Looking at energy distribution across the spectrum is good as a double check combined with listening. But make sure to combine it with careful listening. It is dangerous to rely on the visual curve alone. Many times things which are quite easily audibly apparent will not be visually obvious, and sometimes what appears visually odd may sound just fine.
^
I just wrote that with frequency balance questions in mind, since that is the subject of the thread, and then went on to download the sample file posted back in 2015 to give a listen.. only to find there is a far more fundamental problem than one of frequency balance. The sample features severe overload clipping EQ cannot correct, which actually serves to reinforce the statement made above even more strongly. The SPAN frequency analysis image does not identify the presence of audibly obvious clipping distortion at all.
So, best to use visual display tools as a cross-check to listening and vice-versa.
With regards to the problem with the posted sample-
I don't hear any AGC or limiting working, and the OP states neither was used. I suspect that either the CA-9100 had a dying battery which was starving the preamp circuit during the kick drum hits, or the level setting used for the DR-2d's Line input was set lower than 95 (below which the recorder will "brickwall" clip with a hot input without the meter display indicating any overload problem). Both are forms of analog distortion which occur prior to digitization. I would not suggest use of the 120Hz High-Pass filter on the DR2d, which as applied here serves only to skew the frequency balance toward ovelry bass-light and "anemic" sounding, after the distortion has already been incurred. The HPF is positioned too late in the signal chain to mitigate the distortion.
Avoiding the problem-
Use a fresh or freshly charged battery in the preamp. Turn off AGC and HPF on the DR2d. Run the CA-9100 into the DR2d Line Input with the line input gain set to 100 (no lower than 95, which is set prior to recording via the DUAL button on the face of the recorder, not by using the Mic-input gain toggle-switch on the side of the recorder), then adjust gain on the preamp as necessary to get good levels on the DR2d meters.
That should produce a recording free of self-imposed distortion which can be EQ adjusted to taste afterwards as discussed in the thread.