Sounds like he's only shock gobbling at you, and you only have one box that's loud enough to make him shock gobble. You said you've been after him for three days, is he going to the same area to drum each time, but not leaving that area? Chances are that's an old bird, that won't go looking for hens, just stays put until one shows up or he moves off to his other strut zones until he finds a hen that'll come to him. If that's the case, forget about hen talking to him, set up in that exact area, do a little hen talking then switch and do mostly gobbler or jake talk, super raspy yelps or deep clucks, keeyelps and kee kees. Try that the next time he's in your area. I'm betting he's not gobbling much once he's in his strut zones either? Most old birds that get any preasure on them won't set foot 10 yards out of their travel paths, no matter what you throw at them.