7.1.4
Eleven main output channels: seven bed-layer speakers, one subwoofer feed and four heights. A strong starting point for dedicated Atmos.
9.1.6
Sixteen primary channels: adds wides and six heights. This is where 16-channel processors become especially relevant.
Multiple subwoofers
Four physical subwoofers can either share channels or consume multiple independent processor outputs depending on the bass strategy.
Beyond 16 channels
Large rooms, active crossovers, multiple subwoofer arrays and additional height/bed channels can quickly push systems into 20-, 24- or 32-channel processor territory.
When 9.4.6 becomes a 19-output problem
A 9.4.6 room can require nineteen independent outputs when all four subwoofers are separately processed. This is why the familiar Atmos label needs to be translated into actual processor outputs before selecting hardware.