A popping noise from the subwoofer indicates a power mismatch in the circuit. The popping noise occurs as the amplifier tries to produce more voltage than it can to meet the demands of the subwoofer. This ends up clipping the sound on every cycle.
A power mismatch is not the only issue that causes a popping noise from the subwoofer. The noise may also be due to loose connections in the circuit.
To fix the error, check that the power outage from the amplifier matches the subwoofer's RMS. The amplifier producing much less power than it should could be clipping the subwoofer, but also check if it’s producing more power than the subwoofer can handle. More RMS power from the amplifier gradually heats up the voice coil and may burn it out. A solution to this is getting a condenser that’s used to steady the power and transmit it out in stable currents.
A loose connection may also exist in the wire connections to the amplifier, voice coil or in the subwoofer itself. Carefully check all these wires and ensure that none of them are loose or melted away. Wires connecting the speaker cones and voice coils should also be checked and tightened.