Did some research on the net from a few places since I'm a newbie to ICE. Found this useful info from SG forum, IASCA and other sources. I hope it helps you in your ICE journey as it did in mine.

Tonality

Commonly referred to as tonal accuracy and spectral balance, tonality is that quality of a system that gives the musical instruments their natural sound. If a saxophone is played, for example, it sounds exactly like a real saxophone, and you can tell it is not a trombone, french horn, tuba, or any other brass instrument. Likewise, any instrument has it's own characteristic sound, and a system with good tonality will allow the listener to differentiate the instruments being played.

According to the Official IASCA (International Auto Sound Challenge Association) rulebook of competition, Tonal Accuracy and Spectral Balance is a combination of six characteristics---loudness, pitch, timbre, modulation, duration, and attack and decay. A brief definition: loudness-the magnitude of the sound. pitch-the quality of a sound that determines it's position on a musical scale. timbre-harmonics that give a sound it's sonic signature. modulation-changes in amplitude, phase, or frequency that occur in a sound. duration-length of time a sound is heard. attack and decay-the time it takes a sound to build-up(attack) and die-down(decay).

Here is a quote from the IASCA rulebook summing the Tonal Accuracy section: "Superior systems will sound effortless and natural with any judging track. Weaker systems will exhibit distortion, unnatural coloration, dynamic compression, and frequency response errors. This leads to listening fatigue and lends an unnatural sound to the music."

Listening Position relative to the perceived sound stage

Basically, in a concert, the musicians are on a stage in front of you, and likely they are well in front of you as you'll be sitting in the audience. Good SQ systems will give the illusion of this same perceived stage being well in front of you. Systems with poor "listening positions" will make you feel like the musicians are in your face, around you rather than in front of you, or even worse, behind you. Remember the goal is to simulate watching and listening to a live performance, and as such there are no musicians beside or behind you. The best systems will give you the impression of the stage being a considerable distance in front of you, as if you were sitting a few rows back in the audience.

Stage Width

How wide is the sound stage? Car interiors are horrible for good sound reproduction. However, a wide sound stage is an important factor. Bad systems will have almost no width, sounding as if only a center channel speaker is playing. Better systems have well defined left and right stage boundaries, but these boundaries will stay well within the interior of the vehicle.

The best systems will have stage boundaries, which extend BEYOND the physical area of the vehicle, with noticeable sounds that seem to emanate from a location outside the car (like from the side mirrors). The key to getting good width is to do so WITHOUT affecting center imaging, creating a "sonic hole" in the middle of the stage.

Stage Height

Simply, how high is the sound stage? Additionally, is the stage height stable, meaning even height from right to left? When we sit in an audience, we IDEALLY see the musicians slightly above us. Thus, when we try to reproduce the "live performance" feeling in a car, the stage should seem to be in front of us, at eye level OR slightly higher. Too low, and it doesn't seem real, as our focus is skewed downward and we end up looking at the floor to envision the performance. Too high, and we feel like we are "star-gazing" and again, end up focusing on the sun visors or sunroof, again, it is unnatural. Getting the stage height to be stable means you get the picture of, for example, a guitarist at far left, a drummer in the center, and a harmonica far right. The key to a "stable" stage is to get these locations to project at exactly the same height. Often times, a car with an unstable height will portray the center image nicely, but the left and right images will be very noticeably lower, giving us the "rainbow" effect, and thus a mediocre stage height score.

Likewise, some cars have frequency-dependant stages, where the high frequencies from the tweeters might be at eye level, the midrange frequencies seem slightly lower, and the midbass and sub bass appear to be coming from the floor. This is also unacceptable, and many factors affect this phenomenon. Some of them are speaker location, resonation of speaker enclosures, coloration caused by standing waves inside the enclosures, and poor equalization and sonic balance. We shall cover each of these in depth shortly. So, we want to see a "stable" sound stage projected at eye level in a proper SQ set-up.

Stage Depth

Depth and Position to Soundstage ore often mistaken for one another. Position to Sound stage pertains to how far in front of the listener the sound stage actually is. Stage Depth pertains to the placement of musicians On the sound stage either in front of or behind one another. Often times, for instance, the drum set will be located "behind" the guitarists, and the vocalist will be in front of these instruments, front and center. Systems with no stage depth will portray a flat sounding, one-dimensional stage where every musician appears to be side by side. Systems with excellent stage depth will give the listener a sense of space between the performers, and you should be able to tell that instruments are being played at different distances from you.

Ambience

Ambience is that phenomenon that gives you a sense of space around an instrument. Many people confuse ambience with artificial "surround-sound" echoes meant to add the illusion of music all around you. Every recording contains ambience of some sort, be it a sense of "air" around the instrument or the "sound" of the room the track was recorded in. Using reference recordings where the actual recording room characteristics are known ahead of time, SQ judges can score ambience based on whether the performance "seems" to be played from inside this actual room.

