I tuned passive radiator around 32 hz. A few hz lower than Faitals 35 hz Fs . The deep bass is lissenable to under 30hz. Som i have a +2 db at 26 hz, and -2 db on the rest under 26hz on the equalizer. But the deep bass is good on flat eq too. I did a massage on bass speaker AS IT vill take a long time to play it in , before membran loosenes up. Fatal did not favorisise any frequenzy at all. K48 did that at 40 hz.