Is the + - correct? Are the Ohms matching? Cables and attachments ok? Output wattage: matching? Could also be related to a Shielding problem. The subwoofer power board may be defective, poor contacts, condenser variable resistor is defective, and so may other issues too numerous to mention here. What ever the case, the problem seems to be isolated to the subwoofer itself.

It should go into standby mode when you shut the rest of your system down. The led on the back is supposed to be green when in use and red when on standby. I believe yours should have the "auto on" switch on the back. If you are manually shutting the sub off make sure it is the 1st thing you power down. It should not pop then. As much volume as it puts out you could damage the speaker if you do anything to cause a pop. If it pops while watching a movie or with music, check connections. I believe the manual says left input is the recommended one.