Dr. Sean Olive is a Senior Fellow, Acoustic Research, at Harman International. He has extensive expertise in the areas of perception and measurement of sound quality, particularly in headphones. Part One of our interview appeared in Issue 189. Here, he shares his perspective on the qualities of modern upmixers for immersive audio, the benefits of headtracking technology, some wisdom for audiophiles, and more.
Russell Welton: Dolby mixing for surround sound and immersive audio has now progressed to object-based mixing and Dolby ATMOS, what do you see as the next biggest advancement in headphone playback of differently mixed and recorded music? [Object-based mixing involves keeping every sound as an independent “object” and assigning them a position that is mixed during the reproduction process, rather than the typical means of creating a mix in the recording studio. – Ed.]
Dr Sean Olive: Most music is heard over headphones today, so immersive formats like Sony 360 Reality Audio, Dolby ATMOS Music, and other types of spatial audio have the potential to reach a large audience through headphones. So far, I have been underwhelmed by the quality of the binaural rendering for headphones, especially when you compare the experience of the same music played over a 7.1.4 speaker system [using seven main audio channels, a subwoofer and four height channels]. So, I think there are opportunities to greatly improve the binaural renderers and accommodate head tracking and personalized head-related transfer functions (HRTFs).
I’ve also been disappointed by the inconsistency in production/mixing quality of the immersive music recordings. Much of the releases are old stereo recordings remixed and repurposed for immersive with the aim to make it sound as close to the original recordings, including warts and all. The vast material I’ve heard uses [a] stereo phantom center, which means you only hear the main artist in the center if you sit exactly in the sweet spot. If you don’t sit in the sweet spot, you will hear the artist in the left or right speaker on home and car systems Don’t get me wrong: there are many excellent immersive albums, but right now we are still in the early days of immersive music.
A Dolby Atmos mixing system showing object-based mixing (note the graphic in the lower right of the console). Courtesy of Wikimedia Commons/Nichollas Harrison.
RW: Could you tell us more about head tracking technology, what it is and what its benefits are?
SO: When we listen to a sound source, we localize [it] based on the interaural and time and intensity cues at our ears. A sound source to our left arrives at the left ear slightly before the right ear and it is slightly louder. As we move our head, these localization cues change while the location of the sound source remains stationary. However, while listening to the sound source over headphones, when we move our heads, the localization cues are not updated. As a result, the entire band [or orchestra or performer] shifts [along] with our head. The realism and naturalness of the headphone experience breaks down and we tend to hear the band close to or inside our head. Head tracking can avoid this situation by tracking the position of our heads and updating localization cues used in the binaural rendering so that the band remains stationary – just like in natural hearing.
RW: What is your personal favorite music medium to listen to and why?
SO: I grew up with vinyl in the 1970s but have been listening to digital recordings since the CD was introduced in the mid-1980s. Digital technology has greatly improved since those early days and for me at least, there is no compelling reason beside nostalgia to go back to vinyl. I would guess that 98 percent of my music comes from lossless streaming on Tidal and Qobuz because of its convenience and good sound, and it's a great way to discover new music. I love Roon because it organizes my music and provides great information about the artist and the music, and curates other music that I would otherwise not discover. Now that Apple Music stereo music is lossless and includes Dolby ATMOS Music, I may switch from Tidal to Apple Music. The only thing that stops me is that Apple Music is not supported by Roon.
RW: What advice would you give critical listeners to regain their pleasure in listening to music for music’s sake, rather than always listening from an analytical perspective?
SO: Music has the potential to transform our mood, [and] reduce anxiety, blood pressure, and pain as well as improve sleep quality, mood, mental alertness, and memory. But many people are not achieving the full emotional and intellectual experience because music has become a background activity.
My advice is to disengage from the distractions and give music your full attention. Turn off the phone, lower the lights and sit down and relax. Try listening to an entire album or a symphony rather than a playlist of disparate tracks. People don’t watch three-minute segments of 10 different Netflix movies, so why do we do this with music? When you listen to the complete work the musical journey is more satisfying and emotional for a sustained period.
RW: Do you have any words of wisdom for aspiring audio design engineers that want to get into your field of expertise?
SO: Apart from taking the right engineering, math, physics, and acoustics courses to gain knowledge about the field, I often recommend [that] college students talk to people in the field and apply for summer internships at an audio company. Join the Audio Engineering Society (AES), which is the only professional international society dedicated to audio engineering and includes 13,000 members worldwide, a great networking opportunity. Find a mentor: I met Dr. Floyd Toole 38 years ago on a random field trip to the National Research Council in Canada, and it changed my career path from sound recording to research in reproduced sound. We worked together until he retired from Harman in 2008 and remain friends today.
RW: On another note: could you share any insights which make for the advantageous pairings of preamps and power amps?
SO: I really don’t have much insight to offer other than making sure you have the right set of features for your needs. Does the preamp have subwoofer outputs, room correction, or tone controls to adjust the balance? The trend these days is [towards] powered loudspeakers with built-in streaming, which provides a smooth, easy-to-use, frictionless user experience. The new JBL 4329P [powered bookshelf speaker system] is such a product and I was so impressed with the sound quality and user experience I just ordered a pair. Just pair your tablet or smartphone and you’re up and running.
JBL 4329P Studio Monitor Powered Loudspeaker System.
RW: What are the main mistakes or oversights you encounter that audiophiles are guilty of?
SO: I think most audiophiles should pay more attention to things that matter most to achieving good sound quality in reproduced sound. The loudspeakers are the most critical component and their positioning and calibration in the room will determine the quality and quantity of bass. The best loudspeaker companies and audio review sites provide comprehensive anechoic measurements of their loudspeaker products that are highly predictive of how they sound. Use that information to guide you and if a manufacturer cannot provide it, you might ask them, what are they hiding? Finally, a loudspeaker only sounds a good as the recording played through it. Streaming services can help you find the best-sounding recordings, and you will quickly find that certain labels, artists, recording engineers and producers tend to consistently produce great records.
RW: What do you wish you were asked about in interviews, but never are?
SO: I seldom get asked how I got into audio in the first place. It was not something I originally planned. The best way to describe my career is a journey through audio’s entire circle of confusion: starting as a musician (creating art), becoming a Tonmeister (recording art), and ending up as a scientist in the reproduction of the art. Perhaps in retirement I will return to where I began, playing more music.
Header image courtesy of Dr. Sean Olive.