Open reed calls work the best for me.
Its best to see the bear first and then start calling, since you can control on how fast the bear comes to you.
Unseen bears, its best to call with a partner, since the bear will be coming in fast.
The key is to call in very long sessions and be aware of them crashing in on a fast run.
Most of the time when you stop calling they stop coming in.
yooper77