Unclejeff, with a horizontal biamp, one amp is used to power the mid/tweeter of both speakers and the other amp is used to power both speakers woofer sections. In a vertical biamp one amp becomes the left and the other the right channel with say the designated left channel of that amp powering the mid/tweeter and the designated right channel powering the woofer. The supposed advantage is that one amp is not overly taxed driving both speakers woofer sections. It is thought that there will rarely be high level bass and treble in one channel at the same time and the amps will have a greater power reserve and better dynamics.
