Can you humour me man? What I'm looking for is a low volume test. Put your mic really close to the cone like 1" or 25mm away and do a sweep from 0-300hz. Can you defeat your xover, or if not raise it to the highest it will go like 150hz (or whatever). Looks like maybe you did this in your measurement you posted? This will eliminate the effects of your room as much as possible and show the HF extension of the SDX. It will also show where your tune is with your pr's. you can also while you are doing this, run the same sweep at the same level with the mic 1" away from 1 of the pr's and it will show you what the pr's are doing too. Here is what my graph looks like compared to Illka's. I have a bigger hump in the response at a lower frequency, the low end rolls off faster and the high freq's have a sharper roll off as well. Mine has an xover in effect at 200hz. Illka's does not.
BTW that graph you posted don't look bad. Maybe EQ down the peak at 23hz and the one at 66hz a bit, but other than that...