Wilson Benesch has invested more than twenty five years’ research into emerging carbon fibre composite materials and the complex manufacturing methods required to enable their integration both ergonomically and aesthetically.
The Advanced Composite Technology (A.C.T.) Monocoque forms the principal component of our geometry series cabinets Although carbon fibre is renowned for its high strength-to-weight ratio, the material property of primary concern in cabinet construction is its damping coefficient; its ability to dissipate energy in a controlled manner. Employing this material property of carbon fibre in an optimised U-shaped geometry, the damping capacity of the A.C.T. Monocoque significantly surpasses that of a cabinet constructed using conventional materials.
In house RTM
At Wilson Benesch's state of the art manufacturing facility in Sheffield every A.C.T. Monocoque, used in our geometry series range, is produced in house. Crafted meticulously using a complex technique known as resin transfer moulding (RTM) which has taken decades to perfect.
Multi layer construction
Multiple layers of carbon fibre sheets, fibre glass and a high compression nomex core are sandwiched together to form an extremely high strength, lightweight structure.
In an A.C.T. structure, the carbon fibre is spaced apart by the core, to exploit the advantages of a curved geometric form while pairing two high tensile skins, spaced apart by a high compression core.
Aerospace high compression core comprised of an alveolar like structure with billions of air pockets. This complex structure is deployed in the luggage holds of passenger airliners to mitigate against blast energy. The material creates a super high compression core for the I-section. Similar structures can be found in the McLaren P1 Monocoque, Formula 1 racing cars, and many other high performance systems.
Aerospace grade carbon fibre based composites liberate the designer and provide for a completely different approach to loudspeaker design. Glass fibre is markedly weaker than carbon fibre, but it does make a small contribution to the strength of the final structure. The principal reason for including this additional layer, is to significantly elevate the damping capacity of the monocoque structure. It is the combined effect of the three materials which form a composite and this is the key to attaining unrivaled loudspeaker performance using the A.C.T. monocoque.
The highly optimised arch geometry is an elegant solution, that was developed in collaboration with PERA, a government organization. In 1999, when Wilson Benesch started to manufacture carbon composites using Advanced Resin Transfer Mould Technology, it was one of just four establishments in the UK using the technology. Of the other three, one was Lotus Cars, the other two M.O.D. Research Facilities.
If the sophisticated A.C.T. monocoque structure was judged by purely engineering function, it would lay claim to being one of the worlds lightest, stiffest and most highly damped structures ever manufactured. In terms of energy damping and therefore signal-to-noise ratio, it would exceed with consummate ease the traditional conventional materials typically seen in loudspeaker design to date.
The A.C.T. Monocoque has been engineered and optimised for its critical role in audio reproduction:
1. Composite Structure; Its composite three-layer structure vastly improves the damping property of carbon fibre reinforced plastic (CFRP). The combination of the blast core, carbon fibre and glass fibre creates a composite monocoque with the stiffness of CFRP and the damping properties of the blast core.
2. Fibre orientation; a single toll of carbon fibre consists of billions of microscopic fibres, 1,50,000th the diameter of a human hair. Each fibre presents a boundary between escaping energy inside the loudspeaker cabinet and the listening environment. Furthermore, these fibres are arranged in a regular fashion. The discernible fibrous weave in the A.C.T. Monocoque allows the energy being absorbed by the structure to flow directionally along the weave into the viscoelastic seals which bond the aluminium structures in the speaker.
3. Sound transmission; because of the directional flow of energy down the regular weave and fibres in a carbon composite structure, the velocity of transmission of this energy is greater than any conventional material.
This provides the designer with a significant advantage, allowing the small amount of unwanted sound energy escaping from the loudspeaker cabinet to occur as close as possible to the original sound made by the drive units in the loudspeaker. This avoids unpleasant overhang in a musical performance.
4. Geometrically optimised; the perfect curvature disperses sound energy both internally and externally evenly across its surface. This is critically important in loudspeaker cabinet design. It eradicates what audio engineers term standing waves. This inhibits the ability of the listener to easily locate one point of diffraction, so the loudspeaker cabinet remains silent.
