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For the Marty Friedman album, see Loudspeaker (album)
An inexpensive low fidelity 3.5 inch speaker, typically found in small radios
An inexpensive low fidelity 3. Loudspeaker is an instrumental album by the guitarist Marty Friedman, released in 2006 in Japan, and 2007 in United States. 5 inch speaker, typically found in small radios
An expensive 4-way, high fidelity loudspeaker system.
An expensive 4-way, high fidelity loudspeaker system.

A loudspeaker, speaker, or speaker system is an electromechanical transducer that converts an electrical signal to sound. In Engineering, electromechanics combines the Sciences of Electromagnetism of Electrical engineering and mechanics. A transducer is a device usually electrical, electronic, Electro-mechanical, Electromagnetic, Photonic, or Photovoltaic Signal processing is the analysis interpretation and manipulation of signals Signals of interest include sound, images, biological signals such as Sound' is Vibration transmitted through a Solid, Liquid, or Gas; particularly sound means those vibrations composed of Frequencies The term loudspeaker can refer to individual devices (otherwise known as drivers), or to complete systems consisting of an enclosure incorporating one or more drivers and electrical filters. A Loudspeaker enclosure is a cabinet designed to transmit sound to the listener via mounted loudspeaker drive units Audio crossovers are a class of Electronic filters designed specifically for use in audio applications especially Hi-fi. Loudspeakers, just as with other electro-acoustic transducers, are the most variable elements in an audio system and are responsible for the greatest degree of audible differences between sound systems.

To adequately reproduce a wide range of frequencies, most loudspeaker systems require more than one driver, particularly for high sound pressure level or high accuracy applications. Sound pressure is the local Pressure deviation from the ambient (average or equilibrium pressure caused by a Sound Wave. Individual drivers are used to cover different frequency ranges. The drivers are named subwoofers, for very low frequencies; woofers, for low frequencies; mid-range speakers, for middle frequencies; tweeters, for high frequencies; and, also, the so-called supertweeters, which are basically tweeters optimized for higher frequencies than a normal tweeter. A subwoofer is a Woofer, or a complete Loudspeaker dedicated to the reproduction of bass audio frequencies, from perhaps 150 Hz down A Loudspeaker driver that produces the frequency range from approximately 300&ndash5000 Hertz is known as a mid-range. A tweeter is a Loudspeaker designed to produce high frequencies typically from around 2000 Hertz to 20000 hertz (20000 Hz generally considered to be the upper Because the ear and brain are somewhat tolerant of poor reproductive quality, it is possible to successfully market deliberately (or accidentally due to mistake or confused design) inaccurate speakers; some of these use only one driver. Consider the accuracy of the average clock radio or portable music player; a typical such driver is shown at right.

The terms for different speaker drivers/systems differ depending on the application. Home stereos use the designation "tweeter" for high frequencies whereas professional audio systems for concerts typically designate all types of high frequency drivers simply as HF or "highs". Even in cases in which a professional speaker system uses a (non-horn) direct radiating woofer, if the high frequency driver is a compression horn unit, the entire system will often be called a 'horn'. There is also a distinct difference in some terminology between the U. S. and the U. K.

When multiple, specialized, drivers are used in a system, a "filter network", called a crossover, is required. This separates the incoming signal into different frequency bands appropriate, and also of importance, safe, for each driver. A loudspeaker system with 'N' separate frequency bands is described as "N-way speakers": a 2-way system will have woofer and tweeter speakers; a 3-way system is a combination of a set of woofers, mid-range speakers, and tweeters(HF drivers).

Contents

History

Alexander Graham Bell patented the first electrical loudspeaker as part of his telephone in 1876, which was followed in 1878 by an improved version from Ernst Siemens. WikipediaWikiProject Aircraft. Please see WikipediaWikiProject Aircraft/page content for recommended layout Ernst Werner von Siemens (known as Werner von Siemens) ( December 13, 1816 &ndash December 6, 1892) was a German Inventor Nikola Tesla reportedly created a similar device in 1881, but was not issued as a patent. There have already been discussions about Tesla's ethnicity on the talk page [1] During this time, Thomas Edison was issued a British patent for a system using compressed air as an amplifying mechanism for his early cylinder phonographs, but he ultimately settled for the familiar metal horn driven by a membrane attached to the stylus. In 1898, Horace Short patented a design for a loudspeaker driven by compressed air, then sold the rights to Charles Parsons, who issued several additional British patents before 1910. Charles Parsons may refer to Charles Algernon Parsons (1854&ndash1931 British engineer known for his invention of the steam turbine Charles Several companies, including Victor Talking Machine Company and Pathe, produced record players using compressed-air loudspeakers. Victrola redirects here For other uses see Victrola (disambiguation The Victor Talking Machine Company ( 1901 – 1929 This article deals with the Pathé movie company For their music business see Pathé Records. However, these designs were significantly limited by their poor sound quality and their inability to reproduce sound at low-volume. Variants of the system were used for public address applications, and more recently other variations have been used to test space equipment resistance to the very loud sound levels that launching rockets produce (ca, 165 dB SPL).

The modern design of moving-coil drivers was established by Oliver Lodge in (1898)[2]. Sir Oliver Joseph Lodge, FRS ( June 12, 1851 - August 22, 1940) born at Penkhull in Stoke-on-Trent and educated The moving coil principle was patented in 1924 by Chester W. Rice and Edward W. Kellogg. Chester W Rice was the joint Inventor in 1925 of the Moving coil Loudspeaker along with Edward W Edward W Kellogg, a graduate of Phillips Academy, Andover (Class of 1902 was the joint Inventor of the moving Coil Loudspeaker in 1925 along

These first loudspeakers used electromagnets because large, powerful permanent magnets were generally not available at a reasonable price. An electromagnet is a type of Magnet in which the Magnetic field is produced by the flow of an electric current. A magnet (from Greek grc μαγνήτης λίθος " Magnesian stone" is a material or object that produces a Magnetic field. The coil of an electromagnet, called a field coil, was energized by current through a second pair of connections to the driver. This winding usually served a dual role, acting also as a choke coil filtering the power supply of the amplifier to which the loudspeaker was connected. An inductor is a passive electrical component designed to provide Inductance in a circuit Power supply is a reference to a source of Electrical power. A device or system that supplies Electrical or other types of Energy to an output load An audio amplifier is an Electronic amplifier that amplifies low-power audio signals (signals composed primarily of frequencies between 20 Hertz to AC ripple in the current was attenuated by the action of passing through the choke coil; however, AC line frequencies tended to modulate the audio signal being sent to the voice coil and added to the audible hum of a powered-up sound reproduction device.

