http://www.sdp-si.com/index.asp
Through experimentation and research, I have learned that the best speakers to use with Exertion Instruments are the ones with the largest magnets. Technically, they have the highest "Bl". That means, the highest magnetic field and the longest coils.
So far, I have been finding my speakers at You-Do-It Electronics in Needham, Massachusetts. Please fill in other great places to buy speakers below: