Learn About Car Audio Head Units

Build quality:Some head units are flimsy and weak.before it will function again.Black out face:When the
Some are built to last. Usually the best way tounit is off, the head unit has a completely black face
determine this is by the weight of the unit. Also, checkwith no visible buttons or controls. Come on. Criminals
to see if anything doesn't "fit", or if there are parts thataren't so stupid that they can't see that the head unit
are cheap or flimsy. The truth is this: The bigger namestill has its face attached.Hidden faceplate:This is
units tend to be better. Also, the more expensive unitscommon for DVD players with screens, and one unit
tend to be better. This isn't always a big deal forthat I used to own, the Alpine CDA-7998. Basically, the
everyone, but I believe that build quality is veryface folds into the head unit, and looks exactly like a
important. Afterall, do you want to spend $100 for aunit with the faceplate removed. Neat, but the unit is still
cheap unit that will last two or three years, or $600 onvulnerable.In short, all of these tactics are imperfect.
a unit that will last for 20 years?Basic Head UnitPick the one that makes the most sense to you,
Features:Power output:Most head units have built-inhowever most units only have a detachable faceplate
amplifiers. These drive the speakers. Some head unitsfeature.CD Changer controls/Optional equipment
do not have internal amps, and therefore, require theinterface:This is a feature that allows you to connect
use of an external amp. Head units without amps areother peripherals to your head unit. These peripherals
usually high-end models. Anyway, power is measuredare often CD changers, digital music players, satellite
in WATTS. We'll talk more about watts later, but forradio units, and video equipment. With this feature on
now, just see more watts as more volume. Most headyour head unit, you'll be able to add additional
units (unfortunately) are deceptive about the powercapabilities to your stereo system in a convenient way.
output. Usually, the power output spec on a unit will sayHowever, most of these interfaces are only
"50Wx4 MAX output". This means that when the lawscompatible with the same brand. In other words, you'll
of physics are on your side, it's a clear dayneed an Alpine head unit with the Ai-net interface
everywhere in the world, the planets are aligned, theconnected to an Alpine CD changer with the Ai-net
bass hits really really low and hard, and for about ainterface.Remote Controls:Some head units have
tenth of a second, yeah, your head unit will put outremote control capability. This is a handy feature
50Wx4. However, most of the time, your head unit isbecause you can control the headunit without taking
probably putting out a quarter of that. It's not that theyour eyes off of the road.OK, so these are some of
head unit manufacturer is lying, it's just that they arethe features of head units. Now, let's look at the specs
exaggerating the truth, AND MOST PEOPLE DON'Tof specific types of head units.Tuner Features:Most
KNOW BETTER. So, anyway, many people put a lothead units have AM/FM capability built in. Check out
of importance on a head unit's power output. I don'tthis information on getting the best AM/FM
because head unit amps suck, and no serious carperformance possible.Presets: This feature allows you
audio person uses the head unit's amp anyway. Mostto save your favorite radio stations, and instantly recall
head unit brands have about the same power outputthem at the push of a button.HD Radio: A new radio
anyway. 9 times out of 10, an aftermarket head unitformat that is close in sound quality to CDs. Basically, a
will put out more power than your factory head unit,radio station broadcasts their usual programming, but
and as such, will sound better.RCA Preouts:These arewith an additional signal that can be received by units
used to connect external amps to your head unit.with "HD radio" capability. The availability of units with
These are the same red and white cables that youthis feature is still small, and most radio stations haven't
use for your home system. Basic head units usuallyyet embraced the technology. I do expect this
have one set of preouts (front left, front right). Sometechnology to take off, however because the sound
head units have two sets (front left, front right, rear left,quality is better, and not everyone wants to pay for
rear right), but most decent head units have 3 setssatellite radio.RDS: AKA "Radio Data System". A new
(front left, front right, rear left, rear right, subwoofer left,feature for FM radios. This technology makes it
subwoofer right). One quick note about subwooferpossible for radio stations to transmit text to your
outputs: Sometimes they're called "non-fading" outputsreceiver. This text can be used to show the station
because they are not effected by the head unit's fadetitle or the artist name, and other information.FM
control (front to back balance). If you're not planning onSensitivity: The ability of your unit to tune into a weak
adding an external amp, you don't need to worry aboutsignalFM Selectivity: The ability of your unit to reject
RCA pre-outs. If you want to add an external amp (orinterference from other stations.FM Stereo Seperation:
amps), I would always recommend getting a unit withThe ability of a tuner to recreate the proper left/right
three pre-outs.RCA Pre-out voltage:Usually this spec ischannel sepearation.CD Players:CD-R/CD-RW
next to pre-out spec. It is measured in VOLTS (whichPlayback: This feature guarantees that your unit will
we'll go over later). Basically, the higher the voltage, theplay a CD-R or CD-RW that was made with a CD
