Three Methods for Immersive 3D Audio

I recently had the opportunity to explore the first inaugural LA Audio Show held the first weekend in June at the LAX Sheraton Gateway Hotel. As a strong advocate for surround sound — especially immersive 5.1 music — I was on the hunt for vendors demonstrating state-of-the-art 3D audio reproduction. If you've had the chance to walk the ballrooms and hotel suites of a high-end audio show, you know that 99% of the rooms feature two-channel stereo playback. It's a rare occasion when an audio supplier decides to go with a multi-channel setup at a high-end audio show. Surround sound is more closely associated with home theaters and movies, virtual reality, or gaming. But music listening can also be enhanced when delivered in immersive, 3D audio.

It's true that most musicians and their labels haven't embraced surround music mixes. Despite several attempts with quadraphonic LPs back in the 80s and 5.1 mixes on perhaps 1500 DVDs/SACDs, stereo music seems to have a hard lock on the industry. There are some notable exceptions if you know where to look. Some classic rock/pop albums from the past are available in 5.1 surround including "Pet Sounds" by The Beach Boys, "A Night at the Opera" by Queen, "Rumours" by Fleetwood Mac, and even The Beatles' "Sgt. Peppers Lonely Hearts Club Band,” which was completely remixed in 5.1 by George Martin's son Giles as part of the 50^th anniversary set released in May. Of course, I had to have it and actually sat for 40 minutes of focused, uninterrupted listening like I haven't done in many years. It's brilliant by the way!

How 3D Audio Works by YARRA 3DX Tube Video

Surround music offers listeners increased spatial discrimination over mono and stereo mixes. Engineers and producers can spread individual instruments and vocals in a much larger sound field, which opens up the presentation and gives listeners more places to hear the elements of a song. I heard music and vocal parts in The Beatles 5.1 surround version that I never knew existed before — because they had a place of their own in the mix. Surround music is simply more compelling and real than older formats. But the industry is stuck in a classic "chicken and egg" dilemma. We won't get more surround music without a parallel increase in the demand for it.

But virtually all contemporary music released by the big labels and independent suppliers is broadcast, released, and consumed in two-channel stereo. Music fans haven't been offered a choice because music is largely consumed in systems that aren't surround friendly.  

Things are different in the gaming world. The recent E3 Convention (Electronic Entertainment Expo) introduced new gaming systems supporting immersive, 3D audio (Dolby Atmos) and content specifically designed to deliver it was on display at the expo. Microsoft's new Xbox One X supports Dolby Atmos. The first game to use it is the PC version of Blizzard Entertainment’s "Overwatch". Other anticipated games shown at E3 that will feature Atmos sound include “Crackdown 3” and “Gears of War 4,” both published by Microsoft Studios.

Plantronics, a headphone maker, announced that it had become the exclusive channel for Xbox One X Dolby Atmos gaming headsets.

The advancement of immersive, 3D audio — whether for movies, VR, gaming or music — demands consumers have simple and cost effective ways to experience it. The classic chicken and egg dilemma plays a huge role in the development of surround sound content. If there no easy way to reproduced immersive audio, then why should producers of that content invest the time and effort in creating compelling programming?

The growth of home theaters systems since the emergence of the DVD-Video format back in 1997 has been dramatic. Millions of homes have 5.1 surround sound systems and a large percentage of disc-based and streaming video entertainment comes with a 5.1 surround mix. Gaming engines and systems have also embraced immersive audio. Microsoft's Xbox and Sony's PlayStation support surround audio and most of the biggest games take advantage of multi-channel output via analog, USB, and HMDI connections. And of course, the rapid rise of VR/AR software adds to the demand for easy to use, cheap playback hardware.

If you're a fan — or just want to experience — surround sound, you'll want to know what it takes to pull together a system capable of delivering immersive audio. The following paragraphs describe three different approaches to reproducing 3D audio. They range in price from just a hundred dollars to several hundred thousand dollars.

Method One: Multiple Speakers

One way to create an immersive, surround soundscape is to place multiple speakers around a space. The ITU (International Television Union) has standards for positioning speakers in both 5.1 and 7.1 configurations. When listening to a movie soundtrack or piece of music through a surround sound system, individual elements can be panned to any location along the same flat plane as the listener's head. Dialog, music, and sound effects can seem to emanate from the speakers or anywhere in between. We've all experienced a well-mixed soundtrack. Surround sound works!

Recently, Dolby, DTS, and Auro Technologies have added height channels to their theater sound systems. Not content with sound on a plane, fully immersive, 3D audio is made possible by adding additional speakers on the ceiling. The march for more audio channels and speakers continues unabated. New configurations such as 11.2 or 22.4 are examples of the "more speakers is better" theory. Home theater owners can also migrate up to these new audio formats with upward facing speakers that "bounce" sounds off your ceiling. But, there are limitations to this method one of which requires a flat ceiling to be reasonably effective. A discrete multi-channel speaker system is the ideal way of conveying a true 3D soundscape but not everybody has the real estate or budget for this option.

