THIS invention relates to cables for electronic equipment. Particularly, this invention relates to low impedance cables for electronic equipment, which can supply high currents with low distortion.

Electronic equipment, such as, loud speakers, need to be supplied with high currents from the amplifier, particularly at low or high frequencies, or both depending upon the loudspeaker. Because of the high current, a certain amount of distortion is created at the final output, as a result of the inductance of the cable and the mechanical vibrations created due to the magnetic field along the length of the cable. The longer the cable, the greater the inductance. The inductance, along with the capacity of the output, such as an electrostatic loud speaker, creates a resonant circuit which results in a distortion in the reproduced frequency and in phase response. This distortion depends upon the length of the cable, the ohmic resistance of the cable, and the magnitude of the capacitive load applied.

In view of the foregoing, it is the aim of the invention to achieve the following objects, either alone or in combination:
   to provide a low impedance cable for electronic equipment;
   to provide a cable for electrical/electronic equipment which can supply high currents with low distortion;
   to provide a cable which attenuates the mechanical vibrations due to the magnetic forces between the conductors; and
   to provide a cable which will reduce distortion in the reproduced frequency and phase response in audio circuits.

According to this invention, there is provided a cable for electronic equipment, which includes a first set containing at least one elongate electrically conductive element interspersed with a second set containing at least one electrically conductive element, each member of the first set being electrically connected to every other member of the first set and each member of the first set being electrically insulated from every member of the second set and each member of the second set being electrically connected to every other member of the second set and being electrically insulated from every member of the first set, in such a manner that the current flow in the first set is in one direction, and the current flow in the second set is in the opposite direction, enabling the magnetic field, created by the first set, to cancel the magnetic field created by the second set, thereby at least substantially reducing the inductivity of the cable.

In accordance with one embodiment of the invention, each set comprises a plurality of elongate electrically conductive elements, typically, six strands of electrically conductive wire. Preferably, the strands are of oxygen-free, single-crystal copper, silver or a super conductor material.

The elongate elements may be flexible, in the form of strands strings, films, foils, or rigid, in the form of flats, and may be sheathed or housed in insulating material. In accordance with a preferred embodiment of the invention, insulating material is provided between each member of each set of the cable. The insulating material may even be air or vacuum or foam.

The invention will now be described with reference to the accompanying drawings, in which,

• Figure 1 illustrates the general principle of the cable in accordance with this invention;
• Figure 2 illustrates a schematic view of a relatively flexible cable, in accordance with the invention;
• Figure 3 illustrates a schematic view of a relatively rigid cable, in accordance with the invention;
• Figure 4 illustrates a schematic of the cable in which the elements of the set are in the form of sheets or foils;
• Figure 5 illustrates a schematic view of the cable in accordance with this invention in which the elements of the set are in a three dimensional array;
• Figure 6 illustrates a schematic view of the cable in accordance with this invention in which the elements are in arranged in the form of an annulus; and
• Figure 7 illustrates a schematic view of the cable in accordance with this invention in which the elements are coiled in the form of a spiral.

Referring to the drawings, a cable, in accordance with this invention, is indicated generally by the reference numeral 10.

The cable 10 in its basic scheme comprises a first set 12 containing at least one elongate electrically conductive element interspersed with a second set 14 containing at least one electrically conductive element, each member of the set 12 (if the set 12 contains more than one elongate electrically conductive element) being electrically connected to every other member of the set in such a manner that the current flow in the set 12 is in one direction indicated by the arrow 16, and the current flow in the set 14 is in the opposite direction indicated by the arrow 18. The creation of opposite magnetic fields when a current flows through the cable 10, enables the magnetic field created by the set 12 to cancel the magnetic field created by the set 14 since the current flow in the two sets are in opposite directions thereby substantially reducing the inductivity of the cable 10.

As seen in Figure 2, the cable 10, in accordance with the invention, comprises in its basic scheme, as illustrated in Figure 1, one set 12 of strands 20 being flexible elongate elements and another set 14 of strands 22. The strands 20 of the set 12 are all electrically connected to each other.

Similarly, the strands 22 of the set 14 are electrically connected to each other. As can be seen in Figure 2, the strands 20 of set 12 and the strands 22 of set 14 are interspersed in such a manner that a strand 20 of set 12 alternates with a strand 22 of set 14.

Such interspersion can be achieved by connecting alternate strands or elements in a conventional cable to form the sets 12 and 14. The current flow in one set 12 is opposite in direction to the current flow in the second set 14. Because the wires are intimately coupled by interspersion, the magnetic field induced by one strand in one set is cancelled by the magnetic field induced by its neighbor. This results in cancelling inductivity throughout the length of the cable. Increasing the number of strands in each set reduces the inductance value.

Figure 3 illustrates a rigid cable in which the strands are in the form of rigid flat elements 24 and 26 to form sets 12 and 14 respectively. The elements 24 and 26 are electrically connected and interspersed in the same manner as described in the foregoing description for Figure 2.

In both cases, that is, whether the elongate elements are flexible or rigid, preferably, the elongate elements can be sheathed in an insulating medium to reduce the internal resistance of the cable as well as its inductivity. The resonance effects can be reduced to such an extent that it lies beyond the audible range and therefore, distortion of reproduced sound is attenuated.

Figure 4 illustrates a flat flexible resilient cable 10 in which the sets 12 and 14 are made up of insulated foils, sheets or films . The elements of each set are electrically connected by soldering or other means outside the core conductive area designated by the block 30.

Figure 5 illustrates a three dimensional array of elements 32 and 34 of the sets. The advantage of a three dimensional array is that each of the elements of each set is coupled more intimately than in a two dimensional configuration because each element is is surrounded on three or even all sides, depending upon the depth of the array.

Figure 6 illustrates another alternative configuration of the cable 10 in which the elements comprise tubes or sleeves alternately place annularly around one another. For instance the set of elements 36 are electrically connected and the set of elements 38 are electrically connected in accordance with the teachings of this invention.

Figure 7 illustrates the preferred embodiment of the invention in which the elements 40 and 42 are coiled in the form of a continuous spiral, with insulation layers 44 and 46 interspersed between the elements and between the sets respectively. In this configuration the inductance will be almost completely cancelled because the elements are very intimately coupled. The other advantage of such a configuration is that the mechanical resonance is very low and therefore distortion is attenuated to a great extent.