Choosing Overhead Speakers for an Atmos Setup

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Q It’s my understanding that the overhead speakers in a Dolby Atmos system are meant to create diffused sound. I have a pair of dipole surround speakers with a front-facing woofer and side-facing drivers. Could these be used in a 5.1.2 Dolby Atmos system if I hung them from my cathedral ceiling with the woofer facing down and the side drivers firing to the front and back of the room? — Al Erdelyi / via email

A Let’s take your main point first. The function of the overhead speakers in a Dolby Atmos system is not to create diffused sound, but an enveloping soundfield with individual sonic elements at identifiable locations in space. Dipole surround speakers, which fire sound from opposing sets of drivers acoustically out of phase with each other, are designed to deliver a diffused surround presentation in channel-based home theaters—one that emulates the wash of sound from arrays of wall-mounted surround speakers in conventional, non-Atmos commercial cinemas. In this case, all the surround speakers on the left wall of the auditorium, for example, are fed the identical signal from a single channel. Since listeners will hear output from more than one of these speakers (each at relatively different distances and angles), the overall sensation is a diffused presentation of the surround effects.

Dolby Atmos, however, is an object-based format that requires a spatially specific presentation by speakers (currently up to 64 independent speaker feeds, assigned on the fly by the renderer in the Atmos commercial cinema processor) tasked with conveying the apparent physical location of individual sonic elements within Atmos soundtracks. That’s why direct-radiating speakers are used exclusively in cinema installations.

The rules for home Atmos installations aren’t as rigid, however. Take, for example, this passage from Dolby’s best practices documentation for home Atmos:

Dolby Atmos is a highly flexible solution, so minor variations from these recommendations are unlikely to materially detract from the immersive Dolby Atmos experience.

While Dolby may give you a pass to experiment with Atmos at home, its documentation does go on to recommend using “conventional” overhead speakers with “wide dispersion” characteristics.

Forum discussions I’ve read by home theater integrators have a negative take on the use of dipole speakers for object-based audio formats like Dolby Atmos. Their main argument is that the null section of dipole speakers—the part where the woofer is located on your dipole surrounds—doesn’t allow for the localization that’s key for object-based audio performance. So there you have it from the folks in the field.

Other listeners with Dolby Atmos experience, however, still advocate for the use of diffuse side surrounds, even for Atmos. The main reason is that side surrounds are so much closer to the listener than the other speakers, especially with Dolby’s recommendation of placement at ear height, that the precedence effect takes over and the direct-radiating surrounds end up calling too much attention to themselves.

Now to the subject of your cathedral ceiling. Physical speakers are the only practical solution here, and direct-radiating models with wide, symmetrical dispersion aimed straight down are likely to provide the best experience for listeners in the largest number of seats throughout the room. Dolby does have a workaround to using physical speakers on the ceiling: Dolby Atmos-enabled speakers. These are towers or add-on speaker modules located just above ear height with drivers aimed upward at an angle toward the ceiling. The idea is to bounce some frequencies off the ceiling and back down toward the listeners to give the impression of sound coming from above.

While Atmos-enabled speakers would normally provide you with an alternative option, another section from the Atmos Best Practices guide referring specifically to Atmos-enabled speakers states:

For optimal performance, the ceiling should be flat (not angled or vaulted), with a height of 14 feet or less.

This basically means that cathedral ceilings like yours aren’t a great environment for Dolby Atmos–enabled speakers. Why? Because the ceiling’s angled surfaces and greater reflection distances do not lend themselves to creating the desired psychoacoustic effect.

To sum up, the dipole speakers you intend to use as overhead speakers in your setup are unlikely to provide the sonic cues required to create a convincing overhead experience. Combined with the incompatibility of Atmos-enabled speakers and cathedral ceilings, direct radiators are your best option to achieve the target of object-based audio systems like Dolby Atmos, which is to present an enveloping bubble-shaped audio experience that’s spatially convincing and satisfying.

Pitbull2's picture

Not so much with DTS-X though. way more flexible and I use both . But the sounds with the DTS-X vs. Atmos is a deff a noticeable diff. And im have a dedicated theatre that was built from ground up. I might add certain AVRs can deff give you more flexibility in that area too.

Gmail Iniciar Sesión's picture

Gracias por darme la información útil. Creo que lo necesito! - gmail iniciar sesión

sachinkggn's picture