Not exactly sure what you mean. Are you suggesting that I should be setting 50.1hz around 85-90 db and then see if readings for test tones don't go below 75 db? If that's the case then what's the upper limit if 75 is the lowest? Also I thought that 3-5 db of difference in graph is ok but if I were to set 85 for 50.1 and my lowest reading comes out to 75, its a diff of 10.
As I told you before sub calibration level has nothing to do with the final calibration done by audyssey. What basshead actually means is that your reference target level during calibration should be high enough so you get a good reading down low i.e. 20Hz and below.
But having said that, even if you set your target level as 85-90dB at 50.1Hz reference frequency, you will have the same curve as you would with 75-80dB target level. The only difference will be that 85-90dB target curve will be 10dB higher at every frequency.
Just don't worry and post your graphs.