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RCA Cable
Audio terminology can get very confusing. Here is a list of most basic words (and some more complicated terms) that  you will generally come across. I tried to make it simple enough to understand, but enough to give a good definition.
If you think I have forgotten something important, please Email me with your idea.

Acoustic feedback - a squealing sound when the output of an audio circuit is fed back in phase into the
circuit's input.

Acoustic fiberglass - thin fiberglass material used as damping material inside speaker enclosures. Other materials can be used such as Polyfill or household insulation. In this way, an optimum design may be made up to 20% (or more) smaller due to the extra damping.

Acoustic suspension - a sealed or closed box speaker enclosure. Also called a sealed enclosre, or infinate baffle.

Acoustics - the science or study of sound.

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.
See sealed enclosure.

Alternating (AC) Current - an electrical current that periodically changes in magnitude and direction.

Ampere (A) - the unit of measurement for electrical current in coulombs per second. There is one ampere in a
circuit that has one ohm resistance when one volt is applied to the circuit. See Ohms Law.

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.

Aperiodic Enclosure - an otherwise sealed enclosure design, but with a vent that is stuffed with damping
material, which flattens out the impedance curve of the design. The area of this resistive vent should be about
10 sq. in. per cubic ft. of enclosure volume. This design might take some experimentation with the vent
stuffing, testing the impedance curve several times with different amounts of damping material until the
flattest impedance curve is found. The aperiodic resistive vent damps the driver in much the same way as
fully stuffing a sealed enclosure with damping material (100% fill).

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

Audio Noise - see Noise.

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 enclosre and all of the output emerges through a port(s) on one of the sides. They are difficult to calculate for optimum performance.

Band-Pass filter - an electric circuit designed to pass only a certain range of frequencies. See also High-pass and
Low-pass filters.

Basket - the metal frame of a speaker.

"Bass Blockers" - first order high pass crossovers (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 (low frequencies) - The low end of the audio frequency spectrum. There is no real frequencies where bass is catagoriezed, but it ranges from approximately below 20 Hz up to 400 Hz or so.

Bass Reflex - see ported enclosure.

Beaming - the tendency of a loudspeaker to concentrate the sound in a narrow path instead of spreading it.

Bi-amping and bi-wiring - some higher performance speakers include dual sets of connectors, usually the type known as "binding posts," Models with dual connectors almost always also feature a special type of crossover with separate "high-pass" and "low-pass" sections. Speakers with dual sets of connectors will also work fine when used with a single set of speaker cables. In fact, they usually come from the factory set up for conventional operation with "jumpers" installed between the two sets. These jumpers can be easily removed for bi-amping or bi-wiring.
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 separate channels of a multi-channel amplifier. This way, low frequencies and high frequencies
each receive dedicated amplification.
Bi-wiring involves connecting two sets of cables to your speakers, like bi-amping, but both sets of cables
connect to the same set of output connectors on your receiver or amplifier. Bi-wiring doesn't deliver more
watts to your speakers, so it doesn't offer the dramatic sonic improvement and higher loudness capability of
bi-amping. Still, many audiophiles find that it adds subtle improvements in imaging and detail.

Bipole -- A speaker design which generates equal amounts of sound both forward and
backward, with the two sounds being "in phase". See also Dipole.
Bipolar Speaker

Boomy - the smearing of transients that makes bass reproduction sound muddled, usually because of
improperly designed sealed (to small), ported (to small or tuned improperly), and bandpass enclosures,
although the latter are sometimes designed this way on purpose by car audio manufacturers or install shops
to be loud.

Bridging - combining both left and right stereo channels on an amplifier into one higher powered mono channel. When an amplifier is bridged, the impedance that the amplifier actually "sees" is calculated based upon the resistance of both stereo channels. Here is a simple formula to help define this:

Bridged Mono Impedance = (Y / X)/2
Y = impedance of driver(s) (both drivers should be identical)
X = # of drivers in circuit

EX/ So, hooking up one 8 ohm speaker bridged mono would be equal to hooking up two 4 ohm speakers in stereo, one to
each channel.

