Crossovers are essential in any multi-driver speaker. The crossover frequency (e.g., 2.5 kHz between woofer and tweeter in a 2-way monitor) determines where the signal splits. The slope (e.g., 12 dB/octave, 24 dB/octave) determines how sharply frequencies are divided. Steeper slopes reduce driver overlap but add phase shift.
Active crossovers (before amplification, using DSP or analog circuits) are more precise than passive crossovers (after amplification, using capacitors and inductors). Most studio monitors use active crossovers. Subwoofer integration requires careful crossover setup to avoid a gap or overlap at the crossover point.