hey guys i have an issue...when i play my mark IV connected to my marshall 4x12(g12t75 speakers) or 2x12(g12k100 speakers)... when i move a few feet back and stand facing the cabinet there is a harsh high end fizz... i dont get the same harsh high end when im standing to the side of the cabinet or so....what frequency should i cut to remedy this...i dont want people facing my cabinet at the gig getting that harsh highs..thanks!