| 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 to | | | | unit is off, the head unit has a completely black face |
| determine this is by the weight of the unit. Also, check | | | | with no visible buttons or controls. Come on. Criminals |
| to see if anything doesn't "fit", or if there are parts that | | | | aren't so stupid that they can't see that the head unit |
| are cheap or flimsy. The truth is this: The bigger name | | | | still has its face attached.Hidden faceplate:This is |
| units tend to be better. Also, the more expensive units | | | | common for DVD players with screens, and one unit |
| tend to be better. This isn't always a big deal for | | | | that I used to own, the Alpine CDA-7998. Basically, the |
| everyone, but I believe that build quality is very | | | | face folds into the head unit, and looks exactly like a |
| important. Afterall, do you want to spend $100 for a | | | | unit with the faceplate removed. Neat, but the unit is still |
| cheap unit that will last two or three years, or $600 on | | | | vulnerable.In short, all of these tactics are imperfect. |
| a unit that will last for 20 years?Basic Head Unit | | | | Pick the one that makes the most sense to you, |
| Features:Power output:Most head units have built-in | | | | however most units only have a detachable faceplate |
| amplifiers. These drive the speakers. Some head units | | | | feature.CD Changer controls/Optional equipment |
| do not have internal amps, and therefore, require the | | | | interface:This is a feature that allows you to connect |
| use of an external amp. Head units without amps are | | | | other peripherals to your head unit. These peripherals |
| usually high-end models. Anyway, power is measured | | | | are often CD changers, digital music players, satellite |
| in WATTS. We'll talk more about watts later, but for | | | | radio units, and video equipment. With this feature on |
| now, just see more watts as more volume. Most head | | | | your head unit, you'll be able to add additional |
| units (unfortunately) are deceptive about the power | | | | capabilities to your stereo system in a convenient way. |
| output. Usually, the power output spec on a unit will say | | | | However, most of these interfaces are only |
| "50Wx4 MAX output". This means that when the laws | | | | compatible with the same brand. In other words, you'll |
| of physics are on your side, it's a clear day | | | | need an Alpine head unit with the Ai-net interface |
| everywhere in the world, the planets are aligned, the | | | | connected to an Alpine CD changer with the Ai-net |
| bass hits really really low and hard, and for about a | | | | interface.Remote Controls:Some head units have |
| tenth of a second, yeah, your head unit will put out | | | | remote control capability. This is a handy feature |
| 50Wx4. However, most of the time, your head unit is | | | | because you can control the headunit without taking |
| probably putting out a quarter of that. It's not that the | | | | your eyes off of the road.OK, so these are some of |
| head unit manufacturer is lying, it's just that they are | | | | the features of head units. Now, let's look at the specs |
| exaggerating the truth, AND MOST PEOPLE DON'T | | | | of specific types of head units.Tuner Features:Most |
| KNOW BETTER. So, anyway, many people put a lot | | | | head units have AM/FM capability built in. Check out |
| of importance on a head unit's power output. I don't | | | | this information on getting the best AM/FM |
| because head unit amps suck, and no serious car | | | | performance possible.Presets: This feature allows you |
| audio person uses the head unit's amp anyway. Most | | | | to save your favorite radio stations, and instantly recall |
| head unit brands have about the same power output | | | | them at the push of a button.HD Radio: A new radio |
| anyway. 9 times out of 10, an aftermarket head unit | | | | format 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 are | | | | with 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 you | | | | this feature is still small, and most radio stations haven't |
| use for your home system. Basic head units usually | | | | yet embraced the technology. I do expect this |
| have one set of preouts (front left, front right). Some | | | | technology 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 sets | | | | satellite 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 subwoofer | | | | possible for radio stations to transmit text to your |
| outputs: Sometimes they're called "non-fading" outputs | | | | receiver. This text can be used to show the station |
| because they are not effected by the head unit's fade | | | | title or the artist name, and other information.FM |
| control (front to back balance). If you're not planning on | | | | Sensitivity: The ability of your unit to tune into a weak |
| adding an external amp, you don't need to worry about | | | | signalFM Selectivity: The ability of your unit to reject |
| RCA pre-outs. If you want to add an external amp (or | | | | interference from other stations.FM Stereo Seperation: |
| amps), I would always recommend getting a unit with | | | | The ability of a tuner to recreate the proper left/right |
| three pre-outs.RCA Pre-out voltage:Usually this spec is | | | | channel sepearation.CD Players:CD-R/CD-RW |
| next to pre-out spec. It is measured in VOLTS (which | | | | Playback: This feature guarantees that your unit will |
| we'll go over later). Basically, the higher the voltage, the | | | | play a CD-R or CD-RW that was made with a CD |
