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See also Audio#Acoustics

  • https://en.wikipedia.org/wiki/Loudspeaker - or loud-speaker or speaker, is an electroacoustic transducer; which converts an electrical audio signal into a corresponding sound. The most widely used type of speaker in the 2010s is the dynamic speaker, invented in 1925 by Edward W. Kellogg and Chester W. Rice. The dynamic speaker operates on the same basic principle as a dynamic microphone, but in reverse, to produce sound from an electrical signal. When an alternating current electrical audio signal is applied to its voice coil, a coil of wire suspended in a circular gap between the poles of a permanent magnet, the coil is forced to move rapidly back and forth due to Faraday's law of induction, which causes a diaphragm (usually conically shaped) attached to the coil to move back and forth, pushing on the air to create sound waves. Besides this most common method, there are several alternative technologies that can be used to convert an electrical signal into sound. The sound source (e.g., a sound recording or a microphone) must be amplified or strengthened with an audio power amplifier before the signal is sent to the speaker.
  • Animagraff: How speakers make sound - Speakers push and pull surrounding air molecules in waves that the human ear interprets as sound. You could even say that hearing is movement detection. So what makes a speaker travel back and forth at just the right rate and distance, and how does that make sound? 3D animated infographics that attract thousands of viewers.

  1. Bass Extension
  2. Efficiency
  3. Small Enclosure

"The law is that you can only have two of these three attributes in speaker building. Ideally we would want all three, we want speakers with good bass, can play really loud, and are small. Unfortunately we cannot have all these."


  • FS = free air resonance, resonant frequence of driver, most efficiant vibration speed - Hz
  • Q Values/factors - (unitless) - amount of dampeningresistance to compression/streching
    • Qes - coil and magnet
    • Qms - surround and spider of speaker
    • Qts - based on Qes and Qms, below 0.4 ported, 0.4-0.7 sealed, above 0.7 freeair/ib
  • Vas - volume of air equal to compliance of speaker (affeced by air pressure)
  • Cms - compliance of speaker/stiffness of cone movement, related to spider and surround, Meters per Newton. Low is tight, high is loose suspension. As compliance goes up, resonant frequency goes down. Speed of stopping after em is stopped.
  • Nominal impedence - generally the imedence the amp will see. spike in impedence at resonance frequence because of indicence of voice coil.
  • Resistance (RE) - DC resistance
  • Le - voicecoil inductance (millihenries)
  • BL - motor strength (Tesla Meters) - strength of motor/magnet in relation to voice coil to move cone structure. generally how quickly speaker will respond (taking stiffness into account.
  • Mmd - mass of all moving parts in grams, i.e., cone, voice coil, half the surround, half of the spider.
  • Mms - the above plus the mass of the air that is moving. higher Mms, lower resonant frequency. lighter punchier, higher = lower bass.
  • Sd - cone surface area. deeper = more area.
  • Xmax - distance voice coil can move until windings in gap gets lower
  • Spl - sound pressure level at 1W power

  • https://en.wikipedia.org/wiki/Acoustic_lobing - refers to the radiation pattern of a combination of two or more loudspeaker drivers at a certain frequency, as seen looking at the speaker from its side. In most multi-way speakers, it is at the crossover frequency(ies) that the effects of lobing are of greatest concern, since this determines how well the speaker preserves the tonality of the original recorded content.

  • https://en.wikipedia.org/wiki/Coaxial_loudspeaker - a loudspeaker system in which the individual driver units radiate sound from the same point or axis. Two general types exist: one is a compact design using two or three speaker drivers, usually in car audio, and the other is a two-way high-power design for professional audio, also known as single-source or dual-concentric loudspeakers.


  • https://en.wikipedia.org/wiki/Speaker_driver - an individual loudspeaker transducer that converts an electrical audio signal to sound waves. While the term is sometimes used interchangeably with the term loudspeaker (speaker), 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.

