Head Units
The Head Unit is the most important part of the audio
system. You will always be staring at the head unit and touching it to
control your sound system. It is a good idea to look for something that
is aesthetically pleasing, integrates to your car, has a logical button layout
and has features that best suit your needs.
Head Units Features
CD Changer Controls - Whether you get a
CD, cassette or MD head unit get a model that has CD changer controls, they
only cost a bit more, but give you the opportunity of simply plugging in a
changer in the future.
Power - Probably the most overrated
feature in head units. The power on head units is seldom given in RMS
watts (see amplifiers section for definition). Typically a head unit
has an output of about 5-7 watts RMS per channel, while a high-powered head
unit goes up to 13-15 watts RMS per channel (even if they claim 35 or 40
watts).
RCA Outputs - If you are planning to
run the speakers from the head unit's built-in amplifier, you don't have to
worry about RCAs, but if you plan to add amplifiers in the future, get one
with a set of RCAs (left and right), three sets preferably (left and right
for front, rear and subwoofer). An important feature to look for is
high-voltage RCA outputs. Typically RCA signals are less than 1
volt. High-voltage RCA signals are 2, 3 or even 4 volts. This
allows for better noise immunity and gives you a higher headroom for
amplifier gain settings. Most high-end manufacturers are selling units
with high-voltage RCA outputs which are frequently used in
competition.
Security - There are many security
options for head units nowadays. None of them is 100% effective in
deterring theft. Detachable faces are the most common option.
The front part of the radio comes off, rendering the rest of the unit
useless. The problem is that after a while people forget to take the
face off, or simply tuck it under the seat or in the glove box.
Another option is codes, key CDs (i.e. Blaupunkt,
Eclipse). If power is cut off, the unit asks for a code or a
predetermined CD used as a key. If the incorrect code is entered, it
locks the radio up, requiring service from the manufacturer. This has
proven to be an inconvenience when the owner loses their code or forget
which CD they used to program the radio. Some radios, such as
Blaupunkt are using a smart card, that when removed, renders the unit
useless, but again, people forget to take it out or lose it causing
aggravation to the consumer.
Yet another security protection pioneered by Kenwood is
a flat panel that covers the radio when the ignition key is turned
off. While this will fool some people into thinking there is no radio
in, it won't fool most thieves.
RF modulated CD Changers
FM modulated changers can be hooked up to any radio that
has an FM tuner, whether factory or aftermarket. They use the radio's
antenna to introduce the signal. They are usually simple to hook up
and consist on the changer itself which is mounted in the trunk or under
seats, the control box and the display/remote control. The drawback is
that the sound of the CD changer will not be "CD quality", it will be as
good as the FM tuner is. The signal coming from the CD player has a
wide frequency range but the FM tuner limits the signal, cutting the lower
and upper ends of the
spectrum.
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