Thanks for your help Anthony - after trying all your suggestions I was able to get it working with a combination of low signal level and higher in-room volume. Not ideal, but the calibration curve looked great and I went on to use REW with AMAZING results.
Sorry for the delay in replying - once I got REW working and my HT calibrated I was sidetracked by the amazing SQ!
Sorry for the delay in replying - once I got REW working and my HT calibrated I was sidetracked by the amazing SQ!