I notice mention of AR-11 A and B types here on the board, the ones I have here have a C after the model number. The crossover looks like this picture provided by r_laski: http://www.classicspeakerpages.net/dc/user_files/335.jpg Anyone know who designed these different versions. The A to B version looks like a cost reduction effort with a single crossover board and simplified attenuation switching. Anyone listen to the A and B versions side by side looking for differences? Pete B.