AV systems are designed around multiples of 4 channels: 3 front channels + 1 LFE; 2 surround channels and 2 ceiling channels; 4 surround channels; 4 ceiling channels.
The 4 inputs x 8 outputs DSP controller is the most universal and versatile format.
The Contol 4.8 is a digital active crossover that comprises 4 inputs and 8 outputs. Any of the 4 input signals can be routed to any of the 8 outputs. These signals can also be summed on any single output.