Sewing machine

Pincushion: small firm cushion, which holds pins. This improves the bass response of the system. It is usually made of steel, and is formed by drawing out a thin wire, sharpening the tip, and adding a head. These incorporate a small hole, (called a port), in the speaker cabinet to allow the low frequencies generated by the rear of the woofer cone to escape from the cabinet in phase with that radiated from the front of the cone. Pin: a device used for fastening objects or material together. Many multi driver systems use a bass reflex, or ported, design. Thread: Fine cord of natural or synthetic material with two or more elements twisted together and used for stitching. 'Multi driver' refers to any speaker system that contains two or more separate drive units, including woofers, midranges, tweeters, and sometimes horns or supertweeters.

Pinking shears: Used to cut fabric, leaving a zig-zag edge that resists unraveling. Home cinema systems generally include multi-driver systems. Handwheel: controls movement of presser foot. Despite its name, however, the unit is really a wireless receiver, amplifier and loudspeaker in a single box. Sewing gauge: A useful ruler used to measure the size of a stitch, or the distance between a sewing machine needle and the needle plate. So-called wireless loudspeakers are becoming popular in many applications, such as home theater, due to their convenience, removing the need to run speaker wire. Helps measure seams, button hole openings. See also: Home theater in a box.

Seam gauge: A useful ruler with a sliding marker. It is important to note that the sound channels offered to the speakers may be original individual channels (normal 5.1) or they may decode additional channels from the surround channels (This distribution can be accomplished by a Dolby Digital EX decoder, a THX Surround EX decoder) or they may be simulated (where the two surround channels are spread to center rear or twin rear speakers. There are three different feeding systems for footwear sewing machine. They include :. Feed system: Some times for different operations you need to have different feeding systems or the same feeding systems with different kinds of parts that are involved in the feeding system. There are various different speaker set-ups for home cinema speaker systems. Needle plate: The needle plate must be in perfect condition to stop the thread catching in the needle hole. See also sound reproduction, electronics.

Presser foot: There are three main types for presser feet to fit most sewing machines — screw-on or snap-on low shank. See AudioSpotlights.com for more information. If your machine will not pick up the bottom thread or skips stitches badly, in most cases it's because the needle is in wrong. There are currently two devices available on the market that use ultrasound to create an audible "beam" of sound: the Audio Spotlight and Hypersonic Sound. Needle: The only problem can be that the needle was put in backwards. Pompei. Bobbin case: Unit holding bobbin in a sewing machine. The technology, termed the Audio Spotlight, was first made commercially available in 2000 by Holosonics, a company founded by Dr.

Regardless of where you wind the bobbin, inside the machine, on the top of the handwheel or on the front side near the hand wheel, the basic bobbin rules apply. Joseph Pompei of the Massachusetts Institute of Technology in 1998 (105th AES Conv, Preprint 4853, 1998) fully described a working device that reduced audible distortion essentially to that of a traditional loudspeaker. Bobbin: The most probable cause of the lower thread breaking is an improperly wound bobbin. F. Related terminology. These problems went unsolved until a paper published by Dr. Fold the top and put pins in them. This technology was originally developed by the US (and Russian) Navy for underwater sonar in the mid-1960s, and was briefly investigated by Japanese researchers in the early 1980s, but these efforts were abandoned due to extremely poor sound quality (high distortion) and substantial system cost.

Remove the pins and put more pins in the top and bottom. Anyone or anything that disrupts the path of the beam will disturb the dispersion of the signal, and there are limitations, both to the frequency response and to the dispersion pattern of such devices. Put a pin in each of the four corners and cut out a square. There are some criticisms of this approach. You also need to cut out the pocket. This effect cannot be achieved with conventional loudspeakers, because sound at audible frequencies cannot be focused into such a narrow beam. Cut on the lines. A listener outside the beam hears nothing.

Some other things you need to do to sew are cut out the fabric. The practical effect of this technology is that a beam of sound can be projected over a long distance to be heard only in a small, well-defined area. Slide the scissors under the presser foot and you are ready to sew. The air within the beam behaves in a nonlinear way and demodulates the ultrasound, resulting in sound that is audible only along the path of the beam, or that appears to radiate from any surface that the beam strikes. Then you take the bobbin thread and put it under the presser foot by the thread. The ultrasound is modulated-- it consists of an audible signal mixed with an ultrasonic frequency. Then you take the bobbin out of the extension table, open up the needle plate, and place the bobbin in it and put the needle plate back on. A transducer can be made to project a narrow beam of ultrasound that is powerful enough, (100 to 110 dBSPL) to change the speed of sound in the air that it passes through.

Then you put it under the presser foot and back around. Some speakers are electrostatically driven rather than via the usual electromechanical voice coil, thereby giving a more linear response; the disadvantage, however, is that the signal must be converted to a very high voltage and low current, which can be problematic for reliability and maintenance as they attract dust, and develop a tendency to arc, particularly where the dust provides a partial path; the point where the arc occurs often becomes more prone to arcing, as carbon builds up from the burned dust. Take the thread and carefully put it into the hole in the needle. A newer implementation of the Flat Panel involves the panel and an "exciter", such as the NXT technology. Put the thread through the faceplate and guide it down by the needle. Flat panel loudspeaker designs also work well as electrostatic loudspeakers. Put the thread in the head and put the spool cap on top of the thread. An advantage of flat panel speakers is that the sound is perceived as being of uniform intensity over a wide range of distances from the speaker.

