some spl measurements, 20 square meters room 4.5x4.5m, only hpf and lpf eq, measurement in the center of the room, No smoothing in any graph.
Distortion at 100db SPL
Distortion at 116db SPL
Some measurement comparison between center and back of the room.
With only 2 frontal subs under left and right speakers.
With only 2 lateral sub, under left and right surround speakers.
With all four subs.
The low frecuency response is relly incredible. Its near flat in all the room!
Decay time a lot better than with only one sub. My plan is to use this subs for all low frecuencies of my speaker, under 80, not only lfe channel.
IMO and for me, this four subs are a lot better than bass trap alternative in frecuencies between 10-80 hz. Now I listen same low bass in the center than my clients in the back of the room.
Yeah, decay might have improved, but even with 2" panels and 2" airgap, results will be far better. Maybe this way, with multisub, helps to optimize room reflection, but damping should still be a primary factor.
Those graphs aren't telling us much, you need to add color legend also.