|
Arabic
Bengali
Chinese
English
French
German
Hebrew
Hindi
Italian
Japanese
Korean
Malay
Polish
Portuguese
Spanish
Turkish
Ukrainian
Vietnamese|
ENCYCLOPEDIA OF RADIO ELECTRONICS AND ELECTRICAL ENGINEERING Big speakers in small car boxes. Encyclopedia of radio electronics and electrical engineering
Encyclopedia of radio electronics and electrical engineering / Speakers We all are well aware of the important role that the subwoofer plays in the car interior, and we have been aware for quite some time. And not only, by the way, in the automobile. In a normal apartment salon equipped with a home theater, a subwoofer installation plays an equally significant role. And now, in general, everything is mixed up: they put theaters in a car. From this, however, they cease to be home and become mobile, with all the ensuing circumstances, but they do not change their six-channel essence (the sixth channel just staked out the subwoofer).
Meanwhile, the problem of free space in the car has not become less relevant. In this sense, acoustic manufacturers turned out to be well prepared, having taught sub-bass heads to work in small volume cases. Let's try to track how this happened, and at the same time repeat the anatomy of the bass head at the current stage of development. Let's make a reservation right away that in the first (historical) part of this review, we will talk not only about purely car audio things. Many subwoofer technologies came to our car from home or even professional audio, and this fact cannot be ignored. But the second (anatomical) is entirely dedicated to car speakers.
Putting a big woofer into a small box is no big deal. Another question is how to make him perform his immediate duties - to reproduce what is commonly called a deep, clear, well-articulated bass. As we know, during the operation of the speaker in acoustic design, air is compressed inside the case. Under strong pressure, the air tends to break out, and since it fails, it acts like a kind of spring. The smaller the volume of the box, the stiffer the spring, the more reasons for the occurrence of resonances, bass losses, and even the prerequisites for damage to the speaker, which is not adapted to this volume. For the past 50 years, the thought of the best in the audio industry has been to make the woofers fit into smaller cabinets by increasing the cone's stroke. Various methods were used - from the creation of drivers unique at that time with an increased stroke of the moving system to the design of new acoustic designs. In 1954 Acoustic Research introduced the first long throw subwoofer, the AR-1W, which could play in a relatively small enclosed volume. At the same time, its lower limiting frequency was 20 Hz - very low for that time (and not bad for ours). The long-throw concept caught on, and a few years later Acoustic Research applied a similar technology to its AR-3 full-range stereo system. I must say that a radical change in the audio industry, including acoustics, came with the advent of stereo recordings in the late 50s. This fateful event was followed by the spread of FM radio, also operating in stereo. Audio was phasing out as a do-it-yourself hobby and slowly evolving from an engineering hobby to an industry with a potentially great future. To play music, now it was required not one speaker, but two, and preferably not very large, so as not to take up half the usable area of a mid-sized apartment. It was just with this that it was tense, since power amplifiers then were not what they are today. The 60-watt Dynaco and McIntosh MC275 (two 75-watt channels) looked like monsters at the time compared to everyone else. Therefore, almost the only option was the huge, but sensitive speakers manufactured by JBL and Altec, in size not much inferior to the acoustic systems from cinemas, in which both companies initially specialized. But, of course, it couldn't go on like this for long. In the early 70s, a talented engineer and mathematician, James Novak from Jensen, figured out how to teach woofers to work properly in a bass reflex. Using the new technology, Jensen produced several compact speakers that were orders of magnitude more efficient than Acoustic Research speakers, but still lacked bass depth. Research in the field of packaging was continued by well-known scientists Thiel and Small, as well as Ashley and Benson. By the way, computer programs for calculating acoustic design are based on their then research. The research has borne fruit, but the main drawbacks of the phase inverter remain. It is known that the bass-reflex housing is an order of magnitude more complicated than a conventional closed box. The main trick here is that in order to reproduce frequencies from the very depths of the bass range, the phoso-reflex tunnel must have a large length and a large diameter. Sometimes, in order to reduce the speed of air passing through the tunnel, its area must be even larger than the volume of the body itself, which, of course, is not the case. Here someone Harry Olsen came to the rescue, who put forward the idea of using a passive radiator instead of a phase inverter port: a diffuser with a suspension, but without a magnetic system. In this case, the mass of the diaphragm had to be equivalent to the mass of air passing through the port in a conventional phase inverter. JBL began producing such radiators back in the late 60s, and it was proposed to adjust them by increasing the mass using special steel rings that were attached to the dust cap. But it was very difficult to translate it into mass production. A closed box is much easier. And the search for the "grail" continued. Cerwin Vega founder Gene Cervinsky (not alone, of course, along with the company's staff) contributed to the development of compact subwoofers with a cone diffuser. He began with the