Hi Reiner, the measurement software in the prototype demo units is/was very basic - so bear this in mind. All the measurements and demos we've done have been with a 7.1.4 speaker rig - the four overheads are set to approx 45 degrees azimuth and height, front and back. This is one of the standard Atmos speaker setups, and the rendering engine inside the Realiser was set to this rendering mode. It's also a standard mode for DTS:X and MPEG-H, but not for Auro-3D. This is the maximum native rendering mode for Dolby Atmos or DTS:X within the Realiser at the moment - it's a limitation of the MDS audio decoding module.
So, yes, we set the Atmos rendering engine to this mode, and then made all the measurements in this mode also. Using one speaker you would have moved the speaker to these positions one after the other (or re-orientated yourself).
In a studio the sweet-spot is always where the mixer/engineer sits, so that would be the position to use for the measurement, and then pick out the speakers that correspond to the consumer positions from that seat. The engineer should know these anyway, since Atmos also uses a fixed bed of 10 channels (7.1.2 essentially) for the main sound tracks. I would recommend measuring a 9.1.6 setup in a studio if possible - this adds front wide speakers and four more overheads to the fixed 7.1.2 setup - the front wides would be at approx +/-60 degrees azimuth
