"Vertically it's no secret.(sic)Need a mono conversion switch and viola." Huh? One does NOT need a 'mono conversion switch', whatever that is, to biamp vertically. One merely needs a couple 1-to-2 Y-adapters to get the same signal to both channels of each amp. One connects 2 speakercables to each speaker, and you're now vertically biamping.
Horizontal biamping uses 2 stereo amps with one driving the 2 bass ends of the speakers and the other amp driving the MR/treble ends of the speakers. One needs a gain control on the more-sensitive amp (and that's 1-Watt sensitivity, not full-output sensitivity), or the balance of lower and higher frequencies will be wrong. The easiest way to deal with crossovers is to use those already in the speakers, and this is called passive biamping or filtering. Using active (i.e. line-level) crossovers and bypassing the speakers' crossovers is called active biamping or filtering. There are positives and negatives to both and fans of both, some quite vocal. Both work and both will gain the advantage of being able to use amps that are better suited to the frequencies assigned.
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Horizontal biamping uses 2 stereo amps with one driving the 2 bass ends of the speakers and the other amp driving the MR/treble ends of the speakers. One needs a gain control on the more-sensitive amp (and that's 1-Watt sensitivity, not full-output sensitivity), or the balance of lower and higher frequencies will be wrong. The easiest way to deal with crossovers is to use those already in the speakers, and this is called passive biamping or filtering. Using active (i.e. line-level) crossovers and bypassing the speakers' crossovers is called active biamping or filtering. There are positives and negatives to both and fans of both, some quite vocal. Both work and both will gain the advantage of being able to use amps that are better suited to the frequencies assigned.
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