Car Audio Terms & Dictionary
Baffle – the panel that a speaker or subwoofer is mounted to.
Cancellation – a speaker converts mechanical energy to acoustical energy. It does this as its cone moves back and forth based on the electronic signals sent to it from the power amplifier. Sound emanates from both sides of the cone – the sound waves emanating from the rear of the cone are opposite in phase from those emanating from the front of the cone. If these sound waves are allowed to mix, the net result is decreased output from the speaker. This is called cancellation.
Crossover Network – a network that is designed to divide the audio signal so that ranges of frequencies are sent to either the speaker or power amplifier that is intended to reproduce them. Crossovers can be passive or active:
- Passive crossover networks connect to the output of a power amplifier, divide the output accordingly, and direct the output of the amplifier to the correct speaker components – IE, a woofer at 300 Hz and down, a midrange at 300 Hz – 3,500 Hz, and a tweeter from 3,500 Hz and up.
- Active crossover networks (or electronic crossovers) connect to the output of the source, divide the output accordingly, and direct the output of the source to the correct power amplifiers – IE, a subwoofer amplifier at 80 Hz and down (which is connected in turn to a subwoofer), and a Hi-Pass amplifier at 80 Hz and up (which is connected in turn to a pair of full range speakers).
dB – abbreviation for decibel. A decibel is a defined unit of measurement for Sound Pressure Level (SPL).
Excursion – this refers to the amount of linear travel (forward and rearward motion) a speaker or subwoofer is capable of.
Frequency Response – This refers to a measurement of response over a defined range of frequencies. For example, if a woofer was rated to have a frequency response of 20 Hz – 500 Hz +/- 3dB, that means that it has no more than a 3dB plus or minus deviation in response from flat (0dB) between the specified frequencies.
Hz / Hertz – This is a unit of measurement that relates to frequency of Alternating Current (AC). Hz means cycles per second. A 50 Hz test tone has 50 cycles per second. A 1,000 Hz (1 KHz) test tone has 1,000 cycles per second. Note: a cycle is defined as a sine wave that originates at ZERO, increases to some positive peak, decreases back to ZERO, decreases to some negative peak equal to the positive peak, then increases back to ZERO. This occurs over some period of time.
Level-Matched – when each of the speaker’s output in an audio system is equal in Sound Pressure Level, the speaker system is said to be level-matched. (Does anyone really level match subwoofers in car audio? We sure don’t!)
Logarithmic – defines a mathematical relationship between two numbers (or components) based on logarithms. According to Wikipedia, the logarithm of a number to a given base is the power or exponent to which the base must be raised in order to produce the number. IE – the logarithm of 100 with respect to 10 would be 2 as 102 = 100. Of course, that’s more than you wanted to know . . .
Mid-bass – a speaker designed to reproduce frequencies between 75 Hz and 200 Hz . . . plus or minus a few . . .
Midrange – a speaker designed to reproduce frequencies between 200 Hz and 5,000 Hz . . . plus or minus a few . . .
Mid-bass / midrange – a speaker designed to reproduce frequencies between 75 Hz and 5,000 Hz . . . plus or minus a few . . .
Octave – a range of sound. Specifically, an octave is the interval between one pitch and another when doubling or halving frequency. I.E. – the range of frequencies between 40 Hz and 80 Hz is one octave. There are ten octaves of sound within the range of human hearing – 20 Hz to 20,000 Hz, which is frequently written as 20 Hz – 20 KHz.
Resonant Frequency – the frequency at which a woofer or subwoofer in a sealed enclosure resonates.
RMS – an abbreviation for Route Mean Square. RMS is the widely accepted metric of measuring and stating continuous power capabilities of audio power amplifiers as well as power handling capabilities of speakers and subwoofers.
- RMS power ratings of audio power amplifiers are typically stated at a specific impedance and at a certain level of distortion. Otherwise, they are meaningless. IE – 100 watts RMS per channel into a 4Ω load with less than 0.1% distortion.
- RMS power ratings of speakers and subwoofers are typically just given. IE – 250 watts RMS power handling.
Pay no attention to PEAK or MAX numbers, as they mean nothing.
Side Bias – side biasing is a result of sitting much nearer to one speaker than the other. The result is that the near speaker’s sound arrives to your ears sooner than that of the far speaker and the image is pulled to the near side. This is not desirable and can cause long term listening fatigue.
Subsonic Filter – a high pass filter with a very low crossover point. For example, a high pass filter at 30Hz would prevent musical information below 30Hz from reaching a subwoofer amplifier (and the connected subwoofer(s) ) connected to this filter. Subsonic filters are designed to prevent damage to subwoofers when used in vented or BandPass enclosures and connected to high power amplifiers.
Subwoofer – a speaker designed to reproduce the lowest frequencies of music, specifically the lowest two octaves*. Typically, this would be from 80 Hz to below the range of human hearing (lower than 20 Hz).
Tweeter – a speaker designed to reproduce frequencies between 5,000 Hz and 20,000 Hz . . . plus or minus a few . . .
Woofer - a speaker designed to reproduce frequencies from 20 Hz – 500 Hz (or even higher). Woofers are commonly used in home and pro audio speakers, where their frequency response has to extend all the way to the lower crossover point of the midrange (300 Hz – 500 Hz or so) in a three way system or to the crossover point of the tweeter (1,000 Hz or higher) in a two way system.