A lot is being said about sense or nonsense of biwiring but what it is about is that loudspeakers are nonlinear. If the woofer draws a distorted current, biwiring can prevent this current from causing distortion in the voltage going to the tweeter. What it takes is an amplifier with output impedance much lower than that of the speaker cable. Running two separate cables between the amp and speaker will make a difference. Since the amplifier feedback senses exactly where the speaker cable is connected, you can just connect two sets at the same point and be certain that the common impedance between the HF/LF current loops is just the amplifier's output impedance.
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Use separate cables, not cables that bunch both runs together. You want to avoid coupling between the runs, not promote it. You'll find that with an amp like Ncore, biwiring sounds almost like biamping. Bad for my business to tell you this, I know...
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Likewise, speaker cables do not couple capacitively, they couple inductively. Keeping them apart is the easiest way to prevent them from undoing the benefit of biwiring. Another method is the one used in cat5 cables: use different pitches of twist.