Car Audio Glossary
Amplifiers
Ampere
An Ampere or ‘Amp’ is the unit of measure for current or electrical "flow" through a circuit. (Note:
‘amp’ is also used as an abbreviation of the word amplifier; the two should not be confused.)
AWG
AWG stands for American Wire Gauge. This is the measure of the size of DC power cable as used
for car audio. The smaller the number is, the larger the wire’s diameter is. Most
commonly used sizes are 4 gauge and 8 gauge.
Bridged Power
When you bridge an amplifier, you combine the power output of two channels into one channel.
Bridging allows you to drive one speaker with more power than the amp could produce for two
speakers. Because of this high power output, bridging is an ideal way to drive a single subwoofer.
If your amp is bridgeable, the owner's manual will have directions that tell you how. Do not
attempt to bridge an amplifier unless the manual specifically states this is possible.
Bass Boost Circuitry
Increases the output of low frequencies or ‘Bass’.
Built-in Crossovers
Crossovers are used to control sound passed through to speakers or subwoofers. They
separate high frequency from low frequency and send only the relevant frequencies to the speaker.
This allows for greater efficiency and improved sound quality.
Capacitor
A capacitor is used as a type of buffer between your amplifier and your cars electrical system. It
stores large amounts of electrical current and can release this charge rapidly. It is also recharged
rapidly, thus lowering the strain on the vehicles electrical system.
CEA-2006 Compliant
On May 28, 2003, the Consumer Electronics Association published standard CEA-2006, "Testing &
Measurement Methods for Mobile Audio Amplifiers." This "voluntary" standard advocates a
uniform method for determining an amplifier's RMS power and signal-to-noise ratio. Using 14.4
volts, RMS watts are measured into a 4-ohm impedance load at 1% Total Harmonic Distortion
(THD) plus noise, at a frequency range (for general purpose amplifiers) of 20 Hz to 20,000 Hz.
Signal-to-Noise ratio is measured in weighted absolute decibels (dBA) at a reference of 1 watt into
4 ohms. This applies to both external amplifiers and the amplifiers within in-dash receivers.
CEA-2006 allows consumers to be able to compare car amplifiers and receivers on an equal basis.
Manufacturers who choose to abide by the new standard are able to stamp their
products with the CEA-2006 logo that reads: "Amp Power Standard CEA-2006 Compliant."
* This document is a guide only. Parallel Imported Ltd and the Author take no responsiblity for errors
or any damage caused as a result of this documents use.
© Parallel Imported Ltd
Author: Richard Bryan Eyre
Classes of Amplifiers
An amplifier is classified acco
according to its circuit design and the way its output stages are powered.
Although some may assume that for every portion of the input signal there is corresponding 100%
output from the amplifier, power dissipation (in the form of heat) and distortion of the audio signal
are two key factors in determining the efficiency and fidelity of an amplifier. Each class has its own
performance characteristics and advantages.
•
Class A amplifiers are desirable for the high quality of their sound, but, because of the
configuration of its transistors, a pure class A amplifier is inefficient and runs very hot.
This is because even when there is no audio signal, the output transistors always have
current running through them. The current flowing through the output transistors
(with no audio signal) causes the amp to heat up unnecessarily, and "waste" input
energy. Most car amplifiers that boast "Class A" circuitry are really Class A/Class AB
hybrids.
•
The output transistors of Class B amplifiers actually turn off for half of every signal
cycle. This improves efficiency and saves energy, but introduces distortion during the
switching periods.
•
By far the most common car amp design, Class AB amplifiers also allow current to run
through the output transistors when there is no audio signal, but at a much lower
level. A class AB amplifier runs cooler, and therefore, more efficiently than a class A,
with low distortion and high reliability.
•
Class D amplifiers use output transistors as switches to control power distribution —
the transistors rapidly switch on and off at least twice during every signal cycle. Class D
amps boast higher efficiency, produce less heat, and draw less current than traditional
Class AB designs. Class D amplifiers produce higher distortion than AB designs due to
the high-speed switching on and off of the transistors, but this distortion occurs at
high frequencies that are typically removed by a low-pass filter.
Clipping
Clipping occurs when an audio circuit's maximum capacity is exceeded. The circuit won't reproduce
the excessive parts of the signal, "clipping off" the round tops and bottoms of the musical
waveforms, leaving them square, and introducing a huge amount of distortion into the output
signal. Clipping can be heard as a crunching sound on musical peaks. A clipped signal, especially
one that has been amplified, can be very destructive to your speakers and subs.
Crossover Point
In high-pass filters, low-pass filters, and crossovers, the crossover point is the frequency at which
the level of the output signal has been reduced by 3 dB.
Crossover Slope
The rate at which the crossover attenuates the blocked frequencies. Slope is expressed as decibels
per octave. A 6dB per octave crossover reduces signal level by 6dB in every octave starting at the
crossover point. This means that every time the frequency of the audio signal is changed by a factor
of 2 (one octave), the level of the audio signal will change by 6dB. For example, if your low-pass
filter is set at 80Hz with a 6dB slope, you'll see a drop in level of 6dB at 160Hz. With slopes of
12dB and higher, you'll hear little output beyond the crossover point.
