What's the current thinking on horizontal bi-amping
well... different people mix them up and give them different names.
to me, vertical biamping is one amp for bass, one amp for treble. This method is pointless and has almost no benefit whatsoever. As you still end up running all the bass for R and L off one power supply. It doesnt improve overhead etc.
Horizontal, as I understand it (and have used in the past) is using one stereo amp per speaker, where one channel handles the treble and one handles the bass. The benefits of this method are:
-as with monoblocks, better stereo seperation, as its one amp per speaker
-bass is now split over two amps, so load is halfed and more reserve current should be available. In fact some amps state that with only one channel driven, output is higher.
-you also get any potential benefits of vertical biamping, e.g. seperate runs to the tweeter, seperation of frequencies etc.
Seems to me, vertical biamping has few if any merits, but horizontal has all of the same merits as vertical, but with a few extra of its own. Seems to me, the only sensible way to biamp in a passive system.