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Chapter 10
REFERENCE MATERIAL
Car Audio Dictionary:
A: Attenuation, loss of dB. AC (Alternating Current): An electrical current that periodically changes in
magnitude and direction. Acoustic Fiberglass: Thin fiberglass material used as damping material inside
speaker enclosures.
Acoustics: The science or study of sound.
Air Gap: The space between the top plate and the pole piece. This is where the voice coil sits. Alignment:
A class of enclosure parameters that provides optimum performance for a woofer with a given value of Q.
Alpha: In sealed enclosure designs, the ratio of Vas to Vb, where Vb is the volume of the box you will
build.
Alternator: A device that is turned by a motor to produce AC voltage, which is then rectified (turned into
DC) and used to supply voltage to the vehicle's electrical system.
Ampere (A): The unit of measurement for electrical current in coulombs per second. There is one ampere in
a circuit that has a one ohm resistance when one volt is applied to the circuit.
Amplifier: An electrical circuit designed to increase the current, voltage, or power of an applied
signal.
Amplitude: The relative strength (usually voltage of a signal). Amplitude can be expressed as either a
negative or positive number, depending on the signals being compared.
Attenuation: The reduction, typically by some controlled amount, of an electrical signal.
Audio Frequency: The acoustic spectrum of human hearing, generally regarded to be between 20 Hz and 20
kHz. B: Magnet flux density in gap.
Baffle: A board or other plane surface used to mount a loudspeaker.
Balance: Equal strength provided to both left and right stereo channels.
Bandwidth: The range of frequencies covered by a driver or a network (crossover).
Band-Pass Enclosure: Type of enclosure used for subwoofers where the driver is completely inside the
enclosure and all of the output emerges through a port(s) on one of the sides. They are difficult to
calculate for optium performance.
Band-Pass Filter: An electric circuit designed to pass only a certain range of frequencies.
Basket: The metal frame of a speaker.
Bass Blockers: First order high-pass crossover (non-polarized capacitors), generally used on midbass or
dash speakers to keep them from trying to reproduce deep bass which could damage them at high playing
levels.
Bass Frequencies (Low Frequencies): The low end of the audio frequency spectrum. There are no real
frequencies where bass is categorized, but it ranges from approximately below 20 Hz to 400 Hz.
Bi-amping: Means that instead of driving a speaker full-range with a single channel of amplification,
through a single set of speaker cables, you actually connect two sets of cables, with each set driven by a
separate amplifier, or seperate channels of a multi-channel amplifier. This way, low frequencies and high
frequencies each receive dedicated amplification.
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