SPEAKERS GLOSSARY
Absorption
The absorption of sound is the process by which sound energy is diminished when passing through a medium or when striking a surface. Sound molecules lose energy upon striking the material's atoms, which become agitated, which we characterize as warmth; thus, absorption is literally the changing of sound energy to heat. A material's ability to absorb sound is quantified by its absorption coefficient, whose value ranges between 0 (total reflection) and 1 (total absorption), and just to keep things interesting, varies with sound frequency and the angle of incidence.
Acoustic distortion
This is a term coined by Dr. Peter D'Antonio, founder of RPG Diffusor Systems, for the interaction between the room, the loudspeaker, and the listener.
Acoustic treatments
There are only three classic (physical) tools available for the technician to treat a room: absorbers, reflectors and diffusers. Absorbers attenuate sound; reflectors redirect sound, and diffusers (hopefully) uniformly distribute sound.
Active Crossover -- see Crossover, Active
Ampere (A)
This is the unit of measurement for electrical current, expressed in coulombs per second. There is one ampere in a circuit that has one ohm resistance when one volt is applied to the circuit.
Ambience
The acoustical character of a listening or performing space, determined mainly by the timing, level, frequency balance, and directions of sound reflections in it.
Amplifier (amp)
This is a device that increases signal level. Many types of amplifiers are used in audio systems. A pre-amplifier is used to increase the signal level from an audio source. A power amplifier increases the signal level sufficiently to drive a speaker. Pre-amplifiers and power amplifiers can be purchased as separate units or can be packaged together with other audio functions. A receiver is an audio unit that contains pre-amplifier, control, switching, processing, and power amplifier functions built into a single unit.
Analog
This is the method of representing and storing audio information with continuously variable physical quantities. Audio in an analog signal is represented by the varying of voltage, speed (frequency), and strength (amplitude) to correspond to the way the audio changes in frequency and volume.
Bandwidth (BW)
The range of frequencies a component can reproduce. Represented as the numerical difference between the upper and lower -3 dB points of a band of audio frequencies. Used to figure the Q, or quality factor, for a filter.
Bass
The lowest part of the audio spectrum, from 20 Hz to 150 or 200 Hz. The lower limit of human hearing is said to be about 20 Hz. Frequencies below 20 Hz are said to be subsonic, and are technically felt instead of heard.
Bass Resonance (Fs)
Fs means 'System Frequency', or 'Frequency of the System'. Everything in nature has a natural period or resonant frequency and so do speakers. When the voice coil moves the speaker cone out, something is needed to restore the cone to its normal or resting position. This is the job of the spider attached at the rear of the cone and to the voice coil. So, with the mass of the cone and the spring action of the spider working together, there happens to be one single frequency where the two will work together to spring back and forth until losses in the system cause them to stop. This single frequency is the system resonant frequency. In loudspeakers, we tend to call it the bass resonance frequency, since most of the speakers we use are 8, 10, 12, and 15" in size. These all have system resonant frequencies down around 100hz, which is a bass frequency.
Capacitance
The amount of charge stored in a capacitor, measured in farads.
Capacitor
A capacitor is an electronic component used for storing charge and energy.
In audio, power stabilizing capacitors store the necessary power your
amplifier will need to punch those big bass notes while limiting clipping.
They store energy during intervals when it is not required and release it
when demand exceeds what is available from the power system. This improves
dynamic response.
Ceramic
Ceramic is a process rather than a particular kind of magnet. A powdered ferrous material (Strontium, Barium, etc.) is pressed and pounded into a desirable shape, then fired in a furnace. Ceramic types of magnets aren't as efficient as far as magnetism per pound as AlNiCo magnets, but are much cheaper. For instance, a 40oz ceramic ring magnet for loudspeakers costs about $3 in quantity. A 40oz AlNiCo ring magnet costs about $50. Ceramics require a lot more force to demagnetize than comparable AlNiCo magnets, and are great for high powered speakers where the magnetism from the voice coil might partially demagnetize an AlNiCo magnet.
