Car Stereo Glossary of Terms

Car Stereo Glossary of Terms

If you’re doing repairs or making improvements to a vehicle’s stereo system, you may be confused by some of the terms thrown around by the installer. You’re stuck because you want to ask the right questions, but you also don’t want to seem like you’re uneducated on the subject. So, use this car stereo glossary of terms to stay on track.

The Top 13 Car Stereo Terms

Almost every term used to describe a radio system falls into these thirteen catch-all phrases and types of car stereo terminology.


In the world of car stereos, this is a new but critical term. Just as technology has brought new connections like Bluetooth and WiFi into our homes, the same type of connections come in car stereos. So, connective interfaces are now common in cars, just like inside our houses.

So, like when you’re talking about how your speakers at home connect to your phone, you can have the same conversations regarding your car. Let’s assume you have a mobile phone with a library of songs. When you get in your car, there are two types of connectivity you may want.

The first is wired connectivity. That means physically plugging a wire into your phone so that its music can play through the car’s stereo system. The second type of connection is wireless connectivity, where either WiFi, Bluetooth, or another type of streaming link makes it possible to play your music without needing a physical plug.

Source Unit

This term is another neophyte in the world of car stereos. In the 1980s and 1990s, the head unit was the ‘brain’ of a car stereo. Now, the connections, types of control, and multimedia make the old terminology arcane.

Installers will now use the term source unit when referring to any aspect of the audio and visual interface that controls the car’s onboard systems. For example, if you are using the touchscreen in your BMW 5-series to change stations on your satellite radio feed, tuning the AM or FM radio, pressing a button to play a DVD on the rear seat monitors, you’re using the source unit.

Impedance and Ohms

Electrical circuits have natural impedance or resistance to the flow of electricity from the source unit or another type of media through the speakers. Ohms are the unit of measure used to gauge resistance in a circuit. An installer may use the term impedance to refer to the same thing.

A speaker’s job is to translate electrical impulses into a reproduction of the recorded sound we’re trying to play through the system. Since the electrical impulses come from the source unit, it’s essential that the speakers and the source unit are compatible.

You don’t need to be an expert in Ohm’s Law to realize that high-impedance speakers won’t work with a source unit that requires a low-impedance setup.

Integration Module

Modern cars are getting trickier and trickier to modify. In the old days, as long as the key fit the ignition, the car’s electronic systems would fire up when starting the vehicle. Now, there are many cars on the road that don’t even require a key.

Instead, your car detects the presence of your authorized key fob and allows the vehicle and its electronic systems to turn on. The computer controlling the car and permitting it to start in the presence of your key is an integration module.

Modifications to your vehicle may sometimes require replacement of or adjustments to the integration module, and since you are in effect bypassing the factory logic, some call this component a bypass module.


Pillars are specific locations on a car, labeled by alphabetic characters A, B, and C. Before meeting with an installer about your project, take a good look at your vehicle. There is a section of bodywork that links the hood to the roof, running at an angle alongside each side of the windshield.

That post is the A-pillar. The plastic covering the inside of the A-pillar is sometimes called the sail panel, and it’s a common location for mounting small speakers.

The B-pillar is the car’s middle post, linking the body to the roof. Not every car has a B-pillar. For instance, a convertible coupe lacks this post. But, most sedans and SUVs have a B-pillar. It’s often where the upper link for the front seat belts mound to the body.

The C-Pillars are the most rearward, framing the rear windshield. You can use these terms as geographical references when talking about your car. For instance, you might ask the installer to make sure that your new rear speaker grilles match the C-pillar trim. Or, you might want to hide the wires for your overhead Bluetooth mic behind the A-pillar.

Kick Panels

The term kick panel usually refers to a place where the factory has installed a protective piece of plastic, often to hide wiring or other infrastructure. For instance, if you look down in the footwell on the driver’s side of your car, you’ll probably see a handle for opening the hood, perhaps an electrical connection for diagnostics, or even extra outlets or USB plugs.

The plastic panels holding these features are also covering the sensitive wiring that makes the car’s systems functional. To grab power, run wires, and work with the car’s computers, technicians must often remove these panels and replace them to hide their work.

Woofers, Subs, Tweeters, and Mids

The frequencies of sounds vary considerably, so to reproduce a song accurately, your stereo will need speakers capable of handling as wide of a range of frequencies as possible. There isn’t a single speaker that can cover the whole range.

So, stereo system engineers and aftermarket installers use subwoofers for bass, mid-range woofers and mids for middle frequencies, and tweeters for treble sounds. A subwoofer reproduces sound below 100 Hz.

Larger mid-range speakers are called woofers, and they handle fairly low sounds and some of the middle ranges as well, from about 65 to 500 Hz. True midrange speakers play from about 80 Hz to 6 kHz. Tweeters play the highest-pitched treble sounds from 2 kHz and higher.

Speaker TypeSubwooferWooferMid-rangeTweeter
RangeBelow 100 Hz65 to 500 Hz80 Hz to 6 kHz2 kHz +
Size8 – 15 inches6 – 8 inches2 – 7 inches.25 – 2.25 inches

Coaxial Vs. Component Speakers

Usually, car speakers come in pairs. Sometimes, a pair of woofers or midrange speakers come with matched tweeters. This is called an arrangement of component speakers.

