A loudspeaker enclosure or loudspeaker cabinet is an enclosure (often box-shaped) where speaker drivers (eg speakers and tweeters) and associated electronic hardware, such as crossover circuits and, in some cases, a power amplifier, installed. Attachments can range in design from simple, rectangular DIY rectangular particle boxes to highly complex and expensive computer-designed hi-fi cabinets incorporating composite materials, internal baffles, horns, bass reflex ports and acoustic insulation. The loudspeaker casing has a diverse size of small "bookcase" shelf cabinets with 4 "small woofers and tweeters designed for listening to music with a hi-fi system in a private home up to a large heavy subwoofer enclosure with lots of 18" or even 21 "speakers on large enclosures designed for use in sound reinforcement concert systems for rock concerts.
The main role of enclosure is to prevent sound waves generated by the rear-facing surface of the open speaker driver diaphragm that interacts with the sound waves generated on the front of the speaker driver. Since the sound produced by the front and rear directions is out of phase with each other, any interaction between the two in the listening space creates a distortion of the original signal as intended to be reproduced. Thus, the loudspeaker can not be used without installing it in a certain type of cabinet, or attaching it to a wall or ceiling. Additionally, since sound waves will travel different paths through the listening room, sound waves in the non-mounted speakers will arrive at the listener's position at slightly different times, introducing echo and echo effects not part of the original sound.
Enclosures also play a role in managing the vibrations induced by the drive frame and removing the air within the enclosure, as well as the heat generated by the coil and the driving amplifier (especially where the woofers and subwoofers are linked). Sometimes considered part of the cage, the base, may include "feet" specially designed to separate speakers from the floor. Appendices designed for use in PA systems, sound reinforcement systems and for use by electric instrument players (for example, amps cabinets have a number of features to make it easier to transport, such as carrying a handle on top or sides, metal or plastic protective angles, and metal grilles to protect the speakers). Speakers casing designed for home or studio recording usually do not have a handle or corner guard, although they usually still have a cloth or mesh cover to protect the woofer and tweeters. The speaker grille is a metal mesh or fabric used to protect the speakers by forming a protective cover over the speaker cone while allowing the sound to pass through distorted.
Speaker casing is used in homes in stereo systems, home cinema systems, televisions, boom boxes, and many other audio equipment. Small speaker casing is used in car stereo system. The speaker cabinet is a key component of a number of commercial applications, including sound reinforcement systems, cinema sound systems, and recording studios. Electric instruments created in the 20th century, such as electric guitars, electric basses, and synthesizers, among others reinforced using instrument amplifiers and speaker cabinets (eg, guitar speaker cabinets).
Video Loudspeaker enclosure
Histori
Initially, radio loudspeakers consist of horns, often sold separately from the radio itself, (usually a small wooden box containing electronic radio circuits), so they are usually not placed in a cage. When the driver paper cone loudspeaker was introduced in the mid-1920s, radio cabinets began to be made larger to include electronics and loudspeakers. This cabinet is made mostly for the sake of appearance, with the loudspeaker mounted behind the round hole in the cabinet. Observed that the cage has a strong effect on the bass response of the speaker. Since the back of the loudspeaker emits sound from the phase from the front, there will be constructive and destructive interference for the loud speaker without cover, and the frequency below that corresponds to the baffle dimension of the open loudspeaker (described in the Background section, below). This results in loss of bass and comb filtering (ie peak response and dips in power regardless of signal intended to be reproduced).
Before the 1950s many manufacturers did not fully attach their loudspeaker cabinets; the back of the cabinet is usually left open. This is done for several reasons, not least because electronics (at that time tubular equipment) can be placed inside and cooled by convection in open enclosures.
Most types of enclosures discussed in this article are created to either extinguish sounds out of phase from one side of the driver, or to modify them so they can be used to improve the sound produced from the other side. However, some designs have moved in different directions, trying to combine the natural acoustic properties of the cabinet material rather than turning it off, and forming the cabinet so that the rear can remain open and still provide a good bass response with limited comb filtering.
Maps Loudspeaker enclosure
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In some cases, the ideal installation for low-frequency speakers is a rigid, infinite flat panel with unlimited space behind it. This will completely prevent the disturbing rear sound waves (ie, cancellation of comb filters) with sound waves from the front. A loudspeaker "open baffle" is this estimate, because the driver is mounted on the panel, with dimensions that are proportional to the lowest wavelength to be reproduced. In either case, the driver will require a relatively rigid suspension to provide a restoring force that may have been provided at lower frequencies with a smaller closed or ported scope, so some drivers are suitable for this type of installation.
