I did it ...
Using SPL and audio test tones courtesy of HTS
... I manually entered the measurements in REW and I got this graph ... can somebody please tell me, Is this good or bad???
Green line was the measurements sending the sub output to front speakers and subwoofers and red line was just using the subs ...
I need to check the receiver EQ (I don't remember if I boosted any frequencies, I'm sure this will affect the system response) ... I can wait to run REW
I also measured 250Hz, 333Hz, 417Hz, 500Hz and 100Hz ... but I didn't include them on the graph.
Volume was at reference (-5.0db in my case
)