Coaxial speakers follow the same theme as component speakers, with matched components able to reproduce a wide range of sounds. But, instead of separate construction, each pair of the speakers are built into the same housing. If you have limited space, coaxial speakers systems can help boost your sound quality without requiring a lot of room.

Frequency Response

Frequency response is a measurement of how well a stereo reproduces sound. For example, if you have a subwoofer, its frequency response range may include all of the lower registers you need. But, as the sounds get higher into the range, performance starts to drop.

Your installer will match the subwoofer with woofers or midrange speakers that can handle the transition, so you don’t end up with gaps in your stereo’s abilities. Excellent sound quality starts with outstanding, consistent frequency response over as much of the range as possible.

Decibel (dB) Rating

The decibel scale measures the loudness of sound. Some people make it more complicated than necessary, but the bottom line is fairly simple. The scale is logarithmic, so sounds that are at 50 dB are twice as loud as those at 40 dB. Sounds at 60 dB are twice as loud as those at 50 dB, and so on.

This quick chart of common noises and their decibel ratings is helpful for reference.

Remember, If you’re installing a 150 dB car stereo, the entire vehicle will shake in rhythm with the bass. It will also be about as loud as a jet engine 100-feet away!

Watts and Power

Watts are the units of measurement that describe power. An amplifier will have a power rating listed for each channel. For instance, a 500-watt amp may have two channels with 250 watts each. An installer might use one channel to drive the subs and the other to drive the rest of the car’s speakers.

The drive or power of a stereo system has to match the capacity of the speakers it’s attached to. Otherwise, the speakers can be over- or under-powered, resulting in poor performance, buzzing, or even electronic failure.

That’s because the electrical energy coming from your amplifier passes through the speaker coils and actually moves the cone, reproducing sound. If there is too much energy coming through the system, the speaker cone may break or buzz. When the power level is too low, the cones may not move enough to accurately reproduce the sounds you’re playing.

When it comes to car stereos, more power isn’t always better.

Digital Signal Processing

The digital signal processor (DSP) is a component of a stereo system. They’re not just for car stereos either, as they’re common on all types of sound systems. The DSP’s computer helps to tune the electronic impulses to your speakers by adjusting the frequency equalization or the filtering of signals.

For instance, if you have a crossover that splits sounds between component speakers, the DSP will control the split, enhancing the sound quality. When you go to your source unit and dial the bass down, it’s the DSP that actually makes the change.

A DSP can have many inputs and outputs, so all features of a given system can connect to it. Then, you can control all the different aspects of the system’s sounds. Plus, it can help account for delays in signal processing.

For example, it may take longer for a digital signal to reach the speakers at the rear of your vehicle. So, the DSP can adjust the delay on your front speakers, ensuring that all the speakers hit synchronously.

Fiber Optics

In the old days of audio system engineering, speaker wire was the common way to bring electrical energy from an amplifier to a set of speakers. There were all kinds of cables used to connect components to the head unit, with RCA jacks being pretty common.

Now, some modern vehicles are coming out with fiber-optic connections. These systems use impulses of light to transmit information through strands of glass or plastic instead of traditional wiring. Fiber optic cables are much more difficult to work with, as splicing is often impossible. The interior fibers of an optical connection can be smaller than human hairs.

Those are the downsides. The upside is that these fiber optic cables can transmit information farther and faster than conventional wiring.

Car Stereo Glossary: Additional Terms

These are some other technical terms you might want a quick reference for.

  • Aftermarket – Refers to parts and systems not included in an original vehicle from the factory.
  • Anti-Theft Protection – This is a security feature made to prevent stereo head unit thefts. Some systems allow the owner to take a detachable face out of the car, rendering the system useless. Sometimes, there is a code installed into the system, and without it, no one can turn it on.
  • Damping – When cars have serious bass power, they tend to rattle the door panels, windows, and even the license plate frame. Damping is typically an adhesive sheet of sound-absorbing materials you can install to deaden the vibrations, improving the quality of your system.
  • DIN and Double DIN – DIN refers to the height of a car stereo’s dashboard controller. A single-DIN system was standard on older cars. Now, taller Double-DIN and even larger systems are commonplace.
  • Loudness – Refers to an equalizer setting that boosts lower frequencies for better enjoyment and fuller sounds, even at lower volumes.
  • OEM – Original Equipment Manufacturer means factory-original. Or the opposite of aftermarket.
  • Time Correction – An electronic feature that allows fine-tuning to compensate for delays in reproducing sounds when listening from an off-center position, ensuring that the sounds from left and right speakers simultaneously arrive at the listener’s location.

Car Stereo Glossary: Wrap Up

Now you know all the car stereo terms you need for having a discussion about your vehicle’s system. Now it’s up to you to decide how loud you need to go and how high the quality needs to be for your ears.

Brett Gordon

The engine behind editing at DigMyRide and the brains behind its build. During the day, Brett is a thirty-something dude from SoCal climbing the corporate ladder, but by night, he spends his time contributing to the online world of automotive tech & trends.