Cabin gain - the low frequency boost normally obtained inside a vehicle interior when subs are properly

Capacitor - a device made up of two metallic plates separated by a dielectric (insulating material). Used to
store electrical energy in the electrostatic field between the plates. It produces an impedance to an ac current.
In automotive applications, special "Power Line Caps" can be connected inline to the amplifier to aid the
alternator in supplying current demands of amps. Non-polarized capacitors can be used as first order passive
high pass crossovers, or as components in more complex high pass, bandpass and lowpass crossovers. See
power line caps.

Center Channel - in home theater, sound decoded from the stereo signal sent to a speaker mounted in front
of the listener, specially designed to enhance voices and sound effects from a movie soundtrack. Used in car
audio to help offset skewed stereo imaging due to seating positions in the automotive environment.

Channel - the path an audio signal travels through a circuit during playback. At least 2 channels are required
for stereo sound.

Circuit - a complete path that allows electrical current from one terminal of a voltage source to the other

Clipping - (1) a distortion caused by cutting off the peaks of audio signals. Clipping usually occurs in the
amplifier when it's input signal is too high or when the volume control is turned to high and the amplifier
tries to put out too much current and it sends out direct current to the speakers. (2) when playing at loud
volumes, and the cone of the driver "bottoms out" - it cannot move as far as the signal requires it to, it can
produce a noise. If an amplifier or speaker is left operating in this condition, serious damage may occur.

Cms - mechanical suspension compliance of a driver, consisting of the spider and surround.

Coaxial Driver - a speaker composed of two individual voice coils and cones; used for reproduction of sounds
in two segments of the sound spectrum. Usually used in automotive speakers, although KEF uses them in home speakers.
See also triaxial driver.

Coulomb - 6.25 (10)^18 electrons per second.

Coloration - any change in the character of sound that reduces naturalness, such as an overemphasis of
certain tones.

Compliance - the relative stiffness of a speaker suspension, specified as Vas. Also see Vas.

Cone - the cone-shaped diaphragm of a speaker attached to the voice coil which produces pulsation's of air
that the ear detects as sound.

Crossover Frequency - the frequency at which a driver's is crossed over at - usually when response is down -3dB. See Roll-off.

Crossover Network (Filter) - an electric circuit or network that splits the audio frequencies into different
bands for application to individual speakers. See Electronic and Passive Crossover.

Current (I) - the flow of electrical charge measured in amperes.

Damping - the reduction of movement of a speaker cone, due either to the electromechanical characteristics
of the speaker driver and suspension, the effects of frictional losses inside a speaker enclosure, and/or by
electrical means.

Damping Material - any material added to the interior of a speaker enclosure to absorb sound and reduce
out-of-phase reflection to the driver diaphragm (cone). Usually acoustic fiberglass, polyester batting, or
Polyfill is used in speaker enclosures.

Decibel (dB) - (1) a logarithmic scale used to denote a change in the relative strength of an electric signal or
acoustic wave. It is a standard unit for expressing the ratio between power and power level. An increase of +3
dB is a doubling of electrical (or signal) power; an increase of +10 dB is a doubling of perceived loudness. The
decibel is not an absolute measurement, but indicates the relationship or ratio between two signal levels. (2)
SPL (sound pressure level) can be measured in dB. 0 dB represents the threashold of normal human hearing,
130 dB represents the threashold for pain, 140 dB causes irreparible hearing damage, and 150 dB can cause
instant deafness, anything greater than about 192 dB can kill you.

Diaphragm - the part of a dynamic loudspeaker attached to the voice coil that moves and produces the sound.
It usually has the shape of a cone or dome.

Diffusion - The scattering of sound. Diffusion reduces the sense of direction of a sound source, a useful quality in
surround speakers.

Dipole - A speaker design which generates equal amounts of sound both forward and
backward, with the two sounds being out of phase. Dipoles are often used as surround
speakers. See also Bipole.
Dipolar Speaker

Direct Current (DC) - current in only one direction.

Diffraction - a change in the direction of a wave that is caused by the wave moving past or hitting an obstacle.

Dispersion - the spreading of sound waves as it leaves a speaker.

Distortion - any undesirable change or error in the reproduction of sound that alters the original signal.

Dome Tweeter - a high frequency speaker with a dome-shaped diaphragm.

Double(Dual) Voice Coil (DVC) - a voice coil with two windings, generally subwoofers. Each voice coil can be
connected to a stereo channel, or both voice coils can be wired in parallel or series to a single mono channel.