For example, there is a track on the '97 IASCA SQ competition CD that was recorded by a single microphone at a level of approximately 20' above the stage, INSIDE a large auditorium. With proper ambience, it should seem like you are in that large auditorium when you listen to this track. THAT is proper ambience, not artificial ambience.

Tuning and speaker quality have the most impact on ambience, followed closely by controlling sonic reflections and resonations in the vehicle and speaker placement with proper x/o selection. Some people use ambiently tuned rear fill speakers to try to accomplish this aspect, but in a properly designed and tuned system, rear fill is NOT necessary to acquire excellent ambience.

Imaging

The sound stage should be looked at in 5 separate sections: Left, left center, center, right center, and right. These are the most common locations on the stage used to evaluate the imaging characteristics of the car. By using reference material, the judges know exactly where the different instruments should be "located" on the stage.

A system that images well will have well-defined and focused instruments located exactly where they should be on the sound stage. These images will not wander from their locations, and you could easily close your eyes and point to where each instrument actually is. Many systems exhibit frequency-dependant imaging where as the frequency changes in pitch or scale, the image will move accordingly. This is not good imaging.

Likewise, some systems have good left and right imaging, but fail to get a center-stage focus at all. To many, the center image is the most important location on the stage, and it is easy to tell which cars have good centers and which don't. Speaker placement, path length differences, and proper equalization vastly affect imaging, and to a lesser degree, resonations, reflections, standing waves, and uneven interior surfaces play a role in the imaging characteristics of a system. Again, we will get to these aspects shortly.

Sound Linearity

How well balanced does the system sound at low, moderate, and high volume? A system with good linearity will sound equally balanced at all three loudness levels, remaining accurate tonally and free of distortion of any kind. This depends mainly on proper gain settings and equalizer tuning, though other factors can possibly affect it.

Absence of noise

A good SQ system will be a symbience of many factors coming together to provide a performance free of unwanted noises such as speaker pops, alternator whine, ground loop noise, additional noise floor in the form of extra hiss, on/off thumps or pops, and any other form of unwanted noises. All recordings exhibit a noise floor in the background, It is a byproduct of the recording process that cannot be overlooked, and for this reason, only the noise level present in the original recording will be acceptable.

Dynamic Impact

A superior system should be capable of reproducing the proper "feel" of the music. We need to consider the fact that music has Two dimensions---That which we hear, and that which we feel. If we were to go to a rock concert, sitting front and center, and the drummer decides to go-off on an improve solo while the rest of the band grabs a cold one and some ho-hoes, we are treated to a barrage of dynamic percussion sounds. When facing the stage, we feel the sound waves both in our chest and abdomen as well as on our skin. The bass drum obviously will be the most prominent, however the toms, snare, and even hard cymbal strikes can be felt, and felt easily if the guy is REALLY going off. We can even plug our ears to make this effect more pronounced. Sound is emitted in waves. These waves possess energy levels that are dependant on amplitude (loudness) and the proximity of the listener to the source, thus, we can feel the sound waves as they interact with the touch-receptors in our bodies.

Ever flinch or blink upon hearing an abrupt, loud sound? Well, I am not certain of precise figures, but I'll bet it is about 50% due to what we hear, and 50% due to a subconscious physical reaction to "feeling" the sound wave, causing sudden stimulus in our nerve endings. The best car systems are capable of re-creating this sense of dynamics, as it should be "felt" live. And they should do so without feeling percussive waves emanating from rear mounted subs (Yet another topic we will discuss), making us hear the bass player up front, but he feels like he is behind us at the concession stand getting a sausage dog or something. NOT good.

Sound Quality of a Speaker

Speakers are tools that deliver sound. A good speaker means a speaker of good sound quality. Not all of them are equally good.A good speaker does not have any private sound. The job of a speaker is to deliver the sound exactly the way it is in the source. It will not provide any extra sound. If it does, then it will not be considered a good speaker. If it makes the violin or string sound edgy or if it creates an artificial bass for the male voice, then also it will not be counted as an effective speaker.

Midrange is very important for human listening. This is the range that we hear most clearly. A good speaker must be able to deliver this midrange smoothly and that too without any kind of harsh sound. If the lead portion of a guitar sounds harsh or the midst sound becomes muffled, that means the speaker is not of good quality. In this case the music also will not seem realistic to you.

A very effective way to judge the quality of a speaker is to listen to chorus songs. There has to be four parts in a chorus. Basses and tenors of the men and sopranos and altos of the women. In a proper speaker, you will very easily be able to distinguish all four of them. If the speaker is not good, then it will produce a very blurred sound.

Glossary for I.C.E

Recievers Glossary(What u might find on your Head Unit?)