* This document is a guide only. Parallel Imported Ltd and the Author take no responsiblity for errors
or any damage caused as a result of this documents use.
© Parallel Imported Ltd
Author: Richard Bryan Eyre
Damping Factor
Damping is the ability of an amplifier
a
to stop the speaker cone from continuing to vibrate after the
signal stops. A system with good damping plays sound cleanly with no hint of
unintentional echoes or reverberations. The higher the damping factor, the greater
the accuracy.
Discrete Output Devices
There are three basic types of output devices found on car audio amplifiers — integrated circuits,
bipolar transistors, and Metal Oxide Semiconductor Field Effect Transistors (MOSFETs). An
integrated circuit (or IC) is found only on relatively low-wattage (20 watts RMS per
channel or less) amplifiers called "bridged transformerless" amps. An IC cannot pass enough
current to work on a more powerful amp and is not considered a discrete output device.
Bipolar transistors and MOSFETs are found on the output stages of high-powered amplifiers. They
are fast enough and can handle enough current to send wattage greater than 20 watts per channel
to your speakers. Both of these types of transistors are considered discrete output devices. Usually
there are two per channel, but some amps feature as many as four
per channel.
Feedback
Feedback is when an electronic circuit's output signal is used to modify its own input. This is handy
in getting rid of noise, for example, by subtracting any signal differences.
Heatsink
A heatsink is a metal structure used in electronics to draw heat away from critical components and
dissipate it into the air, usually via cooling fins.
Impedance
The total opposition to the flow of alternating current in an electrical circuit at a given frequency.
Impedance is measured in Ohms. Although car audio manufacturers label the impedance of most
car speakers and subs at 4-ohms, the impedance of a speaker is actually not a constant. It's actual
impedance changes with frequency and can vary greatly. Therefore, though 4-ohms is the standard
impedance in car audio, this standard is more of an average impedance for speakers and amplifiers
when driven within the part of the audio spectrum for which they are designed.
Mono Amplifier
Mono (or monaural) amplifiers are single channel amps, well suited for low-frequency applications
since the human ear cannot distinguish stereo in the extreme bass range. Also, since mono
amplifiers are stable to 2-ohms, you can connect them safely to two 4-ohm woofers (wired in
parallel).
MOSFET
Metal Oxide Semiconductor Field Effect Transistors have a higher switching speed than bipolar
transistors and generate very little heat. MOSFETs offer fast response and high efficiency.
* This document is a guide only. Parallel Imported Ltd and the Author take no responsiblity for errors
or any damage caused as a result of this documents use.
© Parallel Imported Ltd
Author: Richard Bryan Eyre
Ohm
Is the unit of measurement fo
for impedance or resistance. It tells you how much a device will resist
the flow of current. If you take two signals of exactly the same strength and send one to a 4-ohm
speaker and the other to an 8-ohm speaker, twice as much current will flow through the 4-ohm
speaker. In other words, the 8-ohm speaker will require twice as much power (wattage) to play at
the same volume.
Power Handling (RMS)
Root Mean Square. The maximum continuous sine wave power that can be dissipated by a speaker
without failure, measured in watts RMS. Most speakers fail for one of two main reasons:
1.
A speaker is driven with too much power, beyond its rating, and it overheats.
2.
The amplifier is driven into clipping, producing square wave distortion that
destroys the driver.
Preamp output
Preamp outputs let you pass the preamp signal to additional amps, saving you from having to run
more long patch cords to your receiver or to use unreliable y-adapters in order to hook up all your
amps.
Resistance
The opposition to the flow of electrical current. Resistance is measured in Ohms.
RMS Power vs. Peak Power
The amount of continuous power, measured in watts, which an amplifier produces, is called RMS
power. RMS ("Root Mean Square") is a mathematical way of obtaining a useful average when
discussing power capabilities. The higher the RMS figure, the louder and cleaner your music
sounds. When choosing an amplifier, the RMS rating is the power rating you should pay most
attention to.
Also, keep in mind that some manufacturers calculate the RMS power ratings of their
amplifiers at different input voltages. For example, an amplifier rated at 100 watts RMS at 12 volts
can produce considerably more power than an amp rated at 100 watts RMS at the more typical
14.4 volts.
Stereo manufacturers often display peak power ratings on the face of their products. The peak
power rating tells you the maximum wattage an amplifier can deliver as a brief burst during a
musical peak, like a dramatic drum accent. The RMS figure is more significant and more indicative
of the amp's long-term performance.
* This document is a guide only. Parallel Imported Ltd and the Author take no responsiblity for errors
or any damage caused as a result of this documents use.
© Parallel Imported Ltd
Author: Richard Bryan Eyre
RMS Power at 2 ohms
This spec tells you how much more power your amp delivers when presented with a 2-ohm stereo
load. You can achieve a 2-ohm load by using parallel wiring or by using
2-ohm speakers.
Theoretically, amp output should exactly double as the impedance drops from the usual 4 ohms to
2 ohms. However, amp makers use different degrees of regulation on power
supplies, which can restrict the actual increase in output.
Less regulated power supplies come closer to doubling their output into 2-ohm loads. An amp with
little regulation can achieve higher wattage into lower impedances. An amp with stiffer regulation
maintains rated output from your amp as other electrical accessories demand voltage from the
battery.