Driver - a loudspeaker unit, consisting of the electromagnetic components of a speaker, typically a magnet
and voice coil.

Driver Parameters - the physical properties of a driver that determine it's electrical and acoustical behavior.
The minimum parameters used in determining speaker enclosures are Fs, Qts, and Vas. See Thiele/Small

Dual Reflex Bandpass Enclosure - sometimes called a 6th order bandpass. In these designs, Vr is ported as well
as Vf, so that there are 2 resonant frequencies. Vf and Vr are tuned about an octave apart, providing the driver
with excellent damping at resonance, even further reducing distortion. This design is even more efficient than a single reflex bandpass, but with a compromise. The system has the same high frequency roll-off of -12 dB/octave,
but low frequency cut-off is at -24 dB/octave (just like a regular ported enclosure). Power handling is excellent within it's frequency bandwidth, but these designs are similar to ported in that they are subject to low frequency noise upsetting the driver(s) below F3. Transient response is also rather poor, but these enclosures can be made to play very loud. One of
the most difficult enclosures to build and tune.
Dual Reflex Bandpass Enclosure

Dynamic range - the range of sound intensity a system can reproduce without compressing or distorting the signal.

EBP - Efficiency Bandwidth Product. A rating that helps a builder determine whether a driver is suitable for a
sealed or ported enclosure. EBP of less than 50 indicates the driver should be used in a sealed, 50 - 90 indicates
flexible design options, over 90 indicates best for a ported enclosure.
EBP = Fs / Qes

Efficiency rating - the loudspeaker parameter that shows the level of sound output when measured at a
prescribed distance with a standard level of electrical energy fed into the speaker (usually recorded as
XdB/2.83V/1 meter distance. However, a driver with a high efficiency rating needs a larger box to play
a lower frequency than a driver with a lower efficiency rating.

Electronic Crossover - uses active circuitry to send signals to appropriate drivers. More efficient than passive

Enclosure - the box that contains the driver(s).

Equalizer - electronic device used to boost or attenuate certain frequencies.

F3 - the roll-off frequency at which the driver's response is down -3dB from the level of it's midband response,
sometimes called the cutoff frequency.

Fb - the tuned frequency of a ported box.

Fc or Fcb - the system resonance frequency of a driver in a sealed box.

Fs - the frequency of resonance for a driver in free air.

Farad - the basic unit of capacitance. A capacitor has a value of one farad when it can store one coulomb of
charge with one volt across it.

Filter - any electrical circuit or mechanical device that removes or attenuates energy at certain frequencies.
See Crossover Network.

Flat Response - the faithful reproduction of an audio signal; specifically, the variations in output level of less
than 1 dB above or below a median level over the audio spectrum.

Free Air Resonance - the natural resonant frequency of a driver when operating outside an enclosure.

Frequency - the number of waves (or cycles) arriving at or passing a point in one second, expressed in hertz

Frequency Response - the frequency range to which a system, or any part of it, can respond. Unless a limit of
variation in intensity is stated, this specification is meaningless.

Fundamental Tone - the tone produced by the lowest frequency component of an audio signal.

Full-range - a speaker designed to reproduce all or most of the sound spectrum.

Golden Ratio - the ratio of the depth, width, and height of a speaker enclosure, based on the Greek Golden
Rectangle. Usually recommended for home speakers, difficult to use in car audio applications. The Ratio: W =
1.0, Depth = 0.618W, Height = 1.618W.

Ground - refers to a point of (usually) zero voltage, and can pertain to a power circuit or a signal circuit. In car
audio, the single most important factor to avoid unwanted noise is finding and setting a good ground.

Harmonic - the multiple frequencies of a given sound, created by the interaction of signal waveforms.

Harmonic Distortion - harmonics artificially added by an electrical circuit or speaker, and are generally
undesirable. It is expressed as a percentage of the original signal. See THD.

Hertz (Hz) - a measurement of the frequency of sound vibration. One hertz is equal to one cycle per second.
The hertz is named for H.R. Hertz, a German physicist.

High-pass Filter - an electric circuit that passes high frequencies but blocks low ones. See Band-pass and
Low-pass filters.

Hiss - audio noise that sounds like air escaping from a tire.

