Subwoofer

These claims are scientifically disputed and unresolved as of yet. fuel efficiency). They further claim that Kicker's square design puts too much stress on the corners of the cones. Raising overall pressure ratio tends to improve specific fuel consumption (i.e. Sony claims that its pentagon shape reduces standing waves on the surface of the cone as well as improves the overall strength of the cone structure, reducing "cone flex". Either way, raising core flow increases core power and, thereby, the net thrust or shaftpower of the engine. The intent of the triangular design does not seem to be motivated by sound quality or intensity, but rather to encourage creativity in installation and provide flexibility for otherwise awkward positions. Core flow will increase if the original compressor outlet (corrected) flow size is maintained.

However, a triangular design decreases the surface area of the woofer cone relative to a circular or square design in an enclosure of the same size. Supercharging can also be achieved by improving the aerodynamics of the existing blading. The increased surface area translates into moving more air and higher sound pressure levels. If the fan flow is not increased, the bypass ratio will decrease. In enclosures of the same size, it is possible to achieve more subwoofer cone surface area with a square design than a circular design. Pratt & Whitney PW4000) have gained core flow by adding one or more stages to the front of the gas generator, usually in the LP (or IP) compressor. The intent of a square subwoofer is to increase the surface area of the woofer's cone. Many of the large turbofan engine series (e.g.

However, they can be useful in creating unique 'looks' in a car audio system that is meant to be seen as much as heard, and to create brand distinction and recognition. Converting a turbojet into a turbofan, by adding a fan spool, also supercharges the compression system, thereby raising core flow. There is no known auditory advantage to these shapes. If stress considerations prevent any shaft speed increase, there is only a modest increase in airflow. Other companies, such as Sony, have jumped on the bandwagon, producing non-round subwoofers of their own. non-dimensional) speed of original compressor should be maintained, by raising the mechanical shaft speed by a factor √(Tstage1new/Tstage1old). Xtant has introduced a hexagonal subwoofer. Ideally, the corrected (i.e.

Bazooka has introduced a triangular subwoofer. zero) stage to a compressor will not only increase the overall pressure ratio of the cycle, but induce more airflow into the unit, by supercharging the entry plane of the original compressor. Stillwater Designs, nicknamed Kicker, released a square subwoofer several years ago, the Solo-Baric series, and recently, the Solo X. For example, adding an additional (i.e. Within the last few years, the car audio field has seen a variety of subwoofers utilizing non-round shapes. Supercharging is not confined to superchargers - jet engines rely on supercharging as one of the main routes to thrust growth and improved fuel efficiency. Some waterproof models work underwater, or placed on the underside of a deck, to create sound. It is also possible to drive the blower from the crank shaft and use an exhaust turbine for output power.

They can be placed on a large flat surface create a large, though poor, loudspeaker. It also tends to run less hot. These devices typically don't provide as much vibration per dollar as simply placing a reasonably priced subwoofer against the back of the furniture, so at their current prices are most useful for not disturbing anyone than vibrating to audio. This is important in dragsters and small sports cars. However, some feel that the vibrations are a little disembodied from the rest of the auditory experience. The main advantage of an engine with a mechanically driven supercharger is better throttle response. These have recently emerged as a device, called a tactile transducer by at least one brand, that attaches to furniture, such as one's seat, via which vibrations are transmitted to the body; they can be connected to an amplifier as per a normal loudspeaker. For this reason, both the economy and the power of a turbocharged engine are usually better.

Since much bass is felt, sub-bass can be augmented using tactile transducers. The thermal efficiency, or fraction of the fuel/air energy that is converted to output power, is less with a mechanically driven supercharger than with a turbocharger, because the energy of the exhaust pressure is lost. Indeed, hearing loss is one concern, alongside space considerations and neighbour relations. This lag can be addressed by reducing the size of each individual unit such that the combined output is still as great as a single large turbocharger without having to suffer the lag-time required to reach operating speed. Such "SPL wars" have drawn much attention to subwoofers in general, but subjective competitions of sound quality ("SQ") has not gained similar popularity. This gives a large power increase for a given engine speed at the cost of increasing the lag-time for the exhaust to heat up sufficiently to drive the turbochargers. Naturally, these sound levels are not safe for humans. An alternative arrangement utilizes two turbochargers of the same type, known as a "twin turbo".

