Hi @Innocent_Bystander , it will take a while to explain, but thank you for seeking clarification. FYI I have a PhD in digital signal processing, I hesitate to start explaining the concept but it does work.
In summary one needs to think of the impulse response of the loudspeaker into an untreated room and then understand the fluid mechanics of the air in the room and then add on top of that the psychoacoustic perception of human hearing.
In signal processing there is a direct translation between the time and frequency domains. Mathematical techniques allow the prediction of the impulse response from the (complex - I.e including phase information) frequency response and visa versa.
Linn SO predicts the fluid mechanics part of the problem, chooses to limit the effects it introduces to less than 100Hz because of the psychoacoustic perception of human hearing and creates an additional filter (impulse response that is convolved with the music signal) the net effect of which is to create a cancelling (inverted) resonance(s) into the room by amending the signal played through the loudspeakers.
I hope the text explanation above is sufficient, as I do not have any graphs immediately to hand to post in aid of explanation.
All the best,
E of E.