bestbang4thebuck, that was a great post. I had one of those no-sub music systems for 20 years. My Polk Audio RTA-12C speakers claimed to have a frequency response from 17 to 26khz. However, when I added a Sunfire True Subwoofer to the equation about 2 years ago, it was a very dramatic improvement. I did not necessarily hear things I never heard before (especially out of music CDs), but everything sounded better. So your moving diaphragm theory makes a lot of sense to me.