«Back in 1954, Schroeder referred to the frequency at which rooms go from being resonators to being reflectors/diffusors as the “crossover frequency.” We now call it the Schroeder frequency.»
It is the reason why using a grid of tuned Helmholtz resonators and diffusers, i smooth out any disruptive modes, i have around 100 of them from the diameter in millimeters to few inches with various lenght from 8 feet to 6 inches, i dont need a subwoofer with my 7 inches speakers box, and i enjoy all acoustical cues optimally for my room : dynamic, timbre,imaging, soundstage, listener envelopment, intimacy ETC...
Dont buy anything experiment and have fun...
Study basic acoustic WITHOUT any tool save your ears... Train them...
Acoustic phenomenon are not mainly linear mathematical phenomenon.... They are mostly non linear ....You ears are the best tool IN YOUR ROOM....
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