Early home theater audio gear delivered sound in just two dimensions: Audio events could be played only in the front left, right, and front center, and in the rear left and right of a room. The low-frequency effects from a subwoofer are non-directional. You were surrounded by sound, but it was limited to a single plane. The immersive audio formats of Dolby Atmos and DTS:X add a third dimension–height–to immerse you in sound. As a result, movie soundtracks and music encoded in these formats sound more  realistic, more natural, more true-to-life.

The audio for movies and music has always been mastered for 2D presentations only. Fidelity and resolution have increased over the years, but recording engineers have never had the tools to deliver a truly three-dimensional audio experience in which sounds come from above you as well as around you. Sure, you could mount speakers high on the wall or even in the ceiling, but your playback equipment had no way of taking those placements into consideration.

2d surround sound Onkyo

Conventional surround-sound systems, such as this 7.1-channel setup, operate on a single horizontal plane.Dolby Labs and DTS, have been working hard to tackle this problem and transform 2D sound into an immersive, 3D audio experience. After many years of research, both companies have finally unveiled their immersive audio solutions: Dolby launched Dolby Atmos and DTS released DTS:X.

Both Dolby Atmos and DTS:X are object-based audio formats. Unlike traditional audio mixing, which associates a sound with a particular speaker on a 2D plane, object-based audio technology treats each sound (the roar of an airplane, bullets flying through the air, raindrops hitting leaves, birds chirping, and so on) as an individual object. When sound is treated as an object, it becomes a real game-changer.

Each sound object is accompanied by descriptive information—metadata—that describes aspects of that sound, such as where the sound object is located in a room, or in what direction the sound should move along the sound field and at what speed. The decoder in your A/V receiver assembles this information from the source—such as Blu-ray player or home-theater PC—and calculates which combination of speakers should work together to reproduce that sound in your room. This is a really big deal for home theater’s future.

Here’s how each company is approaching object-based sound.

Dolby Atmos

Dolby Labs was first out of the gate with Dolby Atmos. This immersive audio technology was implemented in select commercial cinemas in 2012. The theaters installed new arrays of overhead speakers for the debut of Pixar’s animated feature film Brave, which earned critical acclaim for the way it made you feel like you were in a space as part of the movie. Dolby brought Atmos to home theaters two years later.

To implement Dolby Atmos in your home theater, you’ll need an A/V receiver and one or two pairs of loudspeakers in your ceiling (yes, there are alternatives to ceiling speakers, I’ll discuss them in a moment). This will deliver the sensation of height to create a spherical, 3D sound experience. The ideal Atmos setup consists of one pair of in-ceiling height speakers in front of the listening position and a second pair of in-ceiling height speakers behind the listening position.

Dolby Atmos ceiling speakers Onkyo

To get the best Dolby Atmos experience, you’ll need two ceiling speakers at the front of the room and a second pair in the back of the room.

As with other Dolby surround-sound setups, these height speaker placements are pre-defined. Height speakers are in line with your front left and right speakers and are at a specified angle from the primary listening position: Between 30- and 50 degrees for the front, and 125- to 150 degrees for the rear).

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