The forward and backward loudspeakers emerge from each other's phases because they are produced through opposite movements of the diaphragm and because they travel different paths before they converge in the listener's position. A speaker driver mounted on a limited insulation will display a physical phenomenon known as interference that can produce sound attenuation that depends on the visible frequency. This phenomenon is particularly noticeable at low frequencies where the wavelength is large enough that the disturbance will affect the entire hearing area.
Because unlimited baffles are impractical and limited baffles tend to suffer from poor responses because wavelengths approach the dimensions of the baffles (ie at lower frequencies), most loudspeaker cabinets use some kind of structure (usually a box) to release phase sound energy. This box is usually made of wood, composite wood, or more recently plastic, for reasons of ease of construction and appearance. Stone, concrete, plaster, and even building structures have also been used.
Enclosures can have a significant effect beyond what is intended, with panel resonance, diffraction from the edge of the cabinet and standing wave energy from internal reflection/reinforcement mode being one of the possible problems. Disruptive resonance can be reduced by increasing the mass or stiffness of the cage, by increasing the damping of the enclosure wall or the combination of wall/surface treatment, by adding a rigid crossbar, or by adding internal absorption. Wharfedale, in some designs, reduces panel resonance by using two wooden cabinets (one inside the other) with an intermediate space filled with sand. Home researchers have even designed speakers built from concrete, granite and other exotic materials for the same reason.
Many diffraction problems, above the lower frequencies, can be lightened by the shape of the enclosure, as by avoiding sharp corners on the front of the cage. Research experiments from the 1930s by Dr. Harry F. Olson points out that the curved baffle loudspeaker reduces some irregular responses due to the diffraction of sound waves. It was discovered later that the careful placement of a speaker on a sharp baffle can reduce the problem of response caused by diffraction. Sometimes the difference in the phase response at frequencies shared by different drivers can be overcome by adjusting the vertical location of the smaller driver (usually backwards), or by leaning or stepping the front baffle, resulting in a wavefront of all coherent drivers in and around crossover frequency in the normal speech sound field. The driver's acoustic center determines the amount of rear offsets needed to "manage the time" of the driver.
Type
Boxes used for woofers and subwoofers can be adequately modeled in low frequency areas (about 100-200 Hz and below) using the unified acoustic and component models. The theory of electrical filters has been used with great success for certain types of enclosures. For the purposes of this type of analysis, each enclosure should be classified according to a particular topology. The designer must balance the low bass extension, linear frequency response, efficiency, distortion, loudness and enclosure size, while simultaneously addressing higher issues within audible range ranges such as diffraction from the edge of the enclosure, the baffle step effect when the wavelength approaches the dimension of the enclosure , crossover, and mixing drivers.
Closed (or closed) template
Mass and compliance moves loudspeaker loudspeakers (reciprocity or mutual stiffness of the suspension) determines the driver resonance frequency ( F s ). In combination with the damping properties of the system (both mechanical and electrical) all of these factors affect the low frequency response of closed-box systems. The output falls below the frequency of the resonance system ( F c ), which is defined as the peak impedance frequency. In a closed box, the air inside the box acts as a spring, returning the cone to the 'zero' position in the absence of a signal. A significant increase in the effective volume of closed-box loudspeakers can be achieved by filling fibrous materials, usually fiberglass, bonded acetate fibers (BAF) or long wool fibers. An effective volume increase can be up to 40% and is primarily due to a decrease in the speed of sound propagation through fillers compared to air. The enclosures or drivers must have small leaks so that internal and external pressures can equalize over time, to compensate for barometric pressure or altitude; the nature of a porous paper cone, or a seal that is not sealed, is usually sufficient to provide even distribution of this slow pressure.
Infinite baffle
The variation on the 'open baffle' approach is to install the loudspeaker driver in a very large enclosed sphere, providing a minimum 'air spring' loading force to the cone. This minimizes the change in the driver resonance frequency caused by the enclosures. Some unlimited 'cover' have used adjoining spaces, basements, or closets or attics. This often happens with the installation of exotic rotary woofers, as they are intended to go to frequencies lower than 20 Hertz and replace large volumes of air. "Infinite baffle" or simply "IB" is also used as a general term for the enclosed sphere of each size, the name used because of closed cage capabilities to prevent interaction between forward and back radiation of the driver at low frequencies.
