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KEF is a British loudspeaker manufacturer with international distribution. It was founded in Tovil, Maidstone, Kent in 1961 by electrical engineer Raymond Cooke and named after Kent Engineering & Foundry with which it originally shared the site. Its founder, Raymond Cooke, was made an OBE by Elizabeth II in 1979.

KEF is now owned by GP Acoustics, which is itself a member of the Hong Kong-based Gold Peak Group. Product development, acoustical technology research and the manufacture of flagship products still occurs on the original Tovil site in England.

History[edit]

Raymond Cooke and Robert Pearch founded KEF Electronics Ltd., with a view to creating innovative loudspeakers using the latest in materials technology. KEF Electronics was founded in Kent in 1961 and was physically situated on land adjacent to the River Medway in Tovil which at the time was owned by Kent Engineering & Foundry (a company owned by Robert Pearch and founded by his father Leonard) who at the time manufactured agricultural equipment and industrial sweeping machines. KEF derived its name from the firm.^[1]

Cooke was a Royal Navy WWII veteran who was a design engineer at the British Broadcasting Corporation (BBC) for a year. He was later Technical Director at Wharfedale, then a leading British loudspeaker manufacturer. Following corporate change at Wharfedale, Cooke left to see his own ideas put into action.^[1] Cooke acquired the site of a foundry, makers of agricultural machines, and initially worked in Nissen huts erected on the site in Tovil, Maidstone. In KEF: 50 Years of Innovation in Sound, the authors assert that KEF reduced the average size of bass-rich home loudspeakers from 9–10 cubic feet (250–280 l) to about 2 cubic feet (57 l), based on the work on the 'acoustic-suspension woofer' at Acoustic Research; the company pioneered large-scale production of drivers with cones made of materials other than paper, and the application of fast Fourier transform analysis to the measuring of loudspeakers. KEF was also an early-adopter of modern quality-control principles to driver manufacture.^[1]

The first loudspeaker manufactured was the K1 Slimline for which the drive units used diaphragms made of polystyrene and melinex. Soon after, in 1962, came the famous B139 'racetrack' shaped woofer which allowed the design of the Celeste – one of the first truly high performance bookshelf loudspeakers. As Laurie Fincham, Cooke's successor as chief engineer, later revealed, the only reason the B139 was vertically mounted ovoid-shaped was that the British tax code at the time penalised 2 way speakers below a certain arbitrary width. Professional products were not taxed and professional was defined as above 8 inches for a woofer or as a 3 way speaker.

BBC monitors and beyond[edit]

From the mid-1960s, KEF manufactured BBC-designed monitor loudspeakers such as the LS5/1A for the Corporation and for wider distribution. Cooke's previous relationship with the BBC in the 1950s continued as KEF developed through the 1960s and 70s. In the mid-1960s KEF introduced the bextrene-coned B110 bass/midrange unit and the melinex-domed T27 tweeter which were later used in the diminutive BBC-designed LS3/5A broadcast monitor, of which over 50,000 pairs were sold worldwide and whose initial specification was for use in cramped broadcast vans.^[1] The close co-operation between KEF and the BBC Research department was fruitful for both, as BBC provided stringent performance and production standards with ample capacity for field testing, with KEF being a pioneer in the use of polymers and computerised quality control.

In the 1970s, as 'KEF Electronics Limited', the company was awarded two Queens Awards for Export Achievement (1970 and 1975). This further substantiated Raymond Cooke's choice of location for his factory as it 'was closer to Europe' and hence transportation costs for its goods would be cheaper.

In addition to making speakers, a substantial part of KEF's activity was as an OEM supplier of loudspeaker systems, baffles and drivers.^[2] Cooke decided early on that huge potential benefits could be reaped from selling raw drivers to competitors, that more than outweighed the cannibalisation of their own market position. In a relatively short time, many major and renowned loudspeaker manufacturers came to source their drive units from KEF. Users included illustrious British brands such as IMF, Rogers, Celef, Monitor Audio, as well as manufacturers outside UK, including Sonus Faber and Wilson Audio.^[1]Linn Products of Scotland also elected to use KEF drive units in the Linn Isobarik.,^[3] Linn Sara and Linn Kan speakers. The company's KEFKITs also provided many hi-fi hobbyists with means to apply their woodworking skills into making their own speakers.^[4] At its peak, production of drive units reached 10,000 units per week.^[1] In 1979, Queen Elizabeth II awarded Cooke an OBE.^[1]

The New York Times has recognised KEF as 'a leading audio company in Europe', and also 'well known to American High-End audiophiles'.^[5]

KEF lost its direction after making its last batch of BBC-licensed monitors, and eventually went into receivership in 1992.^[6] It was acquired by GP Acoustics, a member of the Hong Kong-based Gold Peak Group.^[1] Product development, acoustical technology research and the manufacture of flagship products still occurs on the original Tovil site in England.The speakers (from XQ on down) are manufactured in China.

