“Some audiophiles feel that bi-wiring produces an audible improvement over standard single cabling. For example, John Atkinson, writing in Stereophile, states that he observes "subtle but important" differences, particularly in reduction of treble hardness and improvement in bass control in one review.”
And this from Definitive Technology,
“Does doubling the connections double the sound quality?
Bi-wiring is intended to minimize impedance differences between high and low frequencies and its impact on the overall sound you experience. The result is an improvement in the midrange that many enthusiasts believe is significant enough to justify running the additional cable. You may not double the quality of your playback, but you will likely notice a major boost in clarity.”
There’s also this from Polk Audio, who knows something about speakers,
”What is it?
Bi-wiring is the using separate speaker wire connections to split the signal between high and low frequencies.
What does it accomplish?
The theory behind bi-wiring is that it can elevate a great sounding speaker and produce subtle, enjoyable, improvements in overall sound quality. In a sense, bi-wiring is to speaker connections as “star grounding” is to electronics connections.
When a piece of audio equipment uses a single circuit grounding point for all electronic sections as opposed to connecting them in a “daisy-chain” fashion, this is referred to as “star grounding.” The integrity of each ground path is maintained by individual connections to a low impedance point.
The same concept is applied when bi-wiring your audio system. Each “section” of your speaker is independently connected to the low impedance point (output transistors) in your receiver or amplifier. The effects of bi-wiring have been described as “lifting a veil from the mid-range” and that “voices seem clearer, more distinct, and less muffled.””