Back in the 1990s, QED was the UK’s ubiquitous cable brand. The company’s iconic and affordable 42 strand and 79 strand loudspeaker cables are still available and still sell at a prodigious rate. The proceeds from those cables allowed the company to finance investigations (see www.qed.co.uk/qed-academy.htm), to try to equate what can be measured with what we hear in the loudspeaker cable realm. Lessons learned from this report were applied to subsequent QED cable designs, right up to the company’s new flagship Supremus loudspeaker cable.
Having that measurement-to-ear basis has meant QED has long eschewed the more ‘unobtanium’ end of the cable metallurgy and construction spectrum. The Supremus design uses 16 silver-plated, 99.999% pure oxygen-free solid-core copper conductors, creating a 10AWG wire, with a cross-sectional area of 6.2mm2. This represents the largest cross-section of any QED cable to date, and in the process gives Supremus a very low claimed loop resistance of 0.005Ω/m. The design of the cable itself uses QED’s AirCore technology, which uses a foamed polyethylene inner core (around which the conductors are wrapped) with an foamed polyethylene dielectric outer core and further small hollow tubes of foamed polyethylene within the cable jacket to both even out the design and to keep inductance to a low stated 0.49µH/m and capacitance to a suggested 48pF/m. It is also designed to alter the magnetic field across the length of the cable to make high-frequencies travel along the centre of the cable rather than the outer part, thereby limiting any potential skin effect issues.
QED uses a thin layer of enamel on each conductor on the Supremus design. The whole 8mm diameter design is then jacketed (to make a 17mm diameter cable), cryogenically treated, and then terminated in the factory using the company’s own cold-weld AirLoc plugs. A further bonus unique to the Supremus design is these connectors are rhodium plated. This caused a slight delay in the review, because although 4mm plugs were ready right out of the starting gates, spade lugs (required for my Wilson Duette II speakers) were delayed in manufacture. Once they were ready, the cable was good to go, and arrived in a box about the size of a small LP carry case.