Originally Posted by skidog
I asked him if it would hurt anything and he said no, which I am somewhat sceptical of. I have one of those plugs in my hands now but not sure wether I should use it.
Look at the plug on the sub. Are the blades of a different size? If one looks at extension cords around the house, if using contemporary extension cords, they'll note one blade opening is larger than the other and if one looks at the bladed end of the extension cord, they'll note one blade is slightly flared. This is done so short of forcing a plug into an outlet, by design, a person will be forced to properly plug polarized items into polarized wall outlets.
If one were to open up a wall outlet to either 120v or 240v, they'll note the wires are either red, black, white or green. Green is ground and white is Neutral return (ground) and the Red/Black legs are hot leads. Each carry 120v to be carried back to 'Earth," the electric generation plant via the White lead. The ground is for if there's a short to metal casing or the mechanical insides of the appliance, the 120v will be bled off to (Earth) via the Ground lead to allow the current to flow as opposed to shorting and creating heat which can cause a fire. This simply another way for the electricity to access Earth or Ground.
Yada, yada, yada, long story short, as long as the big blade (male) goes into the big blade opening (female) of the power cord , assuming whom ever installed the wall outlet, did so correctly, you're good to go.