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The study of sound. Studying the science of the transmission and production of sound waves through different mediums. Also the information related to absorption, reflection, refraction, interference and diffraction.
The term used to classify parts that weren’t used originally with the vehicle when it arrived from the factory. Aftermarket accessories and parts are a popular way to add customization, technology, personalization and style to a vehicle. See also: OEM.
American Wire Gauge (AWG)
The dimensional characteristic standard of wire that is used to conduct electrical signals and currents. AWG remains identical to B&S (Brown and Sharpe) wire gauge.
This unit of measure how much electrical flow or current runs through a circuit. Ampere is usually abbreviated with the word “amp” but should never be used interchangeably when talking about an amplifier.
An audio device used to increase signal levels and route the increased power to one of more speakers. Car audio amps use switching power supply to increase the provided 12 volts to create a higher voltage amount. With this increase in power, the speakers can produce a higher quality sound, even at high volumes.
This security feature helps prevent theft of car audio systems, in conjunction with the car alarm. You can choose a couple of different anti-theft protection devices:
- Security Code – With the option to set a security code on the stereo, no one without the code can use it, rendering it useless if stolen.
- Detachable Face – The receiver’s control panel comes off, so it’s never left in the car when it’s not in use. No one wants a car stereo receiver that doesn’t have a faceplate, so thieves don’t waste their time.
A connection that permits the addition of an external source component into the video or audio system. This is often done with the use of standard RCA A/V jacks or a 3.5mm mini-jack input.
A range of frequencies assigned to a station by the FCC. In the AM range, bandwidth gets measured by kilohertz, while the FM range uses megahertz. The bandwidth identifies a radio station’s place on the dial.
The lower audio frequency that ranges below 500 Hz (hertz).
Group of cells that are electrically connected and wired in a series. In the automotive battery, the cells store an electrical charge to supply a direct current (DC).
A standard of wireless technology that permits two devices to connect with each other if they are located within 33-feet of one another. Bluetooth applications are found in vehicles to connect mobile phones to in-dash receivers and hands-free devices.
These coaxial speakers hold two elements, both the tweeter for the high notes and a woofer to handle the low notes.
This method of decompressing and compressing sound that’s digitized can be classified in different forms. Both WMA and MP3 are considered codecs. CD audio formats take up 10 megabytes to make one minute of music, where MP3s can convert that minute into just 1 megabyte.
Crossover (High-Pass Filter)
Built-in high-pass filters only permit the frequencies to pass that are above the crossover point. These filters can be used with preamp outputs, speaker outputs or both.
Crossover (Low-Pass Filter)
With a built-in low-pass filter, the only frequencies allowed to pass through are lower. Usually, these filters work with preamp outputs, but occasionally also with speaker outputs.
DAC (Digital-to-Analog Converter)
A CD receiver utilizes the D/A converter when converting digital 0s and 1s back to analog signals. CDs hold audio in a digital, binary format. While the data is accurate, it won’t sound like normal music when played. Instead, the D/A converter must translate that data into what you hear as music.
Adding a restrictive force or mass to an object for resonance control. In car audio systems, damping is used as an adhesive sheet that attaches to the vehicle’s panels, thereby reducing vibration and noise. With damping materials, the audio system doesn’t have to work as hard to reach a desired volume level.
The decibel is a measurement of sound corresponding to one tenth of a bel (B). The smallest audible sound is near total silence, measured at 0 dB. If a sound were ten times as powerful, it would have a 10dB rating. Sounds 100 times more powerful are 20 dB, while the 1,000 times more powerful sound is 30 dB, similar to whisper.
Digital Media Files
Any music that has undergone data compression is considered digital. Many modern formats allow the user to store hours of music, similar to a computer file, which is then decoded and played by the in-dash receiver. Types of digital media files include MP3, AAC, WAV and WMA. Many of these receivers are also compatible with Apple CarPlay and Android Auto.
Digital Media Receiver
These in-dash receivers read digital media without a CD player. Typically, there are inputs included for SD cards, USB drives and iPods. See also: Multimedia receiver.
While the term DIN is a German standard, it also is used to refer to the size of a receiver that fits in the car. See also: Double-DIN.
Car stereo receivers come with a variety of display options, including a multicolor display that improves the readability. With a backlit display, you can see the receiver better in low-light situations. Plus, a folding face display hides the CD opening that is located behind the panel.
