Car Audio Basics
by Cory Roberts
Listening to your favorite music while cruising down the road is as American as apple pie. The first commercially available car radio, the Motorola 5T71, introduced in 1930, gave Americans the ability to take their favorite tunes with them in the car. The rest is history. Car audio systems have come a long way since 1930, from a simple radio and single speaker to complex infotainment systems and are now a standard staple of automotive manufacturing. Continue reading for a brief overview of the basic components of your vehicle's audio system and how they supply the sounds of your daily commute.
Your vehicle's audio system is composed of three primary components. The head-unit, or receiver, is the nerve center of your audio system. It provides the audio signals that are output to the systems other components, and provides the driver with the primary controls for the functions of your audio system. Signals are then sent from the head-unit to the amplifier. In some cases the amplifier is built into the head-unit, but in premium systems from the vehicle manufacturer or custom aftermarket systems an external amplifier is utilized to provide better clarity, louder sounds. Finally, the audio signals are sent from the amplifer to the speakers. The speakers convert the electrical energy to mechanical energy creating the sound waves we hear.
Head-Unit:
The head-unit is commonly refered to as the radio since early receivers were simply AM tuner radios. Later FM tuners were added, and now modern vehicles and aftermarket head-units are being manufactured with HD radio tuners which provide an extremely high quality over-the air broadcast signal. The radio signals are fed into the vehicle's head-unit by way of an attached antennae either as a metal mast, shark fin style aero mast, or as an integrated mast built into the body or glass of the vehicle.
Modern head-units are capable of providing additional audio sources and the driver can easily switch between sources from the units controls, either by button/knob or touchscreen. In the 1960's few models were introduced which actually had a vinyl record player. Manufacturers recognized the demand from consumers for an easier way to bring their music with them. Research and development ultimately led to 8-track players, to cassette decks, to CD players, to multi-disc changers (usually a seperate component), to auxillary jacks, to USB/Ipod, and finally to Bluetooth technology.
Currently available head-units both aftermarket and manufacturer installed offer a vast range of additional features. Steering wheel controls have become almost standard equipment, allowing the driver to control functions of the head-unit from the steering wheel often assisted with a connected microphone for voice controls and Bluetooth phone calls. Bluetooth technology allows for the seamless, wireless connection between a smart phone or tablet. Bluetooth capable head-units give the driver the ability to stream music and video to the head-unit, allow the use of certain apps, and high-end or premium models may offer AndroidAuto or Apple Carplay for better integration with your vehicle. Modern units also typically have built-in, or as an option, satellite services such as GPS/navigation or satellite radio
Most head-units will have, at least, controls to fade and balance the the sound distribution front/back and left/right, and may have options for bass boost, auto-volume control, listening position, etc. More advanced units will have equalizer controls to fine tune audio signals for different listening preferences. Once the the driver has selected the source and set the control settings, the audio signals are ready to be sent to the amplifier. Some head-units have a pre-amp and amplifier built into them to boost the signals before being output to the speakers, however, premium manufactured and aftermarket systems will typically output to an external amplifier capable of much more than what can be squeezed into the small head-unit.
Amplifier:
The audio system's amplifier may have multiple functions, but all systems will use an amplifier to boost low-level output signals from the head-unit before sending those boosted signals to the speakers. The amplifier may be built-in to the head-unit as previously mentioned, however, these systems are fairly basic and only capable of driving simple speaker configurations at limited volume and clarity. Premium system amplifiers and aftermarket amplifiers are larger, use more power to boost the signals, and are capable of processing and filtering the audio signals for much greater clarity and volume control.
External amplifiers, in addition to providing greater amplification of the audio signals, offer the ability to filter the audio through electronic components called crossovers. The crossovers split the audio input signal into different signals for low range (bass), mid-range (mid), and high-range (high); allowing individual specialized speakers to deliver narrow range sound for an overall higher clarity of sound across all ranges. Aftermarket amplifiers can be installed with a single channel or single output to one speaker, or they may have several channels for managaing audio ouput to multiple speakers at different ranges.
Aftermarket amplifiers also have additional controls for fine tuning of the audio system that are not available in amped head-units or premium manufacturer systems. These controls may include crossover controls for filtering each channel, subsonic filtering, dynamic bass boosts, gain level, input/output level, and may include a dash mounted bass control knob. These settings should typically be set by the installer to ensure the best possible car audio experience upon installation or upgrade of your car audio system.
Speakers:
The speakers are the final component in your vehicle's audio system. The speakers are transducers, meaning they convert electrical energy into mechanical energy. The audio signals are sent from the amplifier as an alternating current via wires to the speakers. The signal is then passed around an electrical coil know as the voicecoil. The voicecoil is attached to the speaker cone made of paper, plastic, or other synthetic material; which is suspended over a fixed magnet. When the alternating electrical current passes through the voicecoil it creates an electromagnetic field which causes the speaker cone to push out. The pushing of the cone against the air creates a soundwave.
The way we here the soundwave depends on the controls set by the head-unit (i.e. volume, fade/balance, equalizer settings, bass boost), processing/filtering by the amplifier, and by what kind of speakers are installed. In standard audio systems the speakers are full-range, meaning they will have the full audio range of low, mid, and high played through them. Premium factory installed systems, such as Bose or JBL, will use an amplifer to filter the sound and output to low-range subwoofers, mid-range speakers, and high-range tweeters.
Aftermarket upgraded and custom audio systems will often have more specialized speakers. Subwoofers come in many size, power ratings, dual voicecoils, etc. Mid-bass speakers are optimized for low to mid-range. Tweeters are the highest range speakers and are typically very small. Coaxial speakers have a tweeter built onto the frame of a mid-range or full-range speaker and filter the high-range at the speaker in order to save space. Coaxial speakers, however, don't offer as clear sound as specialized speakers connected directly to an amplifier. Component set speakers are specialized mid-range and tweeters that are installed as a set with an independent crossover to filter the mid and high-range audio with better clarity than full-range or coaxial speakers.
Car audio technology has come a long way in the past 89 years. There are many options available to consumers to customize your vehicle's audio system and the experience that is right for you. Whether you are simply looking to diagnose and repair your factory installed system, build a custom car audio masterpiece, or anything in between. Full Blown Automotive Center has the knowledge, experience, access to top quality aftermarket components, and the passion to serve your car audio needs from mild to wild. Stop by and speak with one of our experts to evaluate your car audio needs for your vehicle, or schedule an appointment online.
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