The quality of loudspeaker systems until the 1950s was poor. Continuous developments in enclosure design and materials have led to significant audible improvements. The most notable improvements in modern speakers are improvements in cone materials, the introduction of higher temperature adhesives, improved permanent magnet materials, improved measurement techniques, computer aided design and finite element analysis.

Driver design

Cut-away view of a dynamic loudspeaker
Cut-away view of a dynamic loudspeaker

The most common type of driver uses a lightweight diaphragm connected to a rigid basket, or frame, via flexible suspension that constrains a coil of fine wire to move axially through a cylindrical magnetic gap. In a Loudspeaker, a diaphragm (also known as the cone) is the thin semi-rigid membrane attached to the central Magnet. When an electrical signal is applied to the voice coil, a magnetic field is created by the electric current in the coil which thus becomes an electromagnet. A voice coil (consisting of a Bobbin, Collar and Winding) is the Coil of Wire attached to the apex of the cone of a Loudspeaker In Physics, a magnetic field is a Vector field that permeates space and which can exert a magnetic force on moving Electric charges Electric current is the flow (movement of Electric charge. The SI unit of electric current is the Ampere. The coil and the driver's magnetic system interact, generating a mechanical force which causes the coil, and so the attached cone, to move back and forth and so reproduce sound under the control of the applied electrical signal coming from the amplifier. Generally an amplifier or simply amp, is any device that changes usually increases the amplitude of a signal. The following is a description of the individual components of this type of loudspeaker.

The diaphragm is usually manufactured with a cone or dome shaped profile. A variety of different materials may be used, but the most common are paper, plastic and metal. The ideal material would be stiff, light and well damped. Absorption refers to the absorption of sound waves by a material In practice, all three of these criteria cannot be met simultaneously, and thus driver design involves tradeoffs. For example, paper is light and well damped, but not stiff; metal can be made stiff and light, but it is not well damped; plastic can be light, but typically the stiffer it is made, the less well-damped it is. As a result, many cones are made of some sort of composite. This can either be a sandwich construction or simply a coating to stiffen or damp a cone.

The basket or frame must be designed for rigidity to avoid deformation, which will change the magnetic conditions in the magnet gap, and could even cause the voice coil to rub against the walls of the magnetic gap. Baskets are typically cast or stamped metal, although molded plastic baskets are becoming common, especially for inexpensive drivers. Casting is a manufacturing process by which a liquid material is (usually poured into a mold which Introduction A press, or a machine press is a Tool used to work Metal (typically Steel) by changing its shape and internal structure The frame also plays a considerable role in conducting heat away from the coil.

The suspension system keeps the coil centered in the gap and provides a restoring force to make the speaker cone return to a neutral position after moving. A typical suspension system consists of two parts: the "spider", which connects the diaphragm or voice coil to the frame and provides the majority of the restoring force; and the "surround", which helps center the coil/cone assembly and allows free movement aligned with the magnetic gap. The spider is usually made of a corrugated fabric disk. The surround can be a roll of rubber or foam or a ring of corrugated fabric, attached to the outer circumference of the cone and to the frame. The most general definition of foam is a substance that is formed by trapping many gas Bubbles in a Liquid or Solid.

The voice coil wire is usually made of copper, though aluminum, and rarely silver, may be used. Copper (ˈkɒpɚ is a Chemical element with the symbol Cu (cuprum and Atomic number 29 WikipediaNaming Silver (ˈsɪlvɚ is a Chemical element with the symbol " Ag " (argentum from the Ancient Greek: ἀργήντος - argēntos gen Voice coil wire cross sections can be circular, rectangular, or hexagonal, giving varying amounts of wire volume coverage in the magnetic gap space. The coil is oriented coaxially inside the gap, a small circular volume (a hole, slot, or groove) in the magnetic structure within which it can move back and forth. The gap establishes a concentrated magnetic field between the two poles of a permanent magnet; the outside of the gap being one pole and the center post (a. k. a. , the pole-piece) being the other. The center post and back-plate are sometimes a single piece called the yoke.

Modern driver magnets are almost always permanent and made of ceramic, ferrite, Alnico, or, more recently, neodymium magnet. The word ceramic is derived from the Greek word κεραμικός ( keramikos) Ferrites are a class of Chemical compounds with the formula AB2O4 where A and B represent various metal Cations usually including Alnico is an acronym referring to alloys which are composed primarily of Aluminium (symbol Al) Nickel (symbol Ni) and Cobalt (symbol A neodymium magnet or NIB magnet (a variety of Rare-earth magnet) is a powerful Magnet made of a combination of Neodymium, Iron, and The size and type of magnet and the magnetic circuit differ depending on design goals. A current trend in design, due to increases in transportation costs and a desire for smaller, lighter devices (as in many home theater multi-speaker installations), is the use of neodymium magnet instead of ferrite types.

Driver design, and the combination of one or more drivers into an enclosure to make a speaker system, is both an art and science. Adjusting a design to improve performance is done using magnetic, acoustic, mechanical, electrical, and material science theory, high precision measurements, and the observations of experienced listeners. Designers can use an anechoic chamber to ensure the speaker can be measured independently of room effects, or any of several electronic techniques. Some developers eschew anechoic chambers in favor of specific standardized room setups intended to simulate real-life listening conditions. Some of the issues speaker designers must confront are distortion, lobing, phase effects, off axis response and crossover complications.

Most loudspeaker drivers are currently manufactured in China. China ( Wade-Giles ( Mandarin) Chung¹kuo² is a cultural region, an ancient Civilization, and depending on perspective a National The fabrication of finished loudspeaker systems is segmented, depending largely on price, shipping costs, and weight limitations. High-end speaker systems, which are heavier (and often larger) than economic shipping allows outside local regions, are usually made in their target market area and can cost $140,000 or more per pair. The lowest-priced speaker systems are mostly manufactured in China or other low-cost manufacturing locations. Although the manufacture of drivers has become largely commoditized, the fabrication and subsequent sale of finished speaker systems still carries high profits. Partly for this reason, manufacturers are increasingly combining power amplifier electronics (a typically lower profit item) with finished speaker systems to create powered speakers with an overall higher market value. Powered speakers (or active speakers) are speakers that have built-in Amplifiers They can be connected directly to a Mixing console or Sound

Driver types

Exploded view of a dome tweeter
Exploded view of a dome tweeter

An audio engineering rule of thumb is that individual electrodynamic drivers provide quality performance over at most about 3 octaves. An exploded view is a representative Picture or Diagram that shows the components of an object slightly separated by distance or suspended in surrounding space A rule of thumb is a principle with broad application that is not intended to be strictly accurate or reliable for every situation Specialized drivers (i. e. , subwoofers, woofers, mid-range drivers, tweeters) are used to evade the practical effects of this limitation, though in some cases, a woofer can work high enough to reach a tweeter's low frequency limit, thus permitting a high quality two-way system. Low quality two-way systems often result when the drivers used don't mesh this way.

