54hz dip is probably the ceiling cancelation in a room with your geometry.
How tall is your ceiling? 54hz is a 5’ quarter wave (see chart below, 54hz is 20 feet long). So most likely the ceiling.
Moving the speakes around probably will not fix it as the ceiling height is fixed. I have a similar issue. You can trap the ceiling (which I did) and it helped a bit but not as much as I had hoped. Subs with DSP, preamp with tone controls or an equalizer are probably the realistic options.
http://www.soundoctor.com/freq.htm
How tall is your ceiling? 54hz is a 5’ quarter wave (see chart below, 54hz is 20 feet long). So most likely the ceiling.
Moving the speakes around probably will not fix it as the ceiling height is fixed. I have a similar issue. You can trap the ceiling (which I did) and it helped a bit but not as much as I had hoped. Subs with DSP, preamp with tone controls or an equalizer are probably the realistic options.
http://www.soundoctor.com/freq.htm