Bi-Amp - Low frequenies and high frequencies are sent from 2 different amplifier channels. They can be from the same amp or from 2 different amplifers. The main concept is that each speaker is driven by 2 different channels. The amp and each speaker would have 4 connections (Hi +, Hi -, Low +, Low-). Best use of this method is with and external crossover and can give better sounding results since the low frequencies can be driven with a more powerful amp.
Bi-Wire - Low and high frequencies are sent from the same amplifier channel. The connectors at the amplifier end has the positive wires connected together as well as the negative wires connected together. Those 4 leads then make the run to the speaker.
Bi-Amping can have the ability to improve the sound quality or change the sound of the speakers, if an external crossover is utilized. You also can emphasize or decrease the bass in the speakers by using a different wattage amp for the low end of things.
Bi-Wire should not dramatically change the sound. You are effectively increasing the gauge of the speaker wire by using 2 runs to the same speaker.
I forget where I read the reference, but in my case using a quad cable 12 gauge speaker wire in bi-wire application is equivalent to using a single run of 9 gauge speaker wire. The main reasons I did it were for aesthetics, and for the fun of making the cables myself.
Hope this clears things up if there was confusion.
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