Head Unit (FAQ)
From SCION-TECH : The Scion Resource : tC, xA, xB, xD
This page covers a variety of frequently asked questions (FAQs) regarding the Scion head units, as well as head units in general.
[edit] ALSO SEE
[edit] INTRODUCTION TO HEAD UNITS
[edit] What is a car stereo?
- A car stereo is the centerpiece of any car audio system. Also known as a radio, receiver, or head unit, today's car stereo performs a variety of complex functions. To understand these functions, it's helpful to think of a car stereo as having 3 different sections:
- Source — This is the part that "plays" the music. Sources may include a standard AM/FM tuner, cassette, or CD player, MP3/WMA decoding, satellite radio, DVD player.
- Preamp — This is where all sound adjustments are made. The preamp section includes controls ranging from simple volume, balance, fader, source selection, and tone adjustments to sophisticated crossovers, equalizers, and time correction.
- Amplifier — The amplifier section boosts the small (low-voltage) audio signal coming from the pre-amp section into a larger (high-voltage) audio signal that's sent out to the speakers.
[edit] Why would I want/need a new car stereo?
- A new stereo will give you better sound and more playback options than the typical factory stereo.
- Better sound quality — Superior built-in power and better circuit design mean that a brand-name car stereo isn't just louder than the typical factory stereo, it also produces cleaner, richer, more detailed sound.
- New sources — One of most common reasons to get a new stereo is to expand your playback capability. Brand-name stereos offer advanced capabilities, such as MP3/WMA playback, iPod support, satellite radio, digital (HD) radio, internal hard drive storage, DVD playback, surround sound support decoding, and even GPS navigation.
- Other popular reasons for purchasing a new car stereo include:
- More features — Advanced features on brand-name stereos include full-color animated displays, customizable color schemes, fold-out monitors, Dolby Digital and DTS® surround sound decoding, and precision sound controls like digital time correction and parametric equalization.
- Cool cosmetics — Brand-name car stereos, with their high-tech displays and cutting-edge layouts, can enhance the appearance of your car's interior.
- Expandability — Auxiliary inputs and audio/video outputs allow you to expand your system by connecting portable music players, rear seat TV screens, external amplifiers, and powered subwoofers to your brand-name stereo.
- Security — Features like detachable face plates and stealth modes help protect your investment from theft.
[edit] GENERAL
[edit] Will a new CD receiver play CD-R and CD-RW discs?
- That depends on the receiver you buy. The vast majority of the CD receivers we sell will play finalized audio CD-Rs. But because music is burned to recordable CDs (CD-Rs) and rewritable CDs (CD-RWs) in different ways, some players have trouble reading CD-RWs. (CD-RWs are less reflective than CD-Rs, so it is more difficult for a laser to read them). Most CD receivers will play CD-RWs, but you should be sure to check the specs of a specific CD receiver before assuming that your CD-RWs will play.
[edit] Will a CD receiver play MP3 files burned onto a CD-R or CD-RW?
- MP3 files are compressed digital data, so your CD receiver must have a MP3 decoder to play MP3 files. Again, many CD receivers are MP3-compatible, but be sure to check the product specs before you buy.
[edit] What's the difference between CD-Rs and CD-RWs?
- Although the "R" in CD-R stands for "recordable," this is a "write-once" technology. That means anything you record on a CD-R is permanent. So if you make a mistake while recording a CD-R — if you change your mind about song order, for example — you can't erase or re-record the disc.
- The CD-RW designation indicates a "rewritable disc" — you can erase and re-record on the same disc over and over. CD-RW blanks cost a lot more than CD-R blanks — they actually use a different technology and disc material. Therefore, a CD receiver that plays CD-Rs will not necessarily play CD-RWs too, though many receivers will do both. Be sure to check the Key Features!
[edit] Can I purchase an in-dash cassette and CD player in the same unit?
- Yes, you can. There are several receivers that give you the versatility you've been asking for — cassette and CD in one, easy-fit in-dash unit. There are CD/Cassette models that fit perfectly in regular DIN (standard size), double-DIN (DD), or GM/Chrysler (CG) DIN-and-a-half size dash openings.
