I had some time today so I did some close measurements. I used 1' since I didn't know what I should use. The results were strange.
I discovered the HB-1s had good output down to 40Hz but had about a 15db range. The manual says 60Hz and a 4db range. They also had a sharp drop-off of about 12db from around 900Hz to just past 2kHz. Ex that the range was about 10db, better but not to spec.
The ULS-15s, in the 20-200Hz range had a total range of about 7db, vs a 2db spec. More importantly, the crossover is set at 80Hz but peak output was just beyond 100Hz. Ex that the range would have been about 5db, but why am I getting a signal like that?
It turns out the peak in the ULS-15s corresponds to a fortuitous dip in the HB-1s just above 100Hz. However, the HB-1s have a huge peak at 200Hz
Now, this might have something to do with using 1'. I don't know what the proper distance is. I just wanted to eliminate room problems. It turns out the only serious room problem is a huge dip around 30Hz, which I could not correct away and another dip from 200Hz to about 350Hz which I could correct. Aside from that the 1' measurements carry over pretty well to listening position measurements.