I've heard that MDF is prone to strip screw holes if you have to disassemble and then reassemble. If having difficulty, Google <striped wood screw repair insert>. You can drill oversize hole for repair insert. If worried that insert will be too close to edge and chip MDF you can drill large enough hole to slip insert into, place metal bolt into hole so it is flush with end of insert, use a nut to lock metal screw in place, tape end of insert that is going into hole, use good glue, epoxy or whatever you know will hold insert. Use bolt to turn insert into hole. Then keeping bolt from turning, back locking nut away from glue, careful not to get any glue on bolt. Then when glue is dry remove bolt. Then reassemble with bolt/metal screw. Try on a scrap piece of wood to perfect tecnic so you are comfortable on speakers. On past projects repairing holes in metal such as door hinges on pickup I have had to place one bolt into hinge, then drill another hole that overlapped 1st bolt, to move hole due to bent hinge that I cold not repair. I never use Heli coils anymore, just drill for oversize hole. Tap for larger bolt, then drill larger bolt to tap for original size bolt. If concerned that oversize bolt won't stay, you can drill smaller hole that intersects the threads, tap and place small bolt, then grind flush if needed. Much less expensive and has worked well for me several times.
You can even build your own insert for using in wood by tapping a piece of round stock metal, or threaded stock that can be obtained at most hardware stores. I have even heard of fixing cracked Tractor engine block by interlaping a series of bolts. Farmer saved the cost of buying new engine, or at least engine block. (I ramble, but you probably know that by now).
Some times I am as Happy as a Frog on a Lilly Pad.
Other times I feel as though I have Just Been Gigged