Full range drivers

A full-range driver is designed to have the widest frequency response possible. A Full-range Loudspeaker drive unit is defined as a driver which reproduces as much of the audible frequency range as possible with High-fidelity, within the boundaries These drivers are small, typically 2 to 6 inches (5 to 16 cm) in diameter to permit reasonable high frequency response, and carefully designed to give low distortion output at low frequencies, though none have sufficient output at low frequencies for many purposes (eg, due to small maximum cone excursion) and limited power handling capacity (eg, due to a small voice coil). Those favoring this approach claim a coherence of sound (said to be due to the single source and a resulting lack of phase interference, and likely to the lack of obscuring electrical crossover components). Disadvantages include a requirement for elaborate cabinets (i. e. , transmission lines, horns, etc) to increase efficiency at low frequencies by better matching the driver to the air at those frequencies, thus increasing the output level at low frequencies. A transmission line is the material medium or structure that forms all or part of a path from one place to another for directing the transmission of energy A horn speaker is a Loudspeaker which uses a horn to increase the overall efficiency of the driving element typically a diaphragm driven by an electromagnet

Full range drivers often employ an additional cone called a whizzer: a small, light cone attached to the joint between the voice coil and the primary cone. The whizzer cone extends the high frequency response and broadens the high frequency directivity, which would otherwise be greatly reduced due to cone material breakup at higher frequencies (the cone area away from the coil fails to follow the area near the coil at higher frequencies in larger cones). The main cone is built so as to flex more in this region at high frequencies than the rest of the cone. The result is that the main cone delivers low frequencies and the whizzer cone contributes most of the higher frequencies. Since the whizzer cone is smaller than the main diaphragm, output dispersion at high frequencies is improved relative to a single larger diaphragm with no whizzer. Full range drivers are one approach to avoiding the possible effects of multiple driver systems, caused by non-coincident driver location and crossover issues.

Subwoofer

Main article: Subwoofer

A subwoofer is a woofer driver used only for the lowest part of the audio spectrum: typically below 100-120 Hz. A subwoofer is a Woofer, or a complete Loudspeaker dedicated to the reproduction of bass audio frequencies, from perhaps 150 Hz down A subwoofer is a Woofer, or a complete Loudspeaker dedicated to the reproduction of bass audio frequencies, from perhaps 150 Hz down Because the intended range of frequencies is limited, subwoofer system design is usually simpler than for conventional loudspeakers, often consisting of a single subwoofer driver enclosed in a suitable cabinet. To accurately reproduce very low bass notes without unwanted resonances (from cabinet panels, for instance), subwoofer systems must be solidly constructed and properly braced; good ones are typically heavy. Many subwoofers are designed to include power amplifiers and electronic filters, with additional controls relevant to low frequency reproduction. These variants are known as "active subwoofers". Passive subwoofers require external amplification.

Loudspeaker system design

Crossover

Main article: Audio crossover
A passive crossover
A passive crossover
An active crossover
An active crossover

Used in multi-driver speaker systems, the crossover is a device that separates the input signal into different frequency ranges suited to each driver. Audio crossovers are a class of Electronic filters designed specifically for use in audio applications especially Hi-fi. Each driver, therefore, receives the frequency range it was designed for, so the distortion in each driver, and interference between the drivers, is reduced. The ideal crossover would have no overlap between the signals sent to the different drivers, but this is not achievable in practice with post amplifier analog filters.

Crossovers can be passive or active. A passive crossover is an electronic circuit using a combination of one or more non-polar capacitors, resistors, and inductors. Audio crossovers are a class of Electronic filters designed specifically for use in audio applications especially Hi-fi. A capacitor is a passive electrical component that can store Energy in the Electric field between a pair of conductors |- align = "center"| |width = "25"| | |- align = "center"| || Potentiometer |- align = "center"| | | |- align = "center"| Resistor| | These parts are connected after the amplifier and divide the signal into individual frequency bands before it is delivered to the speaker drivers. Passive crossover circuits need no external power. An active crossover is an electronic filter circuit which divides the complete signal into individual frequency bands before amplification, thus requiring one amplifier for each bandpass. Audio crossovers are a class of Electronic filters designed specifically for use in audio applications especially Hi-fi.

Passive crossovers are generally installed inside speaker boxes and are by far the most common type of crossover for home and low power use. In car audio systems, passive crossovers are often in a separate box due to the size of some of the passive components used. Passive crossovers convert a non-trivial part of the amplifier power they handle into heat, so when high power output is needed, active crossovers are often used. Active crossovers allow more precise alignment of phase and time between frequency bands; equivalently tight adjustment using only passive components is a difficult engineering problem in part because of wide component part tolerances. Audio crossovers are a class of Electronic filters designed specifically for use in audio applications especially Hi-fi.

Many new loudspeaker designs have begun incorporating active crossover circuitry and onboard amplification. Such designs typically require AC power and take low level signal inputs instead of high level amplifier output connections. Ideally, this approach offers the advantages of close alignment of phase between frequency bands, active protection circuits to protect drivers, and virtually no loss of amplifier power in long cable runs or passive crossover components. Self-powered loudspeakers are being used in many applications such as small-scale computer sound (for one listener) and large-scale concert sound systems (for large halls full of listeners). Self-powered concert loudspeakers provide the additional benefit of improved predictability in sound quality; the touring concert sound engineer need not worry about customized crossover settings in each venue changing the characteristics of a loudspeaker.

Enclosures

Main article: Loudspeaker enclosure
An unusual 3-way speaker system. The cabinet is narrow to reduce a diffraction effect called the 'baffle step'.
An unusual 3-way speaker system. A Loudspeaker enclosure is a cabinet designed to transmit sound to the listener via mounted loudspeaker drive units The cabinet is narrow to reduce a diffraction effect called the 'baffle step'.

