A subwoofer is a loudspeaker designed to reproduce low-pitched audio frequencies, known as bass and sub-bass, that are lower in frequency than those which can be (optimally) generated by a woofer. The typical frequency range that is covered by a subwoofer is about 20–200 Hz for consumer products, below 100 Hz for professional live sound, and below 80 Hz in THX-certified systems. Thus, one or more subwoofers are important for high-quality sound reproduction as they are responsible for the lowest two to three octaves of the ten octaves that are audible. This very low-frequency (VLF) range reproduces the natural fundamental tones of the bass drum, electric bass, double bass, grand piano, contrabassoon, tuba, in addition to thunder, gunshots, explosions, etc.
A loudspeaker is an electroacoustic transducer that converts an electrical audio signal into a corresponding sound. A speaker system, also often simply referred to as a speaker or loudspeaker, comprises one or more such speaker drivers, an enclosure, and electrical connections possibly including a crossover network. The speaker driver can be viewed as a linear motor attached to a diaphragm which couples that motor's movement to motion of air, that is, sound. An audio signal, typically from a microphone, recording, or radio broadcast, is amplified electronically to a power level capable of driving that motor in order to reproduce the sound corresponding to the original unamplified electronic signal. This is thus the opposite function to the microphone; indeed the dynamic speaker driver, by far the most common type, is a linear motor in the same basic configuration as the dynamic microphone which uses such a motor in reverse, as a generator.
Audio crossovers are a type of electronic filter circuitry that splits an audio signal into two or more frequency ranges, so that the signals can be sent to loudspeaker drivers that are designed to operate within different frequency ranges. The crossover filters can be either active or passive. They are often described as two-way or three-way, which indicate, respectively, that the crossover splits a given signal into two frequency ranges or three frequency ranges. Crossovers are used in loudspeaker cabinets, power amplifiers in consumer electronics and pro audio and musical instrument amplifier products. For the latter two markets, crossovers are used in bass amplifiers, keyboard amplifiers, bass and keyboard speaker enclosures and sound reinforcement system equipment.
A woofer or bass speaker is a technical term for a loudspeaker driver designed to produce low frequency sounds, typically from 20 Hz up to a few hundred Hz. A subwoofer can take the lower part of this range, normally up to 80 Hz. The name is from the onomatopoeic English word for a dog's deep bark, "woof". The most common design for a woofer is the electrodynamic driver, which typically uses a stiff paper cone, driven by a voice coil surrounded by a magnetic field.
An electrostatic loudspeaker (ESL) is a loudspeaker design in which sound is generated by the force exerted on a membrane suspended in an electrostatic field.
Thiele/Small parameters are a set of electromechanical parameters that define the specified low frequency performance of a loudspeaker driver. These parameters are published in specification sheets by driver manufacturers so that designers have a guide in selecting off-the-shelf drivers for loudspeaker designs. Using these parameters, a loudspeaker designer may simulate the position, velocity and acceleration of the diaphragm, the input impedance and the sound output of a system comprising a loudspeaker and enclosure. Many of the parameters are strictly defined only at the resonant frequency, but the approach is generally applicable in the frequency range where the diaphragm motion is largely pistonic, i.e., when the entire cone moves in and out as a unit without cone breakup.
A bass reflex system is a type of loudspeaker enclosure that uses a port (hole) or vent cut into the cabinet and a section of tubing or pipe affixed to the port. This port enables the sound from the rear side of the diaphragm to increase the efficiency of the system at low frequencies as compared to a typical sealed- or closed-box loudspeaker or an infinite baffle mounting.
A full-range loudspeaker drive unit is defined as a driver which reproduces as much of the audible frequency range as possible, within the limitations imposed by the physical constraints of a specific design. The frequency range of these drivers is maximized through the use of a whizzer cone and other means. Most single driver systems, such as those in radios, or small computer speaker designs, cannot reproduce all of the audible frequencies or the entire audible audio range.
The chief electrical characteristic of a dynamic loudspeaker's driver is its electrical impedance as a function of frequency. It can be visualized by plotting it as a graph, called the impedance curve.
Acoustic Research was a Cambridge, Massachusetts-based company that manufactured high-end audio equipment. The brand is now owned by VOXX. Acoustic Research was known for the AR-3 series of speaker systems, which used the 12 in (300 mm) acoustic suspension woofer of the AR-1 with newly designed dome mid-range speaker and high-frequency drivers. AR's line of acoustic suspension speakers were the first loudspeakers with relatively flat response, extended bass, wide dispersion, small size, and reasonable cost. The AR Turntable remains a highly sought vinyl record player.