To thread the sewing machine first you need to get out the thread. Some progress has been made using such rigid yet damped material as styrofoam, and there have been several flat panel systems demonstrated in recent years. Threading the sewing machine. There are two, related problems with flat panel technology; firstly, that the flat panel is more flexible than the cone shape and therefore fails to move as a solid unit, and secondly that resonances in the panels are difficult to control, leading to considerable distortion in the reproduced sound. If both threads break together and take more force to break, it means that the tensions are balanced. These can then be either made in a neutral colour and hung on walls where they will be less noticeable, or can be deliberately painted with patterns in which case they can function decoratively. If the broken thread is the color of the bobbin thread, the upper tension is too loose. One such attempt is the development of flat panels to act as sound sources.

If the broken thread is the color of the thread in the needle, it means that the upper tension is too tight. There have also been many attempts to reduce the size of loudspeakers, or alternatively to make them less obvious. Space the hands about 3 inches apart and pull with an even, quick force until one thread breaks. In electronic digital to analog conversion, this is addressed by the use of Low-pass filters to eliminate the spurious upper frequencies produced; however, this approach cannot be used to solve the problem with this digital loudspeaker, since it is the last link in the audio chain. Grasp the bias line of stitching between the thumb and the index finger. Even accounting for the vastly lower efficiency of speaker drivers at such high frequencies, the result was to generate an unacceptably high level of ultrasonics accompanying the desired output. Take a small scrap of the fabric, fold it, and stitch a line ON THE BIAS of the fabric, using different colors of thread in the bobbin and on top. Secondly, since this system is converting digital signal to analog, 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.

To determine whether the upper tension is too tight or too loose for the fabric in use, try the following test. For example, a 16 bit system to be compatible with the 16 bit audio CD standard, starting with a reasonable 2 square inch driver for the least significant bit, would require a total area for the drivers of over 900 square feet. The higher pitch is the lengthwise grain, the lower pitch is the crosswise grain. There are two problems with this design which led to its being abandoned as hopelessly impractical, however; firstly, a quick calculation shows that for a reasonable number of bits required for reasonable sound reproduction quality, the size of the system becomes very large. You will notice a difference in the pitch of the sound. The next least significant bit drives a speaker of twice this area, and so on. Now repeat in the other direction. The next least significant bit drives a speaker of twice the area (most often, but not necessarily, a ring around the previous driver), again to either full amplitude, or off.

Listen to the pitch of that sound. (This allows for high efficiency in the amplifier, which at any time is either passing zero current, or required to drop the voltage by zero volts, therefore theoretically dissipating zero watts at all times). It will make a sound. The design of these is disarmingly simple; the least significant bit drives a tiny speaker driver, of whatever physical design seems appropriate; a value of "1" causes this driver to be driven full amplitude, a value of "0" causes it to be completely shut off. Pull the fabric taut. Actual digital speaker driver technology not only exists, but is quite mature, having been experimented with extensively by Bell Labs as far back as the 1920s. Place one edge of the fabric in each hand with some slack in the fabric. Unfortunately, the recent marketing of plasma displays as high-end television sets and computer monitors has caused the "me-too" labeling of many speakers as "plasma" which have nothing whatsoever to do with plasma [8], much as the advent of digital audio caused the marketing of a large number of "digital" headphones and speakers, when all drive-units are analog in nature.

Determining thread tension. A lower-priced variation on this theme is the use of a flame for the driver [7], flames being commonly electrically charged. Some heavy-duty industrial sewing machines use air cooling to keep the needle from overheating and burning through the thread, especially when sewing multiple layers of canvas or leather. As might be guessed, problems of maintenance and reliability for this design tend to make it very unsuitable for the mass market; the plasma is generated from a tank of helium which must be periodically refilled, for instance. Others have a very long reach — a yard (metre) or more — for sewing wide fabrics, such as tents or sails. 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. Machines have been designed with a very deep reach for sewing at the bottom of a boot shaft. The most exotic speaker design is undoubtedly the plasma arc loudspeaker, using electrical plasma as a driver [5], once commercially sold as the Ionovac [6].

Shoes, gloves, hats, books, upholstery, hosiery, tents, awnings, flags, and sails are sewn on specially devised machines. Piezos have several advantages over conventional loudspeakers when applied to such purposes:. Most of these are now made in Asia and the market is becoming more specialized, as fewer families own a sewing machine. Computer speakers and portable radios are common examples. Modern machines are computer-controlled and use stepper motors or sequential cams to achieve very complex patterns. Piezoelectric transducers, frequently used as beepers in watches etc., are often used as tweeters in cheap speaker systems. As more homes gained power, these became more popular and the motor was gradually introduced into the casing. These include piezoelectric, electrostatic, and plasma arc loudspeakers.