Home Theater - an audio system designed to reproduce the theater sound experience while viewing movies
in the home. Minimally consisting of a Dolby Pro Logic® surround sound receiver, left and right front
speakers, a center channel speaker, and at least (1) surround sound speaker. These plus optional subwoofer(s),
surround speaker(s), and digital formats such as Dolby Digital® can enhance the viewing experience by
drastically improving the sound quality of movie soundtracks.

Horn - a speaker design using its own funnel shaped conduit to amplify, disperse, or modify the sounds
generated by the internal diaphragm of the speaker.

Hum - audio noise that has a steady low frequency pitch.

Imaging - listening term - it is the speakers ability to locate where each instrument or voice is located. See Soundstage.

Impedance - the opposition of a circuit or speaker to ac current; the combined effect of a speaker's resistance,
inductance, and capacitance that opposes the current fed to it. It is measured in ohms and varies with the
frequency of the signal.

Inductance (L) - the capability of a coil to store energy in a magnetic field surrounding it. It produces an
impedance to an AC current. Inductors are commonly used in audio as low pass crossovers. See Le.

Infinite Baffle - a flat surface that completely isolates the back wave of a driver from the front.

Infrasonic (Subsonic) Filter - a filter designed to remove extremely low frequency usually between 8-25Hz or lower, noise from the audio signal. Useful for Ported box designs.

Input - the current fed into a loudspeaker.

Isobarik Enclosure - enclosure where one woofer is buried in the enclosure and a second is mounted up
against the first and wired in reverse polarity (there are other variations for Isobarik designs), but this one works best.
This allows the effective Vas of both drivers working in this push-pull configuration to be half that of a single identical driver mounted normally. Very small enclosures may be constructed as a result, with increased power handling. Less efficient than other designs, but the push pull configuration greatly reduces second order harmonic distortion. The name Isobarik comes from a term that means "constant pressure". See
Isobarik Enclosure

Kilohertz (kHz) - one thousand hertz.

Le - the inductance of a driver's voice coil, typically measured at 1 kHz in millihenries (mH).

Low-Pass Filter - an electric circuit designed to pass only low frequencies. See Band-pass and High-pass

Lobing - the tendency of a speaker system that consists of more than one driver to produce a lobed frequency
response in space with in-phase reinforcement (lobes) from the various drivers occurring at some elevations
and out-of-phase opposition (nulls) at points between the lobes.

Maximum power rating - a value which means almost nothing, but is used nonetheless by manufacturers to
entice the unsuspecting into purchasing their product based solely on the big number. Technically, it is the
maximum wattage that an audio component can deliver/handle as a brief burst during a musical peak. Most
reputable manufacturers will provide both an RMS and Max power rating. Typically, the given value for the
maximum power rating is twice to three times that of RMS.

Microfarads (mF) - a measurement of capacitance.

Midbass - mid level bass, usually frequencies just above the sub-bass range, from around 100 - 400 Hz or so.

Midrange (mids) - the frequency range above bass but below treble that carries most of the identifying tones
of music or speech. It is usually from 300 - 400 Hz to 3kHz or so.

Millihenries (mH) - a measurement of inductance.

Mms - the moving mass of a driver assembly.

Mono - monophonic sound. A method for reproducing sound where the signals from all directions or sources
are blended into a single channel.

MOFSET - Metal Oxide Semiconductor Field Effect Transistors. Used in most modern, quality car audio
amplifiers in the power supply (and sometimes in the output stage). MOSFET's run cooler than normal
bipolar transistors, and have a faster switching speed.

Noise - any undesirable sound reproduced in an audio system.

Octave - a range of tones where the highest tone occurs at twice the frequency of the lowest tone.

Ohm - a unit of electrical resistance or impedance.

Ohm's Law - a basic law of electric circuits. It states that: the current [I] in amperes in a circuit is equal to the
voltage [E] in volts divided by the resistance [R] in ohms; thus, I = E/R.

Out of Phase - when your speakers are mounted in reverse polarity, i.e., one speaker is wired +/+ and -/-
from the amp and the other is wired +/- and -/+. Bass response will be very thin due to cancellation.

Output - the sound level produced by a loudspeaker.

Passive Crossover - uses inductors (coils) and capacitors to direct proper frequencies to appropriate drivers.
These crossover systems can be simple (First Order = 1 component @ -6 dB/octave slope) to complex (Fourth
Order = 4 components @ -24 dB/octave slope).

