63 years later LEAK’s new Sandwich 150 and 250 speakers

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LEAK returned to the HiFi scene in 2020 with its first new products since the 1970s. The arrival of the LEAK Stereo 130 integrated amplifier and LEAK CDT CD transport followed at the end of 2022 by a second integrated amp, the Stereo 230.  The ideas was to fuse the vintage appeal of a classic LEAK design with modern audio circuitry, something we see a lot but not quite in the Leak way.

LEAK’s expands its line up with further with the addition of two loudspeaker models, again inspired by LEAK’s past. The Sandwich 150 and Sandwich 250 take the blueprint established by the original, highly innovative LEAK Sandwich speaker, which debuted in 1961.

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The LEAK Sandwich history

In the 1950s, loudspeaker cones suffered a from a common problem, a lack of stiffness.   Many conventional cone materials paper, impregnated fabric, plastics, aluminium etc exhibit less than ideal stiffness. This results in significantly larger areas of the cone vibrating in motion, uncontrolled by the voice coil. These uncontrolled motions produce transient ‘hangover’, amplitude distortion (peaks and troughs in the frequency response) and intermodulation distortion. All of these
are detrimental to sound quality.

Introduced in 1961, the original LEAK Sandwich speaker tackled this issue in an innovative way. Its mid/bass drive unit was the first to be constructed from a ‘sandwich’ of different materials: expanded polystyrene foam between two sheets of aluminium foil. This made it both very light and extremely stiff, enabling true pistonic motion and therefore more accurate sound.

A publicity photograph produced at the time showed LEAK’s founder, Harold Leak, standing on a Sandwich cone to demonstrate its exceptional rigidity. But the cone was not the Sandwich speaker’s only innovation – for example, the cabinet introduced bracing techniques subsequently adopted by many other manufacturers – and LEAK went on to produce other two-way and three-way iterations through the 1960s and early/mid 1970s to great commercial and critical success.

63 years on new materials and construction techniques have been applied to speaker cones however LEAK’s sandwich cone construction is still as relevant now as it was in the 1960s. The new Sandwich 150 and Sandwich 250 speakers update the concept using modern materials, design technologies and manufacturing techniques, incorporating a stiff aluminium skin for the outer surfaces (where the stresses are greatest) bonded to a core of aircraft-grade polymethacrylimide (PMI) structural foam.

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Two new speakers
The new LEAK Sandwich 150 and Sandwich 250 are both standmount speakers, the former a two-way design with a height of 41.5cm and the latter a much
larger three-way model standing 65.5cm tall. They are designed to work with a wide range of amplifiers and deliver excellent frequency and transient response.

The Sandwich 150 incorporates a 30mm textile-dome tweeter and a mid/bass driver with a 170mm Aluminium-Foamcore Sandwich cone, while the Sandwich 250 combines the same tweeter with 280mm bass and 108mm midrange drivers, both of which feature Aluminium-Foamcore Sandwich cones. The treble unit includes a damped rear chamber to absorb the output from the back of the 30mm dome, isolating it from the rest of the loudspeaker and reducing its resonant frequency to below the crossover region. This allows bass, mid and high frequencies to be sewn seamlessly together with an added

The LEAK Sandwich 150 and Sandwich 250 are supplied in matched, mirror-imaged pairs, with the treble unit (and midrange unit, in the case of the 250) offset from centre. With one speaker optimised for the left channel and the other for the right, a precise stereo image within a deep, broad soundstage is assured when sited appropriately.

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The cabinet walls are sandwiches too
The enclosure of speaker is just as vital as the drivers.  LEAK’s new Sandwich speaker cabinets also use a sandwich construction where the cabinet walls are formed from an outer layer of MDF and an inner layer of high-density particle board – the different densities of these materials help to scatter panel resonances enhanced by a filling of special glue that bonds the layers and provides resonance-damping properties.

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Price and availability

The LEAK Sandwich 150 and Sandwich 250 speakers are available from mid-February at RRPs of £999 and £1,999 per pair respectively. If a customer wishes to purchase the dedicated floor stands with the Sandwich 250, the combined RRP is £2,299.