At first these were standard machines with a motor strapped on the side. Other technologies can be used to convert the electrical signal into an audio signal. Sewing machines continued being made to roughly the same design, with more lavish decoration appearing until well into the 1900s when the first electric machines started to appear. See more details here. Wilcox & Gibbs commercial sewing machines are still made and used in the 21st century. However, in practice it was found necessary to use a very complex cone made up of various materials at different points along its length, in order to maintain the waveform traveling evenly. In partnership with James Wilcox, Gibbs became a principal in Wilcox & Gibbs Sewing Machine Company. This created a very effective omnidirectional radiator (although it suffered the same "planarity" effect as ribbon tweeters for higher-frequency sounds) and eliminated all problems of multiple drivers, such as crossover design, phase anomalies between drivers, etc.

James Edward Allen Gibbs (1829 – 1902), a farmer from Raphine in Rockbridge County, Virginia patented the first chain-stitch single-thread sewing machine on June 2, 1857. As the waves moved down the truncated cone, the effect was to reproduce the omnidirectional soundwave, as with a cylinder that changed diameter. This lasted until 1877 when the last patent expired. This turned normal speaker driver design problems on their head; whereas the normal problem with designing a driver is how to keep the cone as stiff as possible (without adding mass), so that it moved as a unit and did not become subject to traveling waves on its surface, the Ohm drivers were designed so that the entire purpose of the electromagnetic driver was to generate traveling waves that traversed the cone from the electromagnet at the top downwards to the bottom. These four companies pooled their patents, meaning that all the other manufacturers had to obtain a license and pay $15 per machine. The Ohm model "F" speakers invented by Lincoln Walsh feature a single driver mounted vertically as though it were firing downwards into the top of the cabinet, but instead of the normal almost flat cone, having a very-much extended cone entirely exposed at the top of the speaker. In 1856 the Sewing Machine Combination was formed, consisting of Singer, Howe, Wheeler and Wilson, and Grover and Baker. Ribbon tweeters often emit sound that exits the speaker concentrated into a flat plane at the level of the listeners' ears; above and below the plane there is often less treble sound.

Through the 1850s more and more companies were being formed and were trying to sue each other. Ribbon loudspeakers can be very fragile but recently designed planar tweeters have the metal film printed on a strong lightweight material for reinforcement. This had a forward, down, back, and up motion, which drew the cloth through in an even and smooth motion. The advantage of the ribbon loudspeaker is that the ribbon has very little mass; as such, it can accelerate very quickly, yielding good high-frequency response (although its shape is far from ideal). Wilson also invented the four-motion feed mechanism; this is still seen on every machine today. The electrical signal is applied to the ribbon which vibrates creating the sound. This was far quieter and smoother than the other methods and the Wheeler and Wilson Company produced more machines in 1850s and 1860s than any other manufacturer. The ribbon loudspeaker consists of a thin metal-film ribbon suspended between two magnets.

He went into partnership with Nathaniel Wheeler to produce a machine with a rotary hook instead of a shuttle. The stiffness moves self resonances upward in frequency. Wilson decided to change tack and try a new method. The dome is used because it is an easily manufactured stiff structure - as anyone who has attempted to crush an egg the long way can attest to. However, John Bradshaw had patented a similar device and was threatening to sue. Perhaps contrary to intuition, making the moving component in the form of a dome rather than an inverted cone does not help to direct sound evenly in all directions. Allen Wilson had developed a reciprocating shuttle, which was an improvement over Singer's and Howe's. Because the wavelength of high-frequency sound is short (approximately 15 mm at 20 kHz), tweeters must have a physically small moving component or they will create a "beam" of sound rather than sending sound omnidirectionally (as is usually desired).

Meanwhile Mr. This design is typically used for tweeters and sometimes for mid-range speakers. Singer then entered a joint partnership with a lawyer named Edward Clark, and they formed the first hire purchase scheme to allow people to afford their machines. For high frequencies, a variation on the common dynamic loudspeaker design uses a small dome as the moving part instead of an inverted cone. Singer then took out a license under Howe's patent and paid him $15 per machine. Amar Bose of MIT spent many years trying to reproduce this spherical wavefront by constructing a one-eighth sphere covered in small drivers that would be situated in the corner of a room, thus mimicking one-eighth of a spherical wavefront emanating from that corner; in practice this idea never became workable, but Bose's experience with combining multiple small drivers in one loudspeaker cabinet gave rise to the popular Bose speakers which use multiple four-inch drivers, either to direct sound rearwards to reflect it from a wall behind the speakers, for home use, or to provide high power capacity when aimed directly at the listeners, for professional use. Howe won and Singer was forced to pay a lump sum for all machines already produced. Several approaches have attempted to remedy this by approximating the sphere.

