Depending on your budget and personal tastes, there are many different system configurations to suit your needs. Here’s some examples:
System 1: Basic
A lot of times less is better. Less components means lower system cost and the ability to spend a few extra bucks on the components that really count.
When it comes to sound quality, less speakers is definitely better. The more speakers you have, the more harmful interactions and cancellation of sound waves will occur.
Start with a good set of components (two tweeters and mids) that can go down to 60 Hz with no problem in a properly designed enclosure (i.e. custom kick panel pods). Rear speakers are not essential in most cases.
Get a good head unit with a clean signal. If most of your music is in CD format, it is better to spend your money in a good single CD player than a cheaper set of tape player/CD changer combo.
Unhappy with the front speakers sound level? Not to worry, get a good quality amplifier. 100 watts per channel should be plenty. Don’t be too concerned about the power rating on your speakers, unless you drive speakers with ridiculously high power levels. As long as you have good speakers and protected by a crossover with a steep slope (i.e. 24 dB/Octave) on the lower end, you should be fine.
The system should sound pretty darn good by now. If not, fix any system design/installation flaws.
Now for the last part: Bass. You need two things: subwoofer(s) and an amplifier. For audiophile quality sound two 10″ subs will satisfy most people. The trick is a properly designed enclosure and lots of power. 200 watts or more per sub should add plenty of punch for the bottom end of your system.
Subwoofers need more power than speakers because they are bigger and have to move more air. If you have limited finances, go with a mid-end (i.e. Sony, Pioneer, Kenwood) amplifier for the front speakers and a better high-current amplifier for the subs.
If everything is installed properly and tweaked carefully, you will be very happy with the results.
System 2: Competition Level
Competition level systems require deeper pockets and more components. System presentation also becomes a big issue.
The guidelines of the previous system apply, but you need more gear.
Head units and amplifiers need to have impeccable sound quality and no noise (background noise or alternator noise) whatsoever. Most people prefer to take advantage of head units capable of high line level voltages (3 to 8 volts) for minimum background noise.
Equalizers become a necessity to fine tune system’s response. Most competitors prefer to use a mono 30 or 31 band equalizer per channel. Many people have multiple sets of equalizers to quickly change the system’s response from sound quality to high SPL or RTA judging.
If the audio system is to be played when the car is not running for extended periods of time, extra batteries should be added to the car. You might need to add a high power alternator if the car’s electrical system can’t handle the extra loads.
All the components should be very neatly installed. Every detail of the installation must be meticulously executed. Wiring and connectors should be neat and clean. The car should also be treated against rattles and road noise.
System 3: SPL
SPL systems are very different. The idea here is to be as loud as possible, especially in the lower frequencies. For a system to be loud, it needs three things: Lots of power, a lot of speakers and a closed place where all that sound can be concentrated. This costs, as you can imagine, plenty of money.
The first upgrade here is the vehicle’s electrical system. Alternators, capacitors and batteries become essential.
Most people into SPL competition don’t consider staging and imaging as important. Multiple speakers are placed up front, wired in series/parallel combinations to maximize amplifier power output.
A very important aspect of an SPL vehicle are the subwoofers. Subs need to have a big cone area and high excursion (Xmax) to be able to move as much air as possible. The amplifiers moving the subs must be able to handle high current demands and to have low impedance capability.
SPL vehicles should also be treated to be as stiff as possible to minimize loses. Flexing body parts take a toll on output. Serious SPL competitors replace glass with thick Plexiglas, and reinforce the whole inside of the vehicle with steel, concrete, etc. To minimize air leaks many competitors use bolts to hold doors in place, keeping door seals tightly closed.