Throughout this project, each component will be required to be compatible with the other components chosen. The dual purpose for this is to keep cost factor low and facilitating installation. Several adaptors can be eliminated by having compatible components. Five major components will be used in this system, the head unit, the front speakers, the rear speakers, the subwoofer, and the subwoofer amplifier.
Head Unit
The head unit is the most important component and must have certain features to make it adequate for this system. Some of the features we will not be using immediately but will require in case expansion is later desired. There are four major features required in the head unit, the are internal amplifier, Pre-amp out RCA jacks, CD controller and a face-off security feature.

Figure 1Internal AmplifierThe head unit must have an internal amplifier that can produce at least 25 watts-per-channel so it can adequately power a decent pair of speakers. Reproduction of higher frequency sounds (i.e. violin, flute) as well as lower frequency sounds (bass violin, tuba) require more power to be heard at the same level as a midrange sound (voice, trumpet). The internal amplifier in the head unit must be able to generate enough wattage for the SPL (sound pressure level) of the higher frequencies to be heard clear in a space the size of the AEROSTAR.
Pre-amp Out RCA Jacks
To allow for low-level amplification without using an in-line power reducer, the head unit will require low level pre-amplification output jacks. Head units ordinarily come with either front and rear, or just rear RCA jacks. This situation will only require rear jacks since the head unit produces enough wattage sufficient for the front speakers. The sub-woofer system will be powered by an additional external amplifier by using these jacks.
CD Controller
Although cassettes are more versatile at this point in time, CD's are readily available and deliver a more quality sound. It would be a very good choice to assure that a CD Controller is built in. One that controls more than just a specific multi-CD player.
Face-off Security
Full-Panel detatchable security feature will also be required. Most head units have this as a standard feature making this feature, although indisposable, readily available. A unit that has mechanical fast-forward, rewind, and eject buttons will be preferred over a unit that has all these as electronic features. The reason for this comes apparent if ever a cassette tape is left in the unit and the tape is to be ejected without having the ignition key to power the unit.
In the tuner section of the unit, local/distance switchting , dolby noise reduction and at least 12 FM presets will also be advantageous features in our head unit.
The head unit we will be using will be the Pioneer model KEH-P4200. It has a 35 watt-per -channel amplifier built in so it is sufficient for driving front speakers.
This unit features Multi Function Display (MDF) which allows the operator of the system to view many different functions of the unit. The display is an orange colored digital display with the ability to display alpha-numeric, user programmed titles for the optional compact disc shuttle as well as the time, date, call letters for the radio station tuned in.
Another feature included is a new F.I.E. (Front Image Enhancer) that cuts middle and high range frequency output from the rear speakers so that only low range frequencies are output, for an appearance of voices and higher pitched instruments to be in front.
The unit is standard size (7"w X 2"h X 5-7/8" d) and uses the standard auto grounding system and power consumption, allowing an installation without cutting or drilling and appearing factory installed.
The unit utilizes the face-off anti-theft system, which allows the front panel of the unit to be removed as a theft deterrent. Pushing a button in the upper right corner of the panel will eject the panel from the body. To replace the panel, push the panel into the main body.
Caution: Be very careful in handling the front panel.
Do not leave the panel in direct sunlight or high temperatures
Do not drop the panel or otherwise subject it to strong impact
Do not allow volatile agents (i.e. benzine, thinner, insecticides to come in contact with the surface of the front of the panel.

Figure 2Do not touch