Our thoughts on Triad Speakers' "7 things you must know when designing an Atmos system"

by Nyal Mellor September 04, 2016

Triad's View

Triad Speakers have put together a set of "new rules" for the design of Dolby Atmos Home Theater systems:

1. Position ALL Listener Level speakers with their acoustic centers (tweeters) below the wall’s mid-point*. Reserve the upper half of the room for height effects.
2. Use only speakers that can focus an image with accurate panning: Monopoles & Bipoles –NOT Dipoles.
3. Position side & rear surround speakers with tweeters close to the same height (within 1.25 times) as your front LCRs.
4. Position Ceiling Height speakers at least twice the height of listeners’ ear level above their floor or riser.
5. Keep listeners’ ears at least 24 inches (61cm) clear of back and side walls. Further is better.
6. Only 1 Atmos Speaker Per Output Channel.
7. Atmos Sounds Better With More Diffusion Than Absorption.

* Dolby Atmos Enabled height Modules can be positioned in the upper or lower half of the room, but their drivers should be no lower than eye level.

Acoustic Frontiers Thoughts

In general these are all sensible and well thought out Atmos system recommendations, however in the effort to keep things simple I think they have missed out on some important caveats...

1. Position ALL Listener Level speakers with their acoustic centers (tweeters) below the wall’s mid-point*. Reserve the upper half of the room for height effects. In our view LCR speakers should be laid out with respect to the screen / display and "bed" surround speakers with respect to the audience, NOT room height. A very large screen may necessitate LCR placement over the half height point of the room to properly match audio on video. Likewise tiered seating may result in the need to elevate surrounds above the half height point of the room.
2. Use only speakers that can focus an image with accurate panning: Monopoles & Bipoles –NOT Dipoles. Agreed!
3. Position side & rear surround speakers with tweeters close to the same height (within 1.25 times) as your front LCRs. Bed surrounds should be laid out primarily in relationship to the audience (see our comments against point 1), with acknowledgement of LCR height....in that bed surrounds should never be lower than the LCRs.
4. Position Ceiling Height speakers at least twice the height of listeners’ ear level above their floor or riser. What do you do if the ceiling is too close?
5. Keep listeners’ ears at least 24 inches (61cm) clear of back and side walls. Further is better. Agreed! In fact we aim for 48" clear.
6. Only 1 Atmos Speaker Per Output Channel. Agreed, though you can "cheat" by matrix-mixing channels together to create new ones (for example mix side and rear together to create a 2nd side surrounds channel). This may be needed in some installs to provide adequate coverage of 2nd / 3rd rows.
7. Atmos Sounds Better With More Diffusion Than Absorption. We're not sure about this one...in fact we'd argue that control of reflections from all speakers (LCRs, bed surrounds, ceiling surrounds) is even more critical to maintain seamless panning (both spatially and spectrally) of sound objects. We think this might be better rephrased as "Atmos Sounds Better With a More Consistent Acoustic" (as in LEDE type approaches are less relevant now, and ceiling acoustic treatment is very important).

Thoughts? 

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