Cables

Co-founder, Bob Abraham, would surely never have guessed his classic figure-of-eight 79-strand speaker cable (now circa £2/m) would still be going strong some 50 years after its launch in 1976. The QED brand was formed in 1973 and despite dalliances with hi-fi separates and accessories has remained most firmly associated with cables. QED’s design theories were outlined in its 1995 ‘Genesis Report’, this informing the X-Tube (XT) cable range, and refined in the 2007 ‘Genesis Report II’ from which this latest Supremus Zr flagship is derived.

The cable is not offered off-the-reel but only in factory terminated stereo sets priced at £1399/2m, £1799/3m, £2199/4m and £2599 for a 5m pair. QED’s own rhodium-plated ‘Zirconia Airloc’ banana plugs are cold-welded into place, the split pins expanding for a secure fit into your speaker/amplifier terminals via a ‘Zirconia Ceramic’ collar. The same hard, scratch-resistant, non-magnetic vitreous glass is used for the boot that holds the signal and return conductors in place.

Tube travel

Emerging from the heavy and not especially flexible body of the cable, these white-coloured snakes take the form of two ‘conductive Aircore tubes’, each comprising 16 silver-plated 5N copper strands wound around a hollow PE core (white and red in the picture, below). Cryogenically treated, these strands are also individually lacquer-coated to prevent non-linear surface-to-surface conduction. Otherwise, the ‘tube’ approach represents QED’s solution to mitigating the Skin Effect while maintaining a substantial 6.2mm²/10-gauge copper cross-section.

The latter enables the Supremus Zr’s low 5.5mohm/m loop resistance, equivalent to a power loss of just 0.006dB/m into 8ohm, while the superb >300Mohm leakage is testament to the quality of the cable’s build and QED’s choice of dielectrics. The signal and return conductors have a gentle twist that’s reflected in the moderate 0.54µH/m series loop inductance and low 50pF/m parallel capacitance, these ‘lumped parameters’ all indicating that the Supremus Zr cable will be suitable for both short and long stereo runs.

On duty
Let’s cut to the chase – QED’s flagship is already our choice of speaker cable running through the underfloor ducts down the spine of our Listening Room [HFN Yearbook ’25]. Its low resistance maintains the damping factor offered by big integrated amplifiers on test at the back of the room without clobbering them with undue reactance (beyond that presented by the loudspeaker load). QED’s Supremus Zr allowed the scale and rhythmic majesty of Gryphon’s Diablo 333 [HFN Dec ’24] to be fully realised, with a little help from B&W’s 801 D4 Signature speakers [HFN Sep ’23].

Above: Inside the Supremus Zr showing the 16 silver-plated 5N copper strands per conductor, each wrapped around a LDPE cylinder (white and red) and sheathed in a similar polyethylene

We experienced the slam and weight of the crescendos and cymbal crashes of ‘Entry Of The Gods Into Valhalla’, from Wagner’s Das Rheingold [Simon Bolivar Symphony Orc/Gustavo Dudamel; 48kHz/24-bit] fill the large room. Moreover this raw output was coupled to an authentically musical performance packed with detail – both in terms of instrumental colour and soundstaging. Gryphon’s integrated can drop deep, bringing serious heft to the sub-bass, unimpeded by the Supremus Zr.

Another big integrated, Marantz’s M10 [HFN Jun ’25] has its own musical flavour, in part courtesy of its Purifi-inspired Class D tech. Paired with Wilson Alexx Vfx floorstanders via QED’s Supremus Zr cable, the M10’s unfatiguing nature was revealed with a side order of power and exuberance. As the triumphant grooves of Aerosmith’s ‘Dude (Looks Like A Lady)’ [Big Ones; Geffen] were thrust forward, the M10 locked into its swaggering rhythm. Equally, the Supremus Zr was on hand to usher the Devialet Astra’s [HFN Aug ’25] tonally neutral soundscapes into view. I am sure it will remain on duty for years to come.

Hi-Fi News Verdict

The substantial cross-sectional area, and minimal reactive impedance of QED’s larger conductors has made its cables the choice for long runs in our listening room(s) for over 20 years, beginning with the XT-400. That latter cable had a more traditional figure-of-eight geometry but it was also more flexible than the mechanically stiff, if technically and subjectively superior, Supremus Zr. Wrestle this cable into place, and it’ll reward with flagship performance.

Sound Quality: 90%