QED XT25 Bi-Wire Speaker Cable

Low DC Resistance

QED recognise that low d.c. resistance of the loudspeaker cable is of paramount importance for high-fidelity signal transfer. This is because the speaker presents a frequency dependent load to the amplifier of which the cable forms a variable proportion. If resistance is allowed to be too large then audible changes to the frequency response characteristics of the loudspeaker will be introduced which cannot be corrected for by the amplifier’s negative feedback loop. In order to provide a marked improvement over similarly priced cables in both QED’s own and competitors’ ranges without increasing the overall size and flexibility of the cable substantially, the cross-sectional area (CSA) of XT25 has been enlarged to 2.5mm2 of 99.999% oxygen-free copper. This instantly gives the new cable a low d.c. resistance and therefore a more accurate musical delivery.

Low-Loss Dielectric

It is not generally appreciated that the electrical signals moving at or near the speed of light in a wire do so via the medium of electromagnetic (EM) waveforms which exist within the dielectric which surrounds the conductors as well as within the conductors themselves. The movement of electrons along the conductor merely facilitates generation of the EM waveform as their “drift velocity” is only a few centimetres per second. It is therefore important to ensure that the dielectric material used to insulate and protect the central conductors of the speaker cable is of a type which “permits” the establishment of EM waveforms without appreciable loss. Dielectric losses are directly proportional to the “permittivity” of the material used and as this a measure of each material relative to that in a vacuum it should be as close to unity as possible. Like its predecessors, XT25 uses a specially formulated low-density polyethylene (LDPE) dielectric which at 1.69 has the lowest relative permittivity practically available.

Award winning heritage guaranteed

All QED cables are designed using the top down principle. XT25 represents the core musical performance trickled down from the money-no-object Supremus cable in a more affordable package. QED has won more What Hi-fi? Awards than any other single brand and with XT25 this heritage is delivered at a sensible price. Unlike most other manufacturers, QED offer an unlimited lifetime guarantee which means that if your cable ever fails to deliver to its full potential during its lifetime we will replace it free of charge.

X-Tube™ Technology....but with a twist

In loudspeaker cables high pitched sounds are forced to travel towards the outside of the conductor and so are able to use less and less of the available cross-sectional area as the pitch increases. This is called the “Skin Effect”. It means that for high frequencies the resistance of the cable appears to be much higher than it does for lower pitched sounds. Eddy currents in one conductor can affect the current flowing in an adjacent conductor so that currents flowing in the same direction move away from each other. This “Proximity Effect” also increases resistance as frequency increases. These phenomena have a detrimental effect on the fidelity of the sound you hear. The XT25 variation of QED X-Tu Insulation LDPE jacket with 100% coverage of Aluminium Mylar tape wrap Plugs and spades QED Airloc™ Forte banana plugsbe™ Technology solves these problems by creating a hollow tubular conductor geometry out of individual conductor bunches through which each frequency can pass with equal ease when compared to traditional solid or stranded conductors.

Low-Loss Dielectric

Music signals in a loudspeaker cable move back and forth many times every second. The insulating material used to separate the send and return conductors from each other (the dielectric) has to be charged and discharged every time. Not all of the energy stored in the dielectric during each charge cycle is completely returned during each discharge cycle which has a detrimental effect on the fidelity of the sound you hear. That’s why QED use low-loss dielectric materials such as Polyethylene (PE) or Teflon™ (PTFE) in preference to cheaper PVC alternatives found in inferior unbranded cables.

99.999% Oxygen-Free Copper

Speaker cables need to have a large current carrying capacity. If the electrical resistance of the cable is too large, part of the music signal will be lost, causing a detrimental effect on the fidelity of the sound you hear. To stop this from happening QED make the resistance of their speaker cables as small as possible. QED do this by using the largest practical cross-sectional area of copper within the size constraints of each cable. In order to squeeze the last drop of performance from the conductors they make sure that there are no impurities in the copper which would defeat the object of making them so large. That’s why QED use 99.999% oxygen-free copper exclusively.

OUTSIDE DIAMETER

13.1 mm

CONDUCTOR AREA

5.0 mm2

CONDUCTOR CHEMISTRY

99.999% oxygen-free copper

DIELECTRIC PROPERTIES

Air Gap (εr = 1.69)

LOOP RESISTANCE

7.0 mΩ/m

PARALLEL CAPACITANCE

69 pF/m

DISSIPATION FACTOR @ 10 KHZ

0.0001

SELF-INDUCTANCE

0.36 μH/m