Passive Radiator - a device that looks just like an ordinary driver, except it has no magnet or voice coil. A
radiator is usually a highly compliant device, with a similar cone material and surround found on regular
active drivers. The radiator must usually be at least as large (or larger) than the driver it is aligned with. The
passive radiator is tuned to Fb and used in place of a port, providing bass reinforcement for the driver in a
similar fashion as any regular ported box. A clear advantage of the radiator is the absence of port noise, and
some audiophiles claim the radiator provides a better sounding bass than a ported enclosure. Disadvantages
include difficulty in tuning, and the extra required baffle area for the radiator. Most radiators can be tuned
with either weights or silicone, adding material in a balanced manner until Fb is attained.

Pe - Driver's rated RMS power handling capability.

Peak - the maximum amplitude of a voltage or current.

Peak power rating - see Maximum power rating.

Phase - Refers to the timing relationship of two or more signals or soundwaves. It's especially important to be
sure that your stereo speakers are playing "in phase." This means that the drivers (cones and domes) of your right
and left speakers are moving in and out at the same time. If your speakers are "out of phase" you'll hear significantly less bass, and instead of producing a strong center image, the sound tends to stay localized at the speakers.

Phase Coherence - the relationship and timing of sounds that come from different drivers (subs, mids, tweets)
mounted in different locations in the vehicle.

Phase Distortion - a type of audible distortion caused by time delay between various parts of the signal; can
be caused by equalizers.

Polarity - the orientation of magnetic or electric fields. The polarity of the incoming audio signal determines
the direction of movement of the speaker cone. Must be observed when wiring speakers, so that they are "in
phase". See Out of Phase.

Ported Enclosure - a type of speaker enclosure that uses a duct or port to improve efficiency at low
frequencies. Excellent design for lower power systems, as the port often adds up to +3 dB to low frequency
efficiency. F3 can be set considerably lower with proper design, although low frequency roll-off is generally
-24 dB/octave. Good transient response with proper tuning, although the driver loses damping below the
tuning frequency. Excellent power handling about Fb, but source material or frequencies below Fb cause the
driver to progressively perform as if it were not enclosed at all. Due to this, ported enclosures without a low
frequency filter may have lower power handling compared to other designs. More difficult to
properly build and tune than a sealed enclosure, with several "optimum" alignments available
depending upon the Qts of the driver. The best way to model these alignments is with a software program,
where changes in tuning and enclosure size can be immediately noted.
Ported Enclosure

Power (P) - the time rate of doing work or the rate at which energy is used. One equation for Power:

P = Volts^2 / Impedance

Power Line Capacitor - wired inline on the power lead with your car amp, this device stores current for
instant release when short bursts of energy are needed to produce loud, deep bass notes. Best to mount as
close to amp as possible.

Pressure Effect - in sealed box designs, the pressure build-up on one side of the cone which may cause
non-linearity and inhibit dynamic range in the low bass.

Push-Pull Configuration - one driver is mounted normally, the second is mounted so that it faces into the
enclosure, both sharing the same internal volume and wired out of phase with one another. Although
electrically out of phase with one another, the drivers are acoustically in phase since they move in the same
direction. This alignment theoretically reduces second order harmonic distortion. See Isobarik Enclosure.

Q - the magnification of resonance factor of any resonant device or circuit. A driver with a high Q is more
resonant than one with a low Q.

Qes - the electrical Q of the driver.

Qms - the mechanical Q of the driver.

Qts - the total Q of the driver at Fs. Qts = Qes x Qms/Qes + Qms.

Qtc - value for the damping provided for a driver in a sealed enclosure. Denotes the enclosures ability to
control the driver response at resonance. Qtc = 0.707 is the optimum value for sealed enclosures, providing
flattest response and highest SPL for deep bass extension. Enclosures for this value are often rather large.
Lower Qtc can give even better transient response, down to a Qtc of 0.577 for the best damping and
transients, but the enclosure is usually huge and SPL's are down. A Qtc of 1.0 is a compromise between deep
bass and transient response vs. smaller sized enclosure. Larger subs can go with an even higher Qtc, as their
resonant frequency is often very low, but Qtc's above 1.5 can begin to sound very muddled and boomy, and
sacrifice deep bass extension and transient response for enhanced mid-bass peaks (louder).