In international car stereo competitions, over 100 subwoofers driven by some 100,000 watts have been used to generate over 180 decibels. This gives the opportunity of fitting multiple turbochargers to a single engine, such as in a "sequential turbo", where one turbo is tuned to give increased performance at low engine speed and another turbo is tuned to increase the high-speed engine performance. Curiously, some car stereo enthusiasts seem intent on producing ultra-high sound pressure levels in the confines of their vehicle's cabin. The physical space occupied by a turbocharger is significantly less than its direct-drive counterpart. Typically, subwoofers are installed in the trunk. The size of the piping alone is a serious issue; consider that the Vought F4U and Republic P-47 used the same engine but the huge barrel-like fuselage of the latter was, in part, needed to hold the piping to and from the turbocharger in the rear of the plane. The automobile is ideal for the "hidden" subwoofer approach due to space limitations of locations such as doors (ignoring the acoustic problems of a car interior). Yet the vast majority of WWII engines used superchargers, because they maintained three significant manufacturing advantages over turbochargers, which were larger, involved extra piping, and required exotic high-temperature materials in the turbine.

All of these subwoofers tend to have in-built amplification. Better yet the amount of power in the gas is the difference between the exhaust pressure and air pressure, which increases with altitude, so turbochargers generally have much better altitude performance. These can be purchased separately, to be added to an existent system or when considering a set of speakers; or as part of a high-end speaker package. Thus at low altitudes the turbo robs nothing and, as the altitude increases, it can use just as much power as it needs and no more. On the other hand, high-end domestic subwoofers are manufactured by companies such as M&K, HSU, Velodyne, SVS, and REL. In addition the power in the exhaust would otherwise be wasted (except to the extent that the exhaust itself provided thrust) whereas in the supercharger that power is being taken directly from the engine. Further, small satellites systems typically cross over the bass above 90 Hz, introducing the subwoofer "localization effect". Since the turbo is driven off the exhaust gases, simply dumping some of the exhaust pressure is sufficient to drive the compressor at almost any desired speed.

They are too weak to play any real deep bass. It is interesting to compare all of this complexity to the same system implemented with a turbocharger. Most multimedia "subwoofers" should probably have been called "woofers". The two-stage Merlin was losing 400 hp (300 kW) to turn the supercharger but developing between 1500 and 1700 hp (1125 to 1275 kW) at the propeller shaft, depending on model. Particularly among low cost systems, however, it may be little more than a marketing device: it's not likely that a small woofer in a compact cabinet will have better bass performance than good speakers; as mentioned, the term "subwoofer" is no guarantee of particular bass performance. At low altitudes one stage could be turned off completely. The physically separate subwoofer/satellite arrangement has been popularised by lifestyle systems, such as those manufactured by Bose, and multimedia speakers, examples of which include the Klipsch ProMedia. After being compressed "half-way" in the low pressure stage the air flowed through an intercooler radiator where it was partially cooled down before being compressed the rest of the way in the high pressure stage and then aftercooled in another air/air or coolant/air radiator (heat exchanger).

("Bass management" or "Small" mode for the satellite speakers is common among equipment such as Dolby Digital surround processors/receivers.). In order to avoid pre-ignition the "two stage" design was used. All low frequency information is sent to the subwoofer. Compressing a gas always causes its temperature to rise, and an overcompressed fuel-air mixture may therefore prematurely ignite. Note that only one subwoofer need be used, even when using 5 or more satellite speakers—e.g., for surround sound. A final improvement was the use of two compressors in series, which were introduced to solve the pre-ignition problem. Harmonics at higher frequencies (from the satellites) can then be used, by the auditory system, to calculate the directional information. Ultimately it was found that for most engines (excepting those in high-performance fighters) a single-stage two-speed setup was most suitable.

(e.g., it has been suggested subwoofer(s) be placed in the corner of the room, far from large room openings, and closer to the listener.) This is possible since low bass frequencies have a long wavelength; hence there is little difference between the information reaching our left and right ears, and we are unable to easily locate their direction below 90 Hz. These provided more flexibility for the operation of the aircraft although they also entailed more complexity of manufacturing and maintenance. Physical separation of subwoofer and "satellite" speakers not only enables placement in an inconspicuous location, but since sub-bass frequencies are particularly sensitive to location (e.g., due to room resonance and 'modes'), the best position of the subwoofer may not be where the "satellite" speakers are located. In the 1930s two-speed drives were developed for superchargers. (e.g., some speakers include a subwoofer in the lower portion of the cabinet.). Supercharging by itself could not have achieved these improvements; however, when married with fuel improvements, the engine could respond to both. Thus, subwoofers may be part of a package that includes satellite speakers, purchased separately, or built into the cabinet of a conventional loudspeaker. By mid-1940 another increased boost yielded 1310 hp (980 kW).