The mechanism most widely used in speakers to convert the electric current to sound waves is the dynamic or electrodynamic driver, invented in 1925 by Edward W. Kellogg and Chester W. Rice, which creates sound with a coil of wire called a voice coil suspended between the poles of a magnet. There are others which are far less widely used: electrostatic drivers, piezoelectric drivers, planar magnetic drivers, Heil air motion drivers, and ionic drivers, among others.

Moving iron

  • https://en.wikipedia.org/wiki/Moving_iron_speaker - the earliest type of electric loudspeaker. They are still used today in some miniature speakers where small size and low cost are more important than sound quality. A moving iron speaker consists of a ferrous-metal diaphragm or reed, a permanent magnet and a coil of insulated wire. The coil is wound around the permanent magnet to form a solenoid. When an audio signal is applied to the coil, the strength of the magnetic field varies, and the springy diaphragm or reed moves in response to the varying force on it. The moving iron loudspeaker Bell telephone receiver was of this form. Large units had a paper cone attached to a ferrous metal reed.

Old undamped moving iron speakers have a characteristic sound, with probably the worst sound quality of any known type of speaker usable for speech. The first moving iron transducer, the telephone receiver or earphone, evolved with the first telephone systems in the 1870s. Moving iron horn loudspeakers developed from earphones after the first amplifying device which could drive a speaker, the triode vacuum tube, was perfected around 1913. They were used in radio receivers and the first public address systems. Moving iron cone loudspeakers appeared around 1920. Around 1930 they were replaced by the moving coil cone loudspeaker developed in 1925 by Edward Kellogg and Chester Rice. Today the moving iron driver mechanism is still used in some earphones. Modern damped moving iron mechanisms can provide respectable sound quality, and are used in headphones. https://en.wikipedia.org/wiki/Impedance_matching#Acoustics


  • https://en.wikipedia.org/wiki/Piezoelectric_speaker - sometimes colloquially called a "pizo" or buzzer is a loudspeaker that uses the piezoelectric effect for generating sound. The initial mechanical motion is created by applying a voltage to a piezoelectric material, and this motion is typically converted into audible sound using diaphragms and resonators. Compared to other speaker designs piezoelectric speakers are relatively easy to drive; for example they can be connected directly to TTL outputs, although more complex drivers can give greater sound intensity. Typically they operate well in the range of 1-5kHz and up to 100kHz in ultrasound applications. Piezoelectric speakers are frequently used to generate sound in digital quartz watches and other electronic devices, and are sometimes used as tweeters in less-expensive speaker systems, such as computer speakers and portable radios. They are also used for producing ultrasound in sonar systems.


  • https://en.wikipedia.org/wiki/Magnetostatic_loudspeaker - a dipole loudspeaker that is similar to an electrostatic loudspeaker but instead of using high voltages, uses high currents. Permanent magnets provide a static magnetic field and wires or strips carrying audio frequency currents are bonded to a thin diaphragm. The current flowing in the conductors interacts with the magnetic field and creates sound in much the same way as in a conventional dynamic driver. Because of its dipole structure, this kind of speaker creates sound mostly to its front and back.

The impedance of a magnetostatic speaker is often mainly resistive, but in some cases may be so low that the amplifiers have to be ready to accommodate the low impedance load. Magnetostatic speakers provide good sound quality, and may be very thin, but their height and width dimensions are large.


Driver range



kef b139 speaker




Super tweeter


  • https://en.wikipedia.org/wiki/Coaxial_loudspeaker - a loudspeaker system in which the individual driver units radiate sound from the same point or axis. Two general types exist: one is a compact design using two or three speaker drivers, usually in car audio, and the other is a two-way high-power design for professional audio, also known as single-source or dual-concentric loudspeakers.


