8' of copper 16 AWG ... 16' there and back gives us 0.064 ohms for a 3.5Vrms drop you had to be running just over 54 Amps ...(or if 3.5V is peak then 38Amps rms)
Your cable must have been smokin' @ not 50W but 186 Watts (95W if only 38A) at least you now know where to lay the new wire ... just follow the burn marks on the floor.