LOUDER the music will be at your amp. Don't look atrecording device.CD-Text: This feature displays CD
this as "free power" because it is not. In addition, thetext information that is encoded on some CDs. This
higher the voltage, the less noise that will be introducedinformation includes artist names, song titles and album
to your system. Again, this spec doesn't matter if youtitles.MP3/WMA/iTunes Playback: This spec assures
don't plan on using an external amp. If you do plan onyou that certain digital file formats can be played back
using an external amp, try to find the HIGHEST voltageon certain units.ID3 Tag Display: Displays text (such as
you can. 2 volts is basic, 4 is standard for a good unit,song title and album name) encoded into MP3
sometimes you'll see units with 5 volts. I know Eclipsefiles.DAC: Digital to Analog converter. This device
units have 8V(!) pre-outs. In short, more voltage=lesstakes the digital signal from your CD, and turns it into
noise and cleaner sound.Digital time correction:This isan analog signal for your amp. The better your DAC,
used to simulate a perfect stereo environment. Ifthe more "real" your sound will be.CD Frequency
you're at home listening to music, you want to situateResponse: The range of frequencies that the CD
yourself in the middle of the two speakers to get theplayer can reproduce. It should at least cover the
best sound. The same is true in the car, EXCEPT that20hz-20,000hz range.Electronic Shock Protection: This
it's a hell of a lot more difficult. Usually, the passengerfeature prevents your CDs from skipping. If your head
side speaker will be farther from your ear than theunit doesn't offer this, don't buy it. However, most
driver side. Since sound travels fairly slow (comparfedplayers have it, and technology has gotten pretty good
to light), you'll have one ear receiving a portion of soundlately, so it's unlikely that you'll have any problems with
before the other ear. The digital time correction delaysskipping.Signal to noise ratio (s/n): A measure of how
the music slightly so your ears will be perceiving thewell a CD player silences noise. The higher the rating,
same music at the same time. This is a very importantthe less noise.Zero Bit Detect mute: When the CD
feature if you are planning an SQplayer detects a series of 0's on the CD (such as
system.Crossover:This feature is incorporated intobetween songs), it will automatically mute the output.
many components in a car audio system. If your headThis feature isn't really important, but is often
unit doesn't have it, don't worry. Just be sure youradvertised.Oversampling: The CD Audio format has a
amps have it. Basically, this makes sure the rightresolution of 16 bits, with a sampling rate of 44.1khz.
speakers are playing the right sounds. I will go intoWhat the hell does that mean? I really don't know, but
more detail about crossovers later.Equalizer akathink of a digital picture. Zoom in really close to this
EQ:This feature allows you to tweak the sound. Thepicture, and you see pixels. Think of each pixel as a
most basic EQ is a two-band, and controls BASS andsample. When you increase the pixels, you increase
TREBLE. Some head units have 3-bands, BASS,the sharpness and quality of the picture. When a CD
MIDS, TREBLE. More advanced head units haveplayer has oversampling, it takes the 44.1khz, and turns
5-band EQs. If you are serious about tweaking yourit into a bigger number. More samples=More realistic
sound to perfection, you won't use your head unit's EQ;sound. Confused? I know. I am too, but a unit with
You will get an external unit, and some of these unitsoversampling will sound better than one without. Of
have 30 bands! I will go into much more detail aboutcourse, the good news is that pretty much every unit
EQs later.Theft Deterents/Security Features:There arethese days has this feature.Tape decks:Auto Reverse:
a few options when it comes to head unitA feature that will automatically play the reverse side
security...Detachable Faceplate:The most commonof a tape at the end of a side.Dolby noise reduction:
method is a detachable faceplate. Basically, youThere are many Dolby technologies incorporated into
remove the faceplate of the unit (where the screentape decks. Most of these features exist to lower
and controls are), and the unit won't function. This willtape hiss, and raise the signal to noise ratio.Frequency
deter thieves, but please don't leave the faceplate inresponse: Again, the frequencies the tape deck
your car. Thieves know most people do this, and willrespond to. Normal human hearning is from 20 to
still break into your car, find the faceplate and steal20,000 hz.Wow and flutter: This spec tells you how
your head unit.Password:Some other units have astable the tape deck playback speed is. The lower, the
password function. When the unit is disconnected frombetter.Alan Bayer is an entrepreneur and car audio
power, then reconnected, the unit will require someenthusiast. He runs an eBay store selling car stereo
sort of password. The unit will not function until theinstall supplies:stores.ebay.com/honest-aebs-autosound
password is provided.Key CD:A few units use a keyHe also has a GREAT website with car audio articles
CD. Basically, the first time the unit is used, the unit will(such as the one from above). Also on the website,
ask for a key CD. You insert any CD, and the unit willlearn about car audio equipment, how to find the best
now designate that CD as the key CD. If the power isequipment, how to install it, and save big bucks in the
disconnected, the unit will ask for the same key CDprocess!