Signal-to-Noise Ratio
Measured in decibels (dB), this spec compares the strength of the desired signal (music) to the level
of background noise. A higher value indicates less background noise.
Sound Pressure Level (SPL)
SPL is measured in dB — an acoustic measurement of sound energy. One dB SPL is the
smallest audible difference in sound level. 0dB SPL is the threshold of human hearing, while noise
measuring 120dB can damage your hearing.
Speaker-level input
Also called high-level inputs, speaker-level inputs accept signal from a receiver's speaker outputs,
letting you connect the amp to a receiver that lacks RCA preamp outputs.
Subsonic Filter
Also called an infrasonic filter, a subsonic filter cuts off extremely low bass (below the range of
human hearing) that many speakers cannot effectively reproduce, thereby making the amp's power
supply and output devices, and the speaker, more efficient.
Total Harmonic Distortion (THD)
Amount of change in harmonic content of the signal as it is amplified. A lower figure indicates less
change and a more accurate amp. THD below 1% is inaudible.
Tri-Way Output
Sometimes called Dual Mode, this setup powers a pair of stereo speakers and one subwoofer
simultaneously from the outputs of a single 2-channel amplifier. It's an affordable way to drive a
subwoofer. It requires an external Tri-Way adapter that is connected in-line between your amplifier
and your speakers.
Turn On Lead
A small gauge wire, running from a receiver to an amplifier. this triggers the amp to turn on when
the receiver is switched on.
* This document is a guide only. Parallel Imported Ltd and the Author take no responsiblity for errors
or any damage caused as a result of this documents use.
© Parallel Imported Ltd
Author: Richard Bryan Eyre
Head Decks
Anti
Theft Protection
Anti-Theft
A security feature that helps prevent radio theft. There are several types of anti-theft protection
currently in use:
•
Detachable Face — Lets you remove the control panel of your receiver easily, and take it
with you when you leave the car. The stereo is useless to thieves without the faceplate, so
the temptation to break in your car is greatly reduced. All but a handful of the receivers we
offer come with a detachable face.
•
Security Code Some stereos give you the option of setting up a security code. This is usually
in addition to having a detachable faceplate. The security code is a three or four button
combination; usually using the radio preset buttons that has to be entered before the stereo
will function.
Auxiliary Input
An input on the face or rear of the receiver that enables you to connect a plug-and-play satellite
radio tuner or portable music player (CD, MP3, or cassette) to the receiver. The input jack can be
either Mini or RCA.
CD Text
Some compact discs contain encoded text data that can include the artist name, disc name, and/or
track name. Text-capable receivers can decode and display this information on the readout.
CD-R, CD-RW Compatibility
CD receivers with this capability can play audio CD-Rs and/or CD-RWs as well as pre-recorded CDs.
Almost all of today's receivers can play CD-R and CD-RW discs.
Changer Controls
Originally, changer controls referred to a receiver's ability to control a same-brand CD changer.
These days, the changer control connection on a receiver can be used to add one of any number of
peripheral devices. Most stereo brands let you choose from a CD changer, satellite radio, iPod®
adapter, USB adapter, Bluetooth™ adapter, and more.
Codec
A codec is a method of compressing and decompressing digitized sound. MP3 and WMA are
examples of different codecs.
Crossover (High-Pass Filter)
A built-in high-pass filter allows only frequencies above the crossover point to pass through. This
filter may work with the speaker outputs, preamp outputs, or both.
Crossover (Low-Pass Filter)
A built-in low-pass filter allows only low frequencies to pass through. This filter may work with the
speaker outputs (very rare), preamp outputs, or both.
Custom Programming
Some changer controller combinations let you specify exactly which tracks will play on a CD. Disc
title features let you assign each disc a name that will appear on the in-dash display when that disc
is loaded.
* This document is a guide only. Parallel Imported Ltd and the Author take no responsiblity for errors
© Parallel Imported Ltd
or any damage caused as a result of this documents use.
Author: Richard Bryan Eyre
DAC
See Digital
to Analogue Conv
Digital-to-Analogue
Converter
Digital-to-Analogue (D/A) Converter
Your CD receiver uses a D/A converter to convert digital 1s and 0s back into analogue audio signals.
CDs store audio data in binary, digital form. This digital data is an accurate, noise-free reproduction
of recorded signals, but in digital form it doesn't sound like music to your ears. The D/A converter
translates the digital info back into music — that's why it's so important to your CD receiver's
performance.
Digital Media Files
Music which has been subjected to data compression — allowing users to store many hours of
music as computer files. A growing number of in-dash CD receivers have the ability to decode and
play recordable CDs (CD-Rs and CD-RWs) loaded with MP3, WMA, AAC, or WAV files. A single disc
can hold up to ten hours of music.
Digital Media Receiver
Digital media receivers are in-dash receivers that do not have CD players built in. Instead, they
feature multiple inputs for devices like iPods, USB drives, SD cards, and so on.
