Hmm, are you sure it would have no effect on the tweeter output? Because the one speaker I switched got all muffled and the volume went down. Could it have been something to do with the concentric tweeter? I'm just guessing.
Al is right about the configuration. Red to red, black to black, and the two reds are connected by a jumper, as are the two blacks. I'm guessing the connections aren't the problem. There is base, just not extended base. I could be wrong, so I'm open to all suggestions, that's just my thinking so far.
Let me see if I can post some photos.