Most loudspeaker systems consist of drivers mounted in an enclosure, or cabinet. A Loudspeaker enclosure is a cabinet designed to transmit sound to the listener via mounted loudspeaker drive units The role of the enclosure is to provide a place to mount the drivers and to prevent sound waves from the back of a driver from interfering destructively with those from the front -- doing so typically causes cancellations (eg, comb filtering) and significantly alters the level and quality sound at low frequencies.

The simplest driver mount is a flat panel (ie, baffle) with the drivers mounted to it. However, in this design, frequencies with a wavelength longer than the baffle dimensions are canceled out because the antiphase radiation from the rear of the cone interferes with the radiation from the front. With an infinitely large panel interference could be entirely prevented. A sufficiently large sealed box can approach this behavior. [3][4].

Since panels of infinite dimensions are impractical, most enclosures function by containing the rear radiation from the cone. A sealed enclosure prevents transmission of the sound emitted from the rear of the loudspeaker by confining the sound in a rigid and airtight box. Techniques used to reduce transmission of sound through the walls of the cabinet include thicker cabinet walls, lossy wall material, internal bracing, curved cabinet walls or more rarely visco-elastic materials (eg, mineral loaded bitumen), or thin lead sheeting applied to interior enclosure walls. Viscoelasticity is the property of materials that exhibit both viscous and elastic characteristics when undergoing deformation. Bitumen is a mixture of organic Liquids that are highly Viscous, black sticky entirely soluble in Carbon disulfide, and composed primarily Characteristics Lead has a dull luster and is a dense, Ductile, very soft highly

However, a rigid enclosure internally reflects sound which can then be transmitted through the loudspeaker cone, again resulting in degradation of sound quality. This can be reduced by internal absorption using absorptive materials (often called "damping") such as fiberglass, wool, or synthetic fiber batting within the enclosure. The internal shape of the enclosure can also be designed to reduce this by reflecting sounds away from the loudspeaker diaphragm where they may then be absorbed.

Other enclosure types alter the rear radiation so it can add constructively to the output from the front of the cone. Designs that do this (including bass reflex, passive radiators, transmission line, etc) are often used to extend the effective low frequency response, and increased low frequency output, of the driver.

To make the transition between drivers as seamless as possible, system designers have attempted to time-align (or phase adjust) the drivers by moving one or more drivers forward or back, so that the acoustic center of each driver is in the same vertical plane. This may also involve tilting the face speaker back, or providing separate enclosure mounting for each driver, or, less commonly, using electronic techniques to achieve the same effect. These attempts account for some unusual cabinet designs.

Speaker cabinets cause diffraction, causing peaks and dips in the frequency response. Diffraction is normally taken to refer to various phenomena which occur when a wave encounters an obstacle This is usually a problem at higher frequencies where wavelengths are similar to, or smaller than, cabinet dimensions. The effect can be minimized by rounding the front edges of the cabinet, rounding the cabinet itself, using a smaller or narrower enclosure, choosing a strategic driver arrangement, or using absorptive material around a driver.

Wiring connections

Five-way binding posts on a loudspeaker connected using banana plugs.
Five-way binding posts on a loudspeaker connected using banana plugs. A binding post is a connector commonly used on Electronic test equipment to terminate (attach a single wire or test lead A banana connector (commonly banana plug for the male, banana jack for the female) is a single- Wire (one conductor
A 4 Ohm loudspeaker with two pairs of binding posts capable of accepting bi-wiring after the removal of two metal straps
A 4 Ohm loudspeaker with two pairs of binding posts capable of accepting bi-wiring after the removal of two metal straps

Most loudspeakers use two wiring points to connect to the source of the signal (for example, to the audio amplifier or receiver). This article is about a radio receiver for other uses see Radio (disambiguation. This is usually done using binding posts, or spring clips on the back of the enclosure. A binding post is a connector commonly used on Electronic test equipment to terminate (attach a single wire or test lead If the wires for left and right speakers (in a stereo setup) are not connected 'in phase' with each other (the + and - connections on the speaker and amplifier should be connected + to + and - to -) the loudspeakers will be out of polarity. Given identical signals, motion in one cone will be in the opposite direction of the other. This will typically cause monophonic material within a stereo recording to be canceled out, reduced in level and made more difficult to localize, all due to destructive interference of the sound waves. In physics interference is the addition ( superposition) of two or more Waves that result in a new wave pattern The cancellation effect is most noticeable at frequencies where the speakers are separated by a quarter wavelength or less; low frequencies are affected the most. This type of wiring error doesn't damage speakers but isn't optimal.

Specifications

Specifications label on a loudspeaker
Specifications label on a loudspeaker

Speaker specifications generally include:

and optionally:

Electrical characteristics of a dynamic loudspeaker

Main article: Electrical characteristics of a dynamic loudspeaker

The load a driver presents to an amplifier consists of a complex electrical impedance -- a combination of resistance, and both capacitive and inductive reactance, which combines properties of the driver, its mechanical motion, effects of crossover components (if any are in the signal path between amplifier and driver), and effects of air loading on the driver as modified by the enclosure and its environment. A dynamic Loudspeaker driver's chief electrical characteristic is its Electrical impedance versus Frequency. Electrical impedance, or simply impedance, describes a measure of opposition to a sinusoidal Alternating current (AC Most amplifiers output specifications are given at a specific power into an ideal resistive load. However, a loudspeaker does not really have a constant resistance across its frequency range. Instead, the voice coil is inductive, the driver has mechanical resonances, the enclosure changes the driver's electrical and mechanical characteristics, and a passive crossover between the drivers and the amplifier contributes its own variations. The result is a load resistance which varies fairly widely with frequency, and usually a varying phase relationship between voltage and current as well, also changing with frequency.

Electromechanical measurements

Fully characterizing the sound output quality of a loudspeaker driver or system in words is essentially impossible. Objective measurements provide information about several aspects of performance, so informed comparisons and improvements can be made. Examples of typical measurements are: amplitude and phase characteristics vs. Loudspeaker measurement is one of the most difficult aspects of Audio quality measurement, and also probably the most relevant since Loudspeakers have long been frequency; impulse response under one or more conditions (eg, square waves, sine wave bursts, . . . ); directivity vs. frequency (eg, horizontally, vertically, spherically, . . . ); harmonic and intermodulation distortion vs. A distortion is the alteration of the original shape (or other characteristic of an object image sound waveform or other form of information or representation Intermodulation or intermodulation distortion ( IMD) or intermod for short SPL output using any of several test signals; stored energy (ie, 'ringing') at various frequencies; impedance vs. frequency and small signal vs. large signal performance. Most of these measurements require relatively expensive equipment to perform and good judgement, but the raw sound pressure level output is rather easier to report and so is often the only specified value, sometimes in misleadingly exact terms. The sound pressure level (SPL) a loudspeaker produces is measured in decibels (dBspl). The decibel ( dB) is a logarithmic unit of measurement that expresses the magnitude of a physical quantity (usually power or intensity relative to Sound' is Vibration transmitted through a Solid, Liquid, or Gas; particularly sound means those vibrations composed of Frequencies

