Not a safe setup.
Use marrettes as Richard suggested. You will have to cut off the spade lugs or get a terminal block where you can attach the spade lugs under a screw.
+ 100 
+1000
Taping together wires with a possible nebulous connection, then taping them to a flammable material ain't a particularly good idea.
Since this looks like a dedicated cab, I am hoping that any required monitor isolation is being done.
x2
You've already found a solution, but keep the following in mind on future projects. One should have no qualms cutting and capping or modifying a wire if one is dealing with anything over the standard "safe" voltages. Wires are cheap, a couple of dollars at most. Your home, your life, your family etc etc is certainly worth more than a couple of dollars.