Display
•
Fold-down Face — Slot-faced receivers are convenient, but their displays are
smaller out of necessity. A fold-down face, on the other hand, hides the CD slot
behind the control panel, and allows the receiver to include a larger display for
greater legibility. Hiding the slot also increases the unit's reliability by reducing internal
exposure to dust and dirt.
•
Multicolour Display — A multicolour display improves readability and reduces the
amount of time your eyes spend away from the road. Monochrome displays cannot
represent different functions with unique colours, so you spend more time trying to
decipher the readout.
•
Backlight — A backlit display significantly improves visibility under adverse conditions.
For example, if the sun is shining on your faceplate, a backlit display is easier to see.
DVD/CD Receivers
These versatile CD receivers can also play DVD movies, and may play DVD audio discs. Some
models send the video signal to an outboard backseat monitor for on-the-go viewing, while other
models include a built-in screen for stationary viewing. These receivers have digital-to-analogue
converters that are superior to those found in most regular CD receivers, so your CDs will usually
sound better on a DVD receiver.
* This document is a guide only. Parallel Imported Ltd and the Author take no responsiblity for errors
or any damage caused as a result of this documents use.
© Parallel Imported Ltd
Author: Richard Bryan Eyre
Equalizer
A built
in EQ lets you tailor the
th sound to your listening tastes and to your vehicle's acoustics.
built-in
Receivers with built-in EQs will have one or more equalizer "bands" in addition to standard bass
and treble controls. These equalizer "bands" usually have fixed centre frequencies and bandwidths
(although some may be adjustable).
More sophisticated built-in EQs offer parametric equalization, which allows you to set the amount
(in dB) by which a certain frequency band is boosted or cut — and determine the width and/or
centre frequency of this band. This gives you extremely precise control of the tonal balance in your
vehicle.
Equalizer Pre-sets
Preset EQ curves are stored tone settings — boosting and cutting different frequencies can make
big changes in the way your music sounds. Preset EQ curves are stored in memory, and are easily
activated. If you listen to a wide variety of music, these pre-sets are useful for making dramatic
tonal changes instantly. (For example, you could use one EQ preset with heavy bass boost for rap or
reggae, and a second preset with flat bass and a slight midrange/treble boost for jazz. This saves
you from constant readjustment of the
tone controls.)
European Tuning
The European tuning interval of .05 MHz is different from the US tuning interval of .2 MHz. If a CD
receiver also has European tuning, it is compatible with the European scale and can be used in
many European countries.
FM Mono Sensitivity
This figure tells you how well a CD receiver can pick up FM radio signals. The smaller the number,
the greater the ability the unit has to pick up weaker stations. Expressed in decibel femtowatts
(dBf).
FM Stereo Separation
A measure of the ability of an FM tuner to re-create a vivid stereo effect. Measured in dB (decibels),
the higher the figure is the better.
Frequency Response
The range of sounds, from bass to treble, a stereo component can reproduce. It's measured in
Hertz (Hz), and a wider range is better — the bass will be lower and the treble will be higher.
Humans can perceive sounds from 20 to 20,000 Hz. The lowest note on a bass guitar is about 41
Hz. Most male vocalists have a range between 100 and 500 Hz. Cymbals hit at about 15,000 Hz.
Ground Loop
A ground loop occurs when any piece of equipment or any incoming wire is connected to a
different ground or grounds. If your in-dash receiver and amplifier are grounded to different
locations, for example, a ground loop may occur. In this situation, the multiple ground paths can, in
effect, act as an antenna for interference. The interference is turned into noise, and you hear it in
your system.
* This document is a guide only. Parallel Imported Ltd and the Author take no responsiblity for errors
or any damage caused as a result of this documents use.
© Parallel Imported Ltd
Author: Richard Bryan Eyre
Intro Scan
Lets you hear the first few sec
seconds of each track on a CD. Hit the button again when you hear the
song you're looking for. The scanning feature will stop, and that track will continue playing.
Loudness
This control allows you to boost the lower frequencies in your music for full, rich sound at lower
volumes.
MP3
MP3 encoding compresses musical data, enabling users to store many hours of music as computer
files. A growing number of in-dash CD receivers have the ability to decode and play recordable CDs
(CD-Rs and/or CD-RWs) loaded with MP3 files. Also, portable MP3 players can be used to play
these files through a car receiver's auxiliary inputs.
Multi-path Interference
Multi-path interference affects FM radio reception. FM waves travel in a straight line, so anything
between you and the FM transmitter can cause multi-path interference. When FM signals bounce
off buildings and other large objects, the tuner picks up the same signal more than once, at different times. This creates "echoes" that confuse the tuner by mixing with the original signal.
Peak Power
Peak power is measured during a brief musical burst, such as a sudden drum accent. Some
manufacturers display peak power ratings on the face of their products. The RMS power rating is
more significant, and we recommend using it for comparison purposes.
Preamp Outputs
Jacks on the rear of a CD receiver that allow you to use a standard RCA patch cable to add an
external amp. Some receivers have two sets, which help if you plan to add a 4-channel amp or a
second amp. Some receivers have three sets, one of which is usually intended to be used for a
subwoofer amp.
Some receivers offer a "non-fading" set of preamp outputs. Hook your subwoofer amp to the
non-fading outputs, and you can fade the regular speakers front to rear without affecting the
sound of the subwoofer.
