Dont want to sound cocky, but as a med school student with pretty detailed knowledge of the auditory system and its function,as well as physics behind it, and having spent 4 months on the otorhinolaryngology department in the clinical center as a part of a audiology course, worked with hearing aid devices, I think I know something about it. I dont use or need withcraft to describe or understand something. You saying that what I'm hearing while playing a pure 25 hz tone is not the actual tone, because I cant hear it, is irrelevant and in this case totally wrong. If you're going to use that logic, then you're never ever hearing a pure tone, no matter what frequency you're playing trough any sort of headphone or speaker, you're always going to hear something other than the pure tone in addition. Now, I'm pretty sure I know how to recognize a 25 hz tone, and know exactly what it sounds like. What I hear trough speakers or any full size headphones, I hear trough the earbuds as well.