These double-height receivers are twice as high as the standard found in most automobiles. The Double-Din dash opening is roughly 4-inches high by 7-inches wide. These receivers offer a bigger display screen and might be combined with a DVD player or in-dash navigation.
With this versatile DVD receiver, you play movies from your car stereo. The signal can be sent to the backseat monitors or can include a stationary screen upfront.
With a built-in EQ, it’s simple to customize the sound quality to your preferences. Most receivers with the built-in EQ have one equalizer band or more that operate on top of the treble and bass controls. However, some feature parametric equalization, allowing you to change the dB amount by boosting or cutting a certain frequency. These sophisticated equalizers provide advanced control over the tonal balance of sound.
The preset EQ are the tone settings that are stored in the stereo system. These curves get stored in the memory for quick switching. Many people use them when listening to various types of music for quick changes. For example, there could be a EQ preset for rap that offers more bass, plus a setting for jazz that offers a midrange boost and more treble.
The interval for European tuning is 0.5 MHz, which is different than in the United States at 0.2 Mhz. That’s why European receivers are made to work on the European scale, allowing them to be sold across most European countries.
Feedback occurs when an electronic circuit’s output signal modifies its own input signal.
FM Mono Sensitivity
The FM mono sensitivity figure allows you to see how well the receiver picks up FM signals. If the number is small, it will pick up the weaker stations better. This number is rated by decibel femtowatts (dBf).
FM Stereo Separation
The FM tuner’s ability to recreate vivid stereo effects is measured as separation by decibels (dB). If the measurement is higher, that is better.
This range shows the level of sound that a stereo part can reproduce, moving from bass to treble. The measurements occur in Hertz (Hz), with the wider ranges faring better. Bass is listed as the lower number, while treble is high. Humans hear sounds from 20 to 20,000 Hz, with a bass guitar reaching as low as 41 Hz.
This measurement shows how thick an audio wire is. If the number is high, the diameter is thin and vice versa.
Global Positioning System (GPS) is the navigational system that is run by the U.S. Department of Defense (DOD). With a navigation-ready receiver, the satellite signals are coded and sent from at least three satellites each second to ensure accuracy. This system also calculates your geographical location and vehicle velocity.
The ground loop happens when a piece of incoming wire or equipment receives a connection to a varying ground. For example, if the amp and in-dash receiver were grounded to varying spots, a ground loop could occur, causing multiple ground paths to work like an antenna, leading to interference. You will hear this interference as noise in the system.
HD Radios use digital audio broadcasting technology, so they aren’t subject to interference from the atmosphere like most AM and FM signals. These radios have fewer hissing and crackling.
Often referred to as the stereo, this in-dash source controls the volume and music sources, plus the information display. Aftermarket head units come in two sizes, DIN and Double-DIN.
Online radio is a digital audio service that is transmitted through the Internet. Sometimes, this service is called webcasting. Popular streaming services include Spotify, iHeartRadio and Pandora.
With this scan, you can hear a few seconds from every track on the CD. If you hear a song that you want, you can hit the button to stop scanning and the full track will play.
A jumper cable is essentially a short piece of wire that will allow you to ‘jump' one connection to another. Jumpers can be used for a variety of purposes, including on subwoofers and speakers to alter the ohms or most notably to jump your car's battery by connecting jumper cables from a charged battery to your vehicle's dead battery.
With this control, you can boost lower frequencies of the music for a richer, fuller sound, even while playing it at a lower volume.
With MP3 encoding, the music data is compressed allowing the user to store even more music on the disc. Modern in-dash receivers decode CDs filled with MP3 files. Portable MP3 players connect to the auxiliary inputs for play directly.
This in-dash receiver reads digital files without the use of a CD player. Inputs are included for USB drives, iPods, SD cards and more. See also: Digital media receiver.
This form of interference alters radio reception from FM signals. Because the radio waves travel straight, anything that stands between the transmitter and you can lead to multi-path interference. Sometimes, the receiver gets the signal multiple times because the waves are bouncing off of buildings and large objects. This problem leads to echoes.
The in-dash receiver contains a car stereo, monitor and navigation system all in one. Some of them even offer DVD playback, which permits movie viewing anytime you park the car. Installation of these systems can be more complex.
OEM stands for Original Equipment Manufacturer. This term relates to any factory installed components or equipment. See also: Aftermarket.
This is measured when there is a musical burst in brief periods. With some receivers, you can watch the peak power ratings right from the display. However, RMS power is often more significant.
Plug & Play
A plug and play system helps you install equipment faster. The install typically only requires you plugging a component in.
