TAG McLaren Audio recently launched the F1 AvantGarde 'Composite Sandwich Technology' loudspeaker, representing the flagship product of a forthcoming range of loudspeakers. The Calliope AvantGarde loudspeaker incarnates the first model of the new family of 'Aluminium Technology' loudspeakers.
Due to the conflicting demands imposed upon the design of a speaker that will integrate harmoniously into the domestic environment, from the outset there was a strong directive to create a loudspeaker to be an expression of the best modern industrial design and aesthetic style. The target was to design a 'bookshelf' loudspeaker which would make a bold yet beautiful visual statement without sacrificing essential mechanical and acoustical design parameters.
Key Design Parameters
- Modern art sculptural enclosure born of the science of sound radiation.
- Optimised enclosure geometry to combat acoustic diffraction, generating a high precision stereo image, sharp image focus, accurate perspective and impressive depth.
- Diminutively proportioned enclosure
- Small footprint with a visually deceptive volume, looking smaller than it really is
- Attractively narrow front profile
- Excellent performance/physical size ratio
- Exceptionally low distortion
- High dynamic range
The major constraint in speaker design
The loudspeaker's enclosure tends to be the most expensive single component cost of the overall build. Price reduction of a speaker is most easily achieved by cutting the cost and quality of its enclosure which, as a result, severely degrades the performance of such a loudspeaker system.
An ideal loudspeaker enclosure would require an infinitely stiff and perfectly damped cabinet, one without parallel structures (to prevent internal standing waves), avoiding sharp edges or undue symmetry (such precautions minimise diffraction over the enclosure surfaces). Most cabinets of wood-based panel construction, particularly those whose design is driven by cost, do not address these vital parameters. Consequently, they suffer from edge-related diffraction and panel coloration, yielding impaired stereo image precision, a loss of focus and deficiencies in perspective and sound stage depth.
Aluminium, as a raw material, has an inherently high stiffness-to-weight ratio affording the intrinsic structural rigidity required for the loudspeaker enclosure. Additionally, aluminium is nonferrous and therefore does not magnetically couple with the small amount of leakage flux from the drive unit motor systems.
In order to realise the form of the enclosure, aluminium is pre-heated to a molten state and then forced under pressure through a die tool. The formed extrusion length exits the die and is carefully cooled to maintain the desired geometry created by the die tool and cut to length. This relatively simple process allows the designer complete freedom to control the shape and wall thickness of the extrusion in two out of three dimensions.
The top and bottom end caps are also manufactured from diecast aluminium and are tensioned by stainless steel rods with the extruded enclosure compressed between them. This produces an immensely strong, self-damped assembly free from undesirable resonant modes.
Aesthetics versus sound quality
The task of designing an aesthetically pleasing, sculptural enclosure was given to Clive Grinyer, leader of TAG McLaren Audio's Styling team with the brief that fundamental acoustic principles be followed to maximise sound quality.
Internally the Calliope enclosure is reinforced with multiple longitudinal rib sections. The resulting combination of stiff, curved panel surfaces and compression forces arising from the tensioned end caps reduces unwanted acoustic output from the enclosure, essential for a very low coloration sound which is allied to truly natural transient attack. All drive units are rigidly mounted using high tensile machine bolts to prevent sympathetic vibration occurring which would otherwise smear the time response of the output signal.
Inside the enclosure there is a critical selection of high acoustic absorbent felt augmented by tuned volume damping provided by polyester fibre padding.
- 'Aluminium Technology'
- Eye catching, modern art sculptural enclosure born of the science of sound radiation allied to fluent high tech industrial design practice.
- Internal reinforcement using multiple longitudinal rib sections.
- Low distortion, gas flowed duct system for clean bass.
- Electro-acoustical design
- Uniform bass response via careful tuning of the system bass alignment. Affording superior dynamics, the bass system is tuned at 55 Hz. A Quasi-Bessel alignment has been computed for the low frequency output which attains optimum transient response together with superior, room matched low frequency extension.
- Remarkably stable responses and imaging thanks to exceptionally constant directivity through the audible bandwidth. Directivity describes the consistency of sound output at angles other than directly in front of the driver array. This quality of performance owes as much to the low diffraction enclosure form as to the intrinsically smooth driver responses and the precision electrical characteristics of the crossover networks.
- Drive Units
- Two-way design, using a 150mm bass/midrange driver with a die cast magnesium chassis and a 20mm silk dome high frequency unit, the latter is built in a custom faceplate.
- Drive units made to TAG McLaren Audio's specification by Vifa-Speak of Denmark.
- The bass/midrange unit of the Calliope employs a distinctive phase plug at the cone centre instead of the more common dustcap. This significantly improves the off-axis performance and, consequently, the loudspeaker's ability to provide sharply focussed stereo imagery. It also provides a smooth transition to the tweeter ensuring a seamless blend through the critical upper midrange crossover point.
- Use of high-grade electrical components for the crossover network selected for very low loss and high precision. Capacitors are audio grade polypropylene. Inductors are selected for minimum loss and very low distortion, comprising ferrite cored units wound with Oygen Free High-pure Copper (OFHC).
- Bass/Midrange: low pass, 3rd order electrical 6kHz. Tweeter: high pass, 3rd order electrical 6kHz to greater than 20kHz
- Attention to detail has extended to the internal wiring which has been designed as speaker cables in their own right, bandwidth, quality and power matched to the specific drivers they feed.
- All driver connections are hard wired for maximum integrity and reliability.
- Single input connection
- After extensive research It was discovered that at a very high quality level the potential benefits of multi-wired terminals for speaker cable connection were outweighed by the losses incurred in their implementation, e.g. additional contact interfaces and electrical connection straps. The signal path is kept as short and as pure as possible to ensure that the music signal arrives cleanly at the drive unit(s).
- Proprietary OFHC, gold plated binding posts are fitted as they offered clear sonic improvements compared to the typically used alternatives employing high copper content alloys. Furthermore, no nickel plating has been used between the OFHC foundation and the gold finish. Whilst this will lead to some dis-colouration of the binding post due to copper atoms partially diffusing into the anti corrosion gold layer, the customary, nickel plate interlayer is well known (as a ferro-magnetic and hard oxidised metal) to affect sound quality and was eliminated.
- Power requirements & Power capacity
- Easy amplifier loading characteristics. Of 6 ohms nominal impedance, the Calliope minimum value is 4.3 ohms.
- A baseline sensitivity of 87.5 dB allied with a practical and simple impedance response makes the most of good amplification.