Technology[edit]

In the early 1970s KEF was the first company to adopt computers for the testing and design of loudspeakers^[8] leading to the 'Total System Design' methodology and more sophisticated production techniques such as driver 'pair matching'. The radical Model 105 system, released in 1977, embodied this new philosophy and was one of the most highly regarded loudspeakers of its time. KEF, Bowers & Wilkins and Celestion were the 'big three' British loudspeaker makers of the seventies and eighties, and pioneered the use of advanced materials and techniques in audio.

Other technologies developed and brought to the market by KEF have included:

• driver decoupling (Model 105.2, 1979), a technique of reducing cabinet coloration by mounting drivers via controlled lossy coupling
• coupled-cavity bass loading (Model 104/2, 1984), a technique of pairing two bass drive units and feeding their output via a single port
• conjugate load matching (Model 104/2, 1984), a crossover optimisation technique that presents a constant (albeit low) ohmic load to the amplifier
• the 'KEF Universal Bass Equaliser' (aka 'KUBE') (Model 107, 1986), a technique to overcome the unavoidable phase lag present at low frequencies
• Uni-Q (C-Series, 1988), a patented implementation of coincident midrange and tweeter drivers that strives to preserve phase integrity and match dispersion between the drivers resulting in improved stereo imagery

Products[edit]

• KEF Muon
• KEF Blade
• KEF LS50
• KEF LSX
• KEF Egg
• KEF Reference Series
• KEF R Series
• KEF Q Series
• KEF X Series^[9]
• Uni-Q Technology
• Wireless Speaker Technology

References[edit]

Kef Q Lautsprecher

1. ^ ^abcdefghMarks, John (10 February 2012). 'Book Review: KEF: 50 Years of Innovation in Sound', Stereophile.
2. ^'A History of Kef Drive Units from the 1960s and 70s'. KEF Electronics.
3. ^'Iconic Hi-fi' Audio Milestones: Linn Isobarik'Hi-Fi News, November 2011 (courtesy link)
4. ^KEFKITS. KEF Electronics (leaflet no. KK/3 GA6802/20M/4.75)
5. ^Fantel, Hans (3 February 1991). 'Said a Speaker To a Living Room: 'Speak to Me''. The New York Times. Retrieved 23 March 2009.
6. ^The London Gazette: 5th May 1992, Issue 52911, p. 7780
7. ^hifiengine.com 2020, KEF Model 104, retrieved 31 May 2020.
8. ^L.R.Fincham and R.V.Leedham. 'Loudspeaker evaluation using digital fourier analysis'. Presented to the British section of the Audio Engineering Society, London, February 1973
9. ^'KEF - Obsessed with High Resolution - International'. Retrieved 20 January 2015.

External links[edit]

Kef Lautsprecher Q Serie

• Company website KEF loudspeakers
• KEF Reference 1 Bookshelf Loudspeaker (archive-link)

Wireless speakers are loudspeakers that receive audio signals using radio frequency (RF) waves rather than over audio cables. The two most popular RF frequencies that support audio transmission to wireless loudspeakers include a variation of WiFi IEEE 802.11, while others depend on Bluetooth to transmit audio data to the receiving speaker.^[1]

Overview[edit]

Wireless speakers are composed of two units: a main speaker unit combining the loudspeaker itself with an RF receiver, and an RF transmitter unit. The transmitter connects to the audio output of any audio devices such as hi-fi equipment, televisions, computers, MP3 players, etc. An RCA plug is normally used to achieve this. The receiver is positioned where the listener wants the sound to be, providing the freedom to move the wireless speakers around without the need of using cables. The receiver/speaker unit generally contains an amplifier to boost the audio signal to the loudspeaker; it is powered either by batteries or by an AC electric outlet.^[2]

The signal frequency range used by wireless speakers is generally the same as that used by cordless telephones – 900 MHz. The RF signal can traverse walls and floors/ceilings. Most manufacturers claim the signal transmits over a range of 150 to 300 feet (50 to 100 m). Many wireless speakers feature variable transmission channels that can be set using a tuning knob to overcome potential RF interference with other nearby wireless devices, such as cordless phones or baby monitors.

