That is one of the problems that a lot of guys have with them. I've tried them and I can't get it slow enough either. If you slow down then it doesn't sound right because your not getting enough air pressure against the reeds. I've never taken one apart, but to me I think they needed a thicker reed in them, which would required more air pressure but run slower? You have to use the air from your chest, not like you would doing a feeder duck call. Up close they don't sound all that bad, but from a distance it's hard to hear the gobbling sound in them because it's too fast, not like you can on a box call. My opinion your much better off using a deep rasp box call that you can control the sound and speed of your gobbles.
Dodge County NWTF Chapter
WI. Youth Turkey Mentor
*Safe Hunting Is No Accident*
It takes One Second to be Stupid, a Lifetime to be Safe.