Hifi brand LEAK has returned with its first new products since the late ‘70s. In addition to a range of walnut veneered amps and source components, including the just-launched TruStream network player, the revitalised brand has resurrected a landmark loudspeaker design from the Swinging Sixties: the LEAK Sandwich.
Arriving in 2024, the Sandwich 150 and Sandwich 250 took the blueprint established by the original LEAK Sandwich speaker, which debuted in 1961, and applied state-of the-art technologies and materials to deliver the ultimate incarnations of an innovative British classic.
By modern standards, these are standmount models of considerable size – especially the three-way Sandwich 250 – so LEAK decided to create a more compact speaker with the same distinctive driver technologies, re-engineered into a smaller cabinet to suit rooms where space is at a premium.
The result is the new Sandwich 100 – a third contemporary LEAK Sandwich model with dimensions that many will find easier to accommodate. And with an RRP of £499 per pair, it’s more accessibly-priced than the Sandwich 150 (£999) and Sandwich 250 (£1,999).
In the ‘50s, speaker cones suffered from a common problem: a lack of stiffness. This affected their ability to follow the waveform of the signals applied to their voice coils accurately, as both lightness and stiffness are crucial in this regard.
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 and intermodulation distortion, all of which are detrimental to sound quality.
Introduced in ’61, the original LEAK Sandwich speaker tackled this issue in an innovative way. Its mid/bass cone was the first to be constructed from a ‘sandwich’ of different materials: expanded polystyrene foam between two sheets of aluminium foil. This made a cone that was light and 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 ‘60s and ’70s to great commercial and critical success.
Sixty-six years on from the introduction of LEAK’s Sandwich cone, speaker designers continue to face the same challenge: how to make driver cones both very light and extremely stiff. Whilst many new materials and construction techniques have been applied to speaker diaphragms since, the sonic shortcomings caused by sub-optimal stiffness remain widespread.
The latest version of the Sandwich diaphragm is enhanced with a core of Rohacell aircraft-grade structural foam between aluminium skins, bonded with adhesives used in the aerospace industry. The natural qualities of Rohacell make it an ideal component in speaker cone technology, especially because of its exceptional strength-to- weight ratio. Combining this rigid yet lightweight material with an aluminium skin creates a surface that greatly reduces cone break-up, delivers fast transient response and introduces minimal harmonic and intermodulation distortion.
The new 150mm mid/bass driver developed for the Sandwich 100 is built around a long-throw motor system with a high-gauss magnet and low-loss suspension, ensuring linear excursion even at high volume levels. The cone is shaped to naturally reinforce stiffness and suppress breakup modes, maintaining purity across the vocal range and upper bass.
Complementing the Sandwich mid/bass driver is a specially developed 30mm coated textile dome treble unit – larger than typical dome tweeters, especially within this price class. This reportedly allows for lower crossover points and superior power handling in comparison to speakers of similar size and specification.
The treble unit integrates seamlessly with the mid/bass driver thanks to a sophisticated crossover design, developed from extensive listening and engineering trials. It incorporates audiophile-grade polypropylene capacitors, air-core inductors and low-loss resistors, all arranged with a precision layout to minimise phase shift and signal loss.
This design ensures accurate time alignment between drivers, maintaining phase coherence and providing a stable, three-dimensional stereo image across a broad listening axis. Off-axis response remains smooth and predictable, which is crucial for real-world placement – whether listening from the sweet spot or moving around the room, imaging and tonal balance remain consistent.
The Sandwich 100 utilises further advances in cabinet design since the original Sandwich to deliver a modern study in resonance control in this price class.
The mid/bass driver cones are not the only things benefitting from a sandwich construction. 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. This is combined with internal bracing to eliminate panel flex and unwanted colouration, strategically placed acoustic damping material to suppress cavity resonance and a rear port for controlled bass extension.
Externally, the new model takes design cues from the original Sandwich with build quality elevated to meet modern expectations. Their cabinets sport a premium walnut finish, complemented by aluminium driver trims and an aluminium insert around the edge of the front baffle – a visual reference to the Sandwich speaker’s heritage.
The baffle itself is finished in soft-touch matt black, contrasting with the Sandwich 150 and 250 which continue their walnut veneer to the front of the speakers.
“With its innovative aluminium-foam-aluminium cone construction, the original LEAK Sandwich was a landmark loudspeaker design,” says LEAK’s Director of Acoustic Design, Peter Comeau. “Bringing the concept back in 2024 with the Sandwich 150 and 250 speakers was a fascinating project upon which we’ve built with this new, additional model. In developing the Sandwich 100, our intention was to make a more compact speaker offering uncompromising sound for a smaller space. And, at the same time, take our new, evolved version of LEAK’s classic Sandwich design to a more accessible price point, thus broadening its appeal.
“The speaker’s modest footprint belies a performance that is richly detailed, rhythmically confident and emotionally involving. It shines across all musical genres – from jazz trios and string quartets to rock, pop and electronica – delivering natural tone, believable scale and a level of transparency that draws the listener in.”
The Sandwich 100 is available from mid-April at an RRP of £499 per pair.