As already stated, the "shotgun" bi-wire pattern has two completely separate runs of wire that are joined together at the amplifier end -- think of it like a giant "V". The internal bi-wire involves using a single run of wire (usually braided) and separating the braids or wires into two terminations at both the amp and speaker ends.
Richard Vandersteen, in an interview with one of the major audio mags, talked about his research into the merits of bi-wiring (recommended for the Vandy 3A and Model 5 speakers), and stated that the primary benefit of using a true (shotgun) bi-wire is to minimize the effects of interplay between the electrical fields in the two sets of wires. Apparently, this ensures that the mid/high frequency drivers get a clean signal that is "uncontaminated" by interaction with the low frequency signal. Vandersteen also said that speakers with dual crossovers/speaker posts will benefit the most from shotgun bi-wiring.
Richard Vandersteen, in an interview with one of the major audio mags, talked about his research into the merits of bi-wiring (recommended for the Vandy 3A and Model 5 speakers), and stated that the primary benefit of using a true (shotgun) bi-wire is to minimize the effects of interplay between the electrical fields in the two sets of wires. Apparently, this ensures that the mid/high frequency drivers get a clean signal that is "uncontaminated" by interaction with the low frequency signal. Vandersteen also said that speakers with dual crossovers/speaker posts will benefit the most from shotgun bi-wiring.