Anti-Theft Protection
A security feature that helps prevent receiver theft. Following 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. It is also called as Theft Deterrent Faceplate by some manufacturers.
•Security Code - Some receivers give you the option of setting up a security code. This is usually in addition to having a detachable faceplate. The security code is a three or four button combination; usually using the radio preset buttons that has to be entered before the receiver will function.

Auxiliary Input
An input on the face or rear of the receiver that enables you to connect a portable music player (CD, MP3, or cassette) to the receiver. The input jack can be either Mini or RCA.
Generally the AUX-IN jacks are 3.5mm; some receivers have 2.5mm AUX-IN connectors.

CEA-2006 Compliant
This applies to both external amplifiers and the amplifiers within in-dash receivers. CEA-2006 is a standard published by Consumer Electronics Association, on May 28th, 2003. This standard imposes a "Testing & Measurement Methods for Mobile Audio Amplifiers.", a uniform method for determining an amplifier’s RMS power and Signal-to-Noise (S/N) 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.
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: "Amp Power Standard CEA-2006 Compliant."

CD Text
Some compact discs (CD) 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.

CD-R, CD-RW Compatibility
CD receivers with this capability can play audio CD-Rs and/or CD-RWs as well as prerecorded CDs. Almost all of today's receivers can play CD-R and CD-RW discs.

Changer Controls
Originally, changer controls referred to a receiver's ability to control a same-brand CD changer. Nowadays, the changer control connection on a receiver can be used to add one of any number of peripheral devices. Most stereo brands let you choose from a CD changer, iPod® adapter, USB adapter, Bluetooth™ adapter, and more.

Codec
A codec is a method of compressing and decompressing digitized sound. MP3 , WMA and AAC 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. Sony’s “Attrac” format taken even lesser than 1 megabyte.

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.

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.

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.

Digital-to-Analog (D/A) Converter
Your CD receiver uses a D/A (Digital to Analog) 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.
Digital Media Files
Music that has been transformed to be able to store as files, on compact discs or any digital media. 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, WMA, AAC, or WAV files. A single disc can hold up to ten hours of music. CD receivers nowadays, allow you to navigate through the folders and files on the CD.

Display
•Slot-faced - Conventional Slot-faced receivers are convenient, but their displays are smaller out of necessity.
•Fold-down Face - 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.

DVD/CD Receivers
These receivers can play CD and 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. These receivers have digital-to-analog converters that are superior to those found in most regular CD receivers (as DVD decoding usually requires, higher bit D/A converters), so your CDs will usually sound better on a DVD receiver.

Equalizer
A built-in EQ lets you tailor the sound to your listening tastes and sometimes 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). Equalizers with 5 bands are popular, though, nowadays, we can see many built-in 7 band equalizers.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.
Note: Equalization is post-processing of output signal. So, raising or lowering of a band extremely can result in distorted or damped frequencies pertaining to that band. If you have to raise or lower a band by more than 3dB, to get to your listening tastes, You are advised to alter the base sound level, instead.

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 receiver’s built-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.

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).

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. Frequency ResponseThe range of frequencies, a stereo component can reproduce. It is measured in Hertz (Hz), and a wider range is better.
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. Due to advancement in electronics, frequency response of electronic components, nowadays, are very good compared to speakers.

Ground Loop
A ground loop occurs when any piece of equipment or any incoming wire is connected to a different ground or grounds. If the in-dash receiver and amplifier are grounded to different locations, 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.

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.

Loudness
Loudness is the quality of a sound that is the primary psychological correlate of physical strength (amplitude). Loudness control in a receiver allows you to boost the lower frequencies in your music for full, rich sound at lower volumes.

MP3
MP3 codec is invented by Fraunhofer IIS research institute. 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 auxiliary inputs. For superb sound quality with MP3, do not use bitrates lower than 192 Kbit/s. You might even want to consider using 256 kbit/s and higher although differences are rarely conceivable in that area.

Multi-path Interference
Multi-path interference affects FM radio reception. FM waves travel in a straight line, so, When FM signals bounce off buildings and other large objects, the tuner picks up the same signal more than once, at different times. This creates "echoes" that confuse the tuner by mixing with the original signal.

Peak Power
Peak power handling refers to the maximum amount of power output during a brief musical burst. Some manufacturers display peak power ratings on the face of their products. The RMS power rating is more significant, and is recommended to use it for comparison purposes.
Preamp OutputsJacks 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.

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.

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.

Random Play
Mixes up the order of songs during playback. It is also called as “shuffle”. Some CD players offer a "Random Play with Delete" feature that prevents a song from being repeated once it has been played.
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.

Signal-to-Noise Ratio
A measure of how well a CD player silences background noise. Higher ratings, in decibels (dB), indicate less noise.

Subwoofer Preamp Outputs
RCA output jacks (usually coupled with a built-in low-pass filter) for connection to a subwoofer amplifier.
Time Correction
A processing circuit 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. This can provide better sound-staging.
Track Repeat
Plays the same track over and over until you turn the feature off.
Travel Presets or Best Tuning Memory (BTM)
Engage this feature and the 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.
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.

