Since corrective EQ would blow your monitor's drivers, the only practical way to begin to fill in the "Grand Canyon" dip is by installing subwoofers (ideally two, front-corner-loaded to ameliorate the 1st and 3rd width axial mode nulls at the listening position - much to discuss here, beyond the scope of this blog). The general conception of the use of subwoofers is that they extend the low end which of course they can; however, the more valuable advantage is that they can actually correct the Allison effect. The trick is to set the low-pass filter on the subs high enough to catch the dip of the monitors, typically around 125Hz. You'll need to experiment with the subwoofer's phase control to find the best marriage between the subs and the monitors. Full disclosure: you will likely not match the PFS frequency response curve seen at the bottom of this episode, which utilizes analyzing software, high- and low- pass filters with slope and phase control, and EQ. You can, however, by applying the tools coming up in the next episode and implementing subwoofers, substancially improve your monitoring experience. Of note, a common practice is to listen to monitors with and without the subs. Once subwoofers are properly integrated into the monitoring system, and knowing what you have learned so far, it's clear that the subs are part of the system, not to be turned on or off.
Next let's look at the dips we see in the graph at approximately 750Hz and 400Hz and the hump between 130Hz and 300Hz. The dips are caused by the console bounce cancelation that occurs when the reflections that bounce off the console arrive at a later time than the direct signal straight to your ears from the monitors - comb-filtering. The humps are the room's effect on the monitors. The obvious effect of these anomalies will be that you will want to boost the dips and cut the humps and in both cases your mixes will fail until you again "learn" your speakers. Unfortunately, shiny new monitors will not be able to do a thing about these room-generated artifacts. Of note, the frequency response from about 1kHz up is unusually smooth in this well-designed room and more often than not the case.
