If you are new to car audio world and want to start with the basic knowledge, you must know the car audio terms which describes the meaning of it. There are various kinds of terms you will hear from most people which will  be difficult to understand if you are a newbie.

RMS: The RMS terms stands for ROUTE MEANS SQUARE. It is basically the representation of the continuous power output of an amplifier or continuous power handling of the speakers. RMS is one of the car audio terms which is very commonly used when we talk about amplifiers and speakers. Sometimes the manufacturer of the amplifier or speaker will list watts RMS as the continuous power rating along with the max power output. The protocol max power output isn’t ever worth worrying about because it is unrealistic representation that how much power amplifier is actually putting out. You have to always focus on the Watts RMS or the continuous power of the amplifier or the speaker. Same in the speakers if you are getting a speaker of 100 RMS then to match it up you will have to get a 100 RMS power amplifier.

Crossover: The crossover is connected between the amplifier and the speaker mid bass and the tweeters to divide the frequencies which they suppose to get. There are various frequency ranges which the speaker alone or the tweeter alone cannot produce so the crossover takes full range frequencies and then divides it to the midrange the mid frequencies and the tweeters the high frequencies. This is one of the very important car audio terms which is used to tune the speakers. It basically blocks the frequencies which they are designed to cut off. This crossover is called as a Passive crossover which looks like a box and comes mostly with 2 way component speakers or even 3 way component speakers. The crossovers have bands divided into low pass, band pass, high pass.

Low Pass Crossover: It is used for the subwoofer to limit the higher frequency to reach the subwoofer. 80Hz is the standard low pass point for the subwoofers which will allow everything below 80Hz to pass.

Band Pass Crossover: This is basically the combination of a low pass and a high pass crossover where only allows the frequencies between a certain range. This type of crossover is used for the midrange speakers where you don’t want the subwoofer bass to going to it and high notes of tweeter going into it.

High Pass Crossover: It allows all the frequencies above a certain value. This is used for the tweeters as tweeter get blown easily if they get any king of low or mid frequency pass through them.

Full Range: The human ears can hear the frequency from 20Hz to 20000Hz. The full range means the frequencies from 20Hz to 20000Hz all together is considered to be a full range.

Hertz: This is the unit of frequency abbreviated as Hz. Hertz is basically how much cycles per second are occurring with a sound wave. So if we have a speaker which is playing at 20Hz that means it going up and down 20 times a second. A 20Hz sound wave would be low like bass. In contrast we had something like 18000Hz note it would be literally 18000 times a second and would be really high pitched note. 

Roll Off or Slope: Roll off is basically how quickly these frequencies are going to fall off. So with the low pass crossover at 80Hz how quickly is that drop off going to be. 

Running Active: It means your speakers and tweeters are playing directly from your amplifier and your amplifier is controlling the crossover to divide the mid and high frequency. DSP can also control the crossovers for the them. They have tuning flexibility by which you can fine tune the speakers to any level.

Running Passive: It means you have a crossover installed in between amplifier to the mids and highs. People shift from passive to active as the passive crossover eats up some amount of power to run the speakers which results in less output than active setup. Going passive is not a good idea if you are going way too loud audio system. They do not allow any tuning flexibility as well.

Component Speakers: Component means each of the speakers are separate from one another. The midrange speaker and the tweeter will work independently. They cover the mid frequency with the mid bass and high frequency with the tweeters. They can play louder and more clean than the coaxial speakers. they can be 2 way or 3 way. 2 way will have midrange and tweeters and 3 way will have mid-bass for bass, midrange for vocals and tweeters for highs. They are mostly have passive crossovers.

Coaxial Speakers: They are the opposite of the component speakers. midrange and the tweeter is combined in one speaker. They are mainly used in the cars where you have only one mounting location provided and you do not want to display your tweeter separately. They are easier to install but not good in terms of sound.

DSP: This device is connected between any source unit of car to the amplifier. DSP has a bunch of processing ability to tune the system to the next level. It can control Equalizer, Slopes, sensitivity of the speakers and Time Alignment as well which is not easily to have in normal systems. They have the option for separate channels for Front, rear and subwoofer by which the tuning can be done very easily and will sound much better. It can really help to stage the sound in the vehicle.

High level Input: These are the speaker level inputs which are used to connect the line output convertor to make low level inputs.

Low level Inputs: These are the RCA input which are mostly seen in the aftermarket amplifiers and head units. The RCA wire is used to connect the radio to the amplifier, this is known as the low level input.

Head Unit: It is the source unit of the car which play the music and supplies the signals to the speakers and the amplifiers. There are 2 types of head unit single din and the double din. Single din is small and can be installed in any car easily but the double din has big size and requires 7 inch of space for the install. The double din installations are complicated and needs dash kits for the installation into the dashboard of the car. 

SPL: It stands for Sound Pressure Level. In SPL level of setups the loudness is the main word for it and how much loud can the SPL setup can be. Large size subwoofers, multiple batteries, aftermarket high power alternators are used in the SPL setups.

SQ: It stands for Sound Quality. In SQ setup all the focus in on the clarity of the speakers, Loudness is not the considered in these type of setups. 

Sealed Enclosures: These type of enclosure do not have any kind of port on the box and is packed from every side. It will have less output of bass than a ported enclosure but it will have a decent punchy bass performance. This is not recommended for the people who wants bass. Accuracy of the bass can be felt in this enclosure.

Ported Enclosure: This enclosure will have a port for the air passing to produce low bass in the air. These type of enclosures are used for loud setups and have high output of bass than a sealed enclosure. It can have any kind of port in the enclosure, it can be aero port or can have a slot port as well. Ported enclosures are more difficult to make than a sealed enclosure as the port are and port length is calculated and then it is tuned to the frequency of your desire. Ported enclosures comes in various kinds of order according to their design.

Distribution Block: It is used to distribute the power to amplifiers from a single wire to multiple wires. It can be fused or non fused. It is very useful when you installing multiple amplifiers in the vehicle and want to draw a single wire from the battery. 

Wire Gauges: The gauge term describes the thickness of the wire. Gauge is one of the car audio terms which is not known to majority of the people how it works, people think higher wire gauge means thicker wire which is wrong. The lower the number you go, the thicker the wire will become. Suppose you have a 8 gauge wire and a 4 gauge wire, the 4 gauge will be more thicker wire than the 8 gauge wire. 1/0 gauge wire is considered to be the thickest wire than any wire. 

Gain on the amplifier: It is used to control the sensitivity of the amplifier to the input from the volume control of the head unit. This is one of the most important car audio terms which can destroy everything, if it is set wrong or too high. It is not a volume knob so do not use it like that. Setting gains higher than requires will introduce distortion which will damage your speakers and amplifiers.

DB: It stands for decibels which is used to measure the sound pressure or acoustical energy. Higher db means the louder the sound is.