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).

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.

Amplifier Glossary

Ampere Ampere is the unit of measure for current or electrical "flow" through a circuit. It is commonly abbreviated as "amp" or “A” and should not be confused with the word "amplifier," which is also commonly abbreviated as "amp.” Current increases with decrease in impedance.

Bridged Power
Some power amplifiers, allow you to combine the power outputs of two channels into one channel. By bridging, you can drive one speaker with more power than the amp could produce for two speakers. Because of this high power output, bridging is an ideal way to drive a single subwoofer.
If your amp is bridgeable, the owner's manual will have directions that tell you how. Usually, an amp is bridged by connecting the speaker leads to the positive (+) terminal from one channel and the negative (-) terminal from the other channel. However, you are advised to consult your owner's manual before attempting to bridge your amp.Most amplifiers need to see a 4-ohm load when bridged to mono operation. This is in other ways, specified as “4-ohm stable”. If you want to bridge your amp, you should use one 4-ohm speaker or, if you prefer multiple woofers, wire two 8-ohm speakers in parallel. (Again, consult your manual before operating your amp in bridged mode.) Some amps are 2-ohm stable, and even 1-ohm stable also.

Bass Boost Circuitry
Increases the output of low frequencies. Usually centered somewhere between 40 and 90 Hz, many amps have variably controlled circuits that allow you to increase the bass level in dB increments (ie. 0-12 dB at 45Hz). Variable bass boosts allow you to adjust the center frequency, changing the character of the bass. Some recent receivers have Bass Boost Circuitry in the head unit’s amplifier.

Built-in Crossovers
Crossovers consist of both a high-pass and low-pass filter. A low-pass filter prevents high-frequencies from reaching a subwoofer, by allowing only frequencies below the crossover point to be amplified. A high-pass filter allows only frequencies above the crossover point to be amplified — useful for keeping low bass away from small speakers, so they can play more efficiently. Crossovers are usually listed as variable or selectable. Continuously Variable means the crossover can be freely adjusted to any frequency between the listed end points. Selectable means that you can choose from several preset crossover points.

Capacitor
Capacitors are reservoirs of power. Heavy-duty capacitors act as a buffer zone between your amp and your car's electrical system. They store up a reservoir of power, which can supply the amplifier's peak demands without having to get additional current from the battery, which otherwise would impact badly on car’s battery. All amplifiers have built-in capacitors, though high-performance amps use larger, more effective ones.
External capacitors are recommended when you have high-powered subwoofers. External capacitors connect to the power cable just before it reaches your amplifier.

CEA-2006 Compliant
CEA-2006 is a standard published by Consumer Electronics Association, on May 28th, 2003. This standard imposes a "Testing & Measurement Methods for Mobile Audio Amplifiers.", a uniform method for determining an amplifier’s RMS power and Signal-to-Noise (S/N) 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: "Amp Power Standard CEA-2006 Compliant."

Class of an Amplifier
Amplifiers are categorized into different classes based on their performance characteristics. Each class determines a specific design employed in the amp circuitry. And each design has different performance characteristics such as, power dissipation (in the form of heat) and distortion characteristics determining the efficiency of an amp.
•Class A amplifiers are desirable for the high quality of their sound but inefficient and runs very hot. This is because even when there is no audio signal, the output transistor(s) always have current running through them. The current flowing through the output transistor(s) (with no audio signal) causes the amp to heat up unnecessarily, and "waste" input energy. Most car amplifiers that boast "Class A" circuitry are really Class A/Class AB hybrids.
•Class AB amplifiers are most commonly available amp design. They allow current to run through the output transistors when there is no audio signal, but at a much lower level. A class AB amplifier runs cooler, and therefore, more efficiently than a class A, with low distortion and high reliability.
•Class D amplifiers boast higher efficiency, produce less heat, and draw less current than traditional Class AB designs. They use output transistors as switches to control power distribution — the transistors "turn off" when there is too much voltage across them. Class D amplifiers produce higher distortion than AB designs due to the high-speed switching on and off of the transistors, but this distortion occurs at high frequencies that are typically removed by a low-pass filter.
•Class T amplifiers are bit expensive and provide the sort of sonic advantages of conventional Class AB designs, combined with the high power efficiency and low heat production of a Class D design. Class T amps are able to generate 2-4 times more power than a comparably-sized Class AB amp.

Clipping
When Clipping occurs in amplifier, it literally cuts off the tops and bottoms of the musical waveforms that it's trying to reproduce. This occurs when your amplifier is asked to deliver more current to a speaker than the amp is capable of doing. This introduces a huge amount of distortion into the output signal. Clipping can be heard as a crunching sound on musical peaks. And more over, in that time, your subwoofer will have to operate at its peak power handling ratings.