Preamp Output Voltage
The output voltage of the receiver's preamp outputs. Higher preamp output voltage can mean
cleaner sound (better noise resistance) and higher output from your amp.
* This document is a guide only. Parallel Imported Ltd and the Author take no responsiblity for errors
or any damage caused as a result of this documents use.
© Parallel Imported Ltd
Author: Richard Bryan Eyre
Radio Data System
RDS stands for Radio Data System.
Sys
RDS tuners can automatically tune in stations according to the
style of music (or talk) they broadcast. Some RDS tuners can even break in with traffic alerts or
emergency broadcasts when you're listening to a CD. RDS enables your receiver to display text
messages (usually call letters and format info) that many FM stations include on a subcarrier signal
within their normal broadcast signal.
RMS Power
The amount of continuous power, measured in watts, that an amplifier produces, is called Root
Mean Square (RMS) power. The higher the RMS figure, the louder and cleaner your music sounds.
Random Play
Also known as shuffle play. Mixes up the order of songs during playback. Some CD players offer a
"Random Play with Delete" feature that prevents a song from being repeated once it has been
played.
Remote Control
For remote-compatible CD receivers, wired or infrared wireless remotes are either included with a
receiver, or available as accessories.
Satellite Radio Controls
CD receivers with satellite radio controls operate same-brand external satellite radio tuners. A
specialized antenna and service subscription are also required (in addition to the tuner) to receive
the satellite radio signal.
Scan and Seek Tuning
•
Preset Scan lets you push a button and automatically hear a brief sample of what's on
each of your preset stations.
•
Station Scan lets you sample each strong station (regardless of whether it's one of your
pre-sets) — the sampling continues until you hit the station scan button again.
•
Seek tuning moves to the next strong station and stops there — you must hit the
"Seek" button again to repeat the process.
Signal-to-Noise Ratio
A measure of how well a CD player silences background noise. Higher ratings, in decibels (dB),
indicate less noise.
Subwoofer Preamp Outputs
RCA output jacks (usually coupled with a built-in low-pass filter) for connection to a sub
woofer amplifier.
Time Correction
A processing circuit found in some receivers that compensates for the uneven distances between
left and right car speakers and listeners' ears. Time correction delays signals from the closest
speaker(s), so that all the sound arrives at your off-centre listening position at the same time. You'll
get a more accurate, lifelike stereo image.
* This document is a guide only. Parallel Imported Ltd and the Author take no responsiblity for errors
or any damage caused as a result of this documents use.
© Parallel Imported Ltd
Author: Richard Bryan Eyre
Track Repeat
Plays the same track over and over until you turn the feature off.
Travel Pre-sets or Best Tuning Memory
Engage this feature and the CD receiver automatically loads a bank of your preset with the
strongest available signals. It makes finding stations easier when you're driving through unfamiliar
territory. It also makes loading preset a snap when you first install the receiver or any time your
battery runs down or gets disconnected (which wipes out the tuner's preset memory). Some
receivers use a bank or two of your regular station preset for storage; others have dedicated travel
preset plus station preset for manual storage.
Video System Control
Receivers with video system control operate same-brand/compatible video components and play TV
sound through your car audio speakers (when video components are connected).
Zero-bit Detector
Some CD receivers feature a circuit that detects periods of no audio signal (a series of zeros in the
digital bit stream) and mutes the audio output. You'll hear dead silence until an audio signal is
detected again.
* This document is a guide only. Parallel Imported Ltd and the Author take no responsiblity for errors
or any damage caused as a result of this documents use.
© Parallel Imported Ltd
Author: Richard Bryan Eyre
Speakers
Basket
The basket, or frame, is the structural support of a speaker.
Bi-amping
In bi-amping, separate amplifiers (or amp channels) drive the woofer and tweeter of a speaker. This
way, both low-frequency drivers (woofers) and high-frequency drivers (tweeters) receive dedicated
amplification.
Coaxial speaker
Coaxial speakers contain two elements: a woofer, to reproduce the low notes, and a tweeter,
mounted inside the woofer, for the highs. See also "Two-Way Speakers", below.
Component System
Component systems, or separates, use a superior speaker design to give you the best possible
sound. A typical separates system includes 2 woofers, 2 tweeters, and 2 external crossovers — all
of which are designed to work smoothly with one another.
Generally, components are made of better materials than their two- or three-way counterparts. You
can position the separate tweeters for optimal imaging. Given adequate power, separates deliver
exceptional dynamics and detail.
Compression horn
Found in some speakers, a high-frequency (or midrange) driver fires into a horn-shaped enclosure
for powerful, highly efficient output. Adapted from concert systems, compression horn tweeters
and midranges move with less excursion, so they produce less distortion and have higher powerhandling levels than other designs.
Crossover
A network of filters, made up of coils and capacitors, that directs specific frequency ranges to the
appropriate speaker components (woofer, midrange, and tweeter, for instance). That way, the
drivers do not strain to reproduce notes out of their intended range.
Component systems and full-range speakers include passive crossovers, which are designed for the
specific components and mounted between the amplifier and speakers. Active crossovers divide the
frequency range before amplification, and can be adjusted to adapt to any speaker setup.