  • AVS Forum - Home Theater Discussions And Reviews > Audio > DIY Speakers and Subs

  • quarter wavelength loudspeaker design - The most common example of a loudspeaker that relies on a quarter wavelength acoustic standing wave is a transmission line enclosure. This style of loudspeaker has been on the fringe of the audio mainstream for many years with just a few smaller companies building and marketing this enclosure design. Even more exotic and rare in the audio marketplace are the TQWT and the horn loaded enclosure designs. All of these enclosures utilize acoustic standing waves that can be described as multiples of a quarter cycle of a sine or cosine function. Hence my terminology of a "Quarter Wavelength Loudspeaker Design" to describe the content of the articles contained in this website.

Dipole vs. bipole vs. omni arrangement

  • https://en.wikipedia.org/wiki/Dipole_speaker - enclosure in its simplest form is constructed by mounting a loudspeaker driver on a flat panel. The panel may be folded to conserve space. The term dipole derives from the fact that the polar response consists of two lobes, with equal radiation forwards and backwards, and none perpendicular to the axis. By comparison a monopole response consists of one lobe. This can be useful in reducing the stimulation of resonant room modes at low frequencies. It also results in high frequencies being reflected from any rear wall, which can enhance the naturalness of the sound in typical listening rooms by creating more diffuse reverberation, though in theory it could detract from stereo localization. For this reason dipole speakers are often used as surround channel speakers, where a diffuse sound is desired to create ambience.

  • Dipole vs Bipole Speakers: What's the Difference? - How to Remember the Difference Between Dipole vs Bipole Speakers: With a bipole speaker “b”oth driver pairs are firing in-phase with each other. With a dipole speaker, the drivers are firing in “d”ifferent phase from each other. Dipole speakers are more “d”iffuse because they create a null at the listening position. If that doesn’t help you remember, nothing will!

  • YouTube: Dipole, bipole and omnidirectional speakers - Most speakers radiate sound from the front. Apparently that seems to work the best. Or does it. Then why are there also speakers that radiate from the front and the back and even speakers that radiate in all directions equally?

Infinite baffle / free air

Sealed box

  • https://en.wikipedia.org/wiki/Acoustic_suspension - or air suspension or sealed box, is a type of loudspeaker speaker enclosure design which uses one or more loudspeaker drivers mounted in a sealed box or cabinet. Acoustic suspension systems reduce bass distortion that can be caused by stiff motor suspensions in conventional loudspeakers. It was invented in 1954 by Edgar Villchur, and brought to commercial production by Villchur and Henry Kloss with the founding of Acoustic Research in Cambridge, Mass. Speaker cabinets with acoustic suspension can provide tight and accurate bass response, especially in comparison with an equivalently-sized speaker enclosure which has a bass reflex port or vent; the bass vent boosts low-end output, but at the tradeoff of introducing phase delay and accuracy problems. Sealed boxes are generally less efficient than a ported cabinet, so a sealed box speaker cabinet will need more power amplifier wattage to deliver the same amount of bass output.

Test how sealed an enclosure is: push sub in and it should come out slowly

Transmission line

  • https://en.wikipedia.org/wiki/Transmission_line_loudspeaker - a loudspeaker enclosure design (topology) that uses an acoustic transmission line within the cabinet, compared to the simpler enclosures used by sealed (closed) or ported (bass reflex) designs. Instead of reverberating in a fairly simple damped enclosure, sound from the back of the bass speaker is directed into a long (generally folded) damped pathway within the speaker enclosure, which allows far greater control and use of speaker energy, and the resulting sound.

Inside a transmission line (TL) loudspeaker, is a (usually folded) pathway into which the sound is directed. The pathway is often covered with varying types and depths of absorbent material, and it may vary in size or taper, and may be open or closed at its far end. Used correctly, such a design ensures that undesired resonances and energies, which would otherwise cause undesirable auditory effects, are instead selectively absorbed or reduced ("damped") due to the effects of the duct, or alternatively only emerge from the open end in phase with the sound radiated from the front of the driver, enhancing the output level ("sensitivity") at low frequencies. The transmission line acts as an acoustic waveguide, and the padding both reduces reflection and resonance, and also slows the speed of sound within the cabinet to allow for better tuning.

