The trap bar row is one of the most underutilized exercises in the gym. The trap bar (or hex bar, Dead-Squat® Bar, etc.) is great for two reasons.
First, the grip allows a neutral position with natural pull from the lats, teres major, traps, and rear delts. Proper rowing pulls the elbow just above the pelvis for maximum pull from the major back muscles.
Secondly, the hex bar is a great way to pile the weight on while minimizing stress on the shoulder joint. Stack on the plates and feel the fibers get to work.
Start with ranges between 12-15 reps. The starting position is a static hip hinge so the lighter weight will let you get more comfortable with the static hold. Lowest rep range would be 8-12 reps in order to maintain form and minimize low back stress.
Find the trap bar next time you're in the gym and see what this does for your back density!