TAG McLaren Audio F1-RLA & F1 Proteus

TAG McLaren Audio Calliope

TAG McLaren Audio Calliope Center

TAG McLaren Audio F1-RLA

TAG McLaren Audio Calliope

TAG McLaren Audio Calliope

TAG McLaren Audio Calliope & Bass Module

TAG McLaren Audio F1 Range

TAG McLaren Audio Calliope Detail

TAG McLaren Audio Calliope Enclosure Assembly

TAG McLaren Audio F1-RLA & F1 Proteus

Overview

TAG McLaren acquired Audiolab in 1998 and I joined TAG McLaren Audio in 1999 to lead the Loudspeaker team and develop a debut range of loudspeakers. Working with industrial design guru, Clive Grinyer, the F1 loudspeaker was the debut product designed and released. This was followed by the partnering centre channel, Proteus and the Calliope range.

Transducer Design

The F1-RLA drive units were made to TAG McLaren Audio’s specification by Scan-Speak of Denmark. The 250mm and 180mm low frequency drivers had cone diaphragms manufactured from carbon fibre loaded pulp cones, low-loss rubber surrounds and high power voice coils. The 250 mm lower bass unit was mass tuneable by the user from a choice of 3 aluminium mass plates which allowed the loudspeaker to be fine tuned to suit room positioning. The F1 Centre Channel Loudspeaker had two 180 mm bass units working in parallel.

The 150 mm midrange drive unit had a pulp cone, radially slit and damped and also used a central phase plug. The spider was carefully optimised to provide a balanced restoring force required at higher sound levels. This, combined with the die-cast aluminium ‘grasshopper’ chassis designed to allow clean airflow from the rear of the drive unit, reduced compression and non-linearity. The 20mm coated silk dome tweeter was mounted on an alloy front plate, milled from solid aluminium, to prevent microscopic flexure, reducing intermodulation distortion. The rear output of the dome was vented progressively through two rear chambers preventing energy from reflecting back into the dome thus eliminating time smearing.

The Calliope drive units were made to TAG McLaren Audio’s specification by Vifa of Denmark. The 150mm bass/midrange driver had a die cast magnesium chassis, woven glass fibre cone and a phase plug. The 20mm silk dome tweeter had a custom faceplate to minimise the distance between the bass/midrange and the tweeter.

Enclosure Design

The ideal loudspeaker enclosure would require a stiff, dense, resonance free cabinet, without parallel structures, sharp edges or symmetry. This would minimise diffraction and coloration resulting in an unparalleled transparent and spatial sound.

‘Composite Sandwich Technology’, developed for the F1 AvantGarde loudspeakers, used a wet lay-up of gel-coat glass fibre providing a very stiff, dense, resonance free cabinet. The complex curves in the cabinet walls avoided internal symmetry to prevent standing waves and eliminate sharp edges from the external form to minimise diffraction.

The upper bass enclosure had a rear-firing, gas-flowed reflex port moulded into the rear of the enclosure while the lower bass enclosure used a downward firing, gas flowed reflex port which was diffused through the aperture created between the underside of the enclosure and the base plinth.

Composite materials were too expensive to be used in the more affordable Calliope range of loudspeakers so an innovative construction using aluminium was developed. Aluminium, as a raw material, has an inherently high stiffness-to-weight ratio affording the intrinsic structural rigidity required for the loudspeaker enclosure.

In order to create the curved form of the enclosures, the aluminium was 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 allowed accurate design of the form and wall thickness of the extrusion.

The top and bottom end caps were also manufactured from diecast aluminium and were tensioned by stainless steel rods with the extruded enclosure compressed between them. This produced an immensely strong, self-damped assembly free from undesirable resonant modes.

Crossover Design

The crossovers in both the F1 and Calliope loudspeakers used high-grade electrical components selected for very low loss and high precision. Capacitors were audio grade polypropylene and the inductors were selected for minimum loss and very low distortion, comprising ferrite cores wound with Oxygen Free High-purity Copper (OFHC). Gain matching of drive units is usually achieved using series resistors but this method introduces distortion due to the thermal non linearity. To overcome this deficiency, auto transformers were chosen with the added benefit of tighter control of the filter slope.