Terms to Know about Car Audio: Aspects of Sound Quality
Listening to audiophiles go on about the sound quality of their audio systems — from their woofers to their tweeters — can sound a lot like oenophiles going on and on about the qualities of wine. To understand such talk, start by understanding the four basics of sound quality:
- Dynamic range
- Frequency response
- Tonal balance
Clarity is the ability of a system to produce the original signal as intended, without distortion. Distortion can be caused by numerous things — from a head unit that's not level-matched with an amplifier to an amplifier that's clipping, or being overdriven and sending a distorted signal to the speakers. And distortion can come from any component in a system.
A good test is to listen to cymbals, which can have a brassy and off-putting sound when distorted. High-pitched female vocals are also difficult to reproduce and can reveal distortion rather easily.
Achieving clarity and therefore avoiding distortion is all about proper system design and tuning. It's making sure components are of sufficient quality and compatible with one another and that signal levels are well matched between electronics. It also involves using a component as it was intended and not pushing it past its design limits.
Dynamic range refers to the ability of a system to reproduce loud and soft passages in music with the same level of detail. When you're at a live concert, a singer may wail and then whisper or a drummer may hit a drum head with brute force and then back off a bit. Each extreme is an important part of the performance.
If the performance is recorded and reproduced by an audio system, the loud and soft parts should be delivered with the same detail and accuracy. But often a system tends to suppress soft parts and emphasize loud ones, meaning you lose the subtleties of the performance.
A related concept is linearity, which refers to a system's tendency to lose detail when the volume is turned down. A system has great linearity if it can retain the same detail at a low volume that it does when it's cranked up.
Every sound you hear, from the low rumble of thunder to the high-pitch wail of a siren, is caused by vibrations in the air that occur at certain frequencies. These vibrations are measured in hertz (Hz), which refers to the number of times per second these vibrations occur.
Humans can hear frequencies roughly from 20 to 20,000 Hz. A car audio system's frequency response represents how much of the audible frequency spectrum it can reproduce. The frequency response of a car audio system can be measured by an instrument known as a real-time analyzer (RTA), which consists of a microphone attached to a processor with a display that has a graph that shows a system's response.
An ideal car audio system uniformly reproduces the entire audible frequency spectrum from 20 to 20,000 Hz. But no system — at least while playing music — is perfect. Music is dynamic; some parts are loud and some are soft, so a system will naturally have dips and peaks in its frequency response.
Although a system can have these peaks and dips in frequency response, it needs to have good tonal balance — a relatively equal amount of sonic energy across the frequency range — to sound good. Subsequently, system designers and tuners often measure frequency response to gauge which frequencies may need to be boosted or cut as opposed to trying to achieve a flat frequency response. This can be done with an equalizer, although it's best that the system is designed in such a way that it has good tonal balance to begin with.