When Howe learned of Singer's machine he took him to court. A point source or a sphere that varies in size with the amplitude of the desired pressure wave would avoid this problem of beam-formation but is generally physically impossible or impractical. He was granted an American Patent in 1851 and it was suggested he patent the foot pedal (or treadle) used to power some of his machines, however it had been in use for too long for a patent to be issued. This is especially a problem for high frequencies where the loudspeaker may be physically large compared to the wavelength of the sound being reproduced. This machine combined elements of Thimonnier's, Hunt's and Howe's machines. One problem with loudspeakers is that the essentially-planar form of most loudspeakers creates a soundwave that is somewhat directional, that is, the intensity of the sound produced varies depending on the listener's angle relative to the central axis of the speaker. It had a fixed arm to hold the needle and included a basic tensioning system. are mainly due to advantageous interactions with a particular speaker-room combination.

His machine used a flying shuttle instead of a rotary one; the needle was mounted vertically and included a presser foot to hold the cloth in place. It has been theorized by some of the audiophile world that the perceived differences in sound between amplifier/loudspeaker combinations are in fact only differences in their interaction with their environment, rather than absolute differences in sound quality; and similarly, that any perceived differences in speaker cables, past a minimum set of specifications regarding resistance, inductance, capacitance, etc. He thought it to be clumsy and promptly set out to design a better one. This interaction affects the speaker's electromechanical behavior and thus the load it represents to the amplifier, making it difficult to predict the sound a given system will produce in its intended environment without listening tests. Trained as an engineer, he saw a rotary sewing machine being repaired in a Boston shop. A complication is the interaction of the speaker with the listening environment. Isaac Merritt Singer has become synonymous with the sewing machine. and optionally,.

He eventually won his case in 1854 and was awarded the right to claim royalties from the manufacturers using ideas covered in his patent. Speaker specifications generally include:. After a lengthy stint in England trying to attract interest for his machine he returned to America to find various people infringing his patent. In general a higher quality speaker will have a higher sensitivity rating, larger and or heavier magnet, and a higher X_max. The major improvement he made was to put a groove in the needle running away from the point, starting from the eye. As shown in this example, sometimes the speaker with the lower sensitivity rating outputs a far higher amount of acoustic watt output. Elias Howe patented his machine in 1846, using a similar method to Hunt's, except the fabric was held vertically. However at full power may achieve 160+ decibels at 20% to 40% "true" efficiency.

Hunt grew bored with his machine and sold it without bothering to patent it. 80 to 86 dB/(W·m) (sensitivity efficiency of 0.01%). The feed let the machine down, requiring the machine to be stopped frequently to set up again. A few top of the line woofers have a very low "sensitivity" rating i.e. The shuttle passed through the loop, interlocking the thread. A higher X_max indicates that the driver can move a larger volume of air as power increases. The curved needle moved through the fabric horizontally, leaving the loop as it withdrew. In closed or small environments (such as cars or bedrooms) it is far more important to have a speaker with a high X_max (cone eXcursion maximum) as opposed to high (dB/(W·m)) rating.

His machine used an eye-pointed needle (with the eye and the point on the same end) carrying the upper thread, and a shuttle carrying the lower thread. above 140 decibels. Although the credit for the lock stitch machine is generally given to Elias Howe, Walter Hunt first developed it over ten years before in 1834. The ratio of the sound output to the mass of the cone/coil combination grows significantly at high sound pressure levels i.e. A lock stitch is created by two separate threads interlocking through the two layers of fabric, resulting in a stitch, which looks the same from both sides of the fabric. This is partly due to a very high magnetic field and partly to a high amplitude displacement (speaker cone pumping in and out). A stitch more suited to machine production was needed and it was found in the lock stitch. Current state-of-the-art loudspeakers can approach efficiencies of 70% or higher.

The chain stitch has one major drawback: It is very weak, and the stitch can easily be pulled apart. True or absolute efficiency is the ratio of "desired" output power divided by total input power. Unfortunately, other tailors concerned for their livelihood invaded the factory and smashed the machines. As an example, a simple cheerleader's horn makes more sound output in the direction it is pointed than the cheerleader could by herself, but the horn did not improve or increase the cheerleader's total efficiency. Thimonnier was awarded a French patent in 1830 and 80 of these machines were installed in a factory in Paris to stitch Soldiers clothing. From a technical standpoint "sensitivity" is not the absolute reference of efficiency. The easiest way to describe this is to picture the machine working the wrong way round — the stitch was formed on the top of the cloth, not the bottom as with most other chain stitch machine made since. Large horn loudspeakers that used to be used in cinemas, were very efficient by today's hi-fi speaker standards.

The machine was powered by means of a foot pedal. The better the matching, the higher the efficiency. This formed the chain stitch, which held the cloth together. This is especially difficult at lower frequencies. The needle then carried the thread back through the cloth with the upward motion of its stroke. The main reason for this low efficiency is the difficulty of achieving proper impedance matching between the acoustic impedance of the drive unit and that of the air. Inside the arm was a hook, which partly rotated at each stroke in order to wrap the thread (fed from the bobbin onto the hook) around the needle at each stroke. The remainder is converted to heat.

