KEF K1 Slimline (1961)
If you thought today’s trend towards slim tower speakers is something new, think again. KEF’s oldest speaker was born from founder Raymond Cooke’s desire to achieve outstanding sound quality from just such a slim, living-room-friendly enclosure — except that he was going for slim depth, rather than slim width.
At 12.5cm deep, the K1 Slimline incorporated the same driver innovations as the Monitor versions that arrived alongside it in the K1 series: indeed when KEF was founded in 1961 by Raymond Cooke and a small group of likeminded colleagues, the prime objectives were to design loudspeakers using the latest materials technology and with the best engineering methods. The 1960s was a hotbed of innovation in drive unit technology, with significant contributions from a number of commercial companies as well as the BBC’s Research and Design departments.
The first drive units designed and developed by KEF, and used in that K1 series of products, comprised the B1814 bass unit, with a flat diaphragm of polystyrene with aluminium foil laminated to the front and rear surfaces, the M64 elliptical midrange with the same polystyrene/ aluminium foil laminate structure, and the T15 tweeter with a dome made from aluminised Melinex.
The early brochures make a point of emphasising that all drive units in KEF loudspeakers have diaphragms of synthetic materials. Most loudspeakers at the time had diaphragms made of paper compounds, which could suffer from sound-colouring resonances, sensitivity to climatic conditions and batch-to-batch variations in production; the thought was that plastic materials ought to offer significant advantages. The fact that bextrene and later polypropylene came to dominate the market for serious hi-fi drivers pays tribute to this vision.