The previously mentioned LA Audio Show included a very elaborate demonstration of immersive audio. Starke Sound, an LA-based equipment and installation company, took over 2500 square feet at the hotel and transformed the space into two theaters. The large room featured a 52-seat theater showcasing a 13.6.8 Dolby Atmos configuration valued at $250,000. The smaller room was more intimate, with only 13-seats in a 9.4.4 Dolby Atmos configuration with the system price of $145,000.

I had the chance to experience the big room with its 24-channels of audio. There were speakers on the side and front walls, 8 subwoofers tucked in the corners, and 6 speakers on the ceiling. They played a couple of movie clips and a few minutes of a live music concert. It was very impressive. I guess if you've got the money, space, and interest, then wiring up dozens of speakers might make sense.

Clearly, movie soundtracks are enhanced by surround sound and live music concerts benefit from sounds coming from all directions. The examples played in the Starke Sound demo room were loud and made an impact on everyone that sat through their presentation.

But I have heard intimate surround music presentations that recreate very compelling, private, personal performances. The acoustic country duo Hanna-Mceuen singing "Lowlands" in 5.1 surround or new folk artist John Gorka doing "I Saw A Stranger With Your Hair" make much more impact in surround than stereo.

But is it possible to deliver a similar audio experience without the hefty price tag, component count, and dedicated room?

Method Two: Headphones

I'm not a headphone guy. But I recognize that headphones have tremendous advantages over multiple speaker setups like those mentioned above. First, they cost a lot less (unless you go crazy and drop $55,000 on the Sennheiser Orpheus Headphone System — claimed to be the "best headphone sound" in the world!). Headphones can also do something that speakers can't. They can deliver sound to your left and right ears with zero crosstalk. Crosstalk is when information intended for one channel or ear leaks into the other channel or ear. The result is a reduction in the spatial integrity of the source recording. Audiophiles love to wax poetic about the "sound stage" of their rigs. The brass ring for them is a system that can reproduce depth, low-level detail, and accurate sound stages. It's obvious that multiple speakers placed around a listener will suffer from all sorts of crosstalk. Generally speaking, crosstalk reduces the spatial discrimination of a multi-channel mix — either stereo or multi-channel.

But headphones have shortcomings, too. The visceral, low frequency vibrations that come from speakers — especially subwoofers — are missing in headphones. And stereo imagining is severely compromised when listening to music through phones. Sounds seem to be located in the middle of your head and the entire sound stage moves in sync with your head’s movement with any rotational motion. It’s unnatural: the sound source should remain stationary relative to your head’s motions, as it does in real life. This is my biggest complaint about listening to music through headphones or in ear monitors — getting sounds to appear outside of your head is difficult.

Solutions to these problems exist. The Smyth "Room" Realizer (both the A8 and the upcoming A16) is a very clever device that allows owners to experience the characteristics of any room provided they've been "measured" in that space. AIX Records' studio in Los Angeles is a very popular room for getting your ears measured, which results in a personalized HRTF (head related transfer function). The resultant PRIR filter settings are used by their hardware to mimic the characteristics of a great listening room through headphones. You don't have to have a great acoustic listening space. You simply need the measurements of that room, a Smyth Realiser, and a good set of headphones. Smyth owners can get the same sound experience I have in my studio or the best theater in the world in their apartment. Their system really works — I've tried it and actually own one of their boxes.

The Smyth system also uses a small wireless transmitter and receiver to track the rotation of your head and processes the headphone delivery to "lock" the virtual speakers in the same location — the experience is practically identical to playback from the speakers. In fact, many times measurement subjects have sworn that the speakers were still on when actually the headphones were responsible for all of the sound. The Smyth Realizer solves the problem of "inside-your-head" audio AND the head tracking issue.

We experience the world of sound around us binaurally, which means everything we hear comes in through our two ears. Our outer and inner ears in conjunction with our brains, determine the intensity, frequency, timing, and phase of any sound we hear. With binaural sound, we're able to accurately locate sounds in 3D space. We don't need multiple ears placed all around our heads to determine spatial information — just two is enough. Our sense of hearing is amazing. It doesn't care how big your speakers are or how large your listening space is. All that matters is what arrives at your left and right ears. Any "sound field" that you experience is the result of sounds coming to your left and right ears.

So what would it sound like if a source recording made using a binaural recording system were played back through a set of headphones? Theoretically, the listener would hear exactly what the "dummy" binaural head heard during the capture. You can audition binaural recordings by visiting YouTube and doing a search. If you listen through headphones, the effect is rather good. The sound can be perceived as coming from outside your head.

Binaural recording can be made using "dummy heads" with microphones tucked behind their eardrums. There are record labels that specialize in recording and releasing binaural recordings. However, music recorded this way tends to sound hollow and somewhat distant. There's no chance to mix or balance individual instruments after the original recording session — after all everything is captured with a single binaural head. And finally, the musicians have to perform all of the parts — including the vocals — in a single pass. This requirement alone means that virtually all commercially released albums can't be recorded using a binaural recording head. Modern recording practices build commercial tracks one section — or even one part at time.

