It's long but it's good read. http://www.gtaust.com/filter/07/06.shtml Some of the issues covered include:- * Why do we put the speakers in a box? * How the speaker was invented and how it works. * Hermann and the Helmholtz Resonator and it's applications in the creation of vented loudspeakers enclosures. * Horns * Impedance transformation - the compression driver.