In conceptual terms, unlimited baffles are flat baffles that extend infinitely - the so-called "endless plates". An unbounded original baffle can not be built but a very large baffle such as a room's wall can be considered a practical equivalent. An original indefinite loudspeaker has unlimited volume (half space) on each side of the baffle and has no baffle steps. However, the term "unlimited loudspeaker" can be applied to any loudspeaker that behaves (or almost the same) in everything as if the drive unit is installed in the original unlimited baffle. This term is often and wrongly used in a closed sphere that can not exhibit infinite behavior unless their internal volume is much larger than the Thiele/Small Vehicle drive unit. And the front baffle dimensions are ideally some of the wavelengths of the lowest output frequencies. It is important to distinguish between the original unlimited topology and the so-called "unbound sheath" or "IB" that can not meet the original indefinite criteria.The difference becomes important when interpreting the use of the term textbook.
Acoustic suspension
The acoustic suspension or air suspension is a variation of enclosed enclosure, using a box size that exploits almost linear springs so that 30-40 Hz from the box is only one to two cubic feet or more. The "spring" suspension that returns the cone to a neutral position is a combination of a highly suitable woofer (soft) suspension, and air inside the enclosure. At frequencies below the system resonance, the air pressure caused by conical movement is the dominant force. Developed by Edgar Villchur in 1954, this technique was used in the highly successful "bookstick" acoustic research pathway of the 1960s-70s. The principle of acoustic suspension takes advantage of this relatively linear springs. The improved suspension linearity of this type of system is an advantage. For specific drivers, the optimal acoustic suspension cabinet will be smaller than the bass reflex, but the bass reflex cabinet will have a lower -3 dB point. The voltage sensitivity above the tuning frequency remains a function of the driver, and not of the cabinet design.
Isobaric load
The isobaric loudspeaker configuration was first introduced by Harry F. Olson in the early 1950s, and refers to a system in which two or more of the same woofers (bass drivers) operate simultaneously, with a common body of closed air adjacent to one side of each diaphragm. In practical applications, they are most commonly used to improve low-end frequency response without increasing the size of the cabinet, albeit at the expense of cost and weight. Two identical loudspeakers are combined to work together as a unit: they are mounted one behind the other in a casing to determine the air space in between. This "isobaric" space volume is usually chosen to be small enough for convenience reasons. Two simultaneous drivers show the same behavior as one loudspeaker in two cabinets.
Ported_ (or_reflex) _enclosures "> Ported (or reflex) enclosures
Bass-refleks
Also known as a vented (or ported) system, this enclosure has a ventilation or a hole into the cabinet and a port tube affixed to the hole, to increase low frequency output, increase efficiency, or reduce the size of the enclosure. The bass reflex design is used on home stereo speakers (including low-to mid-priced speaker cabinets and expensive hi-fi cabinets), amplifier amplifier speakers, keyboard amplifier cabinets, subwoofer cabinets and PA system speaker cabinets. Ventilated or ported cabinets use cupboard openings or convert and transmit low frequency energy from the back of the speakers to the listener. They deliberately and successfully exploit the Helmholtz resonance. Like enclosed cages, they may be empty, coated, filled or (rarely) filled with dampening material. Frequency of port tuning is cross section function and length. This type of enclosure is very common, and provides sound pressure levels closer to the tuning frequency than the same closed volume enclosure, although it actually has fewer low frequency extensions because the "rolloff" is steeper (24db/ok vs. 12db/oct for enclosed enclosure). Malcolm Hill pioneered the use of this design in the context of live events in the early 1970s.
The design of a ventilated system using computer modeling has been practiced since about 1985, when Thiele and Small researchers first applied the theory of electrical filters systematically to the acoustic behavior of loudspeakers in enclosures. While loudspeaker porting has been produced for many years before computer modeling, achieving optimal performance is a challenge, as it is a tricky amount of special driver properties, enclosures and ports, due to the imperfect understanding of various interactions. This enclosure is sensitive to slight variations in driver characteristics and requires special quality control attention to uniform performance throughout the production process. Bass ports are widely used in subwoofers for PA systems and sound reinforcement systems, inside speaker cabinets and in keyboard speaker cabinets.
Passive Radiator
Passive radiator speakers use a second "passive" driver, or drone, to produce the same low-frequency extension, or increased efficiency, or a reduction in enclosure size, similar to a ported enclosure. Passive drivers are not connected to the amplifier; on the contrary, moves in response to changes in cage pressure. Theoretically, such designs are variations of the bass reflex type, but with the advantage of avoiding relatively small ports or tubes in which air moves, sometimes noisy. Tuning tuning for passive radiators is usually accomplished much faster than with the bass reflex design because such correction can be as simple as the mass adjustment of the drone. The disadvantage is that the passive radiator requires precise construction such as the driver, thus increasing the cost, and having travel limitations.