Channel
A distinct path for a signal. Stereo and binaural signals have two channels. Dolby Digital and other technologies uses additional channels for a center speaker and surround speakers.
Coaxial
A type of two-signal connector in which an inner conducting wire is surrounded a shielding cylindrical outer conductor, commonly used in digital audio connections.
Component
A separate piece of audio or video equipment (containing its own chassis and power supply) that performs one specific function or a set of related functions.
Crossover Network
A circuit of component comprising low-pass, high-pass, or bandpass filters that separate lower-frequency signals from higher-frequency ones. A crossover is used in a speaker that has more than one driver. In a two-way speaker, the crossover sends the low frequencies to the woofer and high frequencies to the tweeter.
Crossover, Active
A loudspeaker crossover requiring power to operate and divides the signal into separate frequency bands before each band is separately amplified. Usually rack-mounted as a separate unit, active crossovers require individual power amplifiers for each output frequency band. Available in configurations known as stereo 2-way, mono 3-way, and so on. A stereo 2-way crossover is a two-channel unit that divides the incoming signal into two segments, labeled Low and High outputs (biamped). A mono 3-way unit is a single channel device with three outputs, labeled Low, Mid and High (triamped). In this case, the user sets two frequencies: the Low-to-Mid, and the Mid-to-High crossover points. Up to stereo 5-way configurations exist for very elaborate systems.
Crossover, Passive
A network built into a speaker comprising some combination of capacitors, inductors (coils), and resistors that divides the audio signal into frequency bands after it is amplified. These are in contrast with active crossovers, which require power to amplify the signal while it separates them.
Damping, Damping Factor
One of the dictionary definitions of the word damp is to deaden a shock. In other words, a device or method is used to stop vibrations or oscillations caused by mechanical shock. Damping is very important in loudspeakers. Quite simply, if the speaker system consisting of the voice coil, the cone, and the spider were allowed to vibrate freely without any kind of damping, it would be very difficult to achieve any kind of recognizable or useable acoustic signal from it. We want to be able to blast the speaker with a big signal, have it respond, then stop vibrating almost instantly when we remove our signal.
Decibel (dB)
A scale to measure the loudness of sound. A difference of 1 dB is usually the minimum perceptible change in volume, 3 dB is a moderate change in volume, and 10 dB is an apparent doubling of volume. Decibels are a logarithmic scale of relative loudness. In audio equipment decibels are used to indicate the range of volume from the quietest to the loudest sound that can be handled. The volume of common sounds in decibels are:
Hearing threshold: 0 dB for humans
Pain threshold: 130 dB
Whisper: 15 - 25 dB
Quite background: about 35 dB
Normal home or office background: 40 - 60 dB
Normal speaking voice: 65 - 70 dB
Orchestral climax: 105 dB
Live rock music: 120 dB+
Jet aircraft: 140 - 180 dB
Diaphragm
The moving surface in an audio transducer such as a speaker or microphone.
Diffused
Sometimes a particular installation causes a speaker to lose its focused projection altogether. It loses clarity, attack, becomes somewhat muddy, and changes character completely. Unfortunately, it seems very few speakers work equally well in both closed back and open back cabinets.
Discrete
The dictionary defines discrete as "separate or distinct", which is how the data appears in a digital data stream (such as a digital audio data stream), in separate, distinct values. This property of distinctness that computer data has is a big problem when it comes to sound (and most other things in real life), since neither time nor amplitude can be measured in nice handy steps. They are analogue and can take any value.
Dispersion
A characteristic of a speaker's radiation patter, particularly at high frequencies, expressed in degrees.
Driver
An individual woofer, midrange, tweeter, or other transducer within a speaker.
Dynamic range
The range between the loudest and the softest sounds that are in a piece of music or that can be reproduced by a piece of audio equipment without distortion. This is a ratio expressed in decibels (dB). In speech the range rarely exceeds 40 dB; in music the range can reach over 75 dB. In audio, higher numbers are better.