The cloth was supported on a hollow, horizontal fixed arm, with a hole on the topside, which the needle projected through at the lowest part of its stroke. Only about 1% of the electrical energy put into the speaker is converted to acoustic energy. His machine worked by using a horizontal arm mounted on a vertical reciprocating bar, the needle-bar projected from the end of the horizontal arm. Loudspeakers are very inefficient transducers. He did not try to replicate the human hand stitch, looking instead for a way of finding a stitch, which could be made quickly and easily by machine. This is called the "sensitivity" rating. A French tailor Barthelemy Thimonnier made the next major breakthrough. The efficiency is measured as dB/(W·m)—decibels output for an input of one nominal watt measured at one metre from the loudspeaker usually on the axis of the speaker.

There were various attempts and patents awarded for chain stitch machines of varying types from 1795 – 1830, none of which were used to any degree of success, many of which didn't work correctly at all. The sound pressure level (SPL) that a loudspeaker produces is measured in decibels (dBSPL). Saint's design had the overhead arm for the needle and a form of tensioning system, which was to become a common feature of later machines. In all cases, replacement or full repair of the driver are the only options. Wilson built a replica to the patent's specifications and it had to be heavily modified before the machine would stitch, suggesting that Saint never actually made a machine of his own. The latter two typically happen when the amplifier dumps a large DC current into the speaker - a condition typical of a failing (or failed) amplifier. Newton Wilson. Electrical damage occurs when the voice coil burns out.

Due to several other patents dealing with leather and products to treat leather, the patent was filed under "Glues & Varnishes" and was not discovered until 1873 by Mr. A large DC fed to the woofer may cause twisting or deformation of the voice coil such that it rubs against the pole-pieces or magnet. 1764 was awarded to Thomas Saint, a cabinetmaker of London. In rare cases, a very loud signal may cause the coupling between the parts of the woofer to simply give way. In 1790 British Patent No. Physical damage occurs if the signal causes the woofer's cone displacement to exceed the safe X_mech limits for prolonged periods. The mechanical limitations meant that the thread had to be kept short, needing frequent stops to renew the supply. Woofers will usually take a lot of power before burning out or suffering damage to their moving systems.

This method of recreating the hand sewing method suffered from the problem of the needle going right through the fabric, meaning the full length of the thread had to do so as well. Most woofers (and mid-ranges) can easily take up to 1.5 times or more power than what they are rated for - however this is dependent on the particular driver and the duration of the abuse or overload. This needle was designed to pass through the cloth by a pair of mechanical fingers and grasped on the other side by a second pair. A badly clipping amplifier may also damage the tweeter despite a crossover, since a clipped waveform generates high-frequency harmonics which can contain sufficient power to heat up the tweeter's voice coil. 701 in 1755 for a double pointed needle with an eye at one end. Thus, feeding a low frequency (or a DC) signal to a tweeter even though electrically it may be within the tweeter's specification may cause permanent damage to the tweeter. He was awarded British Patent No. Thus a tweeter rated for 50 W is meant to be used with a 50 W amplifier only if the signals below the tweeter's lower operating frequency are filtered out.

The first known attempt at a mechanical device for sewing was by the German born Charles Fredrick Wiesenthal, who was working in England. Tweeters are usually designed (and rated) keeping in mind that a typical music signal doesn't contain a lot of power or energy at the higher end of the audio spectrum. The following stitch would pass through this first loop whilst creating a loop of its own for the next stitch, this resembled a chain, hence the name. The tweeters are usually the first to go under circumstances of abuse, since they have the lightest voice coil made of thin wire which easily melts if the temperature rises excessively. This was possible because when the needle was pushed partly through fabric and withdrawn, it left a loop of thread. However they do have limits and exceeding them by a large factor almost always causes permanent damage. This was called a crochet in France and could be used to create a form of chain stitch. Loudspeakers are rugged devices and can take some amount of abuse.

This needle was altered to create a fine steel hook, called an aguja in Spain. Some of the issues in speaker design are lobing, phase effects, off axis response and time coherence. Some looked to embroidery, where the needle was used to produce decorative, not joining stitches. Speaker designers will use an anechoic chamber (essentially a room with soundproofing that inhibits any reverberation or echo) to ensure the speaker will perform the way it is intended to. Most early attempts tried to replicate this hand sewing method and were generally a failure. Adjusting a design is done with instruments and with the ear. Before the invention of a usable machine for sewing or dress design, everything was sewn by hand. The nature of speaker design is considered both an art and science.

. The inverse sound waves and external noise cancel each other out and produce near silence. Some have a work feeder that can move along a curved path, while others have a work feeder with a work clamp. The headphones produce the inverse sound waves of the external noise. Some have a work holder frame. A similar effect is used in sound-cancelling headphones. Some machines can create embroidery-type stitches. The second most noticed will be an unsettling feeling.

