Zak, the calibration should be done with the room in the same condition, including furnishings, as it will be during regular listening sessions. You haven't described what improvement your friend claimed that he experienced. The only possible thing that comes to my mind is that if a particular piece of furniture had been partially blocking the sound from the measuring microphone, the net result may have been better with it removed.If care is taken to position the meter in the clear, as you apparently did, the calibration should be accurate.
