Let's start with a break down the specifics of the Dolby Atmos spec below.
A reference to a Dolby Atmos Standards Speaker Setup can also be found here.
The left, centre, right channels must be identical to ensure good imaging across the front channels. They should be equal distance from the reference listening position (and each other) with their acoustic centre’s on axis to the listener’s ears as well as being on the same horizontal plane as each other. All front speakers must exhibit the same acoustic polarity.
Whenever possible, use the same speakers all around to achieve uniformity. However this isn’t always possible for cost/space reasons. So it is acceptable to use smaller speakers as long as they keep the same “character” – a common solution is to use a smaller version of the L,C,R speakers, but in most cases the same manufacturer would do.
Again the surround speakers should be on axis to the listener’s ears and the arrival timing should coincide with the L,C,R channels.
There are two options for speaker types that can be used to playback the height/overhead channels: discrete and Dolby Enabled.
Discrete speakers are a speaker that is physically mounted to (or in) the ceiling, while Dolby Enabled are specially licensed technology from Dolby that reflect the sound off of the ceiling from the listeners horizontal plane. You commonly see these in commercial products such as sound bars which allow (for example) 5.1 from a single speaker position.
In post pro (and our personal opinion) it is generally recommended that a control room use discrete speakers overhead wherever possible as Dolby Enabled speakers have the potential of creating a more diffuse image at listening position (as directional as sound can be, firing it
at the ceiling then back down does cause diffusion and some loss of level). Discrete speakers offer more precision when mixing and panning creating a more controlled mix that will playback better for the consumer on any Dolby Atmos renderer.
Again wherever possible its best to use the same speakers all around to achieve uniformity. Although this is often harder to achieve with ceiling speakers as many surround speakers don’t have bracketry that can be mounted to ceilings. So the ceiling speakers can be smaller than the surrounds but must maintain the same character as stated above.
The LFE channel requires the use of at least one subwoofer in the monitor system. The bass from any channel that is not reproduced in the main speakers must be redirected to the subwoofer(s) to be bass managed. It is important to correctly integrate the subwoofer(s) in proper relation to the main 5 channels to ensure a wide, smooth and uniform frequency response (it’s meant to be even throughout the space, not directional).
Positioning the subwoofer can be a little bit more tricky than other speaker placements and really should be decided upon by placing the sub in multiple likely subwoofer locations and playing low frequency content to check response (see our install sub blog for some fun reading on boundary effect!). Locations delivering the smoothest bass response should win the prize for final placement location. Keep in mind a certain amount of experimentation should be expected, particularly when retrofitting an existing production room.