The fabric shifting mechanism may be a simple work guide or may be pattern-controlled, e.g., Jacquard-type. The most prominent effect to the untrained ear will be a loss of bass response. Some older machine types are chain stitch machines and sergers. This won't cause silence because reflections from surfaces diminish the effect somewhat but resulting in a major loss of sound quality. Most home sewing machines and many industrial machines use a two-thread stitch called the lockstitch. This type of wiring error creates inverse sound waves which cancel out (to a degree) the sound of the other speaker. They include means for gripping, supporting, and conveying the fabric past the sewing needle to form the stitch pattern. In this case, any motion one cone makes will be 180 degrees opposite the other.

Sewing machines can make a great variety of plain or patterned stitches. If both sets of wires for left and right (in a stereo setup) are not connected in phase, the speakers will be out of phase from each other. Sewing machines make a stitch, called a sewing-machine stitch, usually using two threads, although machines exist that stitch using one, three, four or more threads. All speakers have two wires that must connected from the source of the signal (the amplifier or receiver) to the speaker's input terminals in correct polarity, or phase. A sewing machine is a mechanical (or electromechanical) device that joins fabrics with thread. The Tapered Quarter Wave Pipe (TQWP) is an example of a combination of transmission line and horn effects. This compromise is extremely attractive and used 90 percent of the time in bass horns.

This reduces the theoretical output by 3, but it is still maybe 5 times the output of a simple speaker in a box (no horn). This means instead of using the perfect large size length of say 10ft, they cut it off at a length of say 3.3ft. To minimize the size, some bass horns are designed as a "modified" or "cut" horn. Despite this, they are used about 70 to 90 percent of the time in large stadiums or arenas.

Designs that use horn woofers occupy a large space, and are heavy. Some low frequency horns employ a folded horn design to conserve space. For the bass or low-frequency region the size of the horn becomes exceedingly large and impractical (3ft x 2ft x 2ft, for example). This type has a very high efficiency and reasonably small size for reproducing mid to high frequencies.

A horn (like a cheerleader horn) is an enclosure which has a flare or cone shaped structure attached to the front of the driver (speaker). The baffle dimensions are chosen to get the desired response, with larger dimensions giving a lower frequency before the front and rear waves combine and cancel. A rectangular cross-section is more common than a circular one since it is much easier to fabricate in folded form than a circular cross-section. The baffle may be folded in order to conserve space.

A dipole enclosure in its simplest form is a driver located on a flat baffle. [4]. The payoff is an extended low end response and a characteristic sound that's appealing to many. Transmission lines tend to be larger than the other systems, due to the size and length of the line required by the design.

The transmission line system is a waveguide system in which the guide reverses the phase of the driver's rear output, thereby reinforcing the frequencies near the driver's F_s. PR's do add considerable cost to the system, however. Due to the lack of vent turbulence and vent pipe resonances, many prefer the sound of PR's to reflex ports. Passive radiators add a complication to vented systems which causes a notch in frequency response at the PR's free air resonant frequency and this causes a steeper rolloff below the drone's tuning frequency Fb and poorer transient response than standard vented loudspeakers.

Passive radiators are tuned by their mass (Mmp) and the way their compliance interacts with the compliance of the air in the box. They are also used to eliminate port turbulence and reduce power compression caused by high velocity airflow in ports. Passive radiators are used primarily to tune small volumes to low frequencies, where a port would need to be very long. Sometimes a passive radiator (PR) or drone, similar to a speaker driver but without an electrically activated voice coil, is used instead of a reflex port.

This enclosure is considerably harder to design and tends to be driver-specific. If the enclosure on each side of the woofer has a port in it then the enclosure yields a 6^th order band-pass response. The dividing wall between the chambers has the driver mounted on it and the panel opposite to it (or the chamber into which the driver faces) has a port. In its simplest form it has two chambers.

A 4^th order bandpass is really just the same as a vented box where the contribution from the driver is trapped in a sealed box which modifies the resonance of the driver. This enclosure is the most common as it lends itself to small size and reasonable bass. Reflex ports are tuned by amount of mass within the vent, using appropriate diameter and length to reach this point. The interior of such enclosures are also often lined with fiberglass matting for absorption.

Other types of enclosures attempt to improve the low frequency response or overall efficiency of the loudspeaker by using various combinations of reflex ports or passive radiating elements to transmit the energy from the rear of the speaker to the listener; these enclosures may also be referred to as vented/ported enclosures, bass reflex, transmission lines (see below). The drawback of these speakers is their low efficiency, due to the loss of the power absorbed inside the cabinet. In this case, the true suspension of the driver's cone is the air trapped inside the box which acts as a spring with very close to ideal behavior rather than the mechanical suspension of the speaker driver, which for this application must be very weak, just strong enough to keep the cone centered in the absence of any signal. The box is typically designed with a very small rate of leakage so that internal and external pressures can slowly equilibrate over time, allowing the speaker to adjust to changes in barometric pressure or altitude.

The closed-box or 'acoustic suspension' enclosure, rather than using a large box to avoid the effect of the internal air pressure, uses a smaller, tightly sealed box. The box is usually filled loosely with foam, pillow stuffing, fiberglass, or other wadding, converting the speaker's thermodynamic properties from adiabatic to isothermal, and giving the effect of a larger cabinet. The box must be large enough that the internal pressure caused when the driver cone moves backwards into the cabinet does not rise high enough to affect this. The designer trades off bass response for flatness; the larger the resonant peak in the bass, the lower the speaker will seem to reproduce, but the more over-emphasized the resonant frequency will be.

