Subwoofer count vs channel count
Splitting one output to four subwoofers adds displacement but does not give the processor independent control of each unit. Independent outputs allow individual level, delay and EQ strategies.
Routing and crossover logic
Advanced processors may route bass from different speaker groups to different subs or bass arrays instead of sending every channel into one global mono bass bus.
Delay and phase
Time alignment determines whether subs reinforce or cancel one another around crossover regions and modal frequencies.
Consistency across seats
A single-seat optimisation can create excellent bass at the main chair while making adjacent seats worse. Multi-sub design aims for useful consistency across the listening area.
Arrays and WaveForming
Front/rear arrays take the idea further by treating low-frequency energy as a controllable wavefront.
What to ask of the processor
Ask how many bass channels are truly independent, what filters and delays are available, whether the correction system optimises subs jointly, and whether the architecture can support future arrays.