Without a doubt, I’d have to say “pull-ups” are the most effective exercise that will provide that wide-as-a-barn-door back. A lot of athletes shy away from pull-ups (some times called chin-ups) because they can’t do many of them, but this should not be an excuse.
Particularly if you’re a bigger bodybuilder, pull-ups place a tremendous overload on virtually every muscle in the upper body; the muscles that aren’t doing the lifting, are working hard to stabilize the torso. Forget those modern pull-up machines. If you can’t do one complete pull-up unassisted, work at it until you can. (What kind of bodybuilder are you if you can’t do one pull-up?) Suck it up and get to work.
To incorporate pull-ups into your routine, the best way is to perform them early in your Max-OT workout. The most effective way to do this is to perform the warm up procedure found in Max-OT on the pull-down machine. This will get some much needed heat and lubrication in joints as well as prime the nervous system for high-intensity muscle recruitment. Once this warm up is done, do not do any working sets on this machine. Instead, go straight to the pull-up bar to crank out two working sets of pull-ups.