The Just Customz Blog

The addition of an amplifier and suitable speakers can enhance any car audio system. In this article we will cover the most of the decisions that need to be made when choosing an amplifier for your car.

How Much Power?

Some people will say that you can never have enough power! The power output of the amplifier will ultimately govern the maximum volume that will be available in the system. However the power output of the amplifier must be carefully matched to the power that the speakers can handle. The values that should be matched are the RMS output value of the amplifier and the RMS input value of the speakers. Speakers often supply the peak music input power as well but this shouldn’t be confused with the RMS value. The peak value is the power that the speaker can sustain for short bursts but not continuously.

If the RMS input power of the speaker is regularly exceeded then it will lead to premature failure of the speakers which will probably be caused by a mechanical failure.

How Many Channels?

The number of channels correspond to the number of speakers that can be driven from a single amplifier. The most popular choices are either 2 or 4 channels.

4 channel amplifiers often give the ability to create a bridged connection. This is where 2 channels are combined to give approximately twice the output of a single channel. This gives some flexibility in the system for example you could use 2 channels to power the high/mid range speakers and a single bridged channel for the sub-woofer to give some extra depth to the sound.

Amplifier Inputs

One common problem that maybe experienced is when the factory head unit is to be maintained. The input connections to an amplifier usually consist of a set of RCA sockets. If you are lucky the head unit will provide RCA output connections which can be directly connected to the amplifier. In the majority of cases some kind of adapter will be required to reduce the output level of the head unit to a suitable value for the input of the amplifier.

Power Supply

The supply that the amplifier is connected to is vital to ensure a pure clean sound. To get the optimum sound the supply cables should be routed directly to the battery ideally keeping the cables as far from the other cables as possible. This is to prevent any spurious ‘noise’ being picked up which will manifest itself as buzzes, hums and clicks on the audio from the amplifier.

The amplifier itself is switched on and off by connecting the supply usually used for an electric aerial straight to the remote input of the amplifier.

If buzzes, clicks and hums are present on the audio then a choke can be placed in series with the power supply lines which will reduce and hopefully eliminate it.

Location

The final point that shouldn’t be overlooked is the location of the amplifier. The amplifier must be located in a position where it has good airflow to ensure that it doesn’t overheat. In the event of overheating the amplifier will probably shutdown or at worst it will fail.

It should also be located somewhere where it will not be exposed to electromagnetic radiation such as too close to the engine etc.

An good quality sound system will make an excellent addition to any modified cars.

With the huge choice of car audio equipment available today it is often difficult to decide what car stereo would best suit your needs. This article will hopefully help you negotiate the technical minefield and make the best choice for your requirements.

There are two main contributing factors to the quality of the audio that is produced by any audio equipment which are the frequency response and signal-to-noise ratio (SNR). The frequency response of the ear is around 20Hz to 20KHz although this often diminishes with age. A ‘loud’ facility is sometimes provide to boost the frequencies that become degraded with age. The SNR is important as it is what constitutes the background hiss that is often associated with cheaper audio equipment.

The car stereo or head unit today can play audio from a wide variety of sources which we will now discuss below.

Cassette Deck

If the reason for replacing your car stereo is to allow you to play your CD’s or music from your iPod then please be aware that it is possible to purchase equipment that allows you to play music from an external source. These specialised adapters look like a cassette with a flying lead that plugs into your alternate music source ie iPod, CD player etc. This is often a very cheap and easy alternative if funds are tight!

Audio Cassettes in general do not give as good an audio experience as CD players as their frequency response and SNR is often inferior to that of modern digital equipment.

Although cassette tape sales have declined extensively it is still possible to purchase due to the amount of tapes that are still out there however as a long term investment a CD or MP3 player would probably be a better choice.

CD player

The CD has been around for many years now and is well established in the market-place. A CD can store its information in a multitude of formats but the most popular at the moment is usually just referred to as an Audio CD in the specifications. These are the CD’s that you can buy of the shelf from any major music retail shop.

As with all technology the the common audio format is under threat by a relatively new format referred to as MP3. MP3 is a digital audio compression technique that allows much more audio to be squeezed onto a single CD. A typical compressed song will be roughly 4-6MB depending upon the quality of the audio and a typical CD can store around 700MB of data. So you can see that you can store many more songs using MP3 technology than with the conventional music CD’s.

It is also possible to purchase a head unit that has a remote CD player or CD changer. A CD changer is like a mini duke box that can be located in your boot, glove compartment etc. They typically have between 6 and 12 CD’s within them and often support the ability to play songs randomly between all the CD’s.

USB/Memory Card

With the rapid adoption of MP3 format and the availability of cheap USB memory sticks car audio manufacturers have started to adopt USB ports on their equipment as standard. A USB stick or memory card can be thought of as a very small CD usually about a couple of inches long and about half an inch wide but capable of storing vastly more information than a conventional CD. Something to check when buying a head unit supporting this feature is the upper memory limit of the USB stick or memory card. Typical memory cards today are around 2-4GB which would store many albums however these sizes may not be supported by the head unit.

If you purchase a head unit supporting this type of media then you’ll need to make sure that you have a method of getting the music from you CD collection onto the memory stick. This will involve ‘ripping’ the audio and copying it onto the memory. There are many programs available for doing this such as Windows Media Player.

Radio

Most people are familiar with car radio’s and understand what to look for when purchasing one. However something to keep in mind when looking is the uptake of DAB radio which is the new digital transmission method.

DAB radio uses modern digital compression techniques to offer a greater variety of music and programmes as well as short messages etc that often appear of the display. Since this is a new format and isn’t widely adopted as the mainstream format most DAB radios also still support FM transmissions.

The DIN form factor

Finally something which should be overlooked is the form factor and connections for the head-unit. With early cars there wasn’t really a standard which led to all sorts of problems when replacing the factor standard unit. However there is now a standard size referred to as the DIN which is 2 1/8″ (50mm) tall and 7 1/8″ (180mm) wide and double-DIN which is twice as tall as the standard DIN size.

The connectors used to plug the stereo in are fairly common but there is no one standard connector. Luckily due to the size of the problem there are many different types of adaptor readily available in most car audio shops.

One problem often experience with fitting new audio equipment is with the memory ‘forgetting’ its settings. This is often due to the power supply wires to the head unit being switched over. To over come this problem the manufacturers of the cabling adapters easily enable the yellow and red wire to be interchanged which will fix the problem.

It is always worth checking out many retailers before making a selection on a head unit and I would recommend searching an automotive directory for the best choice.