What is a Head Unit Versus a Stereo, Receiver or Tuner?

The Differences Between Stereos, Head Units, Receivers and Tuners

what is a car head unit or stereo
Car radio nomenclature can get pretty complicated, especially if you just want to listen to some good tunes.  Teerapat Seedafong / EyeEm / Getty

A lot of jargon gets thrown around when you start talking about car audio, and some of it can get pretty complicated. You hear about car radios, car stereos, head units, receivers, and more, and sometimes it seems like there isn't any kind of sharp line drawn around any of them.

Fortunately, this is one area where it’s actually pretty easy to nail everything down. Here’s a basic rundown of some of the most common names for a head unit, and what they actually mean:

  • Car stereo is a catch all term for both head units and car audio systems as a whole.
  • Head unit is another broad term that can refer to any in-dash car stereo unit.
  • Receiver is a specific type of head unit that features a built-in amplifier.
  • Tuner is another type of head unit that doesn’t have a built-in amplifier.
  • Car radio is a catch all term that refers to both receivers and tuners.
  • Controller is a type of head unit that doesn’t include a radio tuner.
  • Mechless is a solid state head unit that lacks a CD, DVD, or cassette player.

Car Stereos and Head Units

Starting at the top of the heap, car stereo is a term that can refer to a huge range of devices and systems. This term can refer to an entire car audio system (including the head unit, amp, equalizer, crossovers, speakers, and everything else), but it is also a synonym for head unit.

Head unit can also refer to a lot of different types of devices, but they are all in-dash stereos. The head unit is essentially the brain or heart of a car audio system, and it can include a radio tuner, CD player, auxiliary inputs, and even built-in components like amplifiers and equalizers.

From this point on, terms become more specialized.

Receivers, Tuners, and Car Radios

Two closely related types of head units are referred to as receivers and tuners. Both of these types of head units include a built-in radio tuner (typically AM/FM), which is the only feature they both include by definition.

For that reason, receivers and tuners are also referred to as car radios. A lot of receivers and tuners also include features like CD players, auxiliary inputs, Bluetooth connectivity and USB ports, but that can vary from one model to another.

The feature that differentiates a receiver from a tuner is a built-in amplifier. Where receivers include built-in amps, tuners do not. Most OEM head units are receivers simply because it’s more expensive to build a car audio system with both a tuner and an external amplifier, although there are some exceptions. The majority of aftermarket head units are also receivers, although tuners are also available for people who are interested in adding an external amp and getting the best sound quality possible.

Of course, it’s also worth noting that some receivers include preamp outputs. That basically just means that although the head unit has a built-in amp, which makes it a receiver, it also has audio outputs that bypass the amp. These head units are great for anyone who is building their system piece by piece, since you can rely on the built-in amp until you get around to installing an external one.

Controllers

Not all head units are car radios. Most head units include a radio tuner, so they are car radios, but some don't. These head units are referred to as controllers because they don’t include built-in radio tuners to receive radio signals. These head units may or may not have built-in amplifiers, and they can include a whole range of different features and options, including:

Choosing the Right Head Unit

If you’re concerned about choosing the right head unit, then these terms can be extremely helpful in the decision making process. For instance, you might want to buy a receiver that includes built-in preamp outputs if you’re building your car audio system piece by piece. This will allow you to keep your options open, since you’ll be able to add an external amplifier at a later date if you decide that you want one.

Conversely, you’ll probably want to buy a tuner if you’re building your whole system at once, and you’re including one or more external amplifiers, and you might even prefer a controller if you never listen to the radio.

In any case, it’s important to remember that these terms aren’t always used properly, which can get confusing. The important thing is to understand the definitions yourself, so that you can apply that knowledge when doing your own research and putting your system together.