In short, yes, bi-wiring the Vandersteen speakers does result in a noticeable improvement in sound, especially at higher frequencies. The sound becomes more clear and open when you bi-wire. Here is why:
The purpose of bi-wiring is to provide two physically separate wire pathways; one for high frequencies and one for low frequencies, which are isolated from each other. The reason for this is that when high and low frequencies travel together in the same cable, the delicate treble information is modulated by the much more massive current and magnetic field associated with the low frequency signal. The large magnetic field blurs and distorts the delicate high frequencies. By separating the high and low frequencies, bi-wiring eliminates this kind of distortion and results in noticeably improved sound.
People often see a bi-wire setup and ask what good it could possibly do to have two separate cables (high and low) both coming from the very same amplifier (actually, the very same output terminals on that amp). The assumption is that the two cables are carrying the same information to each part of the loudspeaker. But this is not the case.
The cable which is attached to the “high” input of the loudspeaker is actually loaded by crossover components (capacitors) that will only "pull" high frequencies (in the form of current) through that particular cable. The same is true of the bass. Your amplifier doesn’t just “push” or send the entire signal through a cable that is attached to a speaker. The speaker “pulls” those frequencies that it wants (based upon the crossover components attached to each cable) from the amplifier.
To understand this better, imagine yourself in NY holding one end of a very long speaker cable, and a friend located in LA holding the other end of that same cable. You connect your end to the output of an amplifier. He connects his end to the high frequency input of a loudspeaker. When you hit play on your CD player the amp does not send the entire signal all the way to Los Angeles only to find out once it arrives that nothing below the treble frequencies are allowed to pass. Instead think of the speaker in Los Angeles as "pulling" only those frequencies that it wants from the amplifier back in NY.
Because of this, when you bi-wire, what you are really doing is moving the dividing action of the crossover from happening inside of your loudspeaker to instead happening right at the output terminals of your amplifier, which means prior to your speaker cable runs. In the NY/LA example, this means you would literally be moving the crossover action of the loudspeaker from occurring in LA to instead happening back in NY.
For an even more thorough discussion of how bi-wiring works go to: http://www.vandersteen.com/pages/Answr7.htm
