I've found that with highly transparent & revealing speakers like my Apogees, vertical bi-amping is the way to go. Mixing'n matching amps between the bass panels and the midrange/tweeter ribbon has always lead to a dynamic discontinuity between the drivers. While it may sound great with sedate music, when things got rough and tumble, one driver would always "stick out" of the presentation relative to the other. This has been true with the various cone'n dome speakers I've had as well (Vandersteen in particular).
The only exception to this in my experience has been with subwoofers. Don't forget adding a powered sub (with the amp and active x-over being either internal or external to the sub)IS active bi-amping. I would also encourage anyone who has a powered sub and using a good active x-over (again internal or external to the sub), to take the low level high pass signal, split it and passively bi-amp with it. By cutting the lows from the midrange/tweeter signal, you're putting considerably less stress on that amplifier channel and the passive x-over that feed the midrange and tweeter. The passive x-over in particular will be much better behaved as the coils and caps will be much less prone to saturation since they are'nt seeing the full range signal anymore. The sonic differences are immediate and obvious, even with less than the best speakers (actually, the difference tends to be more readily noticable with the lower-FI speakers as the x-overs that feed the midranges and tweeters are not that well built and readily appreciate the leaner signal diet).
The above high pass signal stuff is all relative to passivley bi-amping the speakers full range. You still have the signal filtering advantages even if you don't passively bi-amp with the highpass signal from an active sub x-over....It's just that when you do, things go up a couple of more notches over a single amp than you might have expected.
The only exception to this in my experience has been with subwoofers. Don't forget adding a powered sub (with the amp and active x-over being either internal or external to the sub)IS active bi-amping. I would also encourage anyone who has a powered sub and using a good active x-over (again internal or external to the sub), to take the low level high pass signal, split it and passively bi-amp with it. By cutting the lows from the midrange/tweeter signal, you're putting considerably less stress on that amplifier channel and the passive x-over that feed the midrange and tweeter. The passive x-over in particular will be much better behaved as the coils and caps will be much less prone to saturation since they are'nt seeing the full range signal anymore. The sonic differences are immediate and obvious, even with less than the best speakers (actually, the difference tends to be more readily noticable with the lower-FI speakers as the x-overs that feed the midranges and tweeters are not that well built and readily appreciate the leaner signal diet).
The above high pass signal stuff is all relative to passivley bi-amping the speakers full range. You still have the signal filtering advantages even if you don't passively bi-amp with the highpass signal from an active sub x-over....It's just that when you do, things go up a couple of more notches over a single amp than you might have expected.