5. High Resonant Frequency; every object has a natural resonant frequency. Stiff - light structures naturally have a high resonant frequency, where compliant - heavy structures have a low resonant frequency. High frequencies are easily damped, where low frequencies are very problematic and cannot easily be damped. In the Endeavour, structures with a high resonant frequency such as the A.C.T. Monocoque and the aluminium structures are damped using visco-elastic seals, which can easily absorb any high resonant frequencies..
While the Endeavour is ground breaking in many respects, its crowning achievement might well lay directly behind the midrange drive unit. The Endeavour introduces the world’s first Carbon-Nanotech Enclosure which houses the midrange drive unit. Born from research carried out in partnership with the Advanced Manufacturing Research Centre in Sheffield. The Carbon-Nanotech Enclosure is a huge breakthrough in high performance loudspeaker design.
This extra-ordinary structure bestows the following key benefits:
1. Optimal Midrange Air Volume: By partitioning the air volume available exclusively for the midrange drive unit. This critical drive unit, which produces the frequencies within the bandwidth most sensitive to the human ear, is free to work in isolation of the Isobaric Drive. Significant improvements in the midrange dynamics can be achieved as the drive unit no longer competes with the far more powerful Isobaric Drive.
2. Optimal Isobaric Air Volume: In order to achieve powerful, dynamic and low bass frequencies, the bass drive units require a large air volume within the speaker cabinet.
Due to the phenomenal stiffness of the A.C.T. monocoque, Wilson Benesch loudspeakers are releatively free from complex internal bracing found in other designs which subtract from the critical internal air volume.
By isolating the midrange to its own optimised enclosure, Wilson Benesch have significantly increased the air volume afforded to the Isobaric Drive even further.
3. Optimal Energy Control: The Carbon-Nanotech Enclosure isolates the midrange drive unit and its effective ‘open window’ to the listening room from the energy generated inside the cabinet. The Carbon-Nanotech Enclosure is phenomenally well damped, so by adding what is effectively a second composite structure to damp and control out of phase energy within the cabinet, the noise floor is lowered to a new level within the frequency range most sensitive to the human ear. The midrange presentation has a clarity and composure that is beyond previous benchmarks.
4. Optimal Integration: Low frequency energy is delivered by the vertically orientated Tactic II Isoabric Drive that places the voice coils in virtually the same plane as the Tactic II midrange drive unit. This configuration ensures near perfect time alignment with the lowest level of diffraction. Being vertically orientated ensures that no structural displacement occurs even at the highest levels.
5. Optimal Geometry: It is no coincidence that the geometry of the Carbon-Nanotech Enclosure closely resembles that of a classic champagne bottle. The curved structure has a proven ability to cope with enormous pressures.
6. Optimal Material Application: With the numerable critical design goals of the Carbon-Nanotech enclosure, only the most advanced materials technology could be applied to achieve these.
As the structure is placed internally, the aesthetic concerns associated with the A.C.T. Monocoque are largely superfluous, so it has been possible to deploy aerospace quality pre-preg carbon fibre, combined with the strongest material known to man, carbon nanotubes.
By adding carbon nanotubes to the resin matrix it is possible to attain improvements in damping and stiffness that is almost 5x that of similar structures without carbon nanotubes. In terms of the stiffness, the Carbon-Nanotech Enclosure superseeds the A.C.T. Monocoque, however the complex multi layer construction of the A.C.T. Monocoque remains the industry benchmark.
Air volume maximisation
The image to the left shows a comparison of the air volumes in a conventional speaker to one with a bell housing. It shows that the Carbon-Nanotech Enclosure has isolated the midrange and allowed the remainder of the cabinet around the enclosure, including the space at the top of the cabinet for the Isobaric Drive. Maximising the air volume for the bass unit.
Wilson Benesch Ltd | Falcon House | Limestone Cottage Lane | Sheffield | United Kingdom | T +44 (0)114 285 2656
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