You've probably heard a car audio system and was blown away by how great the music sounded - the bass was forceful but tight, the guitars sounded lifelike, and you could hear every nuance of the singer's performance. Then you decide you would like recreate something like it in your own system. But how do you get it if you don't even know what it is?
Understanding What Constitutes Good Sound
Great sound is one of those indescribable traits that, like great art or beauty, is in the eye (or in this case, the ear) of the beholder. Yet there are certain qualities that can be indisputably attributed to a great sounding system: clarity, dynamic range, frequency response, and tonal balance. Some attributes, such as frequency response, can be measured objectively (by instruments) as well as evaluated subjectively (by ear), whereas others, such as dynamic range and tonal balance, are purely subjective. Sound quality is also very personal: What sounds great to you may sound horrible to someone else.
Remember,It's important to design and build your system to suit your tastes. After all, it's your car and your money. So if you want a system that's bass heavy, so be it. Or if you want a system with screaming highs, that's cool too. And although you should always build and tune your system to your own sound-quality standards, as with manners, it's better to know what's proper - or, in this case, what proper sound quality is - before you deviate from it.
I've often been asked why I've never competed in sound-off competitions, in which car audio enthusiasts go head-to-head to determine who has the best system. My glib response was always that I didn't care what other people thought about my car audio system because it was for my enjoyment. I do like to get people's opinions on my system, sometimes, if I feel that they can offer some insight and advice. But I always keep in mind that the system is ultimately for my ears and it's my opinion and enjoyment that matters most.
It's also important to listen to reference systems to establish a benchmark. But first you have to know what you're listening for.
Discovering Aspects of Sound Quality
My intent is not to turn you into an audio snob spouting esoteric terms, but to help you grasp a few key concepts when it comes to evaluating a car audio system's sound.
The four basic food groups of sound quality are:
- Dynamic range
- Frequency response
- Tonal balance
Clarity is the ability of a system to produce the original signal as intended, without distortion. Although this is all but impossible except for the best systems, it's an ideal to strive for. 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. Distortion can come from any component in a system.
Tip: To get a sense of a system with exceptional clarity, you'll need to listen to a reference system and compare it to a system with unexceptional clarity. 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 and 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. It isn't especially difficult for a system to sound great with the volume cranked. But a system has great linearity if it can retain the same detail at a low volume.
Every sound you hear, from the low rumble of thunder to the high-pitch wail of a siren, is caused by a vibrations in the surrounding 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.
Tip: A good way to grasp this concept is to think of a guitar string. When a low E note is plucked on a guitar with a standard tuning, the lowest possible frequency it can produce is at about 80 Hz. That means that the string (and hence the air around it that produces the sound) vibrates 80 times a second.
Humans can hear frequencies roughly from 20 to 20,000 Hz. Our ability to hear high frequencies drops off with age and hearing damage, and women typically have better high-frequency hearing than men. Low bass frequencies are felt as much as they are heard, and that's why you feel bass from a passing boom car audio system sometimes before you hear it.
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.
Ideally, a car audio system would uniformly reproduce the entire audible frequency spectrum from 20 to 20,000 Hz. Music is dynamic, meaning that 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 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.
Experienced ears can often tell where a good system is lacking in tonal balance just by listening to it, and it's generally easy for most people to discern, for example, when a system lacks response in bass frequencies or if it over-emphasizes treble frequencies. That's why radios have bass and treble controls.
From Car Audio for Dummies, copyright © 2008 by John Wiley & Sons, Inc., Hoboken, New Jersey. Used by arrangement with John Wiley & Sons, Inc.