Steerable Dolby Atmos Enabled Speaker Proposal with Video Interview

With Dolby Atmos about to hit the home theater scene, manufacturers are gearing up to provide new speakers in order to allow consumers to achieve the “Atmos experience."  There are currently two options for realizing Atmos at home. However, I propose a possible third option, or a tweak to option #2.

Editorial Note About Dolby Atmos
Dolby Atmos is a revolutionary new audio codec that allows for object-oriented mixing layers with independent sound elements over channel-based audio content for clearer and more accurately positioned sound.  Atmos allows for a more 3D approach to surround sound with up to 32 discrete channels in the home and 64 in the Cinema.  Dolby Atmos utilizes ceiling or wall-mounted speakers to introduce a ‘height’ aspect to home theater sound, which according to Dolby, will dramatically increase the sense of realism and believability

For more information, read: Dolby Atmos Explained

• Option #1: Ceiling mounted speakers firing down at the listening area
• Option #2: “Atmos Enabled” speakers with top-firing drivers that bounce the reflected sound off the ceiling to the listening area
• Option #3: Steerable (pointable), wall-mountable “Atmos Enabled” speakers

 Dolby Atmos Experiment and Proposal for Steerable Speakers

Balancing Ambience and Directionality

The addition of ceiling channels provide two benefits that are difficult to balance in a home environment: Ambience and Directionality. These channels must be directional enough to permit the objects to move within the space of your living room, but not overly directional or they will hot-spot and ruin the effect, thus becoming a distraction. Commercial theaters benefit from tremendous interior volume, so ceiling mounted speakers are far enough away from listeners that ambience and directionality are balanced.   Many home cinemas do not have the cubic volume to properly disperse the sound from overhead channels. Low ceiling height in most domestic rooms and the necessarily small number of Atmos speakers/channels may make them easily localizable, which may not necessarily be desirable.  Careful placement is required and a small sweet spot may be the result.  A good argument could be made that optimizing for ambience over directionality is preferable, but further evaluation of Atmos in the home theater environment is needed.

Option #1: Ceiling Mounted Speakers Firing Down

Pretty much any conventional direct radiating speaker can be utilized for option #1.  Even an in-ceiling coaxial speaker can work.  While not necessarily the most practical solution, option #1 is the most true to form of how Atmos is implemented into commercial cinemas.  It is also, in my opinion, the most accurate way to truly project the height effects for accurate localization and spatial imaging the way the director intended.  Unfortunately many folks are unable to add ceiling mounted speakers due to aesthetic concerns or an inability to run additional wires in existing homes.  In addition, some home installations may not have the ceiling height necessary to fluidly move the objects across the screen.  We will revisit this topic at a later date as it’s beyond the scope of this particular article.

Proposed 5.1.4 Speaker Layout Utilizing Ceiling Mounted Speakers - courtesy of Dolby

The focus of this article is option #2, and my tweaks on option #2, leading to option #3, the steerable wall-mountable “Atmos Enabled” speaker.

Option #2: “Atmos Enabled” Speakers with Top Firing Drivers

For option #2, a specific “Atmos Enabled” speaker is needed.  Essentially, an “Atmos Enabled” speaker is a conventional floorstanding or bookshelf speaker with an isolated top firing driver(s) for the Atmos channels.  Pioneer must be commended for being the first manufacturer to offer integrated  “Atmos Enabled” loudspeakers with their new Andrew Jones-designed concentric driver Elite Speakers.  In my opinion, they got it right with the driver selection.  A coaxial driver -instead of a separate woofer/tweeter solution—has the best potential for projecting focused and cohesive sound waves.  The directivity of the top firing driver also closely resembles the directivity of the main mid/tweeter array for the front firing drivers.  Matching directivities, while certainly not necessarily a hard and fast design requirement, certainly can’t hurt.  Again, kudos to Pioneer for this type of approach. 

See our Preview of the Pioneer Dolby Atmos Speakers for more information about these products.

What About Practicality?

While the “Atmos Enabled” speaker solution seems to be the least painful to implement, like anything, it also comes with several tradeoffs.  For one, the Atmos driver must be bandwidth-limited to reduce omnidirectional behavior at lower frequencies.  Dolby suggests a low frequency cutoff around 180Hz to reduce omnidirectional sound from the Atmos driver, but a midrange driver still exhibits omnidirectional properties a few octaves higher than the 180Hz cutoff, depending on its diameter and size of the baffle it radiates from.  Additionally, the current “Atmos Enabled” speaker solution appears to fire the driver up at the ceiling at a very slight angle, despite the diagrams showing the beam of sound steering very specifically towards ideal ceiling locations to create the front and rear height Atmos effects.  Without the ability to adjust driver direction, it seems that the front and rear speakers will have to be very precisely located to achieve optimal results.

Dolby Atmos Speaker Diagram - courtesy of Pioneer

Editorial Note: Omnidirectional Driver Behavior by Dr. Floyd Toole

The 4" driver will be quite omnidirectional at 180 Hz - wavelength >6 ft - but that will change as wavelength diminishes and it will be quite directional at 3kHz - wavelength about 4.5 inches.  So, if a hard panned sound is directed to such a loudspeaker aimed at the ceiling, only the high frequencies will be reflected from the ceiling in anything resembling an isolated manner.  However, humans localize most strongly to high frequency transients, so it might work better than you think.

