I have done alot of testing myself now and come to that ill drop 2*OS. The benefit is to my ears not perciveable and it was not properly implemented due to double pecision anyway. I think I will keep the double precision math even though it makes the cpu load higher. The filter is now stable in low frequencies.
I am in the process of going through the whole EQ to find possible optimizations.
Any sufficiently advanced technology is indistinguishable from magic.
Arthur C. Clarke, "Profiles of The Future", 1961 (Clarke's third law)http://www.audioteknikk.net