Bipoles and Dipoles
Used in home cinema as a rear channel, bipole and dipole speakers feature a duplication of drivers on two opposite faces of the speaker. When mounted on a wall behind the listening position, this provides an effective spread and more diffused soundstage compared with conventional "monopole" speakers. Although almost identical in operation, the speakers on one side of a dipole speaker operate out of phase to those on the other side (when the drivers on side push out, the others pull in) - whereas the drivers on both sides of a bipole speaker move in phase (in the same direction) at the same time.
Cabinet Speaker
A self contained speaker designed to be installed into a cabinet (entertainment center) or other enclosure to be concealed from sight. Typically any speaker designed void of aesthetic appeal for the purpose of being concealed.
Ceiling Speaker (In-ceiling Speaker)
Any speaker designed for the purpose of being installed into a ceiling. Typically uses the ceiling/floor cavity as the enclosure unless noted as a "self-contained" in-ceiling speaker, in which case it has a full enclosure or back can.
Center Channel/Speaker
The front center speaker, placed between the left and right front speakers. Its primary function is to carry dialogue (movies), but it also carries other sounds, such as that accompanying video movement from one direction to another. It is, therefore, recommended that the center channel be of similar type and timbre as front left and right speakers and to be driven by similar amplification as well for the best clarity.
Cone
Typical shape of a speaker driver.
Crossover
A component that divides an audio signal into two or more parts by frequency, sending, for example, low frequencies to one output and high frequencies to another. Crossovers are also commonly built into amplifiers and equalizers.
Crossover Network
Following final amplification in a sound-reproduction system, an outboard circuit facilitates delivery of high- and low-frequency (AF) components to correct drivers in a speaker array. (Passes correct sounds to correct speakers.)
Custom Installation
Any installation of home automation or theater products which requires some form of construction in order to be installed i.e. in-wall speakers, overhead projector, etc. Most often refers to the application or installation of products by a professional installer or firm.
Decibel (dB)
A measure of the speaker's efficiency. The higher the figure, the easier the speaker is to drive and the less power is required from the amplifier to achieve the same output volume. Most ceiling speakers are between 86 and 92dB. Figures much lower may require more powerful or tolerant amplifiers.
Diaphragm
The part of a dynamic loudspeaker, attached to the voice coil, that produces sound. It actually has the shape of a cone or dome.
Dispersion
The degree of sound that is spread over a listening area.
Distortion
Nonlinear and unwanted changes in an audio signal, often not including the addition of noise, but including harmonic, intermodulation, transient intermodulation, phase, and frequency distortion.
Dome
A type of speaker driver shape usually used for tweeters (convex, not concave).
Driver
A speaker without an enclosure.
Dual Tweeter Speaker (Single Stereo Speaker)br/> A single In-Ceiling Stereo speaker combines the requirement for two speakers into one by offering both the left and right channels of audio through one speaker enclosure. This is particularly useful for small areas where it might be difficult to position 2 individual mono left and right speakers, such as in kitchens, bathrooms, en-suite/dressing rooms.
Dynamic Range
Audio range expressed in dB and measured between low-level noise and overload distortion; also defined as the range between the softest and loudest sound passages.
Efficiency Rating
The loudspeaker parameter that shows the level of sound output when measured at a prescribed distance with a standard amount of energy fed into the speaker. Efficiency rating standard is 1-watt at 1-meter and is measured in decibels.
Ferrofluid
A synthetic fluid with excellent cooling and lubricating properties. Most often injected into the "gap" (space between the voice coil and magnet) to prevent overheating and ultimately failure of the motor structure.
Flat Response
The reproduction of sound without alternating the intensity of any part of the frequency range.
Frequency
Audio frequencies are commonly defined as ranging from 20 to 20,000 cycles per second (Hz), assuming that the air pressure 20 or 20,000 times each second can be heard.
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.
Fs
Frequency resonance of a driver in free-air.
Harmonic Distortion
This is distortion caused when audio equipment adds unwanted overtones to an original signal.
High (frequencies)
Treble frequencies; those over approximately 3,150 Hz. Typically produced by the tweeter in a speaker array.
Home Cinema
Encompasses all types of multimedia equipment that make up an entertainment center or room. Typically refers to surround sound (5.1 or greater) speakers, A/V receivers, display and source units ranging from DVD players to computer or gaming devices but can also include video capturing devices, media servers and other related items.
Hz
Short for Hertz; cycles per-second. Something that repeats a cycle once each second is moving at a rate of 1 Hz.
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
a measure of how much something resists (impedes) the flow of electricity. Large numbers mean more resistance. Measured in Ohms.
In-Ceiling Speaker (ceiling Speaker)
Any speaker designed for the purpose of being installed into a ceiling. Typically uses the ceiling/floor cavity as the enclosure unless noted as a "self-contained" in-ceiling speaker, in which case it has a full enclosure or back can.
In-Wall Speaker
Any speaker designed for the purpose of being installed into a wall or ceiling. Typically uses the wall cavity as the enclosure unless noted as a "self-contained" in-wall, in which case it has a full enclosure.
kHz
One thousand Hz; 1 kHz equals 1,000 Hz and 20 kHz is 20,000 Hz.
LFE (Low Frequency Effects)
This is the .1 channel in Dolby Digital or DTS 5.1/6.1/7.1. The LFE channel contains low frequency effects in the range of 20-100Hz, intended to be reproduced by a subwoofer.