Dynamics processing
Compression, expansion, limiting and de-essing are all forms of dynamic processing. Dynamics processing is the controlled manipulation of the amplitude dynamics of a signal.
Efficiency
When converting from one form of energy to another, there is always some loss, so we express it as a measure of efficiency. In the case of loudspeakers, we are converting electrical power to acoustic power. Most loudspeakers are very inefficient, on the order of 1% or less. The rest of the power is turned into heat. See DB for more information on speaker efficiencies.
Enclosure
The box or other construction that makes up the outer shell of a speaker. Its principal purposes are to hold the drivers in alignment and to prevent the sound from the back of the woofer from reaching the front in an uncontrolled manner (to prevent uncontrolled cancellation of lower frequencies).
Fizz
Fizz can be caused by high frequency ringing of the cone or by the inside of the voice coil rubbing against the center pole. The cone ringing would sound more like a ghost note or single tone, while the voice coil rub would sound more like weak white noise. Both can be annoying if they are pronounced even at low volumes.
Flat
A condition in frequency response in which all input frequencies emerge from the device or medium with the same relative levels as when they entered. A flat frequency response is ideal.
Flux
The concentration of magnet flux in the radial gap around the voice coil is what the voice coil works against to make it move in and out and impart its movement on the cone. The more flux, the better, generally.
Frequency
The measurement of the number of cycles per second in an audio tone or an alternating current. Frequency is represented in cycles per second also known as Hertz, abbreviated as Hz. The range of human hearing is typically considered to range from 20Hz to 20,000Hz. (20Hz - 20kHz)
Frequency response
The range of frequencies (or bandwidth), expressed in hertz (Hz), that a component can handle with specified limits of amplitude error, expressed in decibels (dB).
Hertz (Hz)
A measurement of frequency. One Hertz is equal to one complete cycle per second. Hertz is abbreviated as Hz.
Home theater system
A collection of audio and video components designed and configured to reproduce something like a picture and sound quality that would be experienced from a movie in a high-quality cinema.
Impedance (Z)
The impedance of the speaker is the mathematical combination of reactance and resistance at a particular frequency. Most speakers used in the music business are either 4, 8, or 16 Ohm speakers. A simple way to check the impedance is to measure the DC resistance of the voice coil with a Volt-Ohmeter. If it measures more than 4 ohms but less than 8 Ohms, you call it an 8 Ohm speaker. Same for the 8 to 16. For more information on Impedance or Z, see our Let's Talk Speakers Q & A page.
Inductance
Property of a circuit to oppose a change in current. The moving magnetic field produced by a change in current causes an induced voltage to oppose the original change.
Inductor
Length of conductor used to introduce inductance into a circuit. The conductor is usually wound into a coil to concentrate the magnetic lines of force and maximize the inductance. While any conductor has inductance, in common usage the term inductor usually refers to a coil.
Loudspeaker -- see Speaker
Magnet Assembly
The magnet assembly is made up of the magnet, the back plate, the front plate, and the pole. The magnet is sandwiched between the front plate and the back plate.
Midrange
The segment of the audio frequency spectrum between the bass and treble, which includes most of the fundamental tones of the human voice and most musical instruments. It runs from about 200 Hz or so up to about 3 kHz.
Midrange driver
A speaker driver that is designed to reproduce frequencies from about 200 Hz up to 2 or 3 kHz.
Monitor (Studio Monitor)
A speaker used in recording or other professional applications requiring full-range, accurate reproduction.
Muddy
As you turn up the power and get into audible cone breakup with good texture and tone, the lows might not follow along and sound muddy or suppressed compared to the rest of the signal.
Noise
Any unwanted signals that are not strongly correlated with the desired signal and that usually arise from a random process. Hiss and hum are typical examples of audio noise.
Ohm
The basic unit of electrical resistance or impedance.
Output level
A measure of the strength of the strength of the output signal of a component.
