Single-channel amplifiers are the optimal solution if you want to add a subwoofer to your equipment. Single-channel amplifiers, often also called monoblocks, have only 1 channel, which varies in power according to impedance. As the impedance decreases, the power of the amplifier usually increases, which allows the connection of more powerful subwoofers. The advantage of monoblocs is the possibility of connecting one or more subwoofers with higher power and low impedance.