Efficiency vs. sensitivity

Loudspeaker efficiency is defined as the sound power output divided by the electrical power input. Most loudspeakers are actually very inefficient transducers; about 1% of the electrical energy sent by an amplifier to a typical home loudspeaker is converted to the acoustic energy we can hear. The remainder is converted to heat, mostly in the voice coil and magnet assembly. The main reason for this is the difficulty of achieving proper impedance matching between the acoustic impedance of the drive unit and that of the air into which it is radiating. Impedance matching is the electronics design practice of setting the Output impedance ( Z S of a signal source equal to the Input impedance ( The acoustic impedance Z (or sound impedance) is a frequency f dependent parameter and is very useful for example for describing the behaviour of musical The efficiency of loudspeaker drivers varies with frequency as well. For instance, the output of a woofer driver decreases as the input frequency decreases.

Driver ratings based on the SPL for a given input are called sensitivity ratings and are notionally similar to efficiency. Sensitivity is usually defined as so many decibels at 1 W electrical input, measured at 1 meter, often at a single frequency. The voltage used is often 2. 83 VRMS, which is 1 watt into an 8 Ω (nominal) speaker impedance (approximately true for many speaker systems). Measurements taken with this reference are quoted as dB with 2. 83 V @ 1 m.

The sound pressure output is measured at (or mathematically scaled to be equivalent to a measurement taken at) one meter from the loudspeaker and on-axis or directly in front of it under the condition that the loudspeaker is radiating into an infinitely large space and mounted on an infinite baffle. A Loudspeaker enclosure is a cabinet designed to transmit sound to the listener via mounted loudspeaker drive units Clearly then, sensitivity does not correlate precisely with efficiency, as it also depends on the directivity of the driver being tested and the acoustic environment in front of the actual loudspeaker. For example, a cheerleader's horn produces more sound output in the direction it is pointed, by concentrating sound waves from the cheerleader in one direction, and thus "focusing" them. The horn also improves the impedance matching between voice and the air, which produces more acoustic power for a given speaker power. In some cases, impedance matching (via careful enclosure design) will allow the speaker to produce more power.

A driver with a higher maximum power rating cannot necessarily be driven to louder levels than a lower rated one, since sensitivity and power handling are largely independent properties. In the examples that follow, assume for simplicity that the drivers being compared have the same electrical impedance, are operated at the same frequency which is within both driver's respective pass bands, and that power compression and distortion are low. For the first example, a speaker 3 dB more sensitive than another will produce double the sound pressure level (or be 3 dB louder) for the same power input. Thus a 100 W driver ("A") rated at 92 dB for 1 W @ 1 m sensitivity will output twice as much acoustic power as a 200 W driver ("B") rated at 89 dB for 1 W @ 1 m when both are driven with 100 W of input power. For this particular example, when driven at 100 W, speaker A will produce the same SPL, or loudness, speaker B would produce with 200 W input. Thus a 3 dB increase in sensitivity of the speaker means that it will need half the amplifier power to achieve a given SPL. This translates into a smaller, less complex power amplifier and often to reduced overall cost.

It is not possible to combine high efficiency, especially at low frequencies, with compact enclosure size, and adequate low frequency response. One can, more or less, only choose two of the three parameters when designing a speaker system. So, for example, if extended low frequency performance and a small box size are important, one must accept low efficiency. [5] This rule of thumb is sometimes called Hoffman's Iron Law (after J. A rule of thumb is a principle with broad application that is not intended to be strictly accurate or reliable for every situation A. Hoffman, the H in KLH). KLH is an audio company founded in 1957 as KLH Research and Development Corporation in Cambridge Massachusetts by Henry Kloss, Malcolm S [6]

Listening environment

The interaction of a loudspeaker system with its environment is complex and is largely out of the loudspeaker designer's control. Most listening rooms present a more or less reflective environment, depending on size, shape, volume, and furnishings. This means the sound reaching a listener's ears consists not only of sound directly from the speaker system, but also the same sound delayed by traveling to and from (and being modified by) one or more surfaces. These reflected sound waves, when added to the direct sound, cause cancellation and addition at assorted frequencies (eg, from resonant room modes), thus changing the timbre and character of the sound at the listener's ears. Resonant room modes affect the low frequency response of a Sound system at the listening position Our brains are very sensitive to small variations, including some of these, and this is part of the reason why a loudspeaker system sounds different at different listening positions or in different rooms.

A significant factor in the sound of a loudspeaker system is the amount of absorption and diffusion present in the environment. Clapping one's hands in a typical empty room, without draperies or carpet, will produce a zippy, fluttery echo which is due both to a lack of absorption and to reverberation (that is, repeated echoes) from flat reflective walls, floor, and ceiling. The addition of hard surfaced furniture, wall hangings, shelving and even baroque plaster ceiling decoration, will change the echoes, due primarily to the diffusion caused by somewhat reflective objects with shapes and surfaces having sizes on the order of the sound wavelengths being diffused. This somewhat breaks up the simple reflections otherwise caused by bare flat surfaces, and spreads the reflected energy of an incident wave over a larger angle on reflection.

Placement

In a typical rectangular listening room, this resonant phenomenon happens differently in each of the three dimensions, and there are even more complex interactions involving four or even all six boundary surfaces. It is primarily an issue for low frequencies which are not much affected by such things as furniture or its placement. In addition, the location of the loudspeakers, and the listener, with respect to room boundaries affect how strongly the resonances are excited. Many people are familiar with certain locations in some rooms, clubs, or buildings which have much more, or less, bass - most usually near room walls or corners. This is because standing wave patterns are most easily heard in these locations and at lower frequencies, below the Schroeder frequency - typically around 200-300 Hz, depending on room size.

Directivity

Acousticians, in studying the radiation of sound sources have developed some concepts important to understanding how loudspeakers are perceived. The simplest possible radiating source is a point source, sometimes called a simple source. An ideal point source is an infinitesimally small point radiating sound. It may be easier to imagine a tiny pulsating sphere, uniformly increasing and decreasing in diameter, sending out sound waves in all directions equally, independent of frequency.

