Advantages of Actively Bi-Amped Speakers:
o Dynamic range gain. Even if it appears a bit counterintuitive, with wideband audio signals, like music, an active system with two 100 W amplifiers has a maximum SPL which is 3 dB higher than a passive system with a single 200 W amplifier. Usually the difference is even bigger because of the passive crossover losses, that get removed in the active system, and other minor factors, like bass range amp clipping being filtered by the intrinsic limited bandwidth of the woofers. Most of the times the perceived dynamic range gain is in the 6 dB range, i.e. a two way system with two 100 W amplifiers often sound almost as loud as a passive system with a single 800 W amplifier.
o Better loudspeakers control. The series resistance and losses introduced by the passive crossover components reduces the amplifier damping factor seen by the drivers. This becomes audible, especially in the bass range, where big inductors with series resistances up to 1 Ohm are often used and where the speaker self damping is quite low. With the active approach the drivers are connected directly to the amplifiers, with no series resistance introduced by passive components.
o Each amplifier sees a much more constant load
o Amplifier operates in a narrow frequency band, hence lower IMD (intermodulation distortion, where frequencies combine and spurious distortions arise as a result)
o Drivers are physical separated so one cannot influence the other. Back-EMF from one driver goes straight back to the amp and cannot travel back into the sensitive tweeter.
o It's easy to design the crossovers, you just build them for the freq you want and there is no influence from them on the other crossovers
o Amplifiers may be operating at much lower levels for tweeters than woofers - cheaper amps, and amplifier now operating in much lower distortion range
o Digital crossovers offer new and interesting ways to apply crossovers to the input signal, including some techniques which are simply not available with analog crossovers
o Crossovers are operating with small signal levels (0-2v instead of 0-60V), consequently they can be built using much smaller parts with consequently higher tolerances and quality. The change in components also allows much more accurate crossovers to be built.
o It's possible to "time-align" the drivers. i.e. delay the tweeter signal so that it arrives at the same time as the woofer signal
o Physical relocation of drivers is possible! The most extreme form of the above is advocated by TacT where you physically locate the bass speaker (sub woofer) against a wall where it should work more efficiently, and then add a delay to the main speakers so that the sound from the woofer and main speakers arrives perfectly at the listening position!