Purchased the Hale Fire over the winter and have been practicing with it. It took a while to get anything that sounded close to a gobble. I'm at the point where it doesn't sound too bad. I am hoping it sounds better in the woods and from a distance.
Since I purchased the darn thing, I also did some internet research and learned two ways to gobble with a diaphragm call. I'll be darned if the diaphragm doesn't sound just as good if not better than the Hale Fire! With the diaphragm, you can push the call back farther on the roof of your mouth, and then say "chicka-chocka-chocka-chocka". Cupping your hands in various positions helps to hollow out the sound. Takes a while. The second method is the "buck tooth" (sorry) method, which is to place the call between your upper lip and teeth/gum with the later reeds resting on the bottom lip. You then say "tooka-tooka-tooka-tooka", which is the same sound you use for the Hale Fire.
I have enjoyed working on these gobble calls and I'm very interested in how they will sound in the turkey woods soon.