Mass Loaded Transmission Line

  • Designing MLTL Speakers - Quarter-wave transmission line speakers employ enclosures that are tuned to provide low-frequency extension for the speaker driver. There are several types of transmission line enclosures and one of the more popular ones is the mass loaded transmission line (MLTL). Basically, an MLTL is a quarter-wave transmission line enclosure with a port. Now, some may argue that this is a bass reflex enclosure – and the line is indeed a bit blurry. However, rather than engaging in a lengthy discussion on naming conventions, I will use the term MLTL to describe a ported quarter-wave enclosure.


  • https://en.wikipedia.org/wiki/Horn_loudspeaker - a loudspeaker or loudspeaker element which uses an acoustic horn to increase the overall efficiency of the driving element(s). A common form (right) consists of a compression driver which produces sound waves with a small metal diaphragm vibrated by an electromagnet, attached to a horn, a flaring duct to conduct the sound waves to the open air. Another type is a woofer driver mounted in a loudspeaker enclosure which is divided by internal partitions to form a zigzag flaring duct which functions as a horn; this type is called a folded horn speaker. The horn serves to improve the coupling efficiency between the speaker driver and the air. The horn can be thought of as an "acoustic transformer" that provides impedance matching between the relatively dense diaphragm material and the less-dense air. The result is greater acoustic output power from a given driver.

The narrow part of the horn next to the driver is called the "throat" and the large part farthest away from the driver is called the "mouth". The angular coverage (radiation pattern) of the horn is determined by the shape and flare of the mouth. A major problem of horn speakers is that the radiation pattern varies with frequency; high frequency sound tends to be emitted in narrow beams with poor off-axis performance. Significant improvements have been made, beginning with the "constant directivity" horn invented in 1975 by Don Keele.

The main advantage of horn loudspeakers is they are more efficient; they can typically produce 10 times (10 dB) more sound power than a cone speaker from a given amplifier output. Therefore horns are widely used in public address systems, megaphones, and sound systems for large venues like theaters, auditoriums, and sports stadiums. Their disadvantage is that their frequency response is more uneven because of resonance peaks, and horns have a cutoff frequency below which their response drops off. To achieve adequate response at bass frequencies horn speakers must be very large and cumbersome, so they are more often used for midrange and high frequencies. The first practical loudspeakers, introduced around the turn of the 20th century, were horn speakers. Due to the development in recent decades of cone loudspeakers which have a flatter frequency response, and the availability of inexpensive amplifier power, the use of horn speakers in high fidelity audio systems over the last decades has declined.

  • https://en.wikipedia.org/wiki/Tractrix - In 1927, P. G. A. H. Voigt patented a horn loudspeaker design based on the assumption that a wave front traveling through the horn is spherical of a constant radius. The idea is to minimize distortion caused by internal reflection of sound within the horn. The resulting shape is the surface of revolution of a tractrix.

Multiple-entry / synergy / coentrant horn / unity horn

Folded horn

Tapped horn

Folded tapped horn

Reflex port

  • https://en.wikipedia.org/wiki/Bass_reflex - also known as a ported, vented box or reflex port, 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 closed box (sealed-box) loudspeaker or an infinite baffle mounting.

A reflex port is the distinctive feature of this popular enclosure type. The design approach enhances the reproduction of the lowest frequencies generated by the woofer or subwoofer. The port generally consists of one or more tubes or pipes mounted in the front (baffle) or rear face of the enclosure. Depending on the exact relationship between driver parameters, the enclosure volume (and filling if any), and the tube cross-section and length, the efficiency can be substantially improved over the performance of a similarly sized sealed-box enclosure. Though helpful with improving efficiency, bass reflex cabinets can have poor transient response compared to sealed enclosures at frequencies near the lower limit of performance, causing "smearing" or a longer resonance of the bass notes. Proper adjustment ("tuning") of the cabinet and port size, and matching with driver characteristics can reduce much of this problem.


