In the latest of our Tech Talks series, we’re speaking with Paul Peace, a Senior Manager in Engineering at HARMAN Professional Solutions. Paul is a true innovator with tremendous expertise in cinema sound. He oversees loudspeaker design for cinema, retail and commercial applications and is the designer of JBL 9350, 9300 and 9310 Cinema Surround Loudspeakers.
As an undergraduate, Paul attended the Georgia Institute of Technology, where he earned a Bachelor’s degree in Applied Physics; he is currently completing a master’s degree in Acoustics at Penn State. Before joining HARMAN in 2014, Paul worked extensively in loudspeaker design and development and has commissioned hundreds of cinema audio systems for standard, premium large format (PLF) and IMAX theaters, as well as home systems.
During the last several months Paul has been researching ways to improve loudspeaker coverage areas for both surround and immersive cinema audio in theaters with stadium seating. He recently presented a paper at CineAsia 2016 explaining his revolutionary approach to positioning speakers at theaters using 5.1 and 7.1 configurations. We were interested in hearing about his findings and understanding how his work is impacting the moviegoer experience and exhibitors’ bottom line.
[MM] Throughout your career, you’ve been focused on providing better sound in movie theaters. Can you explain what the challenge is?
[PP] In the late 90s, stadium seating became a trend in theaters, because it improved sightlines. With its introduction, however, room acoustics for surround sound dramatically changed; the new slope created a very difficult scenario.
In a typical stadium seating theater, with 5.1 sound, the screen channels at the front of the theater operate pretty well for everyone except those in the very front rows. As you get closer to the back of the room, the sound pressure level (SPL) from the screen speaker channels obviously diminishes, because you’re further away.
Side surround speakers, however, do not do as good of a job. For 5.1 and 7.1 to work in all seats, the coverage from each group of speakers—the screen channels, the two sides and the rears—should be the same at every seat. However, the angle of the seating creates a rearward bias that results in a hotspot for people in the back of the theater and an inaccurate listening experience for the rest of the audience.
[MM] Can you explain where the rearward bias comes from and why it’s an issue?
[PP] By measuring the sound coverage in each seat, we were able to confirm that almost every position gets more volume from the side surround in front of it than the one behind. If you look at the actual coverage pattern of the two side surrounds closest to a seat, the speaker behind it will typically be 3dB lower than the one in front of it.
From a loudspeaker perspective, that’s called a rearward bias and conflicts with how surround sound is meant to envelop the listener in the soundtrack. For maximum impact in 5.1, for example, film mixers position surround sound to come from behind and just over the shoulder of each person in the audience. Having it come from in front provides a very different and far less atmospheric audio experience.
[MM] In a 7.1 configuration, does stadium seating also impact rear speaker coverage?
[PP] They present an even more challenging problem. Traditional surrounds used in the back of a theater position map completely opposite of the screen channels. As you would imagine, they are loudest in the back of the theater. But, unlike the front speaker coverage, they drop off dramatically. There is only a very small section of the theater where people hear both the front and rear speakers as intended.
The end result is there are actually three zones in the theater and each has a distinctly different experience. In the center, you’re within +/-2dB of the optimum sound coming from the front and back. Outside of that, all bets are off. In the rear, you get too much surround and not enough screen. Meanwhile, in the front, everything is diminished.
My whole goal has been to figure out how to make soundtracks work in all seats by ensuring that they receive the same signal strength from each speaker.
[MM] Is that possible?
[PP] Yes, to a large extent. After analyzing the dispersion of sound in a stadium-seating environment, we designed the JBL 9300 Cinema Surround Loudspeakers with specific directivity for that geometry. We also tilted the surrounds 15 degrees toward the screen. By doing so, we were able to eliminate the hotspot and rearward bias, while considerably broadening the sound coverage in the theater.
We call this arrangement the JBL Sculpted Surround System because it shapes the sound radiation pattern of the room into a pattern that compliments the screen channels. The tests have been so conclusive, that the 9300 is equipped with a mounting mechanism so theater installers can easily position them with the 15-degree tilt.
Besides expanding the audience sweet spot, another major benefit of tilting the surrounds is that the coverage improvements allow us to reduce the number of loudspeakers required in the each theater. Because of the speakers’ specific directivity and new positioning, each covers a slightly larger area, and can, therefore, be incrementally separated along the wall.
To improve the rear channel issue, we developed the JBL 9350, a configurable pattern speaker with three patent pending technologies. It’s the first surround loudspeaker to offer rear coverage directivity as one of its options. When you set them to be positioned in the rear, you only need a single stereo pair for a standard sized theater. Using them as left and right rear mains, there’s no need to have additional speakers in the back of the theater.
[MM] How have the new cinema speakers and tilting concept been received in the marketplace?
[PP] Really well. We recently showcased it for Cinemark—one of the largest cinema chains in the world—and their response was dramatic. Besides the obvious benefit to guests, they recognized how using fewer loudspeakers meant potential savings on amplification, DSP and installation. If you think about all of the infrastructure that goes into setting up theaters, it’s a huge advance. We also recently demoed the system at CineAsia 2016 in Hong Kong. We are currently doing our first installations for one of the largest cinema exhibitors in Asia.
Many thanks to Paul for talking with us today about his latest innovations in cinema sound. If you work in cinema and are excited by breakthrough technologies that improve the guest experience, please share them in the comments.