^ Pay close attention to this.
If it's not this then something is broken, possibly a result of said low EQ abuse.
There's an easy test you can make on any cab with a 1/4" input jack.
9V battery applied across the exposed cable end, tip +ve, will make the speakers pop out when the -ve hits the cable shaft. All going well it will give you a big fright with the bang it makes.
If one or two stay still or move backwards you have miswired or broken speakers.