system. An antiquated name for a head unit is a receiver; this article focuses...
, and is installed in the center of the dash panel between the driver and the passenger. In older vehicles that had audio components as an option, such devices were mounted externally to the top of or underneath the dash.
The headunit itself is usually a multi-purpose device that houses multiple types of components in its housing. The most common components are a radio receiver/tuner
Receiver (radio)
A radio receiver converts signals from a radio antenna to a usable form. It uses electronic filters to separate a wanted radio frequency signal from all other signals, the electronic amplifier increases the level suitable for further processing, and finally recovers the desired information through...
usually with AM and FM bands, and a small amplifier for driving an audio signal to speakers. Other possible components include various media devices, such as (in older vehicles) a tape player (either 8-track or cassette
Compact Cassette
The Compact Cassette, often referred to as audio cassette, cassette tape, cassette, or simply tape, is a magnetic tape sound recording format. It was designed originally for dictation, but improvements in fidelity led the Compact Cassette to supplant the Stereo 8-track cartridge and reel-to-reel...
), CD player, DVD player
DVD player
A DVD player is a device that plays discs produced under both the DVD-Video and DVD-Audio technical standards, two different and incompatible standards. These devices were invented in 1997 and continue to thrive...
, USB flash memory
Flash memory
Flash memory is a non-volatile computer storage chip that can be electrically erased and reprogrammed. It was developed from EEPROM and must be erased in fairly large blocks before these can be rewritten with new data...
, and even a portable hard disk drive typically used in notebook computing. Many head units also feature a DSP
DSP
- Computing :* Digital signal processing, the study and implementation of signals in digital computing and their processing methods* Digital signal processor, a specialized microprocessor designed specifically for digital signal processing...
component, and equalization
Equalization (audio)
Equalization is the process commonly used in sound recording and reproduction to alter the frequency response of an audio system using linear filters. Most hi-fi equipment uses relatively simple filters to make bass and treble adjustments. Graphic and parametric equalizers have much more...
component (such as bass and treble
Treble (sound)
Treble refers to tones of high frequency or range. In music this corresponds to high notes, and for this reason the treble clef is often used for instruments with higher pitch. Examples of treble sounds are guitar tones, female voice , young boy voice, etc. They have frequencies above 9 KHz. Treble...
controls), or a control interface for another feature on the car (such as a back-up/parking camera, navigation system, trip odometer, etc.).
Due to auto manufacturing differences over the years, aftermarket headunit products are manufactured in multiple form factors. The primarily used size is mostly referred to by its legacy name of DIN, which refers to ISO 7736
ISO 7736
International standard ISO 7736 defines a standard size for car audio head units. The standard was originally established by the German standards body Deutsches Institut für Normung as DIN 75490, and is therefore commonly referred to as the "DIN car radio size"...
. DIN headunits come as single DIN or double DIN. A third less common standard is used mostly by Chrysler group and for a time Mitsubishi in their OEM devices.
Speakers
Loudspeaker
A loudspeaker is an electroacoustic transducer that produces sound in response to an electrical audio signal input. Non-electrical loudspeakers were developed as accessories to telephone systems, but electronic amplification by vacuum tube made loudspeakers more generally useful...
s are largely functionally identical to any other loudspeaker design with key components specialized for use in mobile environments, and generally serve an identical purpose. One major key design difference is mult-axial mounting of different types of loudspeakers in the same footprint, such as a tweeter directly mounted over a woofer. Another key difference is non-circular cone shapes, such as square, oval, or even triangular. Both of these features reflect a significant reduction in space and size that a speaker may occupy in a vehicle cabin.
Material construction may also include more exotic and hearty components more suitable to mobile use. Marine speakers may have plating for corrosion resistance. Cones may be coated with a substance to resist expansion and contraction under high vehicle cabin temperatures, known to reach 140 °F (60 °C) in the sun. Subwoofers may also be found in mobile audio applications where a cabin speaker may lack the desired low frequency response on its own.
Before stereo
Stereophonic sound
The term Stereophonic, commonly called stereo, sound refers to any method of sound reproduction in which an attempt is made to create an illusion of directionality and audible perspective...
radio was introduced, the most common speaker location was in the middle of the dashboard
Dashboard
A dashboard is a control panel placed in front of the driver of an automobile, housing instrumentation and controls for operation of the vehicle....
pointing through perforations towards the front windshield
Windshield
The windshield or windscreen of an aircraft, car, bus, motorbike or tram is the front window. Modern windshields are generally made of laminated safety glass, a type of treated glass, which consists of two curved sheets of glass with a plastic layer laminated between them for safety, and are glued...
. In most modern applications, speakers are mounted certain common locations including the front deck (or dash), the rear deck (or parcel shelf), the kick panel (located in the footwell below the A-pillar,) or the doors. In the case of subwoofers, mountings are usually under the seat or in the trunk. Each position has certain strengths and limitations from both a quality of sound, and a vehicle manufacturing perspective.