Crossover Point
In high-pass filters, low-pass filters, and crossovers, the crossover point is the frequency at which the level of the output signal has been reduced by 3 dB.

Crossover Slope
Slope is expressed as decibels per octave. Crossover Slope is the rate at which the crossover attenuates the blocked frequencies. A 6dB per octave crossover reduces signal level by 6dB in every octave starting at the crossover point. This means that every time the frequency of the audio signal is changed by a factor of 2 (one octave), the level of the audio signal will change by 6dB.
Suppose, your low-pass filter is set at 80Hz with a 6dB slope, you will see a drop in level of 6dB at 160Hz. With slopes of 12dB and higher, you'll hear little output beyond the crossover point.

Damping Factor
The ability of an amplifier to control the movement of a speaker — the higher the damping factor, the greater the accuracy.
Damping factor = speaker impedance / output impedance of the amplifier. An amplifier's damping factor will decrease as the speaker's impedance decreases.That's why an amp running at 4 ohms will provide tighter bass than at 2 ohms.

Discrete Output Devices
Three basic types of output devices are found in car audio amplifiers: integrated circuits (or IC), bipolar transistors, and Metal Oxide Semiconductor Field Effect Transistors (MOSFETs). An IC cannot pass enough current to work on a more powerful amplifier and is not considered a discrete output device. It is found only on relatively low-wattage (20 watts RMS per channel or less) amplifiers called "bridged transformerless" amps.
Bipolar transistors and MOSFETs are fast enough and can handle enough current to send wattage greater than 20 watts per channel to your speakers. They are found on the output stages of high-powered amplifiers. Both of these types of transistors are considered discrete output devices. Usually there are two per channel, but some amps feature as many as four per channel.

Impedance
Impedance rating is the total opposition to the flow of audio signal in an electrical circuit at a given frequency. It is measured in Ohms. Most car audio elements have 4-Ohms of impedance. Although car audio manufacturers label the impedance of most car speakers and subs at 4-ohms, the impedance of a speaker is actually not a constant. It's actual impedance changes with frequency and can vary greatly. Therefore, though 4-ohms is the standard impedance in car audio, this standard is more of an average impedance for speakers and amplifiers when driven within the part of the audio spectrum for which they are designed. “Nominal Impedance” is the minimal impedance that the amp. Or speaker can handle.

Mono Amplifier
Mono (or monaural) amplifiers are single channel amps, well suited for low-frequency applications since the human ear cannot distinguish stereo in the extreme bass range. Also, since mono amplifiers are stable to 2-ohms, you can connect them safely to two 4-ohm woofers (wired in parallel). These are also called generally as monoblocks.

MOSFET
Metal Oxide Semiconductor Field Effect Transistors have a higher switching speed than bipolar transistors and generate very little heat. MOSFETs offer fast response and high efficiency.

Ohm
The unit of measurement for impedance or resistance. It tells you how much a device will resist the flow of current. If you take two signals of exactly the same strength and send one to a 4-ohm speaker and the other to an 8-ohm speaker, twice as much current will flow through the 4-ohm speaker. In other words, the 8-ohm speaker will require twice as much power (wattage) to play at the same volume.

Power Handling (RMS)
The maximum continuous sine wave power that can be dissipated by a speaker without failure, measured in watts RMS. Most speakers fail for one of two main reasons:
•A speaker is driven with too much power, beyond its rating, and it overheats.
•The amplifier is driven into clipping, producing square wave distortion that destroys the driver.
Remember that, clipping of an amp, forces the speakers to work at double power!

Preamp output
A preamp output lets you pass the preamp signal to additional amps, and in many cases the internal crossover from the first amp can send a filtered signal, eliminating the need for additional crossovers.

Resistance
Is the opposition to the flow of electrical current. Resistance is measured in Ohms.

RMS Power vs. Peak Power
The amount of continuous power, measured in watts, that an amplifier produces is called RMS power. This is very significant rating one should pay attention to, while buying the amp. The higher the RMS figure, the louder and cleaner your music sounds. Also, keep in mind that some manufacturers calculate the RMS power ratings of their amplifiers at different input voltages. For example, an amplifier rated at 100 watts RMS at 12 volts can produce considerably more power than an amp rated at 100 watts RMS at the more typical 14.4 volts.Stereo manufacturers often display peak power ratings on the face of their products. The peak power rating tells you the maximum wattage an amplifier can deliver as a brief burst during a musical peak, like a dramatic drum accent. The RMS figure is more significant.

RMS Power at 2 ohms
This rating tells you how much more power your amp delivers when a 2-ohm stereo load is presented. You can achieve a 2-ohm load by using parallel wiring of 4 Ohm speakers or by using 2 Ohm speakers.
Theoretically, amp output should exactly double as the impedance drops from the usual 4 ohms to 2 ohms. However, amp makers use different degrees of regulation on power supplies, which can restrict the actual increase in output.Less regulated power supplies come closer to doubling their output into 2-ohm loads. An amp with little regulation can achieve higher wattage into lower impedances. An amp with stiffer regulation maintains rated output from your amp as other electrical accessories demand voltage from the battery.

Signal-to-Noise Ratio
Measured in decibels (dB), this specification compares the strength of the desired audio signal to the level of background noise. A higher value indicates less background noise.

Sound Pressure Level (SPL)
SPL is measured in dB — an acoustic measurement of sound energy. One dB SPL is the smallest audible difference in sound level. 0dB SPL is the threshold of human hearing, while noise measuring 120dB can damage your hearing. In some countries, the maximum SPL of audio systems are restricted to specific values.

Speaker-level input
Number and type of speaker-level inputs. Speaker inputs let you connect an amp to a receiver that lacks RCA preamp outputs.

Subsonic Filter
A subsonic filter or an infrasonic filter, cuts off extremely low bass (below the range of human hearing) that many speakers cannot effectively reproduce, thereby making the amp's power supply and output devices, and the speaker, more efficient.

Total Harmonic Distortion (THD)
Amount of change in harmonic content of the signal as it is amplified. A lower figure indicates less change and a more accurate amp. THD below 1% is inaudible.
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.

Tri-Way Output
Also called as Dual Mode, this setup powers a pair of stereo speakers and one subwoofer simultaneously from the outputs of a single 2-channel amplifier. It's an affordable way to drive a subwoofer. It requires an external Tri-Way adapter that is connected in-line between your amplifier and your speakers.

Speakers Glossary

Basket
Basket or frame is the structure holding the cone, voice coil and magnet rigidly to preserve the proper alignment. It is important, since the voice coil gaps are very narrow. Two types of baskets are popular: Stamped & Cast brackets. Cast brackets are very rigid but expensive.

Bi-amping
In Bi-amping, the woofer and tweeter of a loudspeaker are driven by separate amplifiers. This provides dedicated and flexible amplification of low-frequency (woofer) & high-frequency (tweeter) signals. With such arrangement you can adjust different amp. gains for woofer & tweeter.

Coaxial speaker
Co-axial speakers are usually 2-way speakers. I contain two driver elements: a woofer, for low notes reproduction and a tweeter mounted inside the woofer, for high frequency sound reproduction.

Component System
Component system, also called as "Seperates", includes 2 woofers, 2 tweeters and 2 crossovers. All these drivers and crossovers are designed to work optimally with one another. The separate drivers design provides the manufacturer with very less or almost no compromise in design. And hence, generally they are made of better materials. You can position the separate tweeters for optimal imaging. Given adequate power, separates deliver exceptional dynamics and detail.

Compression horn
Compression horns are generally used in super tweeters. "Compression" name comes from the type of drivers it is made of. These drivers produce high pressure but little displacement. The diaphragm therefore moves very little, which results in less distortion than a conventional radiating driver.

Crossover
Crossovers are also called as frequency dividing network. They are made of filters, coils & capacitors, and direct specific frequency ranges to appropriate speaker components (woofers, midrange and tweeter). The acoustic behavior of low and high frequency drivers outside their recommended frequency ranges may not add up well, thus resulting in poor frequency response. Crossovers avoid this problem and thus provide proper sound staging. Two generic types of crossovers are available:
•High level passive: Fits between the power amplifier and speakers. This type is widely used in car audio.
•Low level active: Fits before the power amplifier. Expensive and used only in profession concert sound systems.

Decibel (dB)
Decibel is a standard unit of measure for expressing relative power or amplitude differences. With audio, it represents loudness. One dB is the smallest change in loudness most people can detect. A 1 dB difference is barely noticeable, but a 10 dB difference is big — a speaker playing at 10 dB higher volumes will sound roughly twice as loud.For any given set of speakers, each 3 dB increase in volume level requires a doubling of the amplifier power.

Diaphragm
Diaphragm (also known as the cone) is the thin, semi-rigid membrane attached to the central magnet. The magnet induces the diaphragm to vibrate, producing sound. This diaphragm is also found in headphones. In woofer, this is the speaker cone. In a tweeter, it is usually dome shaped.

Dual Cone
A dual cone speaker uses an inexpensive design in which a small "whizzer" cone attached to the center of the woofer reproduces the high frequencies.

Dust cap
The dust cap is a gently curved dome mounted over the central hole of most loudspeaker diaphragms. It prevents the inner mechanics (such as the pole piece and the spider) from getting soiled. Dust caps also contribute to structural integrity to the voice coil assembly.In some speakers, dust cap serves as high frequency radiator.

Efficiency
The efficiency rating for a speaker measures how well a speaker converts watts of electrical power into watts of acoustical power. Efficiency is related to the "Sensitivity" rating, but it is a different measure. Most manufacturers choose to provide sensitivity rather than efficiency. Most speakers have a very low efficiency rating — between 1% and 10%.