Rather, the intention may be to use small main ("satellite") speakers (of which there are 2 for stereo, and 5 or more for surround sound) and locate ("hide") the subwoofer elsewhere; to augment an existent speaker to relieve it of reproducing bass and gain output level and/or quality; or because high levels of low bass are required and using a dedicated amplifier and speaker provides the output level and quality required. This allowed the boost on Merlin engines to be increased to 48 inHg (160 kPa) and the power to rise by more than 10% (from 1030 to 1160 hp, or 770 to 870 kW). A conventional woofer may reproduce frequencies up to 200, 300, or in a two-way speaker a mid-woofer (paired with a tweeter) also handles midrange, up to 3,000 hertz or more. In 1940 a batch of 100 octane fuel was delivered from the USA to the RAF. It should be noted that a subwoofer does not necessarily provide superior bass performance to large conventional loudspeakers; they are merely subwoofers because they ought to reproduce only the lowest frequencies. This generally "flattened out" the power below the critical altitude. Considering they operate outdoors and the average listener is hundreds or even thousands of feet away from the devices, they are impressive. As the war progressed two-speed superchargers were introduced using better controllers and, notably, hydraulic clutches, that allowed the boost to be managed over a wide range of altitudes by operating at low rpm down low and at high rpm at higher altitudes.

People who are accustomed to bass in home audio systems and car audio many times think that the subs in a concert PA system aren't putting out that much. For the early years of the war this was simply how it was and this led to the seemingly odd fact that many early-war engines actually delivered less power at lower altitudes, because the supercharger was still using up power to compress air that was not delivering any power back. On average, music applications generally require less capability than movie soundtracks in the very lowest octave, but modern popular music is changing this preconception and this is reflected in the design attention given to the subwoofer section of the PA system nowadays compared to a couple of decades ago. Also, due to the denser air at lower altitudes, the supercharger is not operating at its best efficiency, and this can cause an additional load on the engine. Pro Audio subs have to be capable of very high output levels – after all, concert venues may seat 10,000s of individuals outdoors. Unless other measures are taken, this means that at least some of the power driving the supercharger is wasted. A large horn-loaded version called the BassTech-7 can be found in venues such as theme park rides. Below the critical altitude the supercharger is capable of delivering too much boost and must therefore be restricted lest the engine be damaged.

Another extreme pro audio device is the ServoDrive ContraBass, where the driver's cone is moved using a belt-drive coupled servo motor. British engines were generally able to outperform German ones. Intended for applications such as night club installations and concert sound reinforcement this cabinet is still popular with PA system equipment rental companies. Throughout WWII British superchargers generally had higher critical altitudes than their German counterparts and, when combined with higher octane fuels that the Americans supplied, that allowed for higher boost levels. A now-discontinued but popular Electro-Voice subwoofer employs a "Manifold Technology" configuration to fit four 18-inch drivers into a relatively compact enclosure. The boost is typically measured as the altitude at which the supercharger can still supply sea level pressure (100 kPa or 1000 mbar) and is referred to as the critical altitude. One of the most powerful subs manufactured can play as low as 25 Hz and can cover thousands of feet and uses two 12-inch woofers on a 13-foot (4 m) long folded horn (the EAW bh822e or KF940). A supercharger is only able to supply so much pressure because the compression increases the air temperature, and the engine is limited in maximum charge-air temperature before pre-ignition occurs.

12-inch drivers in very large folded horns are also becoming popular now. For this reason supercharged planes fly much faster at higher altitudes. For electronic music events with at least a thousand audience members there are often more than 20 double-18-inch cabinets on either side of the stage. And while the engine might be fooled into thinking it's at sea level, the airframe is quite aware of the halved air density and the plane thus has half the drag. They are usually direct radiating in a ported enclosure built of 13-ply birch. Yet the benefits are huge, for that 150 horsepower (110 kW) lost, the engine is delivering 1000 hp (750 kW) when it would otherwise deliver 750 hp (560 kW). The 18-inch woofer driver is the primary majority device for pro audio applications. On the single-stage single-speed supercharged Rolls Royce Merlin engine for instance, the supercharger uses up about 150 horsepower (110 kW).

Similar popular PA systems are made by JBL, Electro-Voice, EAW and Meyer Sound. This can take some effort. Popular sub systems in use currently are made by companies such as EAW but usually the subs will be made by the manufacturer of the rest of the PA system such as L-Acoustics and their V-Dosc Line Array with its matching dual 18-inch sub cabinets. A supercharger remedies this problem by compressing the air back to sea-level pressures, or even much higher. Many times the subs are not part of the entire sound mix but are specifically fed just kick drum, bass guitar and other low-frequency content from a separate output on the main mixing console. Since the charge in the cylinders is being pushed in by this air pressure it means that the engine will normally produce half-power at full throttle at this altitude. Similar systems are used in theme park rides, such as "Days of Thunder," which uses sound to simulate a physical impact. As an aircraft climbs to higher altitudes the pressure of the surrounding air quickly falls off—at 6000 m (18,000 ft) the air is at half the pressure of sea level.

