Mitch, thanks!
08-06-13: Hk_fan
In your first scenario the full 400W are being SHARED among all the drivers.
For sake of simplicity lets say there are 2 drivers, and assume that they have exactly the same impedance and efficiency. Therefore the two drivers will perfectly split the 400W, 200W per driver.
Somehow my point is not getting across, and I'm not sure how to explain it any more clearly than I already have.
But in the case of your two-driver example with the 400W amplifier, the two drivers will NOT "perfectly split the 400W, 200W per driver."
The 400W will be divided between the two drivers based on the frequency content of the music, at any instant of time. That is what you seem to be overlooking.
If a bass drum beat is loud enough to require 400W, since most of its energy is at low frequencies the low frequency driver will get most of the 400W, assuming that no other loud notes occur at the same time. While if a cymbal crash is loud enough to require 400W the high frequency driver will get most of the 400W (just before it expires :-)), assuming that no other loud notes occur at the same time.
This is no different than individual drivers connected to a single 200W amp each.
It is very different. In the above situation the biamped 200W amplifiers will only be able to supply 200W to the low frequency driver when the bass drum beat occurs, and they will only be able to supply 200W to the high frequency driver when the cymbal crash occurs. Not 400W (or close to it, depending on the harmonic structure of the note), which could be supplied to that one driver by the single-amped 400W amplifier.
Regards,
-- Al