Any object radiating sound, including a loudspeaker system, can be thought of as being composed of combinations of such simple point sources. The radiation pattern of a combination of point sources will not be the same as for a single source, but rather will depend on the distance and orientation between the sources, the position relative to them from which the listener hears the combination, and the frequency of the sound involved. Using geometry and calculus, some simple combinations of sources are easily solved; others are not.

One simple combination is two simple sources separated by a distance and vibrating out of phase, one miniature sphere expanding while the other is contracting. The pair is known as a doublet, or dipole, and the radiation of this combination is similar to that of a very small dynamic loudspeaker operating without a baffle. The directivity of a dipole is a figure 8 shape with maximum output along a vector which connects the two sources and minimums to the sides when the observing point is equidistant from the two sources, where the sum of the positive and negative waves cancel each other. While most drivers are dipoles, depending on the enclosure to which they are attached, they may radiate as monopoles, dipoles (or bipoles). If mounted on a finite baffle, and these out of phase waves allowed to interact, dipole peaks and nulls in the frequency response result. When the rear radiation is absorbed or trapped in a box, the diaphragm becomes a monopole radiator. Bipolar speakers, made by mounting in-phase monopoles (both moving out of or into the box in unison) on opposite sides of a box, are a method of approaching omnidirectional radiation patterns.

Polar plots of a four-driver industrial columnar public address loudspeaker taken at six frequencies. Note how the pattern is nearly omnidirectional at low frequencies, converging to a wide fan-shaped pattern at 1 kHz, then separating into lobes and getting weaker at higher frequencies
Polar plots of a four-driver industrial columnar public address loudspeaker taken at six frequencies. A public address or " PA " system is an electronic amplification system with a mixer, Amplifier and Loudspeakers used to Note how the pattern is nearly omnidirectional at low frequencies, converging to a wide fan-shaped pattern at 1 kHz, then separating into lobes and getting weaker at higher frequencies[7]

In real life, individual drivers are actually complex 3D shapes such as cones and domes, and they are placed on a baffle for various reasons. A mathematical expression for the directivity of a complex shape, based on modeling combinations of point sources, is usually not possible, but in the farfield, the directivity of a loudspeaker with a circular diaphragm will be close to that of a flat circular piston, so it can be used as an illustrative simplification for discussion. As a simple example of the mathematical physics involved, consider the following: the formula for farfield directivity of a flat circular piston in an infinite baffle is p(\theta) = \frac{p_0 J_1(k_a \sin \theta)}{k_a \sin \theta} where k_a=\frac{2\pi a}{\lambda}, p0 is the pressure on axis, a is the piston radius, λ is the wavelength (i. e. \lambda = \frac{c}{f} = \frac{\text{speed of sound}}{\text{frequency}}) θ is the angle off axis and J1 is the Bessel function of the first kind. In Mathematics, Bessel functions, first defined by the Mathematician Daniel Bernoulli and generalized by Friedrich Bessel, are Canonical

A planar source will radiate sound uniformly for low frequencies whose wavelength is shorter than the dimensions of the planar source, and as frequency increases, the sound from such a source will be focused into an increasingly narrower angle. The smaller the driver, the higher the frequency where this narrowing of directivity occurs. Even if the diaphragm is not perfectly circular, this effect occurs such that larger sources are more directive. Several loudspeaker designs have been built which have approximately this behavior. Most are electrostatic or planar magnetic designs.

Various manufacturers use different driver mounting arrangements to create a specific type of sound field in the space for which they are designed. The resulting radiation patterns may be intended to more closely simulate the way sound is produced by real instruments, or simply create a controlled energy distribution from the input signal (some using this approach are called monitors, as they are useful in checking the signal just recorded in a studio). Studio monitors, also called reference monitors, are Loudspeakers specifically designed for audio production applications such as recording, film An example of the first is a room corner system with many small drivers on the surface of a 1/8 sphere. A system design of this type was patented by, and actually produced commercially, by Professor Amar Bose -- the 1801. Later Bose models have deliberately emphasized production of both direct and reflected sound by the loudspeaker itself, regardless of its environment. The designs are controversial in high fidelity circles, but have proven commercially successful. Several other manufacturers' designs follow similar principles.

Directivity is an important issue because it affects the frequency balance of sound a listener hears, and also the interaction of the speaker system with the room and its contents. A speaker which is very directive (ie, on an axis perpendicular to the speaker face) may result in a reverberant field lacking in high frequencies, giving the impression the speaker is deficient in treble even though it measures well on axis (eg, "flat" across the entire frequency range). Speakers with very wide, or rapidly increasing directivity at high frequencies, can give the impression that there is too much treble (if the listener is on axis) or too little (if the listener is off axis). This is part of the reason why on-axis frequency response measurement is not a complete characterization of the sound of a given loudspeaker.

Other driver designs

Other types of drivers which depart from the most commonly used direct radiating electro-dynamic driver mounted in an enclosure include:

Horn loudspeakers

A three-way loudspeaker that uses horns in front of each of the three drivers: a wide, shallow horn for the tweeter, a long, straight horn for mid frequencies and a folded horn for the woofer
A three-way loudspeaker that uses horns in front of each of the three drivers: a wide, shallow horn for the tweeter, a long, straight horn for mid frequencies and a folded horn for the woofer
Main article: Horn speaker

Horn speakers are the oldest form of loudspeaker system, having been used from very early on for cylinder recording players. A horn speaker is a Loudspeaker which uses a horn to increase the overall efficiency of the driving element typically a diaphragm driven by an electromagnet A horn speaker is a Loudspeaker which uses a horn to increase the overall efficiency of the driving element typically a diaphragm driven by an electromagnet They use a shaped waveguide in front of or behind the driver to increase the directivity of the loudspeaker and to transform a small diameter, high pressure condition at the driver cone surface to a large diameter, low pressure condition at the mouth of the horn. This increases the sensitivity of the loudspeaker and focuses the sound over a narrower area. The size of the throat, mouth, the length of the horn, as well as the area expansion rate along it must be carefully chosen to match the drive to properly provide this transforming function over a range of frequencies (every horn performs poorly outside its acoustic limits, at both high and low frequencies). The length and cross-sectional mouth area required to create a bass or sub-bass horn require a horn many feet long. 'Folded' horns can reduce the total size, but compel designers to make compromises and accept increased complication such as cost and construction. Some horn designs not only fold the low frequency horn, but use the walls in a room corner as an extension of the horn mouth. In the late 1940s, horns whose mouths took up much of a room wall were not unknown amongst hi-fi fans. Room sized installations became much less acceptable when two or more were required.

