Also posted on AVS... A couple of us were getting into this discussion in another thread and rather than take that thread hopelessly off topic, I thought I'd start a new one on this subject. I've seen passive biamping refered to as "fool's biamping". My personal experience with passive biamping is that there was a benefit, but I do concede that it may not have been an apples to apples comparision as I had moved from my receiver's center amp to the its two main amps. The improvement could have been due to the receiver having better quality mains amplifiers than its other channels. Here is what my Paradigm Reference speaker manuals say about passive biamping: "Passive biamping provides a dramatic improvement in clarity, openness and detail with much better bass solidity and definition. The presentation of music is simply more intelligible and transparent. With passive biamping the speaker's internal passive crossover remains connected. An external crossover is not required and cannot be used (there is no direct electrical access to individual drive units). This saves expense and set-up difficulties. Passive biamping fully optimizes your speaker" ... it goes on to explain the differences between horizontal and vertical biamping and the benefits of both. Manufacturer's bull? Or is there perhaps a real benefit to biamping if the speaker has been designed for it?