| LOUDER the music will be at your amp. Don't look at | | | | recording device.CD-Text: This feature displays CD |
| this as "free power" because it is not. In addition, the | | | | text information that is encoded on some CDs. This |
| higher the voltage, the less noise that will be introduced | | | | information includes artist names, song titles and album |
| to your system. Again, this spec doesn't matter if you | | | | titles.MP3/WMA/iTunes Playback: This spec assures |
| don't plan on using an external amp. If you do plan on | | | | you that certain digital file formats can be played back |
| using an external amp, try to find the HIGHEST voltage | | | | on 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 Eclipse | | | | files.DAC: Digital to Analog converter. This device |
| units have 8V(!) pre-outs. In short, more voltage=less | | | | takes the digital signal from your CD, and turns it into |
| noise and cleaner sound.Digital time correction:This is | | | | an analog signal for your amp. The better your DAC, |
| used to simulate a perfect stereo environment. If | | | | the more "real" your sound will be.CD Frequency |
| you're at home listening to music, you want to situate | | | | Response: The range of frequencies that the CD |
| yourself in the middle of the two speakers to get the | | | | player can reproduce. It should at least cover the |
| best sound. The same is true in the car, EXCEPT that | | | | 20hz-20,000hz range.Electronic Shock Protection: This |
| it's a hell of a lot more difficult. Usually, the passenger | | | | feature prevents your CDs from skipping. If your head |
| side speaker will be farther from your ear than the | | | | unit doesn't offer this, don't buy it. However, most |
| driver side. Since sound travels fairly slow (comparfed | | | | players have it, and technology has gotten pretty good |
| to light), you'll have one ear receiving a portion of sound | | | | lately, so it's unlikely that you'll have any problems with |
| before the other ear. The digital time correction delays | | | | skipping.Signal to noise ratio (s/n): A measure of how |
| the music slightly so your ears will be perceiving the | | | | well a CD player silences noise. The higher the rating, |
| same music at the same time. This is a very important | | | | the less noise.Zero Bit Detect mute: When the CD |
| feature if you are planning an SQ | | | | player detects a series of 0's on the CD (such as |
| system.Crossover:This feature is incorporated into | | | | between songs), it will automatically mute the output. |
| many components in a car audio system. If your head | | | | This feature isn't really important, but is often |
| unit doesn't have it, don't worry. Just be sure your | | | | advertised.Oversampling: The CD Audio format has a |
| amps have it. Basically, this makes sure the right | | | | resolution of 16 bits, with a sampling rate of 44.1khz. |
| speakers are playing the right sounds. I will go into | | | | What the hell does that mean? I really don't know, but |
| more detail about crossovers later.Equalizer aka | | | | think of a digital picture. Zoom in really close to this |
| EQ:This feature allows you to tweak the sound. The | | | | picture, and you see pixels. Think of each pixel as a |
| most basic EQ is a two-band, and controls BASS and | | | | sample. 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 have | | | | player has oversampling, it takes the 44.1khz, and turns |
| 5-band EQs. If you are serious about tweaking your | | | | it 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 units | | | | oversampling will sound better than one without. Of |
| have 30 bands! I will go into much more detail about | | | | course, the good news is that pretty much every unit |
| EQs later.Theft Deterents/Security Features:There are | | | | these days has this feature.Tape decks:Auto Reverse: |
| a few options when it comes to head unit | | | | A feature that will automatically play the reverse side |
| security...Detachable Faceplate:The most common | | | | of a tape at the end of a side.Dolby noise reduction: |
| method is a detachable faceplate. Basically, you | | | | There are many Dolby technologies incorporated into |
| remove the faceplate of the unit (where the screen | | | | tape decks. Most of these features exist to lower |
| and controls are), and the unit won't function. This will | | | | tape hiss, and raise the signal to noise ratio.Frequency |
| deter thieves, but please don't leave the faceplate in | | | | response: Again, the frequencies the tape deck |
| your car. Thieves know most people do this, and will | | | | respond to. Normal human hearning is from 20 to |
| still break into your car, find the faceplate and steal | | | | 20,000 hz.Wow and flutter: This spec tells you how |
| your head unit.Password:Some other units have a | | | | stable the tape deck playback speed is. The lower, the |
| password function. When the unit is disconnected from | | | | better.Alan Bayer is an entrepreneur and car audio |
| power, then reconnected, the unit will require some | | | | enthusiast. He runs an eBay store selling car stereo |
| sort of password. The unit will not function until the | | | | install supplies:stores.ebay.com/honest-aebs-autosound |
| password is provided.Key CD:A few units use a key | | | | He 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 will | | | | learn about car audio equipment, how to find the best |
| now designate that CD as the key CD. If the power is | | | | equipment, how to install it, and save big bucks in the |
| disconnected, the unit will ask for the same key CD | | | | process! |