HI Dave, How about coating the driver cone with something to change the mass distribution? I don't know the equations, but someone like Wayne or Martin might. It seems like the peak may be caused by excited resonance because of cone breakup (i am not even sure if cone break-up can cause resonance but I am going to go ahead & speculate anyway!!). Changing the mass distribution may alter this. Just a (very speculative) thought. -akhilesh