In BI-AMP mode, two power amplifiers can be used. This gives you the advantage of being able to select the best power amplifier specifications for each driver inside the loudspeaker. In a BI-AMP configuration, an external crossover is used to separate the frequencies and this splits the signal to the dedicated LF amplifier and the HF amplifier. This way, each amplifier is only working on the given frequency range and, in turn, is powering the corresponding driver inside the loudspeaker.
In PASSIVE mode, a single amplifier can be used to power all drivers inside the loudspeaker. The full frequency range is put into the loudspeaker and the loudspeakers’ internal crossover separates the frequencies, delivering the right frequencies to the right driver. In the example of a 2-way passive loudspeaker, this means that the single amplifier is powering both the HF compression driver and the LF transducer. The internal crossover takes care of both the frequency and power separation.