fullrange.doc

Full-rangeCross-section of a full-range loudspeaker driver using a whizzer cone design.Fostex FE206e (modified) full range drive unit using a whizzer cone.Goodmans Axiette, one of the first single-cone full-range drivers.AFull-rangeloudspeakerdrive unit is defined as a driver which reproduces as much of the audible frequency range as possible, within the limitations imposed by the physical constraints of a specific design. This is so difficult that there are few manufacturers producing full range drivers for high fidelity use, although there are many producing full-range drivers for television and other uses. Most single driver systems, such as those in radios, or smallcomputer speakerdesigns, cannot reproduce the entire audio range.Contents 1Typical designs 2Atypical designs 3Applications 4BGM applications 5Critical reaction 6VendorsTypical designsTypically, a full-range drive unit consists of a single driver element, orvoice coil, used to move and control adiaphragm. Often the cone structure includes optimizations to enhance high-frequency performance. For example, a small low-mass horn orwhizzerconecan be mounted where the voice coil and diaphragm meet, thereby increasing the output at high frequencies. In some designs, the main diaphragm may be coupled(link) to the voice coil using a compliant bond(厄环) such that high frequency vibrations（振动） are not transmitted into it, but instead move the whizzer cone. The shape and materials used in the cone and whizzer are highly optimized（优化的）.Another arrangement, which doesnt employ a whizzer, uses a radiating dome in place of （give way to）the usual dust-cap; it is acoustically active. In most speaker drivers such dust-caps are so constructed (or made of a material) as to be relatively acoustically inert. (无用的) Sometimes the dust cap takes the form of a small conical(圆锥) shape, claimed to improve dispersion（radiation） at higher frequencies. Yet other designs simply modify the diaphragm and dome/whizzer materials instead of compliantly coupling the diaphragm to achieve full-range operation. Technique of using a compliantly coupled (or modified) diaphragm for the low frequencies and auxiliary(辅助的) whizzer or modified dust-cap (dome) for the high frequency response of a speaker is a kind of mechanical crossover.Since the requirements of a full-range driver include both good low and high frequency response (which are contradictory(conflict) in terms of physical construction), a full-range driver is usually limited to covering the audio spectrum(频谱) above perhaps 100Hzleaving lower frequencies to be handled / augmented（expanded） by a separate sub woofer or by a special cabinet design for low frequency reinforcement. These requirements usually mean that the full-range must have good sensitivity (for lower frequencies) with a light voice coil (for high frequencies) these speakers commonly use a larger or more powerful magnet than usual, which improves sensitivity and thus lowers the power requirement at low frequencies as well as allowing a lighter voice coil. In addition, many have limited maximum excursions(振幅), requiring special enclosures which do not require large excursions at low frequencies for reasonable low end output.There are rare exceptions that use multiple elements to drive a common diaphragm, but these should not be confused with coaxial units that use separate and concentrically aligned elements to achieve the desired range of reproduction, and are not, strictly, classified as full-range drivers.Full-range drivers are seen in applications ranging from televisions and computer speakers, to superb hi-fi speaker systems. The performance of the driver is substantially（fully） affected by their enclosure, and enclosures vary from plastic boxes, at the low end of the scale, to largehorn loaded enclosureswith spectacular audio performance.Atypical designsA German company, Manger, produces an unusual full-range driver in the form of a differentially flexing（挠曲） flat diaphragm（平膜片）driver, about eight inches in diameter. Manger claims performance, both maximum level and extended low frequency response, which is rather better than traditional full-range drivers.Another unusual full-range driver design is the Walsh driver, popularized（普及） in Ohm hi-fi speaker systems, where they reproduced almost the entire audible range of frequencies. Early Walsh units were large and expensive. These drivers used a single cone made with paper at the base, reproducing low frequencies, aluminium in the middle area, and titanium（钛） at the neck zone, to produce high frequencies. Slits in the paper area of the cone, covered with silicone damping, together with internal（固有的） foam（泡沫垫）pads provided mechanisms（机械装置） for tailoring（特制） the frequency response to be as flat as possible. Loudspeakers using the Walsh driver are still in production, though they have adopted a tweeter so no longer qualify as full-range drivers. A variation（变化） on the Walsh driver, from a German firm, is available in two forms (a titanium（钛） cone and a carbon fibre（碳纤维） cone) and incorporated（并入） into commercial loudspeaker systems.Largeelectrostatic loudspeakersmay be considered as full-range speakers in the sense（mean） that they are capable of reproducing most of the audio frequency band.ApplicationsFull-range drive units may be found in applications ranging from inexpensivemultimedialoudspeakers to more costly（昂贵的） esoteric（深奥的） systems, the latter often using largetransmission lineorhorn loadedenclosuresto increase low frequency output. There is an active hobbyist（发烧友） speaker construction group on the Web focusing on full-range drivers and enclosures for them.Since every electronic, mechanical or acoustical component in reproduction chain will, regardless of purpose, degrade（退化了） fine detail, the fewer components between the amplifier terminals and the listening room, the better. This includes conventional “mid-kilohertz” crossovers, which, in addition, destroy the natural integrity of the harmonic structure by the abrupt severance（断绝） of the harmonics from the fundamental frequencies. These problems are avoided with the single cone moving coil driver which is to loudspeakers as the wheel is to the car.Edward James Jordan, interviewed by TNT-AudioBGM applicationsA large number of full-range drive units are used in commercial sound systems, which may employ a number of 200 mm (8”) full-range drivers, mounted into suspended ceilings or small back-box enclosures. These convey（spread） music and announcements to workers and visitors in retail stores(零售店), and public spaces. While these drivers are classed as full-range, it may be more accurate to term them wide-range drivers, since their output abilities rarely extend to the extremes of the frequency range. Several manufacturers build small (typically 115 mm (4.5”) diameter full-range drivers into miniature enclosures, and many of these include 25 or 70-volt line transformers, for use on commercial sound systems employing long speaker cables（电缆）. Some full-range speaker systems are designed with limited-range drivers, and must be used with equalizers（均衡器） to flatten（使平） and extend their frequency response, while others achieve acceptable response without electronic assistance. A Canadian manufacturer produces several larger full-range speaker systems, using 250 & 300 mm (10 & 12”) drivers, to achieve higher output levels, and extended bass response.Critical reactionCritics of full range drivers cite their presumed（推测的） inability to reproduce fast and complex musical forms. Reproducing multiple frequencies with the same diap