Part 2 of "Maximizing Loudspeaker Performance in Rooms" has detailed information on how to interpret the axial standing wave graphs.
Maximizing Loudspeaker Performance in Rooms Part 2 - The Acoustical Design of Home Theaters
by Floyd E. Toole, Ph.D.
Acoustical Design and Equalization
MaximizingLoudspeakerPerformanceInRooms.pdfHere is an example from the article:
Figure 2 shows what we measured for the subwoofer, by itself and, as predicted, there
was a prominent peak right around 47 Hz. When we listened, the bass was flabby and
boomy, with a “one-note” quality. Even movie explosions sounded faked. To address
this problem we dialed in a single parametric filter, set to 47 Hz, with the appropriate
bandwidth, or Q, and simply turned the resonance down. Room resonances at low
frequencies behave as “minimum phase” phenomena, and so, if the amplitude vs.
frequency characteristic is corrected, so also will the phase vs. frequency characteristic.
If both amplitude and phase responses are fixed, then it must be true that the transient
response must be fixed – i.e. the ringing, or overhang, must be eliminated. Figure 3
shows that this is so. Equalization of the right kind can work. Notice that we completely
ignored the acoustical cancellation dip at about 73 Hz.