Hi Brian:
Due to the length, you will have to find a larger gauge Extension cord. You will need a Medium Duty extension cord based upon the voltage draw you will need,
Medium-duty cords usually are grounded extension cords, which include the third wire for grounding. They have plugs that accept three-prong grounded appliance cords.
Uses televisions, computers and other devices that draw up to 10 amps of power.
Cord length up to 25 feet: use No. 16-gauge wire.
Cord length up to 50 feet: use No. 14-gauge wire.
Cord length up to 100 feet: use No. 12-gauge wire.
I would recommend a single 100 foot 12 gauge Extension cord. When you add the 3.3 ft from power plug to the transformer and them 16 plus feet from the transformer to the Speaker (for roughly 120 ft total, that should work)
TL/5227