The loudspeaker driver's mass and compliance, i.e. the stiffness of the suspension of the cone, determines the resonant frequency and damping properties of the system, which affect the low-frequency response of the speaker; the response falls off very sharply below the cabinet resonant frequency (Fcb). A variation on the 'open baffle' is to place the loudspeaker in a very large sealed box. The most common enclosure types are listed below. For the purposes of this type of analysis, each enclosure has a loudspeaker topology.

Enclosures used for woofer and subwoofer are applications that can be adequately modelled in the low frequency range (approximately 100–200 Hz and below) using acoustics and the lumped component model. The Acoustic Center of the driver, or physical position of each driver's voice coil, dictates the amount of rearward offset to time-align the drivers. Sometimes the differences in reaction time of the different size drivers is addressed by setting the smaller drivers further back, by leaning or stepping the front baffle, so that the resulting wavefront from all drivers is coherent when it reaches the listener. Diffraction problems are addressed in the shape of the enclosure; avoiding sharp corners on the front of the enclosure for instance.

Home experimenters have designed speakers built from concrete sewer pipes for similar reasons. The speaker manufacturer Wharfedale has addressed the problem of cabinet resonance by using two layers of wood with the space between filled with sand. Problems with resonance are usually reduced by increasing enclosure rigidity, added internal damping and increasing the enclosure mass. Enclosures play a significant role in the sound production, adding resonances, diffraction, and other unwanted effects.

However, for many purposes this is impractical and the enclosures must use other techniques to maximize the output of the loudspeaker (called loading). An 'open baffle' loudspeaker is an approximation to this - the transducer is mounted on a simple board of size comparable to the lowest wavelength to be reproduced. Thus the rear soundwaves cannot cancel the front soundwaves. The ideal mount for a loudspeaker would be a flat board of infinite size with infinite space behind it.

The major role of the enclosure is to prevent the out-of-phase sound waves from the rear of the speaker combining with the positive phase sound waves from the front of the speaker, which would result in interference patterns and cancellation causing the efficiency of the speaker to be compromised, particularly in the low frequencies where the wavelengths are large enough that interference will affect the entire listening area. A loudspeaker is commonly mounted in an enclosure (or cabinet). When used with speakers that do not reproduce low frequencies well, a subwoofer will often be configured to reproduce both the LFE channel and all other bass in the system, the latter being referred to as "bass management". This is because most full-range speakers are incapable of delivering the acoustic power required by the LFE in movies or in some cases, music.

When teamed with a modern surround sound receiver and full range speakers, they are typically driven with the specific LFE (low frequency effects) output channel (the ".1" in 5.1, 6.1, or 7.1 specifications) provided by the receiver. Amplified subwoofers frequently accept both speaker-level and line-level audio signals. Extended periods of high volume bass can cause items throughout a room to "walk" on a flat surface until they fall off. A subwoofer's powerful bass can often cause items in the room or even the structure of the room itself to vibrate or buzz.

Placing it in the corner of a room may produce louder bass sounds. It can instead be hidden out of sight. For the same reason, the subwoofer does not need a special placement in the sound field (for example, centered between the Left Front and Right Front speakers). Because of this phenomenon, it is usually satisfactory to provide just a single subwoofer no matter how many individual channels are being used for the full-spectrum sound.

Localization starts to happen above the 150 Hz point. The very long wavelength of the very low frequency bass sounds reproduced by the subwoofer usually makes it impossible for the listener to localize the source of these sounds. Subwoofers often contain integrated power amplifiers that may incorporate sophisticated feedback mechanisms to assure the least distortion of the reproduced bass acoustic waveform. Because the range of frequencies that must be reproduced is quite limited, the design of the subwoofer is usually quite simple, often consisting of a single, large, down-firing woofer enclosed in a cubical "bass-reflex" cabinet.

A typical subwoofer only reproduces sounds below 120 Hz (although some subwoofers allow a choice of the cross-over frequency). This speaker (and its enclosure) is referred to as a subwoofer. Modern speaker systems often include a single speaker dedicated to reproducing the very lowest bass frequencies. A subwoofer driver is a woofer optimised for the lowest range of the audio spectrum.

A whizzer is a small, light cone attached to the woofer's apex around the dust cap. These employ an additional cone called a whizzer to extend the high frequency response. A full-range speaker is designed to have as wide a frequency response as possible. A tweeter is a loudpeaker which is capable of reproducing the higher end of the audio spectrum, usually from about 1 kHz to 20 or perhaps 35 kHz.

Mid-ranges typically appear where large (>16 cm or 8") woofers are used for the bass end of the audio spectrum. These are used when the bass driver (or woofer) is incapable of covering the mid audio range. The distinction between woofers and mid-ranges is blurred however since many woofers can operate up to 3 kHz. A mid-range loudspeaker, also known as a squawker is designed to cover the middle of the audio spectrum, typically from about 200 Hz to about 4-5 kHz.

