3D Immersive Surround Formats and Loudspeaker Layouts
Immersive 3D Audio or Surround Sound made a breakthrough in 2014 by becoming available in two “native” formats. It was already available in AV receivers equipped with Yamaha’s “CinemaDSP” (5.1 with two additional presence speakers), Yamaha’s “CinemaHD3” (7.1 with four additional presence speakers and an additional subwoofer) and more recently those equipped with Dolby’s “Pro Logic IIz” (7.1 with two additional front height speakers) and Audyssey DSX (7.1 with two additional front height or wide speakers), but all of these were DSP-based upmixing formats. With last year’s introduction of “Atmos” from Dolby and “Auro-3D” from Auro Technologies of Belgium and the launch of the third “native” format, DTS:X this spring, native 3D Audio has arrived in Home Cinema products.
In a previous article about the first announced 3D Audio System Dolby Atmos and Home Cinema I have tried to “translate” a professional Dolby Atmos speaker layout into a possible Home Cinema speaker layout. The key line was “Ideally in-ceiling speakers, but perhaps more practically (or less impractically) the 11.2-setup introduced back in 2007 in Yamaha’s RX-Z11 does the job, as it would be able to pan the objects in the room on all three axes, and, with dual subwoofer setup for seamless bass across all listening seats, would be able to represent the main LFE and subwoofer channel.” A few months later Dolby introduced its “Dolby Atmos Speaker Setup Guide,” in which they proposed a configuration with in-ceiling speakers (the ideal situation), and the controversial solution of upward-firing “Dolby Enabled speakers.” The latter unleashed a lot of discussion both online and offline. The “classic 11.2” configuration mentioned in the article was NOT proposed, which surprises, because one can imagine this configuration to get closer to the “ideal” configuration with four in-ceiling speakers than upward-firing in-ceiling speakers that employ reflection of the height plane above the listening position.
Speaker Layouts: Dolby Atmos
Let’s compare Dolby’s 7.1.4-configuration with a “classic 11.1.” Both configurations start with a basic 7.1 on the floor plane, with clockwise from Left Front (Figure 1):
- Front Left (FL)
- Front Center (FC)
- Front Right (FR)
- Surround Right (SR)
- Back Surround Right (BSR)
- Back Surround Left (BSL)
- Surround Left (SL)
- Subwoofer (SW)
Figure 1: Dolby's 7.1.4-configuration. Courtesy of Dolby.
Dolby’s 7.1.4-configuration specifies four in-ceiling speakers, clockwise from Left Top Front:
- Left Top Front (Ltf)
- Right Top Front (Rtf)
- Right Top Rear (Rtr)
- Left Top Rear (Ltr)
Figure 2: Horizontal angles of basic 5.1 speakers. Courtesy of Dolby.
For the ceiling speakers, Dolby has given also vertical angles min/ideal/max (Figure 3):
- Top Front: 30°/45°/55°
- Top Rear: 125°/135°/150°
Of course 30° Front corresponds to 150° Rear, 45° corresponds to 135° and 55° to 125°. Not following these exact angles doesn’t mean you don’t hear sound coming from above anymore. As the horizontal angles of the basic speakers, it’s an indication how to setup your Home Cinema. These vertical angles are important, as later in this article we’ll get back to these numbers if we wish to play Atmos sound using another speaker layout.
Figure 3: Vertical angles of in-ceiling speakers. Courtesy of Dolby.
Speaker Layouts: Auro-3D
Auro Technologies proposes two speaker configurations for Home Cinema: “Auro 9.1” and “Auro 10.1.” The “Auro 9.1” configuration starts with a basic 5.1, expanded with 4 “Height” speakers, to be positioned above the Front and Surround speakers. This is very similar to “classic 9.1,” that is the basic 5.1 with front and rear presence speakers (Figure 4). The Auro “10.1” adds a 10th speaker on top in the center of the basic circle, the so-called “Voice Of God” (VOG, Figure 5).
Figure 4: Auro 9.1 configuration. Courtesy of Auro.
Figure 5: Auro 10.1 configuration. Courtesy of Auro.
Confused about what AV Gear to buy or how to set it up? Join our Exclusive Audioholics E-Book Membership Program!