Dear Armen,When Ngx released, I completley recovered my computer and I made clean install Fsx and ngx and I have only installed payware aircraft is Pmdg 738 on my computer.No using any more another payware or default planes, even removed all default planes from Fsx.Until Sp1c I was hearing engines from front speakers as well but with Sp1c I can only hear when I move my head left ot right.I installed again Sp1b, sound works without any problem as before, but when I install Sp1c do not work. That means to me somethinks problem with Sp1c.Look at the people please, why they start to complain about sound after Sp1c?That happened deffinitely after Sp1c and while can use surround system with Pmdg sound, why we now need to switch stereo mode?Regards