08-05-13: Hk_fan
If you are bi-amping with 2x200W (@8 Ohms) amps then yes you have 400WPC (@8 Ohms).
As Al said above, the instantaneous power is a function of the impedance of the speaker at a given frequency as well as the power supply of the amplifier.
However, note that I also said the following:
If the amps are rated at 200W into 8 ohms, and if the impedance of the speakers is close to 8 ohms at all frequencies (which is unlikely), 200W will be available at frequencies that are substantially below the crossover point, and another 200W will be available at frequencies that are substantially above the crossover point. But since music consists of many frequencies that are present at the same time, the answer will vary depending on the relation between the specific frequency content of the music at any instant of time and the frequency of the crossover point, as well as the slopes of the crossover.
Let me cite an extreme example to illustrate this point. Suppose that the crossover point is 5 kHz, and the slopes of the crossover filters are sharp. The high frequency amplifier will handle very little energy below 5 kHz, while the low frequency amplifier will handle very little energy above 5 kHz. On nearly all music at nearly all times the energy that is present above 5 kHz is vastly less than the energy that is present below 5 kHz. Therefore most of the power capability of the high frequency amp will almost never be utilized. Very conceivably no more than perhaps 20 watts of its capability will ever be used (20 watts being only 10 db less than 200 watts). Therefore it is incorrect to say that 400W is "available," which was the OP's question.
My understanding is that most music at most times tends to have a roughly equal amount of energy above and below a frequency of something like 350 Hz.
Regards,
-- Al