production of professional concert and club monitors, and only 30 years later he made his first home long-throw woofer for the revolutionary Infinity Servo-Static acoustics. The subwoofer in it had a servo-controlled voice coil and its own amplifier, and the broadband speakers were a pair of dipole electrostatic panels. Soon the famous Stroker was released, again first for professionals, then for home use, and then for automotive use. The characteristic features of the "strokers" were elongated voice coils and huge centering washers - all for the benefit of the power, purity and depth of infrasound. And, of course, the Stroker featured heavy-duty, multi-layered foam suspensions that could handle heavy loads. And the workload kept growing. Electro Voice has released homemade 15" and 18" EVX subwoofer drivers with over two inches of travel. True, they did not receive wide distribution at one time: the technologies turned out to be too advanced, in the sense unreasonably expensive. JL Audio was one of those companies that brought the proven manufacturing methods of home and professional subwoofers to the car. These were mighty speakers, with heavy cones and a large moving system. At the same time, they could play in relatively small (for that time) closed volumes. JL Audio was not only engaged in the practical implementation of foreign technologies, but also invented its own. Let's say, all with the same goal of increasing the working stroke of the cone, the company's engineers decided to move the centering washer away from the speaker housing and at the same time radically increase its diameter. Work was also carried out to increase the rigidity and strength of the cones in order to protect the diffuser from high pressure inside the housing. In the mid-80s, Earthquake products were very popular. The design of Californian car woofers was distinguished by powerful suspensions, large centering washers and prefabricated magnets. At the same time, the company abandoned the proven technology for making corrugations from several layers of foam: suspensions began to be made from one thick layer of the same foam, but with better characteristics. In addition, their geometry changed: the height and width increased, which also contributed to an increase in the length of the diffuser stroke. Interestingly, the methods worked out on car speakers were then used in the production of the company's home compact subwoofers. The pioneers of subwoofer construction also include SoundSrtream, which in 1993 made the long-throw SS-10R speaker. It is impossible to pass by the early period of Velodyne's work. In the early 80s, the company made its name with the ULD-18 18" home theater subwoofer with superb performance. Moreover, the speaker worked in an extremely small, for its size, completely closed volume, about half the permissible minimum. And all thanks to the High Gain/Ultra Low Distortion servo control system. It is known that loudspeaker manufacturers liked the idea of using a closed box, largely because, compared to bass-reflex enclosures in a closed volume, the linearity of the speaker is improved. But this is if the volume is adequate to the parameters of the head. If not, then there can be no question of any linearity. In the ULD-18, a special sensor was installed on the voice coil, which monitored the position of the coil and corrected it. Very soon, Velodyne was among the leaders in the industry, and servo control technology was transferred to the company's car speakers. In general, the trend towards an increase in the working stroke of the diffuser and a decrease in the working volume of the housing continues at the present time. Which is reflected in the design of the speakers accordingly. It's time to talk about her. We will move, if you don't mind, from top to bottom. Just in case, we provide the English equivalents. Sealing collar (Gasket) It is clear by definition that the ledge serves for closer contact with the mounting surface. In the early days of subwoofer construction, paper and cork were mainly used as sealing materials. Now the main material is rubber. There are also foam and various plastics. In the classic version of installation - inside the case - it is glued along the upper plane of the rim of the loudspeaker case. The gasket on the bottom edge for mounting the speaker "out" is less common. Sometimes, to make it easier for installers, an extra gasket is included with the speaker. It also happens the other way around: apparently, for design reasons, many manufacturers have recently stopped equipping their products with gaskets, or there is a side as such, but it serves purely decorative purposes. Suspension (Surround) Currently, butyl rubber, polyurethane foam and santoprene are used for the manufacture of suspensions. The first two materials are more common, they have sufficient strength, they cope well with temperature loads. However, each of them has its own advantages. The rubber is softer, hence the low resonant frequency of the subwoofer, but also the large equivalent volume. That is, the dynamics need space to "sing" in full voice. Polyurethane foam - the material is less durable, more than rubber is exposed to temperature and ultraviolet radiation, but more rigid and lighter, and therefore is able to provide, though not radically, but greater linearity of motion, which is important in modern times. The suspension does just that (not one, of course), which monitors the linearity of the cone oscillations and prevents the voice coil from leaving the magnetic gap and colliding with the magnetic circuit. Many modern dinnostroke woofers have rigid corrugations of increased radius and increased height (although it is not a fact that a wide corrugation is a guarantee of a large stroke). Sometimes the suspension has an area almost equal to