Some wireless speakers use the 2.4 GHz frequency band.

Sound quality[edit]

The most basic models only offer an output power of 3W, which does not allow for an optimal sound quality. Mid-range models go up to 5W and high-end models can go up to 10W and beyond.^{[citation needed]}

I.q Lautsprecher Wiki

The number of speakers can also vary: while entry-level models are limited to a single speaker, more elaborate models can offer two, and thus have stereo sound reproduction. Some wireless speakers add a passive radiator to improve low frequency reproduction and achieve deeper sound.^[3]

Bluetooth[edit]

Recent models generally use Bluetooth 4.0 or even Bluetooth 5, and wireless speakers generally have a range of 10 meters.^{[citation needed]} Bluetooth devices use a radio communication frequency such that the devices do not have to be in a visual line of sight with each other.

Some speakers may benefit from the NFC system to facilitate pairing with the source device.^{[citation needed]}

Battery[edit]

Wireless speakers use rechargeable batteries to power them. The operating time of the speaker before it has to be recharged is usually 6 hours. Models with more powerful batteries can last up to 10 hours or more. Almost all wireless speakers operate on rechargeable batteries that are not replaceable, so that the lifespan of these speakers is that of their batteries.

In order to be recharged, wireless speakers must be connected to an electrical source by means of a Micro Usb cable.^[4] The complete charging cycle generally varies from 3 to 6 hours.

Hybrid wireless speakers[edit]

Starting 2015, some wireless speakers integrate VOIP telephony functions.^[5] Other models have an integrated FM radio. The higher end models add an LCD screen to make it easier to select and store radio stations.

Most wireless speakers have a built-in microphone, which allows to receive and make calls using a mobile phone in hands-free mode. When a call comes in, the music automatically shuts off and resumes as soon as the call ends.

With the development of voice assistants, manufacturers have integrated the ability to pair them with their devices. This way, commands can be passed to the speaker via the integrated microphone, which will then be executed by the voice assistant.^[6]

Shower speaker[edit]

Lautsprecher Q Acoustics

A shower speaker is a Bluetooth speaker designed for use in humid environments such as showers or more generally in the bathroom. There are also shower speakers using Wi-Fi, although this is more rare.

The speaker must first be paired with a Bluetooth device. In general, it is a smartphone or tablet. It is this device that will serve as the source for the music that will be played through the speaker.^{[citation needed]}

A shower speaker must first of all be able to withstand water splashes. This resistance is expressed by an IP (Ingress Protection) index that must be mentioned on the product. The most frequent indexes encountered are the IPX4 index, which indicates that the device is protected against splashes. Other models offer superior protection, such as IPX7. In this case, the enclosure is completely submersible in water to a depth of 1 meter for half an hour.^{[citation needed]} It is then considered waterproof. Some models, rarer those, extend their protection up to index 8.

The shower speaker must be able to be installed in all environments. This is why manufacturers have planned to equip their devices with different ways of fixing them. The suction cup is the most basic system and is found on entry-level speakers. Its main disadvantage is poor adhesion to the shower wall, which can cause the unit to fall off. The mounting bracket is the safest system to fix the speaker, but requires drilling a hole in the wall. The carabiner clip allows the speaker to hang from the shower curtain bar. It is only suitable for the smallest and lightest models.

See also[edit]

References[edit]

1. ^'Best Wireless Speakers 2017'. 30 November 2015.
2. ^'How Wireless Speakers Work'. 1 June 2012.
3. ^'Q. What are the advantages of passive radiator design?'. www.soundonsound.com. Retrieved 2019-11-07.
4. ^'Help Guide Charging the speaker from an AC outlet'. helpguide.sony.net. Retrieved 2019-11-07.
5. ^'10 gadgets to make your old tech smarter'. 11 January 2015.
6. ^'These Smart Speakers Do Your Bidding, And Have Killer Sound Quality'. Fatherly. 2018-09-07. Retrieved 2019-11-07.