Oversampling
Any digital signal processing technique that generates or uses a sampling rate greater than that required by theory to encode the maximum frequency of interest. In a digital to analog converter, a technique whereby multiple samples are mathematically generated from each real sample.
Passive Crossover -- see Crossover, Passive
Peaky
All speakers have peaks and dips in their frequency response. However, some areas of the response may be so pronounced they stand out in the crowd. Sometimes designers will try different sizes and types of dustcaps in an effort to correct the peakiness.
Power amplifier
A component, or part of a component, that strengthens the audio signal from a pre-amplifier so that it can drive speakers.
Power supply
A subsection of a component that takes AC line voltage and converts it to one or more DC voltages to operate the rest of the circuitry. In audio, power supply design can have an enormous influence on noise levels and the maximum output power an amplifier can produce.
Power rating
If you were around in the early 70's, you undoubtedly remember the race to see who could make the biggest HIFI power amp and how much they stretched the truth about their power output rating. They finally standardized on an RMS rating at a certain impedance and distortion, etc. Well, speaker companies didn't standardize on anything and still haven't. The published power ratings and how they are determined vary among manufacturers. One thing is for sure, though, they are usually higher than any of the technical design ratings.
Pre-amplifier
A component, or part of a component, that switches and processes signals from source components.
Q value
In a speaker, Q refers to the sharpness of the speaker's low-frequency resonance and is inversely proportional to damping. In an equalizer, Q is the number that specifies the width of the frequency band relative to its level. The higher the Q, the narrower the band.
Reactance
The portion of the electrical impedance in an AC circuit that is not due to pure resistance. Capacitive reactance causes impedance to rise as the signal frequency decreases, whereas the inductive reactance causes impedance to rise as the frequency increases.
Resistance
Electronic "friction" that turns the flow of electrical charges into heat. Resistance is impedance that is the same for all frequencies.
Resonance
The tendency of a mechanical or electrical system to vibrate at a certain frequency when excited by an external force, and to keep vibrating even after the exciting force is removed. Resonances are undesirable in audio equipment and listening rooms because they can produce distortion and color the sound.
Reverberation
A dense pattern of diffuse and reflected sounds that results when sound is created in an enclosed space. The more reflective the walls and surfaces of the listening space, the louder and longer the reverb. Reverberation can make music muddy and effect the feeling of spaciousness or ambience (less reverb makes the sound seem more closed in).
Sensitivity
A speaker measurement that tells how much sound, expressed as sound-pressure level (SPL) in decibels (dB), is produced at a specified distance (usually 1 meter) from the speaker when it is fed a specified input signal (usually 2.83 volts, which will produce 1 watt into 8 ohms). A speaker that is 3 dB or more sensitive than another requires only half the amplifier power to deliver the same volume.
Sound Pressure Level (SPL)
Acoustic pressure is normally measured in a unit called a Pascal. SPL ratings get exaggerated a little. It is derived from a formula which includes various known parameters of the loudspeaker, such as magnet strength, Q, magnetic energy from the voice coil, weight (or mass) of the system (cone, spider, etc.). Plugging these numbers into the formula yields a calculated, predicted SPL. It's kind of like predicting how fast a car will go when you know the weight of the car, the gearing, and how much horsepower you have.
Signal
An electromagnetic (radio) wave, current, or voltage whose variations have been modified to carry audio or video information.
Signal processor
A component that manipulates line-level audio signals. Equalizers and surround sound processors are the most common signal processors.
Speaker
A component that accepts audio signals from an amplifier and converts them into sound waves for listening at some distance (unlike headphones).
Stereo
The use of two (or more) audio channels to provide spatial realism or directional effects. Nowadays this usually refers only to two-channel programs, equipment, or systems to distinguish it from popular surround sound systems that use more channels.
Subwoofer
A speaker designed to reproduce only low-bass frequencies. A powered subwoofer contains an amplifier and an electronic crossover.
Supertweeter
A tweeter used to reproduce only extremely high frequencies.
Surround
Channels or speakers in a multichannel audio system whose purpose is to create a sense of sonic environment or all-around directionality.
