I'm pretty sure the changes are only minor. If I recall, the 'A' version is just a newer revision of the driver, and that no changes in box calculations were needed.
Wayne Parham Messages: 18748 Registered: January 2001
Illuminati (33rd Degree)
Eminence uses the "A" suffix to designate 8 ohms impedance. Sometimes people omit the suffix, especially on models that are only available in 8 ohms like the Alpha's. Other models are availble in some lines - "B" is 16 ohms, "C" is 4, "CX" is made for coax tweeter mounting and "LF" is tuned low and "HO" is tuned for maximum output.