KEF Model 104
Price unknown (1 unit, released in 1973)
Commentary
A reference series speaker system developed based on the latest research results.
The model104 uses a heat-resistant voice coil spirally wound around the voice coil assembly and a short coil finished with epoxy resin. It achieves heat resistance of at least 250 ℃ for short time use and 180 ℃ for continuous use.
This improves the durability of the speaker unit and reduces problems caused by failure.
The low range features a 20 cm cone woofer (B200/SP1039) and a 32x21cm passive radiator (Dron cone) (BD139/SP1037), enabling low sound playback up to 30 Hz with higher efficiency than driving a single large diaphragm.
The Woofer Unit B200/SP1039 is equipped with a PVC (Polyester Voice Coil), a heat-resistant driving mechanism consisting of an electrically and mechanically combined voice coil and magnet assembly, as well as a strene diaphragm made of New Visco Elastic Body Dump.
The passive radiator BD139/SP1037 was developed from the world-famous B139 bass unit.
This radiator is driven by the low-temperature energy from the back of the B200 to compensate for the low-temperature output, thereby expanding the low-range, increasing efficiency and reducing distortion.
The sandwich-type diaphragm is finely tuned and housed in an aluminum die-cast frame.
The T27/SP1032 dome type tweeter is mounted in the high range.
This unit consists of a pressure-molded Melinex dome part and roll edge part.
The network section is equipped with 6-element DN15/SP1041.
The network has a roll-off slope of 18dB/8ve at 3 kHz, divides the sound domain into two parts, and uses carefully selected stable components and low-loss capacitors for critical parts.
An acoustic control is mounted on the back of the grill so that the response of the speaker can be adjusted according to the shape of the room.
This control allows you to adjust the response characteristics of the middle range in three ways.
To prevent resonance, the enclosure uses dense structural material, strong internal fixing material, sound absorbing moisture-proof material, and special interior material for resonance prevention.
It is equipped with a grill with special mesh on the front.
It is designed to protect the drilling diaphragm without losing sound quality, and the high-frequency attenuation is limited to less than 1 dB up to 20 kHz.
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Model Rating
| Method | 2-way, 2-speaker, passive radiator system, bookshelf type |
| Units Used | For Low Band : 20 cm Cone Type (B200/SP1039) For High Range : Dome Type (T27/SP1032) Other : 32x21cm passive radiator (BD139/SP1037) Network (DN15/SP1041) |
| Frequency range | 30 Hz to 40 kHz |
| Frequency response (Anechoic chamber, measured at 1m on the tweeter axis) |
± 2 dB (50 Hz to 20 kHz) ± 5 dB (35 Hz to 35 kHz) -10dB(30Hz) |
| Impedance | 8 Ω |
| Maximum allowable input | 50W (Music Power) |
| Rated input (sine wave) | 20 V (50W, 100 Hz to 2.5 kHz) 8 V (8W, 3 kHz or more) |
| Adaptive input | 15W ~ 50W (8 Ω) |
| Sensitivity | 96 dB (anechoic chamber, 12.5W input, 8 Ω load, 1m, 400 Hz) |
| Harmonic distortion factor | THD 1% or less (100 Hz to 30 kHz) rel 96dB SPL(400Hz) |
| Crossover frequency | 45 Hz (by acoustic coupling) 3 kHz (Electrical Cutoff, Slope 18dB/oct.) |
| Acoustic control | 3 positions, ± 2 dB (variable around 1.5 kHz) |
| Internal volume | 35.5 liters |
| Applicable Room Size | 280m3Up to |
| Finish | Walnut, cheek, rosewood, white |
| Grill | Black expanded polystyrene |
| External dimensions | Width 330x Height 630x Depth 260 mm |
| Weight | 15.8kg |
| Sold Separately | Dedicated Stand 104F |
Unit Specifications
| Unit | B200/SP1039 | T27/SP1032 |
| Total flux | 132,500maxwell | 247,000maxwell |
| Flux density | 13,500oersted | 12,500oersted |
| Pole piece diameter | 33mm | 20mm |
| Moving mass | - | 350mg |
| Resonant frequency | 25Hz | 1,1kHz |
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The group presented at London AES a new measurement method using digital computers that contributed to the development of the Model104.
In the development of Model104, Fourier analysis using digital computer was introduced.
This evaluation method was presented by L. R. Finchum (then principal researcher at KEF Electronics Limited) and R. V. Ledam (then Audio Group at Bradford University) at the Audio Engineering Society held in London on February 13, 1973.