Surround sound
An audio system or part of a home theater system that creates a three-dimensional, wrap-around sound field as opposed to a front soundstage only.
Sustain
There is a fine line between a speaker being over and underdamped. If it's underdamped, it can be harsh, ringing, and sound brittle. If it is overdamped, it can sound thin, choked and compressed. When it is just right for a particular installation, it has just the right breakup, texture, and sustain.
Texture
The texture of the tone is the overall effect of the comb filtering that occurs during breakup, the control of the breakup itself, and the control of the low end at high power levels. For instance, some like the early breakup sound of a straight, simple cone such as that used on a P12R. This is the typical 50's tweed sound. Others like the smooth, big, clean low end, late breakup, warm sound of a P12N. It's a matter of taste and playing style.
Thiele-Small Parameters
Loudspeakers are electromechanical devices, or more precisely, electroacoustic transducers. The goal is to convert energy in the form of electrical power to energy in the form of acoustic power. Since loudspeakers have both electrical and mechanical properties, it stands to reason that there are specific mathematical quantities that represent both the electrical and mechanical properties. To design a set of mathematical formulas to combine these quantities and then describe the overall characteristics of the loudspeakers was the goal of two acoustic researchers named Neville Thiele and Richard Small, hence the term T-S Parameters. They measured a few of the parameters of the loudspeaker such as electrical resistance of the voice coil, free air resonant frequency, inductance of the voice coil, and the cone size. Then, they would mount the speaker in a sealed box of a known volume and remeasure the resonant frequency as well as a few other parameters. Their extensive set of formulas could then be employed to determine and estimate very accurately the remaining unknown quantities of the loudspeaker (or driver), such as the system Q, the volume of air displaced by the cone, voice coil (motor) strength, overall efficiency, and estimated SPL. The resultant parameters are invaluable to speaker cabinet designers, enabling them to design the cabinet, porting, etc. to match and be compatible with the parameters of the loudspeaker. In very simple terms, if you consider the loudspeaker as a signal source with a specific characteristic impedance, by using the T-S Parameters you would be able to design a cabinet that would match the characteristic impedance of the source. This would allow the loudspeaker to operate at optimum efficiency over its frequency and power band.
THX®
"Tomlinson Holman Experiment" -- This is the trade name for the processing specifications for audio components (i.e. amplifiers, processors, speakers, etc) established by Lucasfilm. THX® specifications are designed to provide consistent audio reproduction as close as possible to what was originally intended. Professional and home audio equipment can carry the THX® logo after obtaining THX® certification from Lucasfilm.
Transducer
Any device that transforms energy of one type into energy of another. Speakers are transducers that convert electrical energy into sound energy.
Transistor
The basic solid-state amplifying element use in most audio components.
Treble
The upper part of the audio spectrum, from 2 or 3 kHz to about 20 kHz.
Tweeter
A speaker driver designed to reproduce treble frequencies.
Ultrasonic
A frequency higher than can be heard by the human ear. Usually higher than 20kHz.
Voice Coil
The voice coil is the real heart of the speaker. It gets energized by your amp's output signal and moves the cone in and out to produce the audible sound. The voice coil is wound on a round former, about 1 1/4" long, and is made of either paper, Nomex, Aluminum, or Kapton. Each has its advantages and disadvantages.
Voltage
The measure, in volts, of the strength of an electrical field. It can be thought of as pressure pushing electrical charges through a circuit, forming a current.
Watt
A unit of electrical power. The audio power of an amplifier is measured in watts.
Watts per channel
A specification of how much power an amplifier or receiver can deliver to each speaker connected to it.
Weak
Thin sounding, no dynamics, reduced lows. In an AlNiCo magnet speaker, it usually means the magnet has been partially demagnetized. If the speaker has been reconed, it may not have been recharged, or remagnetized, since many reconers don't own or have access to a magnetizer.
Woofer
A speaker driver designed to reproduce bass or bass/midrange frequencies. See Subwoofer.
