The near field dip of the drivers in the DCH has had a strange shape, I had suspected that standing waves had something to do with it. Today I took measurements in an other room with the speaker standing on a low table in the middle of the room. Much better! A sharp symetric dip, textbook style

The tip of the dip is further 2 dB down off the scale in this graph. The difference in sensitivity between the 9710 and a Stridbeck/Tyrland is supposed to be 10 dB but it really sounds like 20 dB.  I have to get to work in that 5th harmonic at 200 Hz. But that will have to wait for a while.