The frequency range varies widely according to design and hence while some woofers can cover the audio band from 50 Hz to 3 kHz, yet others may only work up to 1 kHz. A woofer is a loudspeaker capable of reproducing the bass frequencies. [3]. However a loudspeaker of say, a rated impedance of 8Ω/100W can easily overload an amp designed purely with a resistive load of 8Ω/100W as a target.

A typical amplifier is most usually quoted for a given power into a resistive load. It is a combination of resistive, capacitive, inductive as well as mechanical effects. A dynamic loudspeaker presents a complex load to the amplifier as opposed to a pure resistance. The weight and damping of the cone in a dynamic speaker should be appropriate for the characteristics of the rest of the driver and enclosure in order to produce accurate sound.

Despite marketing claims, lighter and more rigid cones do not always sound better. Tweeters are subject to a unique set of variables and parameters; their design and construction is extremely variable. Generally, larger and more powerful magnets are associated with higher quality speakers. The size and type of magnets can also differ.

Baskets must be designed in order to preserve rigidity and are typically cast or stamped metal, although injection-molded plastic baskets are becoming much more common in recent years. Driver cones may be constructed of a variety of materials, including paper, metal, various polypropylenes, and kevlar. When a multi-frequency signal is applied, the complex vibration results in reproduction of the applied signal as an audio signal. The coil and the permanent magnet interact with magnetic force which causes the coil and a semi-rigid cone (diaphragm) to vibrate and reproduce sound at the frequency of the applied electrical signal.

When an electrical signal is applied, a magnetic field is induced by the electric current in the coil which becomes an electromagnet. The parts are held together by a chassis or basket. A typical suspension system includes the 'spider', which is at the apex of the cone, often of 'concertina' form; and the 'surround', which is at the base of the cone. In addition to the magnet, voice coil, and cone, dynamic speakers usually also include a suspension system to provide lateral stability and make the speaker components return to a neutral point after moving.

One magnetic pole is outside the coil, whilst the other is inside the voice coil. The gap is also where the magnetic field is concentrated. The coil is oriented coaxially inside the gap made with a permanent magnet. A "gap" is a small circular hole, slot or groove which allows the voice coil and cone to move back and forth.

The traditional design is a semi-rigid paper fibre cone and a coil of fine wire (usually copper), called the voice coil attached to the apex of the cone. Additional improvements to loudspeaker technology occurred in the 1970s, with the introduction of higher temperature adhesives, improved permanent magnet materials, and improved thermal management. Polypropylene and aluminium are also used as diaphragm materials. For Example, Paper cones (or doped paper cones, where the paper is treated with a substance to improve its performance) are still in use today, and can provide good performance.

acoustic suspension) and changes in materials used in the actual loudspeaker, led to audible improvements. Developments in cabinet technology (e.g. The quality of loudspeaker systems until the 1950s was, to modern ears, very poor. This winding usually served a dual role, acting also as a choke coil filtering the power supply of the amplifier which the loudspeaker was connected to.

The coil of the electromagnet is called a field coil and is energized by direct current through a second pair of terminals. These first loudspeakers used electromagnets because large, powerful permanent magnets were not freely available at reasonable cost. Voigt produced the first effective full range unit in 1928, and he also developed what may have been the first system designed for the home, although using electromagnets rather than permanent magnets. There is some controversy in that an application was made earlier by the Briton Paul Voigt but not granted until later.

Kellogg. Rice and Edward W. The moving coil principle was patented in 1924 by two Americans, Chester W. [2].

The modern design of moving-coil loudspeaker was established by Oliver Lodge in England (1898). This was soon followed by an improved version from Ernst Siemens in Germany and England (1878). Alexander Bell patented the first loudspeaker as part of his telephone in 1876. However, the first documented ^[1] device that might fit this description was created in 1881.

Nikola Tesla is believed to have put electrically charged carbon dust in a cup-shaped device to create the first telephone loudspeaker. . The loudspeaker is the most variable element in an audio system, and is responsible for marked audible differences between systems. The term loudspeaker is used to refer to both the device itself, and a complete system consisting of one or more loudspeaker drivers (as the individual units are often called) in an enclosure.

A loudspeaker, or simply speaker, is an electromechanical transducer which converts an electrical signal into sound. In SDDS, 7.1 is the same as 5.1 but adding center-left and center-right speakers in the front of the listener for better audio positioning. 7.1 channel sound in home theater is identical to 6.1 except that it has left and right rear speakers. 6.1 channel sound is similar to 5.1 but there is an added center rear channel.

This is usually achieved by an amplifier setting of 'large' or 'small' defining the speaker type. This speaker can reproduce the bass frequency from all the main channels or may only do so for those speakers incapable of doing so. A subwoofer (which is counted as ".1" channel because of the narrow frequency band that it reproduces). Left and right surround speakers.

Left, center, and right front speakers. This requires: