So apparently in a rare error, Salk botched my center speaker. Thank goodness it went to Dennis first. He listened to it and measured it. Graph looked horrible below the crossover. He then took the crossover out and fixed a few small errors and put it all back together and remeasured it. Unfortunately the graph still looked ugly below the crossover, right in the mid-bass in exactly the same way. He's going to try again tomorrow, but he so far he's stumped as to why it's screwy.