No monetary value of the world

I had brought my subwoofer.
After a day of subwoofer was there. So far so good!
When unpacking the package, I realized there is no manual, the power cord is too thin to connect the subwoofer to the car battery.
After a brief search, I found only negative things about the subwoofer.

Now I'm trying the subwoofer to send back, but the seller does not answer.

My quote:
Stay away from such cheap things!

Greeting Leo