A loudspeaker enclosure or loudspeaker cabinet is an enclosure in which speaker drivers and associated electronic hardware, such as crossover circuits and, in some cases, power amplifiers, are mounted. Enclosures may range in design from simple, homemade DIY rectangular particleboard boxes to very complex, expensive computer-designed hi-fi cabinets that incorporate composite materials, internal baffles, horns, bass reflex ports and acoustic insulation. Loudspeaker enclosures range in size from small "bookshelf" speaker cabinets with 4-inch (10 cm) woofers and small tweeters designed for listening to music with a hi-fi system in a private home to huge, heavy subwoofer enclosures with multiple 18-inch (46 cm) or even 21-inch (53 cm) speakers in huge enclosures which are designed for use in stadium concert sound reinforcement systems for rock music concerts.
The isobaric loudspeaker configuration was first introduced by Harry F. Olson in the early 1950s, and refers to systems in which two or more identical woofers operate simultaneously, with a common body of enclosed air adjoining one side of each diaphragm. In practical applications, they are most often used to improve low-end frequency response without increasing cabinet size, though at the expense of cost and weight.
A guitar speaker is a loudspeaker – specifically the driver (transducer) part – designed for use in a combination guitar amplifier of an electric guitar, or for use in a guitar speaker cabinet. Typically these drivers produce only the frequency range relevant to electric guitars, which is similar to a regular woofer type driver, which is approximately 75 Hz — 5 kHz, or for electric bass speakers, down to 41 Hz for regular four-string basses or down to about 30 Hz for five-string instruments.
An acoustic transmission line is the use of a long duct, which acts as an acoustic waveguide and is used to produce or transmit sound in an undistorted manner. Technically it is the acoustic analog of the electrical transmission line, typically conceived as a rigid-walled duct or tube, that is long and thin relative to the wavelength of sound present in it.
The Air Motion Transformer (AMT) is a type of electroacoustic transducer. Invented by Oskar Heil (1908–1994), it operates on a different transduction principle from other loudspeaker designs, such as moving coil, planar magnetic or electrostatically-driven loudspeakers, and should not be confused with planar or true ribbon loudspeakers. In contrast to a planar ribbon loudspeaker, the diaphragm of the AMT is of pleated shape similar to a bellows. The AMT moves air laterally in a perpendicular motion using a metal-etched folded sheet made of polyethylene terephthalate (PET) film. The circuit path embossed on the PET membrane, acts as the voice coil unit. The diaphragm is then housed between 4 stacks of steel pole-plate pieces positioned at 45° within a high-intensity, quadratic, opposing magnetic field. The air motion transformer with its sheet film equally exposed at 180° behaves as a dipole speaker, exciting front and rear sonic waves simultaneously.
Acoustic suspension is a loudspeaker cabinet design that uses one or more loudspeaker drivers mounted in a sealed box. Acoustic suspension systems reduce bass distortion which can be caused by stiff suspensions required on drivers used for open cabinet designs.
wOOx Technology is a brand created by Philips to identify loudspeaker systems that employ passive radiator technology along with active equalisation to maximize the output of the passive diaphragm. wOOx Technology optimizes the active bass driver, the passive bass radiator, and the active equalisation curve to obtain maximum low-frequency reproduction in a relatively compact configuration.
An electrodynamic speaker driver, often called simply a speaker driver when the type is implicit, is an individual transducer that converts an electrical audio signal to sound waves. While the term is sometimes used interchangeably with the term speaker (loudspeaker), it is usually applied to specialized transducers which reproduce only a portion of the audible frequency range. For high fidelity reproduction of sound, multiple loudspeakers are often mounted in the same enclosure, each reproducing a different part of the audible frequency range. In this case the individual speakers are referred to as drivers and the entire unit is called a loudspeaker. Drivers made for reproducing high audio frequencies are called tweeters, those for middle frequencies are called mid-range drivers, and those for low frequencies are called woofers, while those for very low bass range are subwoofers. Less common types of drivers are supertweeters and rotary woofers.
Veritone Minimum Phase Speakers, or VMPS, was a loudspeaker manufacturer founded in 1977 by speaker designer Brian Cheney. Many VMPS speakers received favorable reviews from audio critics, such as the RM40, which was awarded Best of CES in the High-End Audio category in 2002. VMPS was in operation for over 35 years, from January 1977 to December 2012, when it closed soon after the death of company owner Brian Cheney on December 7, 2012.
A transmission line loudspeaker is a loudspeaker enclosure design which uses the topology of an acoustic transmission line within the cabinet, compared to the simpler enclosures used by sealed (closed) or ported designs. Instead of reverberating in a fairly simple damped enclosure, sound from the back of the bass speaker is directed into a long damped pathway within the speaker enclosure, which allows far greater control and use of speaker energy and the resulting sound.
