Non-mach stereo Issues

The speakers on the left side of my car stopped working. What are the chances its the wiring? I'm thinkin about just going and getting a new head-unit installed. I don't have a voltage tester, but also now if I turn it up past 1/2 volume the speakers on the right side crackle really bad. Any input would be helpful.
 
Hello blown speakers! If they went out at the same time, it might be the wiring, but since you said the right ones are crackling now, I am sure they are both toast. Is the car a vert or coupe and are they the factory speakers running off an aftermarket headunit?