the area of the diffuser itself. Which, first of all, affects two important parameters: the length of the working stroke (Xmax) of the moving system (increases) and sensitivity (decreases). The latter, as is known, largely depends on the area of the radiating surface of the diffuser. With power delivered to the speaker no longer an issue, there has been a tendency to sacrifice sensitivity in favor of increasing Xmax. Dust Cap Here, too, the main function lies in the name. The dust cap is located in the middle of the cone, on top of the voice coil (often glued to it), and prevents the penetration of foreign particles, in particular dust, into the magnetic gap. These particles can interfere with cone movement and damage the voice coil. If earlier these design details of the subwoofer inevitably had a convex shape, now the tradition is increasingly being violated. There are more and more woofers with flat as well as concave caps or without them at all. There is another extreme: a dust cap (the word "cap" in this case is not suitable) occupies almost the entire radiating surface. The experiments were dictated by the desire of manufacturers to increase the stiffness of the diffuser by any means, which is a particularly important factor when operating at high powers. In addition, it is believed that the concave shape, which continues the geometry of the cone, contributes to the formation of more regular sound waves and reduces non-linear distortion. Although, I must say that in comparison with mid-bass and mid-range in the ultra-low-frequency link, the effect is less noticeable. In terms of materials, dust caps are often made from the same material as the speaker cone. Plastic is also widespread. Diffuser This is where the field for experiments on the part of manufacturers, and the field is already well plowed. Of course, the purpose of the diffuser remains the same and the same for everyone - the piston in its essence, it sets the air in motion and creates sound waves. But in terms of geometry and materials, the solutions can be very different. If dust caps used to be only convex, then the diffusers are only concave, that is, conical - hence the English name cone (cone). Now not everything is so clear. Although conical shapes continue to dominate, a number of companies make the front side of the "piston" in the form of a flat diaphragm to increase the rigidity of the "piston" and reduce non-linear distortion. The other "row" is all for the same, on the contrary, working to increase the curvature of the cone. Both quite often succeed. A couple of years ago, the American Still Water Designs was the first to encroach on the decades-old "round" status quo of car acoustics. This encroachment was expressed in the creation of square low-frequency Kicker Solobaric L7. The company from Oklahoma motivated such "blasphemy" by the desire to increase the area of the radiating surface. She achieved her goal: the increase was 30 percent, which in the first place had a positive effect on the amount of undistorted power that L7 was able to provide. So far, the initiative of Still Water Designs has not found a wide response. According to our information, Power Akoustic also makes square subwoofers, and hexagonal woofers have been produced under the notorious Xtant brand since last year. The rest are looking closely, so it's too early to draw conclusions. As for materials, lately, as a result of an intensive search for a golden compromise between three factors - rigidity, lightness and strength - there have been so many that it hardly makes sense to list everything, but it’s probably worth naming the main ones. Interestingly, the list of leaders still includes cellulose (and not only for cheap models), since, according to established opinion, it is considered a very "musical" material. It is clear that today it is not crossed with anything. Polypropylene is very common - just like that and with various coatings and impregnations (nickel, titanium), which again serve to increase the rigidity of the cone and improve heat dissipation from the voice coil. Not uncommon are composite materials using carbon and fiberglass, as well as three-layer cones with honeycomb cores. Quite, although not as well as paper and polypropylene, aluminum diaphragms, the birth of which was given by Alumapro, took root. Approximately the same degree of prevalence was received by Kevlar (Eton, Focal, Power Acoustik). When the formula of the "golden diffuser" will be derived, we do not undertake to predict. However, judging by the brochures, many manufacturers bring it out every year. Basket
It is also often referred to as the "frame", but in fact it is the speaker housing in which its components are based. It is clear that at the sound pressure levels that modern subwoofers are able to reproduce, increased requirements are placed on the baskets. The main thing is freedom from resonances. Die-cast aluminum frames are said to be less resonant, which is why casting is the primary method of making expensive woofer models. In addition, the basket is, in a sense, the heatsink of the loudspeaker, and aluminum is the champion in terms of heat dissipation. On the other hand, among very thoroughbred subwoofers there are stamped steel baskets coated with a special compound to reduce resonances, and nothing, they do not ring, they work as they should. Sometimes the damping of resonances is facilitated by the shape of the case, the presence of stiffening ribs in the basket. Baskets made of plastic composites have also recently begun to appear. Leading contacts (Terminals) Here, too, uniformity is not observed, however, it can be stated that more and more manufacturers are trying not to save on contacts. Now, even in fairly inexpensive models, there are solid screw terminals, and gilding has become quite a standard coating. An alternative to "screws" are spring clips, which also provide a reliable connection to the amplifier outputs. And, of course, no one forbids (although it does not recommend) using traditional spatulas in subwoofers in order to reduce the cost of the product, but for larger calibers, screw or spring clamps are still preferable. Centering washer (Spider)