Frequency Response
Frequency Response of a device describes its correctness in terms of passing the signal from its input to its output with regard to the signal amplitude & frequency. This tells us the usable range of signal frequencies with this speaker.
Usually, frequency response of woofers will be above 100Hz up to 2 kHz.
Frequency response of Tweeters will be above 2,500 Hz and below 21,000 Hz (or sometimes up to 25 kHz).
Component systems specify the combined frequency response of its tweeter and woofer elements. Usually it will be above 50Hz and up to 25 kHz.Subwoofers have frequency response below, 100 Hz.

Full-range Speakers
These are capable of reproducing both low and high level ranges of frequencies. They accurately reproduce your music's frequency range by mounting a tweeter inside the woofer cone. This is also known as a coaxial or 2-way speaker. Some versions may add midranges or supertweeters to better reproduce other parts of the frequency spectrum. These are also referred to by the number of drivers (3-way, 4-way, etc.). Due to size limitations, Full-range speakers used in car generally don't reproduce very low frequency ranges. For very low frequency range, subwoofers are used.

Imaging
Imaging is a qualitative term used to explain the live sound reinforcement capability of the audio system. Optimal imaging creates a listening experience that seems natural and lifelike. The key to attaining the best possible imaging is to have equal (or as close to equal as possible), unobstructed path lengths between your tweeters and your ears. The ability to mount your tweeter separately, as with components, or in an angled mount, as with some full-range speakers, can improve imaging.

Impedance
Impedance is a measure of the resistance of a speaker's voice coil to the audio current supplied by the amplifier.Strictly speaking, actual impedance of speaker varies considerably with frequency of input audio signal. So, few manufacturers mention impedance ratings at specific frequencies.
Nominal impedance is more dependable rating that tells the minimum impedance the speaker offers to the input load. Most speakers use 4 ohm coils. This rating should be matched with amplifier's output impedance rating.

Magnet
The magnet provides a stationary magnetic field against which the voice coil reacts to create sound. The magnets used in speakers are permanent magnets usually made of ceramic, ferrite, Alnico, or, more recently, rare earth (Neodymium magnet).

Maximum RMS Power Handling
"RMS" is an abbreviation for Root Mean Square. Maximum RMS Power-Handling refers to the maximum amount of power a speaker can handle on a continuous basis. This is the most dependable power rating in speakers.

Midrange Speaker
A midrange speaker reproduces the middle frequencies. Component systems often use separate midranges, as do systems that amplify the low, midrange, and high frequencies separately. Some full-range speakers include a midrange element for better detail. Usually midrange speaker sizes range from 3-1/2" to 6-3/4".
Most component systems are made of: 2 midrange woofers + 2 tweeters+2 crossovers.

Peak Power Handling
Peak power handling refers to the maximum amount of power a speaker can handle during a brief musical burst.

Plate Speaker
Since a round woofer is more accurate than an oval one, Plate speakers feature a separate round woofer and tweeter, mounted side by side on a plate that's designed to replace oval-shaped 4"x6" and 5"x7"/6"x8" speakers. A plate speaker reproduces music more accurately than an oval speaker. However, the woofer cone on a plate speaker is smaller than a similarly-sized oval speaker, so its bass output will usually be slightly lower.

Polarity
The positive and negative terminal connections decide the direction in which the speaker diaphragm moves. Polarity should be checked before connecting the input signals to ensure, proper terminal points. Polarity should be maintained in all the speakers and other elements such as amplifiers & crossovers for the proper working of overall setup. If you wire your speakers improperly, one speaker cone will move backward while another is moving forward, cancelling out much of the sound both speakers are trying to make.

Pole piece
A pole piece concerns the metal piece in a speaker that concentrates and focuses energy from the speaker magnet into creating a magnetic circuit. Because heat can accumulate during this process, many manufacturers vent pole pieces for cooler, more efficient operation.

Power handling
All car speakers require a power source (receiver or amplifier). Power handling rating is usually specified in range. The lower number of a power-handling rating tells the absolute bare minimum wattage required in getting acceptable sound from the speaker, and the higher number tells the maximum amount the speaker can handle for an extended time. For best results, match your power source level (RMS, or continuous watts) to the upper part of the speaker's recommended range (RMS rating).

Resonance
It is vibration of a speaker's cone. All speaker cones vibrate at a certain frequency. Too much resonance can interfere with a speaker's accuracy.

Sensitivity
Sensitivity is the sound level produced by a given input power at a specified distance directly in front of the speaker. A sensitivity rating tells you how effectively a speaker converts power (watts) into volume (decibels). It is specified in dB SPL at one meter in front of the speaker with 1 Watt input signal.Note: An increase of 3dB in sensitivity creates an increase in sound pressure level in front of the speaker that is same as doubling the amplifier power!As many receivers provide usually 22watts (RMS) power per channel, amplifier is recommended for most speakers for better sound.In case, you are not using power amplifier and directly powering the speakers from receiver, speakers with high sensitivity ratings may be chosen for better sound.

