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By Jim Kerr

While most vehicle owners are satisfied with their factory audio systems – especially quality systems from manufacturers such as Bose, Mark Levinson or Sony – there are others who want more power, better range and theatre-like sound from their audio systems.

That’s where the aftermarket comes in.

Selecting a good sounding aftermarket sound system is more than just selecting components: dual 12-inch subwoofers in a large cabinet may produce volume, but the key to a good sound system is clarity. Clarity of sound can be achieved by selecting the correct components that compliment each other and then installing them correctly. Otherwise the audio system can have distorted sound that power alone can’t correct.

The sound starts at the head unit. This is the receiver, CD player or DVD player that produces the audio signal. The better this initial sound source, the better the final sound will be. Many aftermarket systems come with low-level audio outputs that can feed directly to an auxiliary amplifier, without having to pass through the main power amp in the head unit. On some vehicles, installing an aftermarket head unit can be a tricky job. Not only is there the cosmetic looks of the installation to consider, there is also space limitations and interfaces with the factory vehicle wiring that must be dealt with. The support of a good audio dealer will help overcome these details, but for some owners, they may wish to stay with the factory audio system and just add to it.

The next important part to consider is the amplifier or amplifiers. They come in a wide range of power ratings, but when comparing them always look for the RMS rating. This is useable power instead of just peak power. Most aftermarket systems start with an amp that powers two or four channels for low frequency response or an amp for very low frequency, for that “boom boom” subwoofer sound you hear. The head unit internal amp can power the higher frequency sounds easier, but adding another amp for high frequency sound will help with system clarity too.

There are many features to look for in an amp besides power. Many have built-in crossovers that let you adjust the sound frequencies the amp sends to the speakers connected to it. Other amps may have pre-amp outputs, so you can connect a second amplifier to the first and have each produce separate frequency ranges. A single channel amp can be used to drive a subwoofer, but many dual channel amps can be “bridged” or power taken from both channels to power the single large speaker.

Speakers come in many materials, sizes and power capacities. Small tweeters reproduce high frequencies, while large woofers, eight-, 10-, 12-, 15-inch or even larger in diameter reproduce low notes. Coaxial speakers contain tweeters in the same housing as a mid-range speaker and make for easier installation, but many systems place each speaker separately, with tweeters up high so the frequencies aren’t muffled.

With any large speaker, the box or enclosures they are mounted in can be as important as the speaker itself. You need a solidly built enclosure that will not vibrate and produce distortion. Just bolting a speaker to the package tray won’t produce the best sound.

The audio system wiring is an often overlooked part of the system. For a powerful sound, you need to provide a lot of electrical energy to the amplifier. The main power cable needs to come directly from the battery with an in-line fuse close to the battery in case the cable touches a ground. The longer the cable, the bigger it needs to be. A 4-gauge wire (about 5-mm diameter) will provide power for most installations, but you may need a bigger wire if you are using multiple amplifiers. The ground cable should be the same size. Don’t use small wire or the amp will run out of power and distort the sound.

Finally, planning a quality system is important to achieving the sound you want. Read the specifications, ask questions and do your research. The whole system doesn’t need to be installed at once so work within your budget. You can get some real quality sound, and if you like, you can crank up the bass and wake up the neighbours with that “boom, boom, boom.”

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