the 1.6's probably average -7 or -8 db. from 80 hz. to 290 hz. (the range of this test CD is 10 hz. to 300 hz. in 1 hz. increments)....
FYI- The 1.6's are -15db. @ 35hz., -7db. @ 40hz. -3db. @ 47 .hz or so.
1 - don't measure in 1Hz increments. No speaker/room will measure smoothly at that level. Use either broad band noise or a slow moving sweep type signal to measure.
2 - Are you interpreting your measurements correctly? Rather than a broad dip from 80 to 290Hz, do you really have a boost in the 40 to 80Hz octave? If so, it's a fairly common problem that in relatively easily solved. How does the overall bass level compare to midrange (400 to 2000Hz) levels?