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QED XT25 Speaker Cable
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QED XT25 Speaker Cable

The QED speaker cable story began in 1973, with the launch of the world’s first specialist speaker cables, QED 42 and 79 strand, now household names in the audio industry. Building on this longstanding British speaker cable heritage, QED embarked on an exhaustive rese ... more
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Man. Part No.: QED XT25

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QED XT25 Speaker Cable
Per Metre

(Unterminated)

QED XT25 Speaker Cable

 

The QED speaker cable story began in 1973, with the launch of the world’s first specialist speaker cables, QED 42 and 79 strand, now household names in the audio industry. Building on this longstanding British speaker cable heritage, QED embarked on an exhaustive research program into cable parameters which began in 1995 and continues into 2017 with the release of “The Sound of Science”, a 40 page White Paper distilling the research published since 1973 by QED.

These reports set out the “top down” design-principles that have resulted most recently in the development of QED XT25 loudspeaker cable – the new class leading standard in budget to mid-range speaker cables. 

X-Tube™ technology first came to prominence in 2005 with the launch of the world renowned Silver Anniversary XT, the most highly awarded mid-range cable in the world, winning the What Hi-Fi Product of the Year three years in a row. These design principles also grace the multiple award winning XT40 speaker cable and XT25.

As frequency increases, electrons flow more and more towards the periphery of a conductor so that if the frequency is high enough only a very thin layer (or skin) on the outside of the conductor is used. This “skin depth” varies for different materials at a fixed frequency and in copper it means that if a conductor has larger than 0.66 mm2 cross-sectional area not all of that area is available for an analogue music signal to use. In SAXT the “skin effect” problem was effectively eliminated by the use of X-Tube™ Technology which works by placing all of the conducting material around a central hollow insulating rod. However, for a.c. signals, changing magnetic fields generated by the flow of current set up eddy currents in nearby conductors which force current to flow only in areas furthest away from conductors carrying current in the same direction and vice versa. 

This “proximity effect” has a detrimental influence on current distribution in a speaker cable even if it utilises X-Tube™ Technology. With XT25 we tackle the proximity effect and the skin effect by combining our existing Aircore™ and X-Tube™ Technologies into a new X-Tube™ variation. By forming the conductors into a tube-like shape with a hollow centre, current densities at higher frequencies are maintained because the electric field which contributes towards the skin effect acts towards the centre of the conductor from where the conductive material has been removed. At the same time instead of using a braided structure a ring of conductors is formed into separate bundles with only a loose electrical association which are then twisted into a 90 mm lay so that no single conductor bundle remains on the inside or outside of the cable (and therefore prey to the proximity effect) for long enough for it to become an audible problem. This geometry promotes a more consistent signal distribution making for a more accurate musical reproduction.

Low DC Resistance

At QED we 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 our own and our 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.

QED research has shown that low capacitance cables are generally preferred in listening tests over high capacitance counterparts and this is usually because low-loss dielectrics have been utilised. The use of LDPE and careful control of conductor spacing results in a cable with a very low capacitance per meter and a dissipation factor (loss tangent) of 0.0001 at 10 kHz.

What is the result of all these techniques?

The graph below shows how the dc resistance of XT25 remains effectively unchanged across the entire audible frequency band when compared to a conventional cable of the same cross-sectional area. Combined with the sonic advantages of a low loss dielectric the improvements in current distribution place the new cable in a class well above cables with a less sophisticated geometry.

So, unless you invest in XT25 with QED X-Tube™ technology you can be losing a lot of the performance of your expensive loudspeakers.

What makes XT25 unique?


1. Award winning heritage guaranteed
All QED cables are designed using the top down principle. XT25 represents the core musical performance trickled down from our 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.

2. 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-Tube™ 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.

3. 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 at QED we use low-loss dielectric materials such as Polyethylene (PE) or Teflon™ (PTFE) in preference to cheaper PVC alternatives found in inferior unbranded cables.

4. 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 we make the resistance of our speaker cables as small as possible. We 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 we make sure that there are no impurities in the copper which would defeat the object of making them so large. That’s why we use 99.999% oxygen-free copper exclusively.

Specification


Cross-sectional area 2.5 mm2
Wire gauge 14 AWG
Jacket outside diameter 3.96 mm
Loop inductance 0.52 μH/m
Loop resistance 13.4 mΩ/m
Capacitance 35.0 pF/m
Dissipation factor @ 10 kHz 0.0001
Conductors 10 x 19/0.13 mm
Insulation LDPE jacket with 100% coverage of Aluminium Mylar tape wrap
Plugs We recommend QED Screwloc ABS 4mm plugs

Additional Information

Promotion No
Manufacturer's Part No. QED XT25
EAN No
Length N/A
Amplifier Award 5 Star
Connections No
Audio Interconnect No
Profile Normal
Video Features No
Features No
Bi Wire No

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*Finance is available to UK applicants 18 years of age or older and subject to status. Finance is not available for business customers. Prices are correct at time of going to press and are subject to change during the term of this offer without notice. Terms and conditions are available on request. Finance agreements are available on orders between  £389 and £10,000 (including VAT and shipping). Please ensure you are able to keep up repayments of any finance package taken.

Now Group UK Ltd trading as Exceptional AV operates under a Consumer Credit Licence, No. 560813.
This licence is issued by The Director General of Fair Trading at the Office of Fair Trading in accordance with the Consumer Credit Act 1974.

QED XT25 Speaker Cable

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Changing your Mind
It's OK to change your mind but please be aware that all goods must be returned in as new, unused and re-saleable condition. This means that all packaging must be intact, all accessories are complete in their original wrappers and any free items are also returned with the goods. Essentially the product must be returned in the same condition as you would expect to receive a new unit in. In all cases the cost of returning the goods will be the customer's responsibility. All faulty items must be returned complete and will be repaired under the manufacturer's warranty.

 

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Depending on how long you have had the goods there are different options availble to you. In the case of faulty items, if the item fails due to a manufacturing fault between 1 and 28 days from delivery we will exchange it for a brand new one of the same model. Any items which are found faulty after 28 days from delivery will be repaired under the manufacturers warranty. For returns where you have changed your mind, please find our policy below:

Returns

Exchange
This is were you return your item and we will exchange it for another item of equal or higher value. If the item you wish to change to is of higher value you only pay the difference. If the item is of a lower value we will issue you with a credit note for the difference which you can spend with us at a later date.

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If your item is returned to us between 29 and 90 days from delivery we will charge a restocking fee of 25% of the price you paid for the item initially. This will be deducted from the value of the exchange or credit note which is issued to you. This is because  technology in the AV marketplace moves fast, and as a result the value of items decrease very quickly.

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