Passive radiator

  • https://en.wikipedia.org/wiki/Passive_radiator_(speaker) - PR, usually contains an "active loudspeaker" (or main driver), and a passive radiator (also known as a "drone cone"). The active loudspeaker is a normal driver, and the passive radiator is of similar construction, but without a voice coil and magnet assembly. It is not attached to a voice coil or wired to an electrical circuit or power amplifier. In the same way as a ported loudspeaker, a passive radiator system uses the sound otherwise trapped in the enclosure to excite a resonance that makes it easier for the speaker system to create the deepest pitches (e.g., basslines). The passive radiator resonates at a frequency determined by its mass and the springiness of the air in the enclosure. It is tuned to the specific enclosure by varying its mass (e.g., by adding weight to the cone) Internal air pressure produced by movements of the active driver cone moves the passive radiator cone. This resonance simultaneously reduces the amount that the woofer has to move.

Line array

  • https://en.wikipedia.org/wiki/Line_array - a loudspeaker system that is made up of a number of usually identical loudspeaker elements mounted in a line and fed in phase, to create a near-line source of sound. The distance between adjacent drivers is close enough that they constructively interfere with each other to send sound waves farther than traditional horn-loaded loudspeakers, and with a more evenly distributed sound output pattern.
  • YouTube: Metallica's Secret Weapon: The Meyer Sound TM Array™ (HD) - Big Mick Hughes and Paul Owen discuss the latest innovation in live sound - the TM Array™. Using a revolutionary configuration of Meyer Sound subwoofers hung center-stage, the crew is able to achieve uniform, low-frequency coverage in-the-round like never before. A band as legendary as Metallica requires powerful sound on tour, and the TM Array delivers. Filmed in Portland Oregon on November1, 2008.


  • https://en.wikipedia.org/wiki/Midwoofer-tweeter-midwoofer - called MTM for short, is a loudspeaker configuration created by Joseph D'Appolito as a way of correcting the inherent lobe tilting of a typical mid-tweeter (MT) configuration, at the crossover frequency, unless time-aligned. In the MTM arrangement the loudspeaker uses three drivers: Two mid-range (or mid-woofer/woofer) for the low frequencies and a tweeter for the higher frequencies, with the tweeter being placed between the mid-range drivers (as shown in the second image below). D'Appolito initially configured his design using a 3rd order (18 dB/oct or 60 dB/dec) crossover, D'Appolito has since amended this original recommendation in favor of 4th order topology. However, this does not impart any significant effect on the MTM design's unique characteristics.


3D printed


  • https://en.wikipedia.org/wiki/Studio_monitor - loudspeakers in speaker enclosures specifically designed for professional audio production applications, such as recording studios, filmmaking, television studios, radio studios and project or home studios, where accurate audio reproduction is crucial. Among audio engineers, the term monitor implies that the speaker is designed to produce relatively flat (linear) phase and frequency responses. In other words, it exhibits minimal emphasis or de-emphasis of particular frequencies, the loudspeaker gives an accurate reproduction of the tonal qualities of the source audio ("uncolored" or "transparent" are synonyms), and there will be no relative phase shift of particular frequencies—meaning no distortion in sound-stage perspective for stereo recordings. Beyond stereo sound-stage requirements, a linear phase response helps impulse response remain true to source without encountering "smearing". An unqualified reference to a monitor often refers to a near-field (compact or close-field) design.

  • SOS: The Yamaha NS10 Story - Love or hate the Yamaha NS10, this unassuming little speaker has found a place in the studios of many of the world's top producers. We trace its history, and investigate why a monitor whose sound has been described as "horrible" became an industry standard.



See also Audio