This was simply a set of large sub-woofers designed to create infra-bass (felt but not heard). A more natural use of the supercharger is with aircraft engines. An unusual example of the use of sub-woofers came with the release of Earthquake in 1974 where they used a system called Sensurround to create a feeling of an earthquake. There are three types commonly used in today's automotive world: Roots type supercharger, twin-screw type supercharger, and Centrifugal type supercharger. The bulk of the sound system is usually "flown" (suspended from the ceiling by chain hoists) and the subs are usually stacked on the stage or the ground in front of the stage to the left and right of the performance space. Also, improperly installed or excessive boost will greatly reduce life expectancy of the engine as well as the transmission (which may not have been designed to cope with additional torque). Large concert sound systems always use subwoofers (referred to as "subs" by the engineers and crew). Nevertheless, adding boost to a car will often void the drivetrain warranty.

Note that movie theatre speakers (situated behind a perforated screen) typically use 15" drivers (woofers), so the use here is only to reproduce the lowest frequencies at high sound pressure levels. Gas mileage can also be saved with a turbo because the engine does not have as much displacement, therefore not needing to inject as much petrol in the the cylinders. Some of these applications require subwoofers designed for very high sound levels, such as the JBL 4645 – certified for THX movie theatres – which uses an 18" driver (woofer). This also results in better gas mileage, as mileage is often a function of the overall weight of the car and that is based, to some degree, on the weight of the engine. Subwoofers are found in professional applications such as live concerts, movie theatres, various other sound reinforcement applications (ranging from nightclubs to theme restaurants) and studios. For this reason boosting is commonly used in smaller cars, where the added weight of the supercharger is smaller than the weight of a larger engine delivering the same amount of power. This track is often used aggressively by mixing artists. Boosting used to be an effective way to dramatically shorten an engine's life but, today, there is considerable overdesign possible with modern materials and boosting is no longer a serious reliability concern.

The .1 channel is usually dedicated to extended bass frequencies, for example, the low frequencies of a gunshot, string bass, or thunder. Boosting has made something of a comeback in recent years due largely to the increased quality of the alloys and machining of modern engines. The need to reproduce these frequencies has increased since older formats, such as vinyl records, have been displaced by digital formats, such as CD, and particularly 5.1 formats such as Dolby Digital, in which the ".1" channel is dedicated solely to the subwoofer. Since then superchargers (as well as turbochargers) have been widely applied to racing and production cars, although their complexity and cost has largely relegated the supercharger to the world of pricey performance cars. Subwoofers are usually powered by a high power amplifier, and often an electronic crossover ensures that higher frequencies will not be directed to the subwoofer. It wasn't long after its invention before the supercharger was applied to custom racing cars, with the first supercharged production vehicles being built by Mercedes and Bentley in the 1920s. Diameter tends to be advantageous because low frequencies involve shifting a great deal of air; a recent trend has been for high excursion, i.e., how far the cone can linearly travel from its resting position; for example, some can move as much as 2.5" in or out, yielding an overall displacement of 5" (this is controlled movement range). This design is the basis for the modern Roots type supercharger.

Subwoofers use drivers (woofer) with cones typically coming in 10" or 12" sizes, but can be as large as 34", and as small as 4". His first superchargers were based on a twin-rotor air-pump design first patented by American Francis Roots in 1860. . In 1900 Gottlieb Daimler (of Daimler-Benz / Daimler-Chrysler fame) became the first person to patent a forced-induction system for internal combustion engines. It is difficult for small loudspeakers to reproduce frequencies below 40 Hz, especially above 100 dB, and so it is often advantageous to use a loudspeaker dedicated to this task. By pushing the air into the cylinders, it is as if the engine had larger valves and cylinders, resulting in a "larger" engine that weighs less. So-called subwoofers which reproduce frequencies from about 35 Hz to about 150 Hz are more properly described as bass modules than true subwoofers. In cars, the device is used to increase the "effective displacement" and volumetric efficiency of an engine, and is often referred to as a blower.

Frequencies 16 Hz or lower are more felt than heard. . A subwoofer is a loudspeaker which reproduces bass frequencies from about 5 Hz to about 90 Hz. In applications where a massive amount of power is more important than any other consideration, such as top-fuel dragsters and vehicles used in tractor pulling competitions, superchargers are extremely common. Superchargers may absorb as much as a third of the total crankshaft power of the engine, and in many applications are less efficient than turbochargers. It is similar in purpose to the closely related turbocharger, but a turbocharger is powered by the flow of the engine's exhaust gases driving a turbine.

A supercharger is powered mechanically by belt- or chain-drive from the engine's crankshaft. The additional mass of oxygen that is forced into the cylinders allows the engine to burn more fuel, which improves the volumetric efficiency of the engine and makes it more powerful. A supercharger (also known as a blower, or a centrifugal pump) is a gas compressor used to compress air into the cylinders of an internal combustion engine.