WOOx Technology

wOOx technology (rendered wOOx) is a brand created by Royal Philips Electronics to identify loudspeaker systems that employ passive radiator technology and active equalization to maximize the output of the passive diaphragm. wOOx technology is primarily concerned with low frequency reproduction, in which resonant systems are commonly employed to augment the output of bass drivers to improve the overall efficiency of the loudspeaker system through the bass frequency range. wOOx Technology involves the synergistic optimization of three components of the loudspeaker system: the bass radiator, the active bass driver, and active equalization.

The wOOx Bass Radiator

The primary element of a wOOx Technology speaker system is the bass radiator. The wOOx bass radiator (referred to in marketing literature as the wOOx-Slave) is functionally indistinguishable from typical "passive radiator" diaphragms previously employed in loudspeaker systems. Early wOOx radiators used a patented design with two foam-rubber suspension rings instead of the typical single ring, and a symmetrical sandwich construction.

Typical passive radiator theory dictates that the passive radiator should be capable of displacing at least twice the volume of air that the active driver displaces through its own stroke. In order to satisfy this design guideline, passive radiators have been traditionally employed that have a larger surface area than the active driver. The dual-suspension design of the wOOx bass radiator allows the radiator to undergo extreme excursions, allowing the wOOx radiator to displace the necessary air volume without being larger in diameter than the active driver, enabling it to be more easily integrated into consumer electronics products. More recent embodiments of the wOOx bass radiator use a single-roll suspension.

The wOOx radiator incorporates a mass element in the center of its diaphragm, which is used to adjust the tuning frequency of the loudspeaker enclosure. In this sense, a loudspeaker enclosure with passive radiators emulates a mass-spring system, much like the helmholtz resonator devices (bass reflex ports) more commonly used to tune loudspeaker enclosures. However, the amount of mass which may be suspended on a passive radiator diaphragm enables extremely deep tuning frequencies to be possible in small enclosures. However, like any passive radiator system, it is possible to damage the bass radiator by driving it beyond its mechanical limits. To avoid this, some wOOx systems use an additional reflex vent, having the same tuning as the wOOx radiator, in order to relieve excess pressure that could otherwise tear the bass radiator apart.

Design of the Active Driver

In a loudspeaker system incorporating passive diaphragms, the term 'active driver' is used to refer to the loudspeaker driver itself, which contains the voice coil, in order to distinguish it from the 'passive' diaphragms which have no voice coil of their own. In loudspeaker systems which rely upon resonant augmentation of the output of the active driver (these include bass-reflex systems, passive radiator systems, bandpass systems, and transmission-line systems), the resonant system absorbs the acoustic load from the active loudspeaker driver, decreasing the necessary cone excursion to achieve high output at low frequencies. However, it is advantageous to have a loudspeaker driver with a strong magnetic structure for high electrical damping of the driver cone, in order to supply the maximum possible force to the loudspeaker cone and create the maximum possible excitation of the resonant system.

The same is true for systems employing wOOx technology, in which the wOOx radiator absorbs the acoustic load from the active driver. Because the wOOx radiator is capable of greater excursion than the active driver without increasing distortion, it is desirable to excite the wOOx radiator as much as possible, to keep the excursion of the active driver at a minimum while maximizing the output of the loudspeaker system. Thus it is desirable to employ a more powerful magnetic structure. To protect the moving structure of the active driver from potential overexcursion, the driver is designed with a higher degree of mechanical excursion capability.

Active equalization

One benefit of the wOOx bass radiator (and passive radiators in general) when compared to the more common bass-reflex vents is that there is no possibility of air turbulence noise if the resonant system is greatly excited. As a result, additional equalization applied near the enclosure's tuning frequency can increase system output without generating extraneous noises or greatly increasing cone excursion of the active driver. Many wOOx-equipped mini-stereo systems produced by Philips feature a three-level equalization control which applies additional bass equalization at frequencies which excite the wOOx bass radiator, improving the visceral 'impact' of the bass through the wOOx radiator's extreme air displacement capability. This use of active equalization to increase overall system output is the primary characteristic that differentiates wOOx technology from typical loudspeaker systems equipped with passive radiators.

Products with wOOx

In addition to Philips' own use of wOOx Technology, the technology also appeared in products sold by Kenwood and Microsoft. Also, some Philips products display "wOOx²" branding, though there does not appear to be a fundamental change in the nature of the wOOx system. The only likely difference between wOOx and wOOx² is in the amount of active equalization applied to the system.

A common marketing slogan used by Philips for products with wOOx Technology is "Hear the bass, feel the difference".

This is a list of products which feature wOOx Technology, though it is not exhaustive. Not all of these products were sold in the U.S. market.

Executive and Shelf Systems
*FWC717
*FWC780
*FWC80
*FWC85
*FWC870
*FWM70
*FWM75
*FWM777
*FWM779
*FWM922
*FWR55
*MC70
*MC77
*MC80

Home Theater Systems
*MX1015D
*MX1060D
*MX3700D
*LX700
*LX8000SA
*LX8200SA
*LX8300SA

Portable Music Systems
*AZ2555 CD Soundmachine
*AZ2558 CD Soundmachine

Televisions
*PF9630
*PF9731

Products From Other Manufacturers
*Microsoft Digital Sound System 80
*Kenwood KSC-WA62RC Powered Automotive Subwoofer
*Kenwood NV 301 Executive System

Other Products
*MMS305 PC speaker system
*MMS306 PC speaker system
*AJ300D iPod/GoGear Docking Clock Radio

See also

*Philips
*Passive radiator (speaker)
*Bass Reflex

References

United States Patent No. 5892184 "Passive radiator and system comprising the passive radiator." U.S. Philips Corporation (New York, NY)