[edit] Can my factory speakers handle a high-powered CD receiver?
- Your factory speakers should have no problem at all handling the output from one of our high-powered in-dash CD receivers, but there are limits to their performance. Turn up your new radio with the car sitting still, make a note of the volume level at which your factory speakers start to distort, and avoid cranking the radio up past that point.
- Speaker performance is critical to listening enjoyment, so we recommend adding quality, aftermarket speakers as soon as you can, so that you can really take full advantage of the big, rich sound your new receiver has to offer.
[edit] How much power does my factory system have
- While we don't have exact power ratings for the systems in specific vehicles, we can tell you that factory systems have traditionally been lower power units of about 3 to 5 watts RMS (continuous) power. In recent years, however, we have seen some higher-powered factory stereos.
- Bear in mind that, for example, the 100-watt factory system described by your car dealer probably consists of 4 channels of 25 watts peak power. This translates to roughly 10 watts RMS (continuous) watts x 4 — substantial power, but a far cry from the power ratings of most current aftermarket CD receivers.
- But even if your factory system seems relatively powerful, there are still benefits to going with an aftermarket CD receiver. These advantages typically include better overall specs, improved FM reception, more extensive tone control, easier (and less expensive) integration with equipment such as disc changers and amplifiers, and the enhanced reliability you can expect from a recognized audio brand name.
[edit] How much power do I need to get optimum performance?
- Since every car stereo is different, there's no magic "wattage formula." As long as you stay within the recommended power range of your speakers, increasing power will always add richness and depth to your music. Compare a spinet piano to a concert grand. The small piano is good enough to play music clearly, but move up to a grand and you'll gain better tone, greater harmonic detail, and more volume. The larger instrument is simply more powerful.
- Here are a couple things to consider, though:
- How efficient are your speakers? Your speakers themselves have a direct influence on the overall "power" of your system. If you're planning on powering your speakers with your in-dash receiver, efficient speakers (sensitivity of 90 dB or higher) will give you more bang for the buck. Installing high-performance component speakers? An outboard amp will generate maximum performance.
- Are you adding a subwoofer? Subs need substantial amounts of power to reproduce the lowest tones, so it's essential to use an outboard amplifier with them. You should count on using more power for bass than you use to power all your full-range speakers. If your receiver puts out 20 watts RMS x 4 channels (80 watts total), send at least 80 watts to your sub. Using a 50 watt x 4 amp to drive your components? Dedicate at least 200 watts for bass.
- How good is your wiring? Your system's chain of components is only as strong as its weakest link, so don't cheat your amps and speakers with substandard power cable and speaker wire.
- Before you buy, consider your car. If you drive a quiet car with the windows up, you'll need much less power than someone who offroads in a Wrangler. Speaker location, extraneous road/car noise, noise damping material, and personal taste are factors that may affect how much power you'll need in your ride.
[edit] DEFINITIONS
[edit] Anti-Theft Protection
- A security feature that helps prevent radio theft. There are several types of anti-theft protection currently in use:
- Detachable Face — Lets you remove the control panel of your receiver easily, and take it with you when you leave the car. The stereo is useless to thieves without the faceplate, so the temptation to break in your car is greatly reduced. All but a handful of the receivers we offer come with a detachable face.
- El Kameleon — A JVC exclusive. When the unit is off, the display illumination turns completely off, and the rotary knob and control panel (which runs along the lower edge of the unit) retract into the unit. With the display illumination off and the control panel retracted, all you see is a flat, blank, glossy black front panel.
- D MASK — Enjoy having two theft deterrence options with Kenwood's D MASK self-hiding faceplate. You can detach your Kenwood faceplate and take it with you, or flip the faceplate around manually so that a featureless blank panel is visible. Either way, there's nothing to attract a thief. D MASK+ steps up to a motorized faceplate (also with the option to detach) that pivots automatically to display the flat, black panel.