Decibel (dB)
The standard unit of measure for expressing relative power or amplitude differences. With audio, it
represents loudness. One dB is the smallest change in loudness most people can detect. A 1 dB
difference is barely noticeable, but a 10 dB difference is big — a speaker playing at 10 dB higher
volume will sound roughly twice as loud.
Another dB fact: For any given set of speakers, each 3 dB increase in volume level requires a doubling of the amplifier power.
* This document is a guide only. Parallel Imported Ltd and the Author take no responsiblity for errors
or any damage caused as a result of this documents use.
© Parallel Imported Ltd
Author: Richard Bryan Eyre
Diaphragm
A speaker diaphragm is the su
surface that radiates sound. For a woofer, this is the speaker cone. In a
tweeter, it's usually dome-shaped.
Dual Cone
A dual cone speaker uses an inexpensive design in which a small "whizzer" cone attached to the
centre of the woofer reproduces the high frequencies.
Dust cap
A dust cap covers the centre of a speaker's cone and keeps dirt out of the voice coil gap.
Efficiency
Although a speaker's efficiency rating is almost always correlated to its sensitivity rating, it's actually
a different measurement. The efficiency rating for a speaker measures how well a speaker converts
watts of electrical power into watts of acoustical power. Most speakers have a very low efficiency
rating — between 1% and 10% — so manufacturers rarely provide this information, choosing
instead to list sensitivity ratings.
Frequency Response
The range of frequencies the speaker will reproduce (lowest frequency to the highest). The optimal
range is 20-20,000 Hz, the range of human hearing. Many high-quality tweeters, however, are able
to reproduce frequencies well above 20,000 Hz. While the human ear can't detect these ultra-high
frequencies, they do contain harmonics that affect the way listeners perceive sound and its
nuances.
Full-range Speakers
Full-range speakers accurately reproduce your music's frequency range by mounting a tweeter
inside the woofer cone. This is also known as a coaxial or 2-way speaker. Some versions may add
midranges or super tweeters to better reproduce other parts of the frequency spectrum. These are
also referred to by the number of drivers (3-way, 4-way, etc.).
Imaging
Imaging describes the extent to which a stereo system reproduces the location of instruments and
vocalists as they were positioned during recording and mixing. (See also soundstage below).
Optimal imaging creates a listening experience that seems natural and lifelike. The key to attaining
the best possible imaging is to have equal (or as close to equal as possible), unobstructed path
lengths between your tweeters and your ears. The ability to mount your tweeter separately, as with
components, or in an angled mount, as with some full-range speakers, can improve imaging.
Impedance
Impedance is a measure of the resistance of a speaker's voice coil to the audio current supplied by
the amplifier.
* This document is a guide only. Parallel Imported Ltd and the Author take no responsiblity for errors
or any damage caused as a result of this documents use.
© Parallel Imported Ltd
Author: Richard Bryan Eyre
Magnet
The magnet provides a stationary
station
magnetic field against which the voice coil reacts to create sound.
Maximum RMS Power Handling
Maximum RMS Power-Handling refers to the maximum amount of power a speaker can handle on
a continuous basis.
Midrange Speaker
A midrange speaker ranges in size from 3-1/2" to 6-3/4" and reproduces the middle frequencies.
Component systems sometimes use separate midranges, as do systems that amplify the low,
midrange, and high frequencies separately. Some full-range speakers include a midrange element
for better detail.
Peak Power Handling
Peak power handling refers to the maximum amount of power a speaker can handle during a brief
musical burst.
Plate Speaker
Plate speakers feature a separate round woofer and tweeter, mounted side by side on a plate that's
designed to replace oval-shaped 4"x6" and 5"x7"/6"x8" speakers. Since a round woofer is more
accurate than an oval one and is not encumbered with a cone-mounted tweeter, a plate speaker
reproduces music more accurately than an oval speaker. However, the woofer cone on a plate
speaker is smaller than a similarly-sized oval speaker, so its bass output will usually be slightly lower.
Polarity
In order to get the polarity right, you must wire the positive speaker terminal to the positive amplifier terminal, and the negative speaker terminal to the negative amplifier terminal. Proper wiring
ensures that all the cones in a multiple speaker setup will move in the same direction at the same
time. If you wire your speakers improperly, one speaker cone will move backward while another is
moving forward, cancelling out much of the sound both speakers are trying to make.
Pole piece
A pole piece concerns the metal piece in a speaker that concentrates and focuses energy from the
speaker magnet into creating a magnetic circuit. Because heat can accumulate during this process,
many manufacturers vent pole pieces for cooler, more efficient operation.
Power handling
All car speakers require a power source (receiver or amp). The lower the number of a powerhandling rating tells the absolute bare minimum wattage required to get acceptable sound from
the speaker, and the higher number tells the maximum amount the speaker can handle for an
extended time. For best results, match your power source level (RMS, or continuous watts) to the
upper part of the speaker's recommended range (RMS).
* This document is a guide only. Parallel Imported Ltd and the Author take no responsiblity for errors
or any damage caused as a result of this documents use.
