Filmmixer explained this properly.
However, dts created this issue (yes, it's an issue) by following Dolby's nomenclature of HEIGHT and TOP for positioning, but mucking up the angles and screwing up manufacturers attempt for finding a proper universal placement.
Dolby's definition of TOPS is that they be placed ~45° & 135° and HEIGHTS ~30° & 150°.
Dts [in their infinite wisdom] defined TOPS at ~60° & 120° and HEIGHTS ~45° & 135°.
Dts:X does not have a placement which corresponds to Dolby's HEIGHTS at 30° & 150°.
Whether speakers are mounted on-wall, on-ceiling, or in-ceiling is of no consequence. Elevation Angle is what matters.
Dts HEIGHTS and Dolby TOPS correspond. Unfortunately, if you chose TOPS Atmos would render properly (without phantom imaging) but dts:x would not. It HEIGHTS were selected, it was optimal for dts:X but not Atmos.
It was expected that manufacturers would rectify this. Has anyone tested the latest D+M (ADI) or Yamaha (TI) AVRs or firmware? Theta's (ADI) implementation did not and doesn't even have an option to select HEIGHTS and now Lyngdorf (ADI) has not.
The solution is easy (in my mind), always report to the dts decoder that HEIGHTS are deployed and not TOPS. No one [in their right minds, at least] is building around dts:X primarily and placing speakers at 60° & 120°
Until then, two separate configs have to be maintained and switched between (easy on Yamahas). This may end up the case if Lyngdorf does not address it.
Originally Posted by sdurani
Atmos Tops fall close to DTS:X Heights. Problem is, if you designate that location as Tops in your AVR, it will be correct for Atmos but incorrect for DTS:X (which calls those same locations "Heights"). If you designate that location as Heights in your AVR, it will be correct for DTS:X but incorrect for Atmos (which calls those same locations "Tops"). Hence the compromise of one of the formats.