- Keycard — A Blaupunkt exclusive. A Keycard is a credit card-sized smartcard with an embedded microchip. This card serves as a theft protection system (the unit will not operate without it) and has a personal memory bank for FM and AM presets, bass, treble, balance, fader, and other settings.
- Active Black Panel — A Sony exclusive. With the power off, all you see is a black panel — it looks as if the face has been removed. Power up, and the extra-large, multicolor dot-matrix display can be controlled by the wireless remote. Hit the open key, and the faceplate pivots down to reveal the CD slot, another display, and the soft-touch controls.
- Magic Flap — An Aiwa exclusive. When you turn the receiver off, the multicolor display flips over and the controls retract, leaving a nondescript black panel in your dash.
[edit] Auxiliary Audio Input
- An input on the face or rear of the receiver that enables you to connect a plug-and-play satellite radio tuner or portable player (CD, MP3, cassette, or MD) to the receiver. The input jack can be either Mini or RCA.
[edit] CEA-2006 Compliant
- On May 28, 2003, the Consumer Electronics Association published standard CEA-2006, "Testing & Measurement Methods for Mobile Audio Amplifiers." This "voluntary" standard advocates a uniform method for determining an amplifier's RMS power and signal-to-noise ratio. Using 14.4 volts, RMS watts are measured into a 4-ohm impedance load at 1 percent Total Harmonic Distortion (THD) plus noise, at a frequency range (for general purpose amplifiers) of 20 Hz to 20,000 Hz. Signal-to-Noise ratio is measured in weighted absolute decibels (dBA) at a reference of 1 watt into 4 ohms. This applies to both external amplifiers and the amplifiers within in-dash receivers.
- CEA-2006 allows consumers to be able to compare car amplifiers and receivers on an equal basis. Manufacturers who choose to abide by the new standard are able to stamp their products with the CEA-2006 logo that reads: "Amplifier Power Standard CEA-2006 Compliant."
[edit] CD Text
- Some compact discs contain encoded text data that can include the artist name, disc name, and/or track name. Text-capable receivers can decode and display this information on the readout.
[edit] CD-R, CD-RW Compatibility
- CD receivers with this capability can play audio CD-Rs and/or CD-RWs as well as prerecorded CDs.
[edit] Changer Controls
- Receivers with changer controls operate same-brand/compatible CD/MiniDisc multi-disc changers or digital music players (devices which store and play back MP3, Windows Media Audio, or WAV files).
[edit] Codec
- A codec is a method of compressing and decompressing digitized sound. MP3 and WMA are examples of different codecs. In the standard CD audio format, one minute of music takes up roughly 10 megabytes. When converted to MP3, that same minute of music takes up only about 1 megabyte.
[edit] Crossover (High-Pass Filter)
- A built-in high-pass filter allows only frequencies above the crossover point to pass through. This filter may work with the speaker outputs, preamp outputs, or both.
[edit] Crossover (Low-Pass Filter)
- A built-in low-pass filter allows only low frequencies to pass through. This filter may work with the speaker outputs (very rare), preamp outputs, or both.
[edit] Custom Programming
- Some changer controller combinations let you specify exactly which tracks will play on a CD. Disc title features let you assign each disc a name that will appear on the in-dash display when that disc is loaded.
- Sony's Custom File Plus systems, for example, let you display the titles of all loaded CDs without interrupting playback, and also let you program two separate twelve song sequences.
[edit] Digital-to-Analog (D/A) Converter
- Your CD receiver uses a D/A converter to convert digital 1s and 0s back into analog audio signals. CDs store audio data in binary, digital form. This digital data is an accurate, noise-free reproduction of recorded signals, but in digital form it doesn't sound like music to your ears. The D/A converter translates the digital info back into music — that's why it's so important to your CD receiver's performance.
[edit] Digital Media Files
- Music which has been subjected to data compression — allowing users to store many hours of music as computer files. A growing number of in-dash CD receivers have the ability to decode and play recordable CDs (CD-Rs and CD-RWs) loaded with MP3, Windows Media Audio, or WAV files. A single disc can hold up to ten hours of music.
