The amplifiers can be two channels of a 4 channel amp, or a 7 channel amp or whatever is most convenient. Any of these combinations will work, however completely seperate monoblock amps would totally avoid any power supply interaction. An amplifier with seperate power transformers per channel will act like monoblocks.

The next best thing would be to use two channels that share a common power transformer (and associated power supply components) for the left and right woofers, and two other channels that share a common power transformer for the left and right tweeters. This avoids interaction between the low frequency amps and the high frequency amps.

The world will not come to an end however if you use, say, an amplifier that has one power transformer for 4 channels. Unless you really crank the amplifier to the edge of clipping, the interaction will likely be below audibility.

There is another benefit to active bi-amping you should be aware of. You can use a much lower powered amplifier for the high frequency drivers since the power demands are nowhere near those of the low frequencies. If you have a 100 watt amplifier for the woofers, you could probably use something in the neighborhood of a 30-50 watt amp for the highs (depending on the crossover frequency - the lower it is, the more power you need in the high frequencies).

This also opens up the door for using something like a class "A" amplifier (or a class "A/B" amp that runs rather more into the "A" class than the "B" class) for the high frequencies. Tube amps are ideal for the highs because the power demands are less, the damping factor requirements are less, and class "A/B" tube amps by their nature run very rich bias - they run essentially class "A" up to a significant amount of their rated power. This makes these amps practically immune to crossover distortion. A single-ended triode tube amp would run pure class "A" and there would be no crossover distortion since there is no crossover, but this type of amp is probably not warranted unless you have extremely sensitive speakers like I do (or else you simply like SET amps).

Whether you go solid state or tubes for the highs, an active bi-amp system will sound worlds better than using speakers with passive crossovers.


[This message has been edited by soundhound (edited May 12, 2004).]