But traditional surround audio can also be processed from discrete multi-channel mixes (5.1 or 7.1 or 11.2) into two-channel stereo binaural signals using specialized software. This is what the Smyth Realizer does when you plug in an HDMI cable from your Blu-ray player and watch a movie. It calculates what signal processing needs to happen to make the Left Surround channel appear to come from over your left shoulder when played back through headphones. So there's hope for immersive, surround sound delivered through headphones. Sources have to have been recorded binaurally or the multi-channel mixes have to have been binaurally processed in software.

Traditional music mixes and headphones are unable to deliver an "outside-of-your-head" experience. It just doesn't happen.

I learned about a new crowd sourcing campaign offering yet another set of headphones the other day. This group's headphones use drivers with graphene speakers instead of Mylar. They claim this revolutionary new material delivers increased frequency response (up to 63 kHz!!) and a more linear response. I'm sure the specifications for the new phones are very good but they're not likely to magically reverse the "inside-your-head" phenomenon. They have a few testimonials on the Kickstarter site (including comments from some Grammy-winning engineers) that say exactly that — the sound seems to come from across the room. I'm skeptical.

Method Three: Sound Bars

Sound bars, those small linear arrays of speakers typically tucked under a television monitor, are the best selling audio accessory after headphones according to the Consumer Technology Association (CTA). More home theater owners purchase sound bars than discrete systems involving 5 or 7 or more speakers. Why? Because they're far cheaper, less obtrusive, and they produce a reasonable approximation of surround sound. Prices range from a couple of hundred dollars to more than five thousand dollars.

But how do they work and how good is the sound they project? Sound bars have multiple small speakers arranged in a linear array. Some manufacturers send the left and right surround channels to portions of the array that are pointed past the listening position. They're counting on these channels being reflected off of the walls in your home theater and being perceived as "non-direct" sounds. It's not exactly the same as having a speaker located over your shoulders but it does create an effect that is "surround-like". Yamaha and Denon employ this method of "directing" sounds beyond traditional stereo setups.

Other manufacturers employ clever signal processing to "focus" or "magnify" the presence of sound in specific locations. These "smart" sound bars can actually deliver an immersive, 3D audio experience — just like a binaural mix in headphones — as long as the content is properly prepared. Remember that a complete sound field — any sound field including 3D immersive audio — can be reproduced by steering left channel information to your left ear and right channel information to your right ear. As we've seen, headphones can do that. And it turns out beamforming speakers can do it too.

Imagine a small array of identical speakers, each driven by a DSP chip and digital amplifier, pointed at your listening position. By precisely adjusting the phase and amplitude of each signal, it is possible to "beam" discrete channels of audio to specific locations in space  and newer designs can actually track your movements and make realtime adjustments to the sound field. Listeners are not locked into the traditional "sweet spot" any more.

The first time I experienced this remarkable capability was at the SpatLab (Spatial Audio Lab at the University of California at San Diego). My close friend (and the former director of the Music Technology program at UCSD) stood at 12 o'clock, while my wife and I stood opposite each other at 3 and 9 o'clock in relation to a small sound bar called the YARRA 3DX. Believe it or not, we all heard a different audio program. The YARRA 3DX sound bar was able to focus three discrete audio programs to three specific areas of the room. There was no "crosstalk" or bleed. I was amazed.

It is possible to use "beamforming" techniques to minimize crosstalk in an acoustic space and deliver a 3D immersive audio program to a listener without headphones! But what does it cost?

There are several commercially available speakers that use beamforming to "expand" realism and deliver 3D audio but they're very expensive — costing over $50,000! In comparison, the previously mentioned YARRA 3DX speaker and subwoofer combination is priced at $599.

The YARRA 3DX is a sound projection system that can deliver immersive, 3D audio for home theater owners, gamers, high-end music fans, and VR/AR applications. The main speaker array has twelve 33 mm identical drivers, controlled by an iOS or Android App, to up to three locations in a room. Users can switch the unit between near (10-36") and far field modes (7-15 feet) to accommodate different applications. The main array is only 21" long and 3" high. The self-powered subwoofer is roughly 10 inches square and has an internal power supply (120-240/50-60 Hz).

Comhear Inc., a San Diego-based technology company, is developing the YARRA 3DX product and will be launching a Kickstarter campaign to bring their product to market in early July. They demoed the unit at the LA Audio Show and won an "Alfie" award in the "Best of: Speakers" category. The judges didn't quite know what to make of the little speaker in front of them but they said, "it blew them away!" If you're interested in taking advantage of discounts of up to 50% off the MSRP of $599 for this innovative product, you'll want to visit www.yarra3dx.com and sign up for their VIP list right away.

Conclusion

Surround sound, immersive audio, and 3D sound are growing in popularity and importance as gaming, VR, movies, and music embrace multi-channel audio. Users have choices when it comes to experiencing multi-channel audio. We've looked at the three methods in the discussion above: multiple strategically-placed amplified speakers, headphones with motion tracking and binaural content, and beamforming sound bars. All three can deliver enhanced listening, but vary tremendously in cost and convenience. For the money, a smart sound bar might be just what many home theater enthusiasts need especially if their goal isn't to reach theater reference levels that can cause one to get evicted from their condo. A smart sound bar also offers a compact solution that occupies the least amount of real estate and offers the easiest set up.