Compound or band-pass
4th order electric bandpass filters can be simulated with a ventilated box in which the contribution of the driver's cone rear surface is trapped in a sealed box, and radiation from the cone front surface enters the ported chamber. It modifies the driver's resonance. In its simplest form, the compound enclosure has two chambers. The dividing wall between the rooms holds the driver; usually only one ported space.
If the enclosure on each side of the woofer has a port in it then the enclosure generates a 6th order band-pass response. It's much harder to design and tends to be very sensitive to driver characteristics. As with other reflexes, ports can usually be replaced by passive radiators if desired. The eighth order bandpass box is another variation that also has a narrow frequency range. They are often used to achieve a level of sound pressure in which a certain frequency bass tone will be used compared to any music. They are complex to build and must be done very precisely in order to function as expected.
Aperiodic Appendix
This design lies between the acoustic suspension and the bass reflex enclosure. This can be regarded as a leak-covered box or ported box with a large number of port attenuation. By adjusting the ports, and then blocking them appropriately with sufficiently dense fiber loading, it is possible to adjust the port damping as desired. The result is a control of the resonance behavior of the system that increases the reproduction of low frequencies, according to some designers. Dynaco is the main producer of this enclosure for many years, using a design developed by Scandinavian driver makers. The design remains uncommon amongst the commercial designs available today. The reason for this is probably that the addition of damping materials is an inefficient method of increasing attenuation; the same alignment can be achieved simply by selecting the loudspeaker driver with the appropriate parameters and precisely setting the enclosures and ports for the desired response.
Similar techniques have been used in aftermarket car audio; it is called "aperiodic membrane" (AP). Resistive mats are placed in front or right behind the loudspeakers (usually mounted on the rear deck of the car to use the luggage as a cover). The loudspeaker guides are sealed to the mats so that all acoustic output in one direction must pass through the mat. This increases mechanical attenuation, and the resulting decrease in the magnitude of the impedance at resonance is generally a desirable effect, although no perceived or objective benefit to this. Again, this technique reduces efficiency and the same results can be achieved through the selection of drivers with lower Q factors, or even through electronic equalization. This is reinforced by AP membrane suppliers; they are often sold with an electronic processor that, through equalization, restores lost bass output through mechanical damping. The effect of equalization is opposite to the AP membrane, resulting in loss of attenuation and effective response similar to that of loudspeakers without aperiodic membrane and electronic processor.
The dipole shell
A dipole enclosure in its simplest form is a driver located in a flat baffle panel, similar to an older open cabinet design. The baffle edge is sometimes folded backwards to reduce pseudo size, creating a sort of open-backed box. A rectangular cross section is more common than a curved cross section because it is easier to fabricate in folded form than in a circle. Baffle dimensions are usually chosen to obtain a certain low frequency response, with larger dimensions providing lower frequencies before the front and back waves interfere with each other. The dipole enclosure has a "number eight" radiation pattern, which means there is a reduction in sound pressure, or loudness, on its sides compared to front and rear. This is useful if it can be used to prevent the sound from being loud in some places like the others.
Attachment horn
A horn loudspeaker is a horn system that uses horns to match the driver's cone into the air. The horn structure itself does not strengthen, but improves the coupling between the speaker and air driver. Properly designed horns have the effect of making conical speakers transferring more electrical energy in the voice coil into the air; consequently the driver seems to have higher efficiency. Horns can help control dispersions at higher frequencies that are useful in some applications such as sound reinforcement. The mathematical theory of horn coupling is well developed and understood, although its implementation is sometimes difficult. Horns are designed appropriately for small high frequencies (above say 3 kHz or more, several centimeters or inches), those for mid-range frequencies (maybe 300 Hz to 2 kHz) are much larger, maybe 30 to 60 cm (1 or 2 legs)), and for low frequencies (below 300 Hz) is very large, several meters (tens of feet). In the 1950s, some high fidelity fans actually built a full-sized horn whose structure was built into the walls of the house or dungeon. With the coming of stereo (two speakers) and surround sound (four or more), the plain horn becomes more impractical. Various speaker manufacturers have produced folded lower frequency horns that are much smaller (eg, Altec Lansing, JBL, Klipsch, Lowther, Tannoy) and are perfectly fit in practical rooms. This is a compromise, and because they are physically complex, they are expensive.
Many entry horn
Double entry horns (also known as horns coentrant , horns of unity or horn synergy ) are the design of speaker type; it uses several different drivers that are mounted on the horn at a distance being explored from the top of the horn, where high frequency drivers are placed. Depending on the implementation, this design offers an increase in the transient response because each driver is aligned in phase and time and out of the mouth of the same horn. More uniform radiation patterns across the entire frequency range are also possible. A uniform pattern enables the arrangement of multiple seamless attachments.
