What is stereo?

There are now two system of high fidelity, monophonic (monaural) and stereophonic. Monophonic is a system that starts from one microphone and is fed through a single high fidelity set. Stereophonic is a double system. Two separate microphones are placed at different sides of the orchestra and two different systems are used to keep the two signals or channels separated. Two separate speakers are used, placed on different sides of you room. Stereo is much like 3-D photography, two slightly different sound reach your ears giving you a new dimension in sound.

H.H. Scott '59

KEF Model 103 Reference Series

With exceptional power handling for a compact loudspeaker Model 103 offers unique flexibility of installation and precise stereo image formation.
The drive units are centre-line mounted on a rotable, steel, speaker panel which can be turned (by successive right angles) through 360°. No matter how the system is positioned in the room the speaker panel may be placed to give the broadest, uniform, sound dispersion in the horizontal plane, ensuring accurate stereo imaging and the minimum of tonal variation.

The greatest enemy of natural sound reproduction is colouration. It alters the tonal character of instrumental sounds, upsets balance and distorts acoustic perspective.
Colouration is mainly caused by uncontrolled vibrations in the drive units and the cabinet enclosure. The radiating diaphragms in KEF loudspeakers are made from highly damped plastic materials pioneered by KEF in conjunction with renowned organisations such as the BBC, the diaphragm of the low frequency unit in Model 103 is made of a specially formulated rubber-modified polystyrene laminated to a visco-elastic damping layer with a high internal loss factor. This construction effectively dissipates unwanted stored energy in the diaphragm thus preventing diaphragm colouration.
Coloruation due to cabinet wall vibration is reduced by internal bracing partitions and the use of laminated materials. Layered bituminous, anti-resonant linings effecticely cancel any remaining resonances.

Power Handling Capability
Wide range loudspeakers of compact size are necessarily inefficient and high power amplifiers make great demands on power handling capabilities if realistic sound pressure levels are to be achieved. The special motor construction of the Model 103 low frequency unit is designed fro low distortion and high heat dissipation. The anodised aluminium voice coil former and special heat resistant epoxy resin allow the coil to operate safely at temperatures up to 350°C whilst the advanced design of the magnet assembly ensures perfect magnetic linearity. Model 103 will handle the output from 100 watt amplifiers on musical programme.

Drive Units and Dividing Network
High Frequency Radiator T52 Type SP1049.
A new high frequency unit providing high power handling capabilities with exceptional transient response, wide dispersion and smooth frequency response.

Low Frequency Radiator B200 Type Sp1039.
This very special low/mid frequency unit is fitted with a coated Bextrene diaphragm and plasticised PVC cone suspension. The voice coil assembly will safely with stand short term overload to at least 350°C and continuous operation at 250°C

Dividing Network DN16 Type SP1050.
Capacitors selected to a 5% tolerance range and low hystersis ferrite cored inductors ensure close adherence to design crossover frequencies and slopes. Total harmonic distortion due to filter network is less than 0-1% at 50 watts (20V RMS)
 Environmental Adaptability
Model 103 provides broad, uniform sound dispersion for accurate stereo image formation. This is accomplished by centre-line mounting the low and high frequency unit very close together on a rigid steel panel with accurate matching of phase and amplitude between systems.
Accurate stereo image formation over the widest possible listening area also demands precise location of the loudspeaker systems. Multi-unit bookshelf systems can only provide maximum horizontal dispersion when used vertically or horizontally - but not both. When, for practical or visual considerations the systems cannot be used in the intended manner the acoustic performance will be degraded or compromises must be made.
Model 103 frees the user from these restrictions and anables positive stereo image formation whatever cabinet attitude is adopted. This is simply achieved by rotation of the steel speaker panel.
KEF engineers developed the rotatable speaker panel which permits Model 103 to be used on any of its four sides even in elevated locations

Specification:  Model 103
System Type:  Two-way, bookshelf/stand-mount
Enclosure Type:  Closed box
Input Impedance:  8 Ω
Rated Maximum Power:  100W programme
Amplifier Requirements:  25-100 watts per channel into 8 Ω
System Resonance:  58 Hz, Q=0.9
Nominal Frequency Range:  30 - 20,000 Hz 
Specific  Frequency Response:  50 - 20,000 Hz  ±2dB
Sensitivity:  25 watts into nominal 8 Ω produces 96 dB at 1 m and 400 Hz in anechoic conditions
Harmonic Distortion:  1% T.H.D. 100 - 20,000 Hz ralative to 96 dB SPL at 400 Hz, 3% T.H.D. at 50 Hz
Crossover Frequency:  3,000 Hz (electrical cut-off slope 18 dB/8ve)
Finishes:   Walnut, Teak
Grille:  black microcellularfoam
System:  SP1048
Drive units: 
B200 bass unit (SP1039),
T52 tweeter (SP1049)
Crossover:  SP1050
Internal Volume:  25,4 litres
Dimensions (W x H x D):  500 x 303 x 225 mm (19.7" x 13" x 8.9")
Weight:  19.5 kg (41,88 lb)

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