Amplifier - Commonly called an "amp", an amplifier is a device that takes in low-level signals from a source unit, boosts them, and converts them into wattage that can drive a speaker.
CD & DVD - I hope you know what these are.
MP3 & WMA - These are compressed audio formats that can be "burned" onto CDs and DVDs. Most new in-dash source units and disc changers read all these formats, but some only read certain formats. Also note that the reason MP3s are so small is because they are compressed and compressed and compressed. This depletes the sound quality considerably. I have had a few MP3s that sounded really good, and I've had tons that sound like crap. WMAs are the way to go for sound quality. They may take up more space than MP3s, and you probably won't get as many songs on the CD had you used MP3s, but it really makes a difference. But if you don't listen to music in your car, it doesn't make much of a difference.
Coaxial - A generic term describing midrange and tweeter(s) mounted together with a simple passive crossover. When a tweeter is mounted to the center of a midrange speaker, they share the same axis or become coaxial. Today, any speakers that are mounted together are just called coaxials, even if they arn't on the same axis.
Component Speaker - Matched speakers with external passive crossover networks and necessary hardware are all contained within one box. They are easier to install than raw drivers. Some allow the tweeter to be mounted in the center of the woofer and some are permanently mounted that way, although these are not called coaxials because of their high quality.
Crossover - This can be either passive or active. The active version gets wired up like an amplifier or equalizer, and installed in-line before the amplifier(s), directing appropriate frequencies to their respective amplifiers. The passive version is comprised of capacitors, coils, and resisters and is wired between the speakers and amplifiers. Systems can have both active and passive crossovers.
Equalizer - This electronic device can boost or cut various predetermined frequencies so that a sound system's frequency response can be adjusted or tuned. They are available with various bands that can be independently adjusted as though each band had its own volume knob.
DIN - This is a standard source unit measurement in regards to the shape of the faceplate. Expressed as single DIN, 1.5 DIN, and Double DIN.
Head Unit - The interface used to accessthe audio/video system, which can be a cassette player, CD player, or in-dash monitor that will play CDs and DVDs. Other names for head unit include: radio, source, source unit, deck, monitor, and CD-player.
Hertz (Hz) - This stands for cycles per second. Woofer cones and tweeter diaphrams move back in forth in various cycles per second, ranging from 20Hz to 20,00Hz. Subwoofers cover from below 20Hz to up around 250Hz, midrange woofers cover around 250Hz to 3,500Hz, and tweeters coverup everything else from 3,500Hz and up.
Installation Kit/Wiring Harness - This allows for conversion from oversized or non-standard factory radio in order to accomodate DIN-sized source units. These are offered with prefabricated harnesses that fit directly into a car's factory car stereo Molex plug and must then be wired to the source unit's wiring harness.
Midrange - Woofers generally ranging from 3 1/2 to 10 inches in diameter. Different ones will cover different frequencies. Smaller ones will not go as low as larger versions, but they will be able to produce higher frequencies.
Neodymium - These are small, lightweight , and expensive magnets with the same magnetic flux as standard, heavy magnets several times their size.
Power Handling - This is a method of closely matching speakers to amplifier wattage in terms of RMS power. The most important speaker specification for the casual consumer.
RCA - These are cables used to connect source units to other items, such as equalizers and amplifiers. They are sold in pairs for left and right channels, and available in coaxial and in twisted pair types. Twisted pair cables are of a higher quality and are less likely to induce noise.
RMS(Root Mean Square) - This is the most important type of amplifier power rating. An amplifier with a 100-watt RMS rating may have a 200-watt peak rating, which is only good for a few seconds with a high rate of distortion.
Tweeter - This is a speaker with a small, lightweight cone capable of producing frequencies as high as 20,000Hz. There are all different types available in various sizes, although for a car, they are typically small in overall size.
Woofer - This is a speaker comprised of a cone attached to a voice coil that moves back and forth against a magnetic field when current is applied. Made in different sizes ranging from a huge 18 inches (Kicker makes this beast) to a little 3 1/2 inches, they are designed to cover different frequency ranges, including sub-bass, midbass, and midrange.
Well this took me about 2 hours to write so enjoy!
Rollin through ya hood like Gs.