[edit] Display
- Fold-down Face — Slot-faced receivers are convenient, but their displays are smaller out of necessity. A fold-down face, on the other hand, hides the CD slot behind the control panel, and allows the receiver to include a larger display for greater legibility. Hiding the slot also increases the unit's reliability by reducing internal exposure to dust and dirt.
- Multicolor Display — A multicolor display improves readability and reduces the amount of time your eyes spend away from the road. Monochrome displays cannot represent different functions with unique colors, so you spend more time trying to decipher the readout.
- Backlight — A backlit display significantly improves visibility under adverse conditions. For example, if the sun is shining on your faceplate, a backlit display is easier to see.
[edit] DVD/CD Receivers
- These versatile CD receivers can also play DVD movies, and may play DVD audio discs. Some models send the video signal to an outboard backseat monitor for on-the-go viewing, while other models include a built-in screen for stationary viewing.
[edit] Equalizer
- A built-in EQ lets you tailor the sound to your listening tastes and to your vehicle's acoustics. Receivers with built-in EQs will have one or more equalizer "bands" in addition to standard bass and treble controls. These equalizer "bands" usually have fixed center frequencies and bandwidths (although some may be adjustable).
- More sophisticated built-in EQs offer parametric equalization, which allows you to set the amount (in dB) by which a certain frequency band is boosted or cut — and determine the width and/or center frequency of this band. This gives you extremely precise control of the tonal balance in your vehicle.
[edit] Equalizer Presets
- Preset EQ curves are stored tone settings — boosting and cutting different frequencies can make big changes in the way your music sounds. Preset EQ curves are stored in memory, and are easily activated. If you listen to a wide variety of music, these presets are useful for making dramatic tonal changes instantly. (For example, you could use one EQ preset with heavy bass boost for rap or reggae, and a second preset with flat bass and a slight midrange/treble boost for jazz. This saves you from constant readjustment of the tone controls.)
[edit] European Tuning
- The European tuning interval of .05 MHz is different from the US tuning interval of .2 MHz. If a CD receiver also has European tuning, it is compatible with the European scale and can be used in many European countries.
[edit] FM Mono Sensitivity
- This figure tells you how well a CD receiver can pick up FM radio signals. The smaller the number, the greater the ability to pick up weaker stations. Expressed in decibel femtowatts (dBf).
[edit] FM Stereo Separation
- A measure of the ability of an FM tuner to re-create a vivid stereo effect. Measured in dB (decibels), the higher the figure the better.
[edit] Frequency Response
- The range of sounds, from bass to treble, a stereo component can reproduce. It's measured in Hertz (Hz), and a wider range is better — the bass will be lower and the treble will be higher. Humans can perceive sounds from 20 to 20,000 Hz. The lowest note on a bass guitar is about 41 Hz. Most male vocalists have a range between 100 and 500 Hz. Cymbals hit at about 15,000 Hz.
[edit] Ground Loop
- A ground loop occurs when any piece of equipment or any incoming wire is connected to a different ground or grounds. If your in-dash receiver and amplifier are grounded to different locations, for example, a ground loop may occur. In this situation, the multiple ground paths can, in effect, act as an antenna for interference. The interference is turned into noise, and you hear it in your system.
[edit] Intro Scan
- Lets you hear the first few seconds of each track on a CD. Hit the button again when you hear the song you're looking for. The scanning feature will stop, and that track will continue playing.
[edit] Loudness
- This control allows you to boost the lower frequencies in your music for full, rich sound at lower volumes.
[edit] MP3
- MP3 encoding compresses musical data, enabling users to store many hours of music as computer files. A growing number of in-dash CD receivers have the ability to decode and play recordable CDs (CD-Rs and/or CD-RWs) loaded with MP3 files. Also, portable MP3 players can be used to play these files through a car receiver's auxilary inputs.
[edit] Multi-path Interference
- Multi-path interference affects FM radio reception. FM waves travel in a straight line, so anything between you and the FM transmitter can cause multi-path interference. When FM signals bounce off buildings and other large objects , the tuner picks up the same signal more than once, at different times. This create "echoes" that confuse the tuner by mixing with the original signal.