Rear fill - in autosound, the ambience created by a pair of rear speakers that helps complete the soundstage. A
set of high quality components for the front powered by an external amp and a set of coax mounted on the
rear deck powered by the head unit or small amp is a good example of a rear fill application. Rear fill
speakers should be faded so that they create a richer ambience, but you should not be able to isolate any
sounds coming from them.

Resonance - the tendency of an object to vibrate most at a particular frequency.

Resonance Frequency - the frequency at which the speaker tends to vibrate most at a certain frequency.

Resistance (Re) - in electrical or electronic circuits, a characteristic of a material that opposes the flow of
electrons. Speakers have resistance that opposes current.

RMS - an acronym for "root mean square." Used in audio to help rate the continuous power output of an
amplifier or input capability of speakers. This is the preferred method for comparing anything in audio

Roll-off (cut-off) - the attenuation that occurs at the lower or upper frequency range of a driver, network, or
system. The roll-off frequency is usually defined as the frequency where response is reduced by -3 dB.

S or (Q') - the overall damping of a 4th order bandpass enclosure. i.e., if you were to figure a 4th order
bandpass enclosure with a Qtc of 0.70 for Vr (the sealed chamber), then you would also figure Vf (ported
chamber) with an S of 0.70.

Satellite speaker - A small speaker with limited bass response, often designed to be used with a matching

Sd - effective piston area of a driver.

Sealed enclosure - air tight enclosure that completely isolates the back wave of the driver from the front. Very
tight, defined sound (with Qtc = 0.707) with very good transient response and power handling.
Low frequency roll-off is at -12 dB/octave. Less efficient than other designs, and higher distortion
levels at resonance. Easy to design and build. Originally this design was pioneered and marketed by
companies like Acoustic Research. See Qtc.
Sealed Enclosure

Signal - the desired portion of electrical information.

Signal-to-noise (S/N) - the ratio, expressed in dB, between the signal and noise.

Sine wave - the waveform of a pure alternating current or voltage. It deviates about a zero point to a positive
value and a negative value. Audio signals are sine waves or combinations of sine waves.

Single Reflex Bandpass Enclosure - sometimes called a 4th order bandpass. A design where the driver is
completely "buried" in the enclosure, mounted in asealed chamber (Vr) and firing into a second ported
chamber with the sound emanating from one or more ports. This second chamber (Vf) is tuned to the sealed drivers Fcb. Band-pass enclosures pass only a limited range of frequencies, negating the need for crossovers in the circuit. In a typical single reflex bandpass, the cutoff rate below and above the "pass-band" is at a rate of -12dB/octave. These designs are very efficient within the operating bandwidth, with superior power handling, but generally inferior transient response to sealed (all the sound has to come out of the vent). Transient response can be very good if the enclosure is configured
with a S of 0.70. Can be very difficult to design and build.
Single Reflex Bandpass Enclosure

Skin Effect - technically, a physical phenomenon that relates to the limited penetration into a conductor of an
RadioFrequent signal according to its frequency. In a direct current case everything is constant and so nothing
seems to happen. With an alternating current, however, there is a delay in the magnetic field's response to
the change in current and the 'old' magnetic field tends to push the current towards the outside of the
conductor. As the frequency increases, so does the effect until at very high frequencies the entire current
flows in a very narrow skin on the conductor - hence the name. Skin effect is negligable in car audio

Sound Pressure Level (SPL) - the loudness of an acoustic wave stated in dB that is proportional to the
logarithm of its intensity.

Sound Stage - the sound systems ability recreate an imaginary stage. A good speaker will faithfully make
the stage seem close to the actual hight, width and depth of the actual performance stage where recorded.
Imaging is similar, but the speaker must be able to place each instrument or voice in the corect location on
the soundstage. The reproduction of the way the music would sound if you were actually watching the musicians
play in front of you. The stage should always appear to be in front of you, with a proper "image" of where each
musician is playing on the imaginary soundstage.

Spider - the flexible material that supports the former, voice coil, and inside portion of the cone within the
speaker frame.

Standing wave - a buildup of sound level at a particular frequency that is dependent upon the dimensions of
a resonant room, car interior, or enclosure. It occurs when the rate of energy loss equals the rate of energy
input into the system. This is what you hear when you listen into a sea shell.