Low (frequencies)
Bass frequencies; those below approximately 200 Hz.
Midbass
The middle of the bass part of the frequency range, from approximately 50 to 100 Hz (upper bass would be from 100 to 200 Hz). Also drivers designed and used produce both bass and midrange frequencies.
Midrange
The middle of the audio frequency range, from approximately 200 to 3,150 Hz. A "midrange driver" typically produces the "voice" or vocals in music or cinema.
Octave
The difference between two frequencies where one is twice the other. For example, 200 Hz is one octave higher than 100 Hz.
Ohm
A measure of resistance. Speakers have an average resistance which is most commonly about 8 ohms. As a general rule, amplifiers can cope happily with speakers rated at between 4 and 8 ohms. Some less common models have resistances outside of this range. Such speakers may require more tolerant amplifiers.
On-Wall Speaker
A self-contained (fully enclosed) speaker typically designed with a low-volume (low-profile) enclosure intended to be installed (or hung) onto a wall.
Passive Subwoofer
A speaker designed specifically to reproduce low frequencies only, which requires a separate amplifier to drive it.
Passive Radiator:
An undriven loudspeaker cone that is mounted in a bass-reflex (sealed) enclosure with other, actively driven speakers to aid in the tuning of output.
Polarity
The 180-degree difference in the phase of audio signals that must be observed when wiring speakers.
Port
An aperture in a loudspeaker enclosure used to help tune the output. A ported enclosure is also called a vented or bass reflex.
Power Handling
Measured in Watts is the electrical power transferred from an audio amplifier to a loudspeaker. The electrical power delivered to the loudspeaker and its sensitivity determines the sound power level generated (with the rest being converted to heat). A larger figure denotes a higher power handing, but this figure has no bearing on the power of the amplifier necessary to drive the speaker. For example, a speaker which can handle 100 watts can be driven by a 20 watt amplifier. What has a bigger bearing on a speaker’s ability to be driven by a given amplifier, is its efficiency (measured in dB) and impedance (measured in ohms).
Q
The magnification of the resonance factor of any resonant device or circuit. A driver with a high Q is more resonant than a driver with a low Q.
Qes
The electrical Q of the driver.
Qts
The total Q of the driver at fs.
RMS (Root Mean Square)
A measurement of the continuous power output produced by an amplifier. The higher the RMS number, the cleaner and louder (without distortion) the sound will be. (Note: one of the primary specs on which to base an amplifier purchase.)
Sensitivity Rating
The loudspeaker parameter that shows the level of sound output when measured at a prescribed distance with a standard amount of energy fed into the speaker. Efficiency rating standard is 1-watt at 1-meter and is measured in decibels.
Single Stereo Speaker (Dual Tweeter Speaker)
A single In-Ceiling Stereo speaker combines the requirement for two speakers into one by offering both the left and right channels of audio through one speaker enclosure. This is particularly useful for small areas where it might be difficult to position 2 individual mono left and right speakers, such as in kitchens, bathrooms, en-suite/dressing rooms.
Sound Field
A volume of space or material containing sound waves. Commonly refers to the area in which a speakers or speakers direct sound.
Soundstage
The area that seems to be occupied by sonic images. Like a real stage, a soundstage should have width, height and depth.
Stereo Separation
Some ceiling and in-wall speakers employ patented technology to increase their apparent stereo separation thus enabling the speakers be positioned close together and still give a wide stereo separation. The optimal distance apart that you place your speakers should be equal to the distance that you are located when listening to the speakers thus forming an equilateral triangle between you and the two speakers.
Subwoofer
A speaker designed and dedicated to reproduce low frequencies (bass) from the .1 LFE Dolby Digital or DTS channel, and/or from the bass received from other channels if their lower frequencies are crossed-over to the sub with a low-pass control. Bass being non-directional, placement of the subwoofer can be anywhere in a listening area. Subs (or woofers) can range in size from five to 18 inches in diameter and come in active or passive applications. Some of these enclosures are ported (with a hole on the side or bottom), which helps to add a thump to bass response.
Surround Effects Channels/Speakers
Typically placed to the sides or rear of listening area, these speakers carry directional effects (Dolby Digital/DTS) or sound field enhancements (Dolby Digital, DTS, Pro Logic, Circle Surround). Surround channels/speakers can also be placed in the rear as an additional center speaker or in the ceiling for added surround effect. Speakers for discrete, full-bandwidth surround formats, like Dolby Digital/DTS, should be capable of handling a full frequency response of 20-20kHz and be sufficiently larger to handle loud passages. Rear surround speakers are either bipole or dipole, by design. Dipoles produce sound from the rear and front speakers out-of-phase from each other. For bipoles, the front and rear speakers are in-phase and sound equal.
Timbre
This is the tonal characteristic of a sound determined by its harmonic structure.
Transient Response
A term frequently used to describe a driver's (speaker's) time measurement for peak to peak movement; the distance at which a speakers maximum and minimum excursion and incursion begin.
Treble
The higher part of the audio signal range, approximately 3,150 Hz and up.
Tweeter
A speaker driver designed to reproduce very high frequencies, those over approximately 5,000 to 10,000 Hz.
VAS
The volume of air that offers the same degree of restoring force on the cone as that of the cones suspension.
Woofer
A speaker driver designed to reproduce low frequencies.