[edit] Peak Power
- Peak power is measured during a brief musical burst, such as a sudden drum accent. Some manufacturers display peak power ratings on the face of their products. The RMS power rating is more significant, and we recommend using it for comparison purposes.
[edit] Preamp Outputs
- Jacks on the rear of a CD receiver that allow you to use a standard RCA patch cable to add an external amp. Some receivers have two sets, which help if you plan to add a 4-channel amp or a second amp. Some receivers have three sets, one of which is usually intended to be used for a subwoofer amp.
- Some receivers offer a "non-fading" set of preamp outputs. Hook your subwoofer amp to the non-fading outputs, and you can fade the regular speakers front to rear without affecting the sound of the subwoofer.
[edit] Preamp Output Voltage
- The output voltage of the receiver's preamp outputs. Higher preamp output voltage can mean cleaner sound (better noise resistance) and higher output from your amp.
[edit] Radio Data System
- RDS stands for Radio Data System. RDS tuners can automatically tune in stations according to the style of music (or talk) they broadcast. Some RDS tuners can even break in with traffic alerts or emergency broadcasts when you're listening to a CD. RDS enables your receiver to display text messages (usually call letters and format info) that many FM stations include on a subcarrier signal within their normal broadcast signal.
[edit] RMS Power
- The amount of continuous power, measured in watts, that an amplifier produces is called Root Mean Square (RMS) power. The higher the RMS figure, the louder and cleaner your music sounds.
[edit] Random Play
- Also known as shuffle play. Mixes up the order of songs during playback. Some CD players offer a "Random Play with Delete" feature that prevents a song from being repeated once it has been played.
[edit] Remote Control
- For remote-compatible CD receivers, wired or infrared wireless remotes are either included with a receiver, or available as accessories.
[edit] Satellite Radio Controls
- CD receivers with satellite radio controls operate same-brand external satellite radio tuners. A specialized antenna and service subscription are also required (in addition to the tuner) to receive the satellite radio signal.
[edit] Scan and Seek Tuning
- Preset Scan lets you push a button and automatically hear a brief sample of what's on each of your preset stations.
- Station Scan lets you sample each strong station (regardless of whether it's one of your presets) — the sampling continues until you hit the station scan button again.
- Seek tuning moves to the next strong station and stops there — you must hit the "Seek" button again to repeat the process.
[edit] Signal-to-Noise Ratio
- A measure of how well a CD player silences background noise. Higher ratings, in decibels (dB), indicate less noise.
[edit] Subwoofer Preamp Outputs
- RCA output jacks (usually coupled with a built-in low-pass filter) for connection to a subwoofer amplifier.
[edit] Time Correction
- A processing circuit found in some receivers that compensates for the uneven distances between left and right car speakers and listeners' ears. Time correction delays signals from the closest speaker(s), so that all the sound arrives at your off-center listening position at the same time. You'll get a more accurate, lifelike stereo image.
[edit] Track Repeat
- Plays the same track over and over until you turn the feature off.
[edit] Travel Presets or Best Tuning Memory
- Engage this feature and the CD receiver automatically loads a bank of your presets with the strongest available signals. It makes finding stations easier when you're driving through unfamiliar territory. It also makes loading presets a snap when you first install the receiver or any time your battery runs down or gets disconnected (which wipes out the tuner's preset memory). Some receivers use a bank or two of your regular station presets for storage; others have dedicated travel presets plus station presets for manual storage.
[edit] Tripath
- Tripath Technologies is the developer of the Class-T® amplifier design, which combines the low distortion and excellent sound quality of the Class AB design with the efficiency advantages of the Class D design. Tripath uses switching transistors to achieve very high power efficiency (around 90%), low heat production, and compact chassis-size.
[edit] Video System Control
- Receivers with video system control operate same-brand/compatible video components and play TV sound through your car audio speakers (when video components are connected).
[edit] Zero-bit Detector
- Some CD receivers feature a circuit that detects periods of no audio signal (a series of zeros in the digital bit stream) and mutes the audio output. You'll hear dead silence until an audio signal is detected again.