It’s unclear how the sound is being angled very specifically up at the ceiling from a top mounted driver that appears to be firing almost directly up at the ceiling with a very minimal angle in the baffle, as can be seen in the Pioneer diagram above.  In addition, the ceiling must be flat and without absorption to be able to bounce the sound waves back down towards the listening area.  Even then, a ceiling will exhibit some absorptive properties at higher frequencies (above 10kHz).  This diagram doesn’t show the omnidirectional radiating pattern that the driver exhibits well above the 180Hz bandwidth low frequency cutoff as discussed earlier.  If a speaker is positioned too closely to the listener, it may produce undesired localizable effects and unintentionally muddy up the soundstage of the “Atmos Enabled” front and surround channels.

The up-firing “Atmos Enabled” speakers certainly provide ambience but their ability to provide directionality is highly dependent on the ceiling height, composition, and seating position.  There is a chance that this option is initially well received but over time may feel gimmicky and like 3D video, become a niche product.  At the very minimum, its arguably a compromise to discrete down-firing ceiling mounted speakers in terms of preserving accurate directionality.

Option #3: A Proposal for a Steerable Wall-Mountable Atmos Speaker

While option #2 seems appealing, most folks are unable to use such a speaker for a surround solution for aesthetic reasons.  The majority of home theaters utilize wall mounted or in-wall side surround speakers mounted a few feet above ear level.  This helps reduce the localizability of surround speakers in close proximity to the listening area.  Wall mounted speakers are also often considered a more aesthetically acceptable solution.  Getting the side surround speakers off the floor and slightly above ear level may greatly reduce the perceptual omnidirectional behavior of the Atmos driver as well. It will also bring the Atmos driver closer to the ceiling to further reinforce the reflections heard at the listening area.  In my opinion, reinforcement of the reflections will likely help create a more realistic beaming effect back towards the listening area, creating a more pinpoint localization of sounds to get the speaker to behave more like the ceiling mounted downfiring option #1 approach.

Presenting the Steerable "Atmos Enabled" On-Wall Surround Speaker - courtesy of RBH Sound

Editorial Note about the Steerable "Atmos Enabled" Surround Speaker

I asked RBH Sound to sketch a concept speaker for the illustrative purposes of writing this article.  RBH has no plans to produce this type of speaker at this time.  However, this concept can be expanded to any type of loudspeaker, not just an on-wall type.

In addition, having a wall mountable “Atmos Enabled” speaker will allow consumers to preserve their current 5.1 or 7.1 speaker layouts without having to radically reposition speakers to be more suitable to accommodate Atmos height channels.  A manufacturer could even implement an Atmos driver on a di-bipole surround speaker since many enthusiasts prefer those types of side wall surround speakers over direct radiating monopoles.  Also, a conventional direct radiating wall mountable speaker can be fitted with an Atmos driver so that it can be used as both a front width channel and Atmos front speaker for those that want to continue to enjoy PLIIz post processing and/or Atmos.  In fact it could be argued that a front height “Atmos Enabled” speaker could be flipped upside down for installs with high ceilings to aim the Atmos driver towards the listening area.  The possibilities are endless with this sort of approach. 

However, in order for this to really work, I suggest the Atmos driver’s radiational direction should be steerable or adjustable; in fact, not just the driver alone, but the baffle itself.  Having an adjustable driver/baffle combo will reduce baffle diffraction typical of adjustable in-ceiling type speakers that have the driver recessed inside of the actual baffle.  Instead, this type of speaker would have an adjustable baffle perhaps in 5 or 10 degree increments up to 30 degrees. Once you angle the speaker, the top baffle will raise up from the backside of the speaker accordingly, as can be seen in our crude concept diagram above.

This is why I propose that loudspeaker manufactures looking to produce “Atmos Enabled” speakers consider creating a steerable on-wall option.  Doing so will allow the user to customize the dispersion of the sound in hopes of beaming it down more precisely to the listening area.  The consumer could use a mirror pointed at the ceiling from the listening position and that would identify the exact “target” spot on the ceiling where the Atmos speaker should aim towards. Having a steerable speaker makes this very easy.  This not only has the potential to improve the fidelity and realism of the projected sound, but it also opens up placement flexibility while allowing current home theaters to maintain the speaker layouts they are currently using, whether they have 5.1 or even 11.1 systems.  In addition, creating a steerable on-wall or wall-mountable “Atmos Enabled” speaker may be an easier alternative to getting consumers to ceiling mount a single pair of height speakers in the middle of the room, or to place another set of floorstanding or bookshelf speakers near the seated area.  It not only reduces the disruption to existing 5.1/7.1 systems but can be household-friendly, even appearing as a wall sconce.  The user can place and tune the speaker in a down-fire approach or using the ceiling to diffuse the sound to balance ambience and directionality.

Conclusion

Only time will tell if consumers will be flocking to upgrade their existing home theaters to Dolby Atmos and whether they will choose ceiling mounted speakers or Dolby Atmos Enabled” speaker solutions.  Aesthetics aside, we must ponder if consumers will prefer the precise directionality that ceiling mounted speakers offer over the more ambient and diffused sound effects that upward firing drivers provide from “Atmos Enabled” speakers in the home environment. 

I propose the best way to ensure success for the new format in the home environment is to make implementing Atmos as easy as possible.  If consumers are able to retrofit existing theater rooms by simply replacing a few speakers, as opposed to repositioning or doing away with certain speaker options, they are likely to more readily adopt the new format and upgrade their systems.  Everybody wins!

Let us know what you think in the forums.  Are you currently running a 9.1 or 11.1 system with height channels to take advantage of PLIIz or DTS Neo X post processing? Would you consider simply upgrading one or two pairs of your speakers to accommodate Atmos? Which Atmos option is most appealing to you?