A horn loaded speaker can have a sensitivity as high as 110 dB @ 2. 83 volts (1 watt @ 8 ohms) @ 1 meter. This is a hundredfold increase in output compared to a speaker rated at 90 dB sensitivity, and is invaluable in applications where high sound levels are required or amplifier power is limited.

Piezoelectric speakers

Piezoelectric speakers are frequently used as beepers in watches and other electronic devices, and are sometimes used as tweeters in less-expensive speaker systems, such as computer speakers and portable radios. A watch is a timepiece that is made to be worn on a person The term now usually refers to a wristwatch, which is worn on the wrist with a strap or Bracelet. Piezoelectric speakers have several advantages over conventional loudspeakers: they are resistant to overloads which would normally destroy most high frequency drivers, and they can be used without a crossover due to their electrical properties. There are also disadvantages: some amplifiers can oscillate when driving capacitive loads like most piezoelectrics, which results in distortion or damage to the amplifier. Additionally, their frequency response, in most cases, is inferior to that of other technologies. This is why they are generally used in single frequency (beeper) or non-critical applications.

Piezoelectric speakers can have extended high frequency output, and this is useful in some specialized circumstances; for instance, sonar applications in which piezoelectric variants are used as both output devices (generating underwater sound) and as input devices (acting as the sensing components of underwater microphones). Sonar (which started as an Acronym for sound navigation and ranging) is a technique that uses Sound propagation (usually underwater to navigate They have advantages in these applications, not the least of which is simple and solid state construction which resists the effects of seawater better than, say, a ribbon based device would.

Electrostatic loudspeakers

Main article: Electrostatic loudspeaker

Electrostatic loudspeakers use a high voltage electric field (rather than a magnetic field) to drive a thin membrane between two perforated conductive plates called stators. An electrostatic loudspeaker is a Loudspeaker design in which Sound is generated by the Force exerted on a Membrane suspended in an Electrostatic An electrostatic loudspeaker is a Loudspeaker design in which Sound is generated by the Force exerted on a Membrane suspended in an Electrostatic Because they are driven over the entire membrane surface rather than from a small voice coil, they can provide a more linear and lower distortion response than dynamic drivers. They have the disadvantage that the diaphragm excursion is severely limited because of practical construction limitations. The further apart the stators are positioned, the higher the voltage must be to achieve acceptable efficiency, which increases the tendency for attracting dust and producing electrical arcs. For many years electrostatic loudspeakers had a reputation as a generally unreliable and occasionally dangerous product. Arcing remains a potential problem with current technologies, especially when the panels are allowed to get collect dust or dirt, or when driven with high signal levels.

Electrostatics are inherently dipole radiators and due to the thin flexible membrane cannot be used in enclosures to reduce low frequency cancellation as with common cone drivers. Due to this and the low excursion capability, full range electrostatic loudspeakers are large by nature, and even so are not outstanding performers at the lowest frequencies. To reduce the size of commercial products, they are often used as a high frequency driver in combination with a conventional dynamic driver which handles the bass frequencies.

Ribbon and planar magnetic loudspeakers

A ribbon speaker consists of a thin metal-film ribbon suspended in a magnetic field. The electrical signal is applied to the ribbon which moves with it, thus creating the sound. The advantage of a ribbon driver is that the ribbon has very little mass; thus, it can accelerate very quickly, yielding very good high-frequency response. Mass is a fundamental concept in Physics, roughly corresponding to the Intuitive idea of how much Matter there is in an object Ribbon loudspeakers are often very fragile -- some can be torn by a strong gust of air. Most ribbon tweeters emit sound in a dipole pattern; a very few have backings which limit the dipole radiation pattern. Above and below the ends of the more or less rectangular ribbon, there is less audible output due to phase cancellation, but the precise amount of directivity depends on ribbon length. Ribbon designs generally require exceptionally powerful magnets which make them costly to manufacture. Ribbons have a very low resistance that most amplifiers cannot drive directly. As a result, a step down transformer is typically used to increase the current through the ribbon. The amplifier "sees" a load that is the ribbon's resistance times the transformer turns ratio squared. The transformer must be carefully designed so that its frequency response and parasitic losses do not degrade the sound, further increasing cost and complication relative to conventional designs.

Planar magnetic speakers (having printed or embedded conductors on a flat diaphragm) are sometimes described as "ribbons", but are not truly ribbon speakers. The term planar is generally reserved for speakers which have roughly rectangular shaped flat surfaces that radiate in a bipolar (ie, front and back) manner. Planar magnetic speakers consist of a flexible membrane with a voice coil printed or mounted on it. The current flowing through the coil interacts with the magnetic field of carefully placed magnets on either side of the diaphragm, causing the membrane to vibrate more or less uniformly and without much bending or wrinkling. The driving force covers a large percentage of the membrane surface and reduces resonance problems inherent in coil-driven flat diaphragms.

Some planar magnetic designs have small cavities between the magnet structures and the diaphragm. This can cause a "cavity resonance" response peak that requires correction. Failure to correct this cavity resonance is likely the cause the steely or shrill sound sometimes attributed to these designs.

Bending wave loudspeakers

Bending wave transducers use a diaphragm that is intentionally flexible. The rigidity of the material increases from the center to the outside. Short wavelength sound therefore radiates primarily from the inner area, while longer waves reach the edge of the speaker. To prevent reflections, long waves are absorbed by a surrounding damper. Such transducers can cover a wide frequency range (80 Hz to 35,000 Hz) and have been promoted as being close to an ideal point sound source. [8][9]

Flat panel loudspeakers

There have been many attempts to reduce the size of speaker systems, or alternatively to make them less obvious. One such attempt was the development of voice coils mounted to flat panels to act as sound sources. These can then be made in a neutral color and hung on walls where they will be less noticeable than many speakers, or can be deliberately painted with patterns in which case they can function decoratively. There are two related problems with flat panel techniques: first, a flat panel is necessarily more flexible than a cone shape in the same material, and therefore will move as a single unit even less, and second, resonances in the panel are difficult to control, leading to considerable distortions. Some progress has been made using such lightweight, rigid, materials as Styrofoam, and there have been several flat panel systems commercially produced in recent years. Styrofoam is a trademark for polystyrene Thermal insulation, a material manufactured by Dow Chemical Company.