You can expand the audio system with the help of external devices such as processors and amplifiers through your RCA connections. If a unit is capable of handling three pre-amp outputs, you would have a subwoofer, rear and front. However, some units only include one or two of these outputs.
Preamp Output Voltage
This is the voltage as read by the receiver’s preamp outputs. If the system contains high preamp output voltage, you will hear a cleaner tone because of improved noise resistance. There will also be a higher output coming from the amp.
Radio Data System
The RDS tuners automatically tune into stations based on preferences. RDS tuners also break through with any emergency broadcasts and traffic alerts, even while listening to CDs. The RDS also permits the receiver to display call numbers, format info and text messaging on the display.
The receiver is responsible for playing any compatible music source, but it also sends audio signals to the speakers. Many receivers come with built-in amps that power the speakers directly. Some receivers also have pre-amp outputs to send signals off the external amp, allowing the signal to be boosted as it goes to the speakers. The term receiver is also commonly interchanged with stereo, e.g. car stereos.
This continuous power measurement is listed in watts. Root Mean Square (RMS) power is what the amp produces. If the figure is high, the music sounds cleaner and louder.
This shuffle play function mixes the song’s order played from a CD or streaming service.
Infrared or wired remotes can be used with compatible receivers to adjust volume, change channels or play CDs without touching the display. Some remotes can be purchased as an aftermarket accessory.
Satellite Radio Controls
Receivers that operate SiriusXM tuners will have unique controls, such as a scan and seek tuning, preset scan, plus station scan. These receivers require a service subscription and special antenna to work correctly.
Cars that were built through the 1980s might have this three-hold mounting configuration in the dash opening. It can also be found in other cars, requiring a special mounting kit.
This is the measure of the ability of a player to silence any background noise. The higher the rating is in dB, the less noise that should be heard.
The subwoofer is also known as a sub. It acts as a loudspeaker to boost low-frequency sounds at a higher power. This frequency is referred to as bass. Most subwoofer frequency ranges are 20 to 200 Hz. Adding a sub promotes a greater sound depth to a music system. These large speakers often measure 10- to 15-inches and are placed in a unique enclosure that resists deformation with the greater air pressure needed for the low frequency.
Subwoofer Preamp Outputs
The RCA output connections for a sub amplifier. They are typically coupled with the built-in low-pass filter.
This flash drive acts as a smaller data storage device you plug into your USB port. It holds a massive amount of data, allowing you to carry many music files with you on the go. If the car receiver comes with a USB port, the drive can be plugged in so you can play your music directly from this device.
Some receivers contain a special processing circuit that compensates when there is an uneven distance from the right and left car speaker to the user’s ears. This time correction occurs at the speaker that is closest to ensure the sound arrives at the off-center position simultaneously.
This feature replays the same track until it is turned off.
Otherwise known as best tuning memory, this feature found on the receiver loads the preset bank automatically with the strongest signal first. When you drive through an area that isn’t home, it allows you to navigate the stations easier. It’s also helpful when the car battery is disconnected, therefore wiping out the memory in the receiver.
This speaker is responsible for reproducing the higher frequencies, named after the high-pitched tones that a bird makes. Most tweeters output frequencies of 2,000 to 20,000 Hz, considered to be the top limit of normal human hearing. When combined with other types of speakers, it helps create a full sound range.
Most tweeters use a fixed magnetic field that suspends a voice coil. When current runs from the amp into the coil, the magnetic field is created. The coil then works against that magnetic field of a magnet inside the tweeter. When the forced coil moves, it also creates movement with the diaphragm. The amount of movement is determined by the signal coming from the amp.
Tweeter material affects the sound quality. Softer materials, such as silk, textile blends or polypropylene, will create a mellow, refined sound. In comparison, harder materials such as graphite, ceramic and metal create a snappy, bright tone.
There are several kinds of tweeters to choose from, including the cone tweeter, dome tweeter, bullet tweeter and horn tweeter.
Video System Control
Receivers containing the video system control use the same branded or other compatible components for video and will play the TV audio through the speakers in your car.
This measurement evaluates real power, which is the product of the current and voltage in a resistive circuit.
WMA (Windows Media Audio)
Originally developed by Microsoft, WMA is still one of the most known Internet audio formats, even though it isn’t quite as popular as the MP3.
Compatible CD receivers that have a specialized circuit detecting times of zero audio signals will mute the output during that time. When this occurs, all that is heard is silence until the audio signal is re-detected.
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