© Parallel Imported Ltd
Author: Richard Bryan Eyre
Resonance
The vibration of a speaker's cone.
c
All speaker cones vibrate at a certain frequency. Too much
resonance can interfere with a speaker's accuracy.
Sensitivity
A sensitivity rating tells you how effectively a speaker converts power (watts) into volume (decibels).
The higher the rating, the louder your speakers will play with a given amount of amplifier power.
Sensitivity is often measured by driving a speaker with one watt and measuring the loudness in
decibels at one meter.
The chart below illustrates that a few dB in sensitivity can make a big difference:
Speaker
Sensitivity rating
Power needed
to produce a given volume
Speaker A
85 dB
100 watts
Speaker B
88 dB
50 watts
Speaker C
91 dB
25 watts
A speaker with a sensitivity rating that's 3 dB higher than another speaker's only needs half as
much power to deliver the same amount of sound.
Soundstage
The soundstage refers to your sense of width, depth and height when you listen to music — just as
you would sense the placement of different instruments in a live concert setting. Individual vocal
and instrumental "images" make up your stereo system's soundstage.
Spider
The spider is a flexible ring that keeps the voice coil aligned in its gap and secures the rear of the
speaker cone to the frame while still allowing the voice coil and the cone to vibrate freely.
Super tweeter
A small driver dedicated to ultra-high-frequency reproduction. You can usually find super tweeters
alongside tweeters in 4- or 5-way full-range speakers.
Surround
The surround refers to the flexible ring encircling the edge of the woofer cone — it connects the
cone to the speaker basket. It must be pliable enough to let the woofer travel freely, yet strong
enough to guide and control cone movement. (The further the cone can travel, the stronger the
bass.) Surrounds are usually made of cloth, foam, or rubber. Rubber tends to last the longest.
Three-way speaker
Three-way speakers take the separate woofer and tweeter from a two-way design and add a
midrange driver for enhanced warmth and texture. Select three-ways use a super tweeter, instead
of a midrange, for extended high-frequency response. Four-ways combine a woofer, a midrange, a
tweeter, and a super tweeter for even more detail.
* This document is a guide only. Parallel Imported Ltd and the Author take no responsiblity for errors
or any damage caused as a result of this documents use.
© Parallel Imported Ltd
Author: Richard Bryan Eyre
Tinsel leads
Tinsel leads are flexible
flexible, strand
stranded wires that connect the voice coil to the speaker's terminals.
Tweeter
A small driver dedicated to high-frequency reproduction. Cone tweeters are efficient and the most
economical. Most home speakers use dome or "edge-driven" tweeters — they disperse sound over
a wider area for smoother, more accurate reproduction. Semi-dome (or balanced-dome) tweeters
use a combination cone and dome construction for excellent sound clarity and dispersion.
Tweeters are made from a variety of materials — paper, aluminium, titanium, or synthetic films such
as polyetherimide (PEI) or Kaladex (polyethylene naphthalate). It's best to listen to a variety of
tweeters to determine which one you prefer.
Two-way speaker
Two-way, or coaxial, designs reproduce your music's frequency range accurately. These speakers use
a separate tweeter — mounted inside the woofer — to deliver the high-frequencies.
Voice coil
The voice coil (a small coil of wire) creates a magnetic field that varies according to the amplified
signal sent to the speaker. In conjunction with the permanent magnet and the speaker's other
parts, the voice coil converts electrical signals into mechanical energy to produce sound. Many of
the speakers on this site offer a heat-resistant voice coil to prolong speaker life.
Voice coil former
The voice coil former is the part of the speaker around which the voice coil is wound, usually made
from a heat-resistant material like aluminium or Kapton.
Voice coil gap
The voice coil gap is the space between the magnet and the pole piece where the voice coil can
freely move in and out, creating vibrations in the speaker cone resulting in sound.
Woofer
The woofer, a speaker's largest cone, reproduces bass and lower midrange notes. To operate
efficiently, a cone should be made of material that is stiff, yet lightweight. Cones made of
aluminium, synthetic film (like polypropylene), poly mixed with other materials (like mica), or
treated paper provide excellent sound, and stand up to the heat, cold, and moisture that car
speakers face on a daily basis.
* This document is a guide only. Parallel Imported Ltd and the Author take no responsiblity for errors
or any damage caused as a result of this documents use.
© Parallel Imported Ltd
Author: Richard Bryan Eyre
Subwoofers
Basket
The metal frame that holds all the components of a subwoofer together. The basket's rigidity and
resistance to resonance help determine the sub's sound quality.
Box volume
This measurement, listed with each component subwoofer, tells you the recommended interior
volume in cubic feet that an enclosure should have to get the best performance from the sub. A
variation of 10-20% is generally acceptable.
Damping factor
The ability of an amplifier to control the movement of a subwoofer — the higher the damping
factor, the greater the accuracy. Damping factor is calculated by dividing the subwoofer impedance
by the output impedance of the amplifier. An amplifier's damping factor will decrease as the sub's
impedance decreases — that's why an amp running at 4 ohms will provide tighter bass than at 2
ohms. This spec is not always given for all amplifiers.