Soundstage
The soundstage refers to the sense of width, depth and height your ears' perceive, when you listen to music — just as you would sense the placement of different instruments in a live concert setting. Individual vocal and instrumental "images" make up your system's soundstage. Note that, tweeters are more directional, and are thus provides more sound localization. Hence, the tweeters must be position properly for better soundstage. Subwoofers are least directional.

Spider
The spider is a flexible ring that keeps the voice coil aligned in its gap and secures the rear of the speaker cone to the frame while still allowing the voice coil and the cone to vibrate freely.

Subwoofer
Subwoofer refers to either a woofer, or a complete loudspeaker dedicated to the reproduction of bass audio frequencies, typically from 150 Hz down to 20 Hz. Subwoofer sizes typically measure from 10" to 12". As subwoofers require more power, a power amplifier is always recommended.

Supertweeter
A small driver dedicated to ultra-high-frequency reproduction, usually above 10 kHz. You can usually find supertweeters alongside tweeters in 4- or 5-way full-range speakers. Typically these are either compression drivers or piezoelectric drivers.

Surround
The surround refers to the flexible ring encircling the edge of the woofer cone — it connects the cone to the speaker basket. It must be pliable enough to let the woofer travel freely, yet strong enough to guide and control cone movement. (The further the cone can travel, the stronger the bass.) Surrounds are usually made of cloth, foam, or rubber. Rubber tends to last the longest.

Three-way speaker
Three-way, or triaxial, speakers take the separate woofer and tweeter from a two-way design and add a midrange driver for enhanced warmth and texture. Select three-ways use a supertweeter, instead of a midrange, for extended high-frequency response. Four-ways combine a woofer, a midrange, a tweeter, and a supertweeter for even more detail. In theory, n-way speaker will have 'n' number of drivers.

Tinsel leads
Tinsel leads are flexible, stranded wires that connect the voice coil to the speaker's terminals.

Tweeter
A small driver dedicated to high-frequency reproduction. Cone tweeters are efficient and the most economical. Most home speakers use dome or "edge-driven" tweeters — they disperse sound over a wider area for smoother, more accurate reproduction. Semi-dome (or balanced-dome) tweeters use a combination cone and dome construction for excellent sound clarity and dispersion.

Tweeters are made from a variety of materials — paper, aluminum, titanium, or synthetic films such as polyetherimide (PEI) or Kaladex (polyethylene naphthalate). It's best to listen to a variety of tweeters to determine which one you prefer.

Two-way speaker
Two-way, or coaxial, designs reproduce your music's frequency range accurately. These speakers use a separate tweeter — mounted inside the woofer — to deliver the high-frequencies.

Voice coil
A voice coil (consisting of a bobbin, collar and winding) is the coil of wire attached to the apex of the cone of a loudspeaker. It provides the motive force to the cone by the reaction of a magnetic field to the current passing through it. Many of the speakers on this site offer a heat-resistant voice coil to prolong speaker life.

Woofer
The woofer, a speaker's largest cone, reproduces bass and lower midrange notes. To operate efficiently, a cone should be made of material that is stiff, yet lightweight. Cones made of aluminum, synthetic film (like polypropylene), poly mixed with other materials (like mica), or treated paper provide excellent sound, and stand up to the heat, cold, and moisture that car speakers face on a daily basis.

Stock HU
Tonality - Very poor
Stage Width - Narrow
Stage Height - At our Foot, way below where our ears are
Stage Depth - In your face -- right in the center
Ambience - No space at all
Imaging - Moderate Left, and Right. No center.
Sound Linearity - Extremely Poor at Low, Moderate at Mid, and Distorted at High
Absebse of Noise - Good
Dynamic Impact - None whatsoever.

The above is my judgement Though there is some hope in recovering lost ground. For example, you can get a tuner to correct the Stage width, Height, Depth, Ambience and Imaging -- Ice Voodo is one such example. You then can turn your DSP to DSP FLAT to get some Dynamic Impact and recover lower tonality, but you may suffer in other arears for doing so. Ultimately, to get good sound experience, you will then end up needing to add/change equipment.

Wow blue, you are really into it eh ...

Great info!

walao ehh .... hail the 8GCC ICE sifu ...... !!

now we got Ah Long, then Ice Sifu ....

great info bro ... me also confuse with the meaning ...

I felt like a beginner attending a master course, totally lost

Thumbs up to you, great information,

Theres one HIDDEN ICE freak and sifu among the above replies(not including me of course). Pioneering ICER and freaking sensitive ears hehe You know who you are bro and I wont divulge the info unless you wanna haha

Heard the Pioneer P-80 and P-90 was not good enough for you hahaha

*Die lor, afterwards somebody going to ketuk me over the net de