Leak Sandwhich Speakers

[Elite-ist]

I've been waiting to try out these speakers. I, only, needed the tube amplifier of the same vintage to power them. I had a Dual TD28 tabletop reel to reel deck already tucked away. I wanted to round up a system of the same decade: 60's. I believe the Heathkit AA-32, these Leak Sandwhich speakers, and the Dual R2R fit the bill. I paid $45 for the pair, found at my local mini flea market, earlier this year.

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Here's an excerpt, courtesy of Wikipedia, as a quick reference to the Leak Sandwhich speakers:

"LEAK Sandwich


From Wikipedia, the free encyclopedia




The LEAK Sandwich was an innovative loudspeaker design introduced by the English hi-fi company H. J. Leak & Co. in 1961. Harold Leak engaged Don Barlow, who had devised a way of making the cone of the loudspeaker from expanded polystyrene foam sandwiched between two sheets of aluminium foil. This made it both very light and extremely stiff, and correspondingly accurate in sound.

Contemporary publicity photographs show Harold standing calmly on top of one of his sandwich cones to demonstrate its exceptional rigidity. The speaker was innovative in other ways as well and was produced, relatively unchanged, for about 10 years.

The original Leak 'Sandwich' hi-fi speaker was a large two-way system employing a 330 mm (13") low frequency element, with the sandwich cone, cambric roll suspension, and cast aluminium chassis. As was common at the time, the 75mm (3") high frequency unit was a miniature version of the woofer, and was mounted onto the grille assembly, so fitted neatly into its own foam lined cavity on the face of the 60 litre bass enclosure. A large wood block was bolted between the back of the woofer magnet and the back panel of the enclosure, as a structural brace, a technique later used by other manufacturers. Crossover network components were attached onto three sides of this block. Since it was designed for use with tube amplifiers, the system was rated at 15 Ohms."



Nando.

[Ricardus]

Aha. Very cool.

[Bob Boyer]

Hope they sound as good as they look. You can already see that very-British "monitor" look that has come to define the contemporary Spendors, Harbeths, Rogers and others in these speakers. They're gorgeous.

[bob955i]

Hey Nando,

Nice classic looking speakers you got there - I've got a pair of the later 2030s - these also used the Sandwich woofer but were/are 3-ways.

[Mr_rye89]

I like me some samiches!-noteeth- what are the woofer cones made of?

[Elite-ist]

I like me some samiches!-noteeth- what are the woofer cones made of?

This copied information explains the composition of the woofer, Mr_rye89:

"To understand the impact of this invention one must remember that to obtain low distortion the movement of a loudspeaker diaphragm or cone should follow as accurately as possible the waveform of the signals present applied to its speech coil. The ability of the cone to follow these impulses depends on the lightness as stiffness of the cone assembly.

"Conventional cones (paper, impregnated fabric, plastics, aluminium) suffer from low stiffness. This results in significantly large areas of the cone vibrating in motions uncontrolled by the speech coil. The uncontrolled motions produce transient "hangover", amplitude distortion, and intermodulation distortion. These shortcomings are inherent in all direct radiator loudspeaker systems using conventional cones, irrespective of cost.

"All of the above shortcomings of conventional cone loudspeakers are overcome by the Leak Piston-Action Sandwich construction. Using engineering principles as applied to airframe construction, the "Sandwich" cone comprises stiff aluminium skins for the outer surface where stresses are greatest, bonded to a thick core of featherweight expanded aluminium where stresses are lowest, giving far greater stiffness than the same total weight of either material used separately. This use of the most suitable material in optimum proportions and dispositions gives immense stiffness and rigid piston-action over a range of more than 6 octaves".

Nando.

[Socal Sam]

IMO, Leak was far ahead of his time in treating the cone as an aerodynamic AND sound foil.

[Nakdoc]

Reminds me of the Mitsubishi aluminum honeycomb woofer in the MS 10,20,30,40 series of speakers. Bass definition out the wazoo! In their literature they showed a man standing on a cone to demonstrate its strength. 'Heavy Weather" was a great demo for those speakers.

[Mr_rye89]

This copied information explains the composition of the woofer, Mr_rye89:

"To understand the impact of this invention one must remember that to obtain low distortion the movement of a loudspeaker diaphragm or cone should follow as accurately as possible the waveform of the signals present applied to its speech coil. The ability of the cone to follow these impulses depends on the lightness as stiffness of the cone assembly.

"Conventional cones (paper, impregnated fabric, plastics, aluminium) suffer from low stiffness. This results in significantly large areas of the cone vibrating in motions uncontrolled by the speech coil. The uncontrolled motions produce transient "hangover", amplitude distortion, and intermodulation distortion. These shortcomings are inherent in all direct radiator loudspeaker systems using conventional cones, irrespective of cost.

"All of the above shortcomings of conventional cone loudspeakers are overcome by the Leak Piston-Action Sandwich construction. Using engineering principles as applied to airframe construction, the "Sandwich" cone comprises stiff aluminium skins for the outer surface where stresses are greatest, bonded to a thick core of featherweight expanded aluminium where stresses are lowest, giving far greater stiffness than the same total weight of either material used separately. This use of the most suitable material in optimum proportions and dispositions gives immense stiffness and rigid piston-action over a range of more than 6 octaves".

Nando.

so it's not just a delicious Name.*drool* super stiff laminate cones, big boxes. dat bass.....