In English - spider, that is, a spider. In appearance, it also resembles an eight-legged insect, as well as a product of its activity. The centering washer is traditionally located directly under the cone and is responsible for the linearity of the voice coil, and hence for the linearity of the movements of the entire moving system. This part of the speaker is usually made of cotton, a mixture of cotton and polymer (conex), or Nomex. Sometimes metal tape conductors are woven into the corrugation of the washers, which are designed to increase its strength and durability. Usually, a large centering washer indicates a large mechanical stroke of the diffuser. Distinguish between concave and flat washers. The former are less common, mostly in inexpensive speakers, and the concave shape in this case is used to limit the travel of the voice coil. Much more common in long-throw subwoofers are flat washers with a carefully calculated number and geometry of kinks, which allow for high linearity of the voice coil. As long-throw drivers become popular, progressive corrugation profile washers (with increasing pitch from the center to the periphery), as well as double centering washers, are increasingly used. Cases are known when in subwoofer speakers with an inverted magnetic system, centering washers were placed on the front side of the cone. Voice Coil Perhaps the most important element of a speaker. The voice coil is located in the magnetic gap, attached to the cone of the diffuser and to the centering washer; under the influence of a magnetic field sets them in motion, which ultimately results in the formation of acoustic energy. The voice coil is a wire wound on a frame. The standard diameter is 2 inches. The frame is usually made of materials with good thermal conductivity - aluminum, mylar, fiberglass and kapton. Of great importance for the length of the diffuser stroke and the maximum power supplied from the amplifier is the length of the winding and the gauge of the wire (usually made of copper or aluminum). Another factor that should not be underestimated is the quality of the glue with which the wire is glued to the caracas. The standard voice coil impedance of a car subwoofer is 4 ohms, but as they say, variations are possible. Moreover, in recent years, cases of the production of speakers with two-winding coils have become more frequent. They are usually connected in parallel to maximize the potential of the amplifier. It is clear that as the power increases, so do the temperatures. Therefore, in modern high-power speakers, various tricks are used to ventilate the voice coil: from the end hole in the lower magnetic circuit to complex systems with cooling fins or even air filters. Top magnetic circuit (Top Plate)
Fastened (bolted or glued under pressure) directly to the bottom of the basket. The task of the "top cover" is to direct the magnetic flux into the magnetic gap. This structural component is made of steel, necessarily with a low carbon content, since it reduces the strength of the magnetic field. But this is just not a problem: carbon-free steel is cheaper. Magnet
Most often, a subwoofer speaker is judged by the weight and height of the magnetic system. Which is basically understandable. Especially now, when the desire to force the woofer to play in a cramped cabinet has led to a radical increase in the weight of the moving system and, accordingly, a decrease in sensitivity. The only way to compensate for the large weight of the moving system is to increase the weight of the magnetic system. That is why modern "long-stroke", as a rule, are equipped with heavy magnets of double or even triple height. Recently, prefabricated structures have appeared from several "stacks" of small-sized ferrite beads arranged in a circle: it is believed that in this way it is possible to achieve a greater uniformity of the magnetic field. Ferrite is still the most common material. Recently, however, a number of companies have shown subwoofers with a "front" miniature rare-earth (as in tweeters) magnet, but it's still too early to talk about any trend. Rear magnetic circuit (Back Plate) The "back cover" of the magnetic system, like the front cover, is made of low carbon steel. Almost everywhere in the rear magnetic circuit of modern long-throw subwoofer speakers there is a vent to cool the voice coil. And more often not just a hole, but a well-thought-out ventilation system. Also, for a larger voice coil travel, it is not uncommon to use conical thickenings at the end of the speaker. Publication: 12voltsmagazine.com
Artificial leather for touch emulation
15.04.2024 Petgugu Global cat litter
15.04.2024 The attractiveness of caring men
14.04.2024
▪ Cap of invisibility from ordinary lenses ▪ Firefly Shine Synchronization ▪ Virtual mobile operator Google Project Fi ▪ Android Polaroid Mirrorless Digital Camera
▪ site section Preamplifiers. Article selection ▪ Article Reveler idle. Popular expression ▪ article Why is a fake called a linden? Detailed answer ▪ article Forwarder. Job description ▪ article Active TV signal splitter. Encyclopedia of radio electronics and electrical engineering
Comments on the article: Andrew What za modeli dinamika tot s 3 magnitami takoi tipo litaia aliuminevaia rama?
Home page | Library | Articles | Website map | Site Reviews
www.diagram.com.ua |
See other articles Section 
Latest news of science and technology, new electronics:
All languages of this page