Dual voice coil subwoofer
While typical speaker drivers have one voice coil, dual voice coil (DVC) subwoofers allow you the
advantage of flexibility in wiring your system. Parallel wiring provides for maximum amplifier
output, while series wiring lets you configure multiple woofers to one amplifier at an acceptable
impedance. In series/parallel mode, you can wire 4 woofers to a single amp, for example, and still
maintain a compatible impedance. Independent wiring lets you drive a single sub without bridging
(or by bridging a four channel amp to one sub).
Enclosure types
•
Sealed box — A sealed box is an airtight enclosure housing your subwoofer. A sealed box is
best for any music that demands tight, accurate bass. Expect flat response, deep bass
extension, and excellent power handling. Since a sealed enclosure tends to require more
power than a ported box, use an amplifier with ample wattage for optimum performance.
•
Ported box — A ported box uses a vent (called a port) which allows movement of air in and
out of the enclosure chamber. This additional air movement reinforces low bass response.
You get more output from a ported box than you would from a sealed box at any given
level of amplifier output. Some people simply prefer the sound of ported boxes for rap,
techno, or any hard-driving music because they play louder than comparable sealed boxes.
•
Bandpass box — A bandpass box is a special type of ported box designed for maximum
slam. The woofer is mounted inside a dual-chambered box; the woofer fires from the sealed
chamber into the ported chamber, and sound waves emerge from the ported side. Because
the sound that comes out of the port is extra loud within a narrow frequency range, band
pass boxes are considered super-efficient. Their aggressive sound is popular with many
hip-hop, techno, and metal fans.
•
Free-air subwoofers — A free-air system consists of woofers mounted to a board attached
to the rear deck or placed in the trunk against the rear seat. The trunk acts as the enclosure
housing the subwoofer. Free-air systems save space and have flat frequency response. The
woofer must be specifically designed for free-air use, and the trunk must be airtight for
best results.
* This document is a guide only. Parallel Imported Ltd and the Author take no responsiblity for errors
or any damage caused as a result of this documents use.
© Parallel Imported Ltd
Author: Richard Bryan Eyre
Frequency range
The range of sounds from low
lowest to highest that the subwoofer is capable of reproducing. The
figures listed with the drivers are furnished by the manufacturers. The actual range you'll hear can
vary depending upon the type of box, crossover point, and the vehicle the
subwoofer is installed in. Under most circumstances, a typical sub will play slightly deeper than its
published figures indicate. So, don't base your choice solely on this spec.
Impedance
The resistance offered by an electric circuit to the flow of alternating current — measured in ohms.
A subwoofer rated at 2-ohm impedance will produce more output than a 4-ohm subwoofer, given
similar input wattage, because the resistance is lower.
Peak power
The amount of power the subwoofer can handle as a brief burst during a musical peak. You should
not drive your subwoofer continuously with wattage equal to the peak power rating.
Polarity
In order to get the polarity right, you must wire the positive speaker terminal to the positive amplifier terminal, and the negative speaker terminal to the negative amplifier terminal. Proper wiring
ensures that all the cones in a multiple speaker setup will move in the same direction at the same
time. If you wire your speakers improperly, one speaker cone will move backward while another is
moving forward, cancelling out much of the sound both speakers are trying to make.
In multiple component subwoofer systems, getting the polarity wrong could short-circuit the
amplifier's output, resulting in overheating and damage to the system.
Pole Piece
A solid piece of steel which protrudes up through the magnet into the voice coil assembly,
concentrating the energy from the magnet.
Power range
An external power amp is required to drive any raw component subwoofer. (Don't try to drive one
with your in-dash receiver's built-in amplifier.) The low number listed is the absolute bare minimum
wattage required to get acceptable sound from the subwoofer. For best results, use an amplifier
that provides a power level (RMS, or continuous watts) in the upper part of the subwoofer's
recommended range (RMS).
Sensitivity
Also referred to as efficiency (measured as SPL — sound pressure level), this specification is quoted
in decibels (dB). The higher the number, the more efficient the subwoofer is at turning amplifier
power into sound, and the louder it plays. A subwoofer rated 3 dB more than another will require
only half the power to produce the same output.
Spider
The spider (also known as the damper) controls the cone's movement and keeps the voice coil
centred in the air gap. It acts like a shock absorber, smoothing out the cone's ride.
* This document is a guide only. Parallel Imported Ltd and the Author take no responsiblity for errors
or any damage caused as a result of this documents use.
© Parallel Imported Ltd
Author: Richard Bryan Eyre
Thiele/Small Parameters
These are terms used to describe
descr
the characteristics of a particular subwoofer. They include
resonance frequency of the driver, the woofer's excursion, and air displacement, among others.
These figures are useful in predicting subwoofer performance and constructing appropriate
enclosures.
Top mount depth
Tells you the depth of the woofer when it is installed from above the mounting surface. The depth
will be greater for subwoofers that are mounted from below the mounting surface.
Voice Coil
The voice coil consists of a former (or bobbin) with wire wound around it. The voice coil is attached
to the bottom of the cone and extends into the air gap surrounding the pole piece. The voice coil
translates the magnet's energy into cone motion.
* This document is a guide only. Parallel Imported Ltd and the Author take no responsiblity for errors
or any damage caused as a result of this documents use.
© Parallel Imported Ltd
Author: Richard Bryan Eyre