Tap horn
Both sides of the high-power rider travel long in a horn enclosure flanked ported to the horn itself, with the length of one long and other short lanes. These two paths join in the phase in the mouth of the horn in the desired frequency range. This design is very effective at subwoofer frequencies and offers a reduction in the size of the enclosure along with more output.
Transmission line
The perfect transmission channel sheath has a long unlimited line, filled with absorbent material such that all the rear of the driver's radiation is fully absorbed, down to the lowest frequency. Theoretically, the hole at the far end can be closed or open without performance difference. The density and the materials used for stuffing is very important, because too much stuffing will cause the reflection due to back pressure, while insufficient stuffing will allow the sound to pass through the vents. Filling is often a different material and density, changing as one gets further from the back of the driver's diaphragm.
As a consequence, a practical Transmission Line loudspeaker is not true Transmission Lines, as there is generally output from ventilation at the lowest frequency. They can be considered a waveguide in which the structure shifts the driver's output phase at least 90 °, thereby amplifying the frequency near the driver F s . Transmission lines tend to be larger than ported enclosures of nearly comparable performance, due to the size and length of guidance required (typically 1/4 of the longest wavelength of interest).
The design is often described as non-resonant, and some designs are quite filled with absorbent material which is not much of an output from the channel port. But it is an inherent resonance (usually at 1/4 wavelength) that can improve the bass response in this type of enclosure, albeit with less absorbent stuffing. Among the first examples of this cage design approach were the projects published in Bailey's Wireless World by Bailey in the early 1970s, and the commercial designs of the dead IMF Electronics that received critical acclaim almost the same time.
The variation on the transmission line channel using a pointed tube, with terminus (open/port) has an area smaller than the throat. The oval tubes can be rolled to the lower frequency driver casing to reduce the dimensions of the loudspeaker system, resulting in shells like appearance. Bose uses a similar patented technology in the Wave and Acoustic Waveguide music system.
The numerical simulations by George L. Augspurger and Martin J. King have helped refine the theory and practical design of this system.
Quarter wave loop
A quarter wave resonator is a transmission line tuned to form a standing quarter wave at frequencies below the driver's FS frequency. When properly designed, a port that is much smaller in diameter than the main pipe located at the end of the pipe then generates backward radiation of the driver in phase with the speaker driver itself; greatly increase bass output. Such designs tend to be less dominant in certain bass frequencies than the more common bass reflex designs and such design followers claim the advantage in bass clarity with better suitability of the fundamental frequency to the tone.
Some loudspeaker designers such as Martin J. King and BjÃÆ'¸rn Johannessen consider the term "quarter wave" as a more fitting term for most transmission lines and because of the acoustics, a quarter wavelength produces standing waves inside the enclosure used to produce the bass response originated from the port. This design can be regarded as a massively charged transmission line design or bass reflex design, as well as a quarter wave scope. The quarter wave resonators have seen a resurgence as a commercial application with the onset of neodymium drivers that allow this design to produce relatively low bass sound in relatively small speakers.
A quarter tapered wave pipe
The tapered quarter-wave pipe (TQWP) pipeline is an example of a combination of transmission lines and horn effects. This is greatly appreciated by some speaker designers. The concept is that the sound emitted from the back of the loudspeaker loudspeaker is increasingly reflected and absorbed along the tube windings, almost completely preventing the reflected sound internally transmitted through the loudspeaker cone. The bottom of the pipe acts as a horn while the top can be visualized as an extended compression chamber. The entire pipe can also be seen as a tapered transmission channel in reverse form. (The tapered, confusing traditional transmission line is also sometimes referred to as TQWP, having a smaller mouth area than the throat area.) The relatively low adoption of commercial speakers can largely be attributed to the resulting dimensions of the generated speakers and the large cost. making rigid oval tubes. TQWP is also known as Voigt pipe and was introduced in 1934 by Paul G. A. H. Voigt, original designer of Lowther drivers.
See also
- Audio crossover
- Speaker complete
- Tweeter
- Super tweeter
- Midrange loudspeakers
- Woofer
- Subwoofer
- Acoustic transmission line
- The guitar speaker cabinet
- Supported speakers
- Soundbar
- Scrolling speakers
Note
External links
- How to Work Holes-in-the-Box - information about bass reflexes.
- Quarter-Wave - details about the design of the transmission line
- Humble Homemade Hifi - DIY site with examples & amp; plan some types of speaker enclosures
- Free Speaker Plan - Design of a community-oriented DIY loudspeaker plan, common resources, and forums.
Source of the article : Wikipedia
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