Thanks guys, but I also tried different amps, Behringer digital EQ and Copland room correlator. This equipment improves amplitude, but in same time you have problems with distortion, handling, not to mention converters who are responsible for all others things... My point is: I dont think that anything will fill 10dB dip, but can contribute. I tried with lower class subs and I had better results if you compare with other mentioned experiments. Finally, N802 need some extra energy below 30Hz. At least in my room!