Distributed mode loudspeakers

A newer implementation of the flat panel speaker system involves an intentionally flexible panel and an "exciter", mounted off-center in a location such that it excites the panel to vibrate, but with minimal resonances. Speakers using such techniques can reproduce sound with a wide directivity pattern (paradoxically somewhat like a point source) and have been used in some computer speaker designs and bookshelf loudspeakers. [10]

Heil air motion transducers

Dr. Oskar Heil invented the air motion transducer in the 1960s. Oskar Heil (1908 in Langwieden / Rhineland-Palatinate – 1994 was a German electrical engineer and inventor In this approach, a pleated diaphragm is mounted in a magnetic field and forced to close and open under control of a music signal. Air is forced from between the pleats in accordance with the imposed signal, generating sound. The drivers are less fragile than ribbons and considerably more efficient (and able to produce higher absolute output levels) than ribbon, electrostatic, or planar magnetic tweeter designs.

ESS, a California manufacturer, licensed the design, employed Dr. Heil, and produced a range of speaker systems using his tweeters during the 1970s and 1980s. Radio Shack, a large US retail store chain, also sold speaker systems using such tweeters for a time. RadioShack Corporation (formerly Tandy Corporation) (  is a chain of electronics retail stores in the United States, as well as parts of North America At present, there are two manufacturers of these drivers, both in Germany, one of which produces a range of high end professional speakers using tweeters and midrange drivers based on the technology.

Plasma arc speakers

Main article: Plasma arc loudspeaker

Plasma arc loudspeakers use electrical plasma as a radiating element. In Physics and Chemistry, plasma is an Ionized Gas, in which a certain proportion of Electrons are free rather than being bound Since plasma has minimal mass, but is charged and therefore can be manipulated by an electric field, the result is a very linear output at frequencies far higher than the audible range. In Physics, the space surrounding an Electric charge or in the presence of a time-varying Magnetic field has a property called an electric field (that can Problems of maintenance and reliability for this approach tend to make it unsuitable for mass market use. In 1978 Dr. Alan Hill of the Los Alamos National Laboratory designed the Hill Plasmatronics, an $8000 tweeter whose plasma was generated from helium gas. Los Alamos National Laboratory (LANL (previously known at various times as Site Y, Los Alamos Laboratory, and Los Alamos Scientific Laboratory) is a Helium ( He) is a colorless odorless tasteless non-toxic Inert Monatomic Chemical [11] This avoided the ozone and nitrous oxide produced by RF decomposition of air in an earlier generation of plasma tweeters made by the pioneering DuKane Corporation, who produced the Ionovac (marketed as the Ionofane in the UK) during the 1950s. OZONE is an object oriented Operating system written in the C programming language. Nitrous oxide, commonly known as " laughing gas," is a Chemical compound with the Chemical formula N 2 O. Radio frequency ( RF) is a Frequency or rate of Oscillation within the range of about 3 Hz to 300 GHz Currently, there remain a few manufacturers in Germany, and a do it yourself design has been published.

A less expensive variation on this theme is the use of a flame for the driver, as flames contain ionized (electrically charged) gases. [12]

Digital speakers

Main article: Digital speakers

Digital speakers have been the subject of experiments by Bell Labs as far back as the 1920s. Digital speakers are a form of Loudspeaker technology Not to be confused with modern digital formats and processing they are a mature technology having been experimented with Digital speakers are a form of Loudspeaker technology Not to be confused with modern digital formats and processing they are a mature technology having been experimented with Bell Laboratories (also known as Bell Labs and formerly known as AT&T Bell Laboratories and Bell Telephone Laboratories) is the Research organization The design is simple; each bit drives an independent speaker driver. A bit is a binary digit, taking a value of either 0 or 1 Binary digits are a basic unit of Information storage and communication Increasingly significant bits drive speakers of twice the area of the previous (often in a ring around the previous driver). In Computing, the most significant bit ( msb) is the Bit position in a binary number having the greatest value A value of "1" causes that driver to be driven to full amplitude; a value of "0" causes it to be completely shut off.

There are two problems with this design which have led to it being abandoned as impractical for the present. First, for a reasonable number of bits (required for adequate sound reproduction quality), the size of the system becomes very large. Secondly, due to analog digital conversion, the effect of aliasing is unavoidable, so that the audio output is "reflected" at equal amplitude in the frequency domain, on the other side of the sampling frequency, causing an unacceptably high level of ultrasonics to accompany the desired output. An analog-to-digital converter (abbreviated ADC, A/D or A to D) is an electronic integrated circuit which converts continuous signals to This article applies to signal processing including computer graphics Sampling theorem The Nyquist–Shannon sampling theorem states that perfect reconstruction Not to be confused with Supersonic. Ultrasound is cyclic Sound pressure with a Frequency greater than the upper

The term "digital" or "digital-ready" is often used for marketing purposes on speakers or headphones, but these systems are not digital in the sense described above. Rather, this is a somewhat deceptive marketing tactic, in which the manufacturer is trying to capitalize on the popularity of digital sound recordings and equipment.

References

  1. ^ Tesla and the Loudspeaker. Retrieved on 2007-02-21. Year 2007 ( MMVII) was a Common year starting on Monday of the Gregorian calendar in the 21st century. Events 362 - Athanasius returns to Alexandria. 1245 - Thomas, the first known Bishop of Finland
  2. ^ Loudspeaker History. Retrieved on 2007-02-21. Year 2007 ( MMVII) was a Common year starting on Monday of the Gregorian calendar in the 21st century. Events 362 - Athanasius returns to Alexandria. 1245 - Thomas, the first known Bishop of Finland
  3. ^ Q. What's the difference between ported and un-ported monitors?
  4. ^ Infinite baffle
  5. ^ Loudspeaker Design Tradeoffs
  6. ^ Hoffman's Iron Law
  7. ^ Polar pattern image: Speaker is a Bosch 36 watt LA1-UW36-x columnar model with four identical 4-inch drivers arranged vertically in an enclosure 841 mm (33 inch) high. Polar prediction software is CLF viewer. Loudspeaker information was gathered by the manufacturer into a CF2 file.
  8. ^ Manger loudspeakers
  9. ^ Stereophile magazine. Ohm Walsh 5 loudspeaker (review by Dick Olsher, June 1987)
  10. ^ NXT. Distributed Mode Loudspeaker FAQ
  11. ^ Hill Plasmatronics described. Retrieved March 26, 2007
  12. ^ Re: Could You Please Find Research Re:Sound Reprodution Via Gas Flame & Electri

See also

External links

Dictionary

loudspeaker

-noun

  1. An electromechanical transducer that converts an electrical signal into audible sound.
  2. An encasing containing one or more loudspeaker devices and usually other electrical equipment such as a driver.
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