Sub-bass - portion of bass that is very low, usually from 20 Hz - 100 Hz or so.

Subwoofer - a loudspeaker designed to reproduce bass frequencies.

Surround (suspension) - the outer suspension of a speaker cone; holds the diaphragm in place but allows it to
move when activated. Usually made of foam or rubber.

Surround Sound - usually representative of the monophonic sound extracted from the stereo signal sent to
smaller rear or side speakers used in a home theater. See Home Theater.

Timbre - The quality of a sound related to its harmonic structure. Timbre is what gives a voice or instrument its
sonic signature -- why a trumpet and a saxophone sound different when they play the same note.

Thiele/Small parameters - numbers that specify the behaviour of drivers, as defined and analyzed by two
engineers, Neville Thiele and Richard Small. See Driver Parameters.

Three-way - a type of speaker system composed of three ranges of speakers, specifically a woofer, midrange,
and tweeter.

Total Harmonic Distortion (THD) - the percentage, in relation to a pure input signal, of harmonically derived
frequencies introduced in the sound reproducing circuitry and hi-fi equipment (including speakers).

Transient Response - the ability of a speaker to respond to any sudden change in the signal without blurring
(smearing) the sound. A speaker that can react quickly to rapid changes in sound has "good transient response".

Transmission Line Enclosure - a design in which the driver is at one end of the enclosure, with an internal
path which consists of a series of bends or curves that lead to a port at the other end of the enclosure. The
path length is a fraction of the wavelength at low frequencies. The length of the path is increased by stuffing
the box with either long fiber wool or polyester batting, and produces a phase shift in the back wave that
reinforces bass at low frequencies. Enclosures must be very large, but low end response of these systems is
legendary among audiophiles. Drivers with Qts of less than 0.4 that work well in ported should work well in
these designs, but no standardized method for configuring these enclosures exists that engineers have yet to
agree upon. Power handling is generally less than in other designs, but drivers may be capable of responding
down to Fs. One of the most difficult enclosures to design and build, and much experimentation may be
necessary to get things right. "Labyrinths" and "Tapered (Stuffed) Pipes"are both variants of this type of

Treble (highs) - the upper end of the audio spectrum reproduced by tweeters, usually 3 - 4 kHz and up.

Triaxial driver - a speaker that is composed of three individual voice coils and cones; used for the
reproduction of sounds in three segments of the sound spectrum.

Tri-way output - when a special passive crossover is used with an automotive amplifier to safely power a
subwoofer in bridged mono (low pass circuit) as well as a pair of stereo speakers (high pass circuit). Normal
inductors and capacitors can be used for Tri-way output.

Tweeter - a speaker designed to reproduce the high or treble range of the sound spectrum.

Two-way - a type of speaker system composed of two ranges of speakers, usually a woofer and tweeter.

Vas - the equivalent volume of compliance, which specifies a volume of air having the same compliance as
the suspension system of a driver.

Vb - total box volume, usually in cubic feet or liters. Used specifically in sealed and ported designs.

Voice-matched - Speakers that are "voice-matched" have a similar timbre or tonal quality.
Voice-matched speakers in a home theater system will result in more seamless, consistent,
convincing wraparound sound.

Vf - front volume of a bandpass design.

Vr - rear volume of a bandpass design.

Voice coil - the wire wound around the speaker former. The former is mechanically connected to the speaker
cone and causes the cone to vibrate in response to the audio current in the voice coil.

Volt (E) - a unit of measurement used to measure how much "pressure" is used to force electricity through a

Watt - a unit of electrical power. A watt of electrical power is the use of one joule of energy per second. Watts
of electrical power equals volts times amperes.

Wavelength - the length of a sound wave in air. It can be found for any frequency by dividing the speed of
sound in air (1120 feet per second) by the frequency of the sound, or: WL = 1120 / Freq.

Whizzer - a small supplementary cone attached to the center of the speaker's main cone for the purpose of
increasing high frequency response.

Woofer - a bass loudspeaker designed to reproduce low-frequency sound only. A woofer and subwoofer are
usually the same type of loudspeaker, but their application (crossover frequency) differentiates them.

Xmax - maximum linear cone excursion of a driver, measured in inches or millimeters. This can be determined by subtracting the air gap height from the voice coil height then dividing by two.

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