Art & Science of Immersive Recording

with Hyunkook Lee and Andrew Scheps

Art & Science of Immersive Recording

with Hyunkook Lee and Andrew Scheps

Professor Hyunkook Lee of Huddersfield University and Grammy Award-winning mixer/producer Andrew Scheps recently sat down for an in-depth discussion of Immersive Audio recording techniques at the 2024 AES Convention in New York City. In this conversation, hosted by Schoeps at their booth, they explore the art and science of capturing spatial audio, the fundamentals behind immersive microphone techniques, and what considerations regarding microphone quality matter most. Watch their full discussion below to discover insights that bridge technical precision with creative expression. 

A Meeting of Art and Science 

When Hyunkook Lee and Grammy Award-winning mixer/producer Andrew Scheps first connected at the AES International Conference on Spatial and Immersive Audio, it was the beginning of a fruitful collaboration. Andrew, impressed by Hyunkook's organ recital recording, described the experience: "When we listened back to the exact same recording, just mapped channel to speaker, no processing whatsoever... it was breathtaking. The low end was just absolutely amazing." 

What captivated Andrew was how the recording didn't just recreate but enhance the live experience. "I'm watching the feet hit the pedals, and it was like, 'oh, there's something low.' But in the recording, the power and emotional response to the pedals on a church organ was there in a way that it wasn't in the room." 

The Fundamentals of Immersive Recording 

At the heart of this conversation is the approach to capturing natural soundscapes in three dimensions. Developed after years of research at the University of Huddersfield's Applied Psychoacoustics Lab, Hyunkook's techniques address a fundamental question: How should microphones be arranged for height channels in immersive audio? 

"The traditional approach is having spacing between all microphones," Hyunkook explains. "But I came up with this idea: our ears are horizontally spaced, but everything from above is picked up at one point. So do we actually need spacing?" 

 

Three Main Approaches to Immersive Arrays 

According to Hyunkook, there are three main approaches to immersive microphone arrays: 

  1. Horizontally spaced, vertically spaced - Arrays with spacing between all microphones 
  2. Horizontally spaced, vertically coincident - maintains horizontal spacing but has coincident vertical placement 
  3. Horizontally coincident, vertically coincident - Fully coincident approaches like Ambisonics, which have some advantages but require sitting in a precise sweet spot 

The key concept in Hyunkook's preferred technique is a horizontally spaced, vertically coincident array. This approach allows for natural spatial reproduction while maintaining excellent downward compatibility to formats like 5.1 and stereo. 

 

The Science Behind the Technique 

Hyunkook's journey with his recommended microphone array technique "PCMA-3D" began in 2013 with a series of experiments on the effect of microphone spacing on spatial impression. "We found that none of [vertical] spacings made any difference. 0, 0.5 meter, 1 meter, 1.5 meter didn't make any difference," Hyunkook explains. This revelation became the foundation for his array design. 

The technique was originally developed as a 5.1 array with "one microphone [sub-array] pointing forward and the other microphones pointing backwards," allowing engineers to mix these signals to create "virtual zoom-in and zoom-out effects" with more ambience when steered toward the back or more direct sound when pointed forward.  (A similar technique is the “OCT-3D" technique developed by Theile and Wittek)

After his 2013 experiments, Hyunkook realized he could "angle it more upwards so you can actually pick up the main sound and the height at one point, just like our ears capture the sound." 

 

PCMA-3D Versions and Configuration 

The PCMA-3D is a flexible technique with the key concept being a horizontally spaced, vertically coincident array (The ORTF-3D technique shares the same principle).

Hyunkook explains that the standard configuration includes: 

  • LCR (Left-Center-Right) microphones typically spaced one meter apart 
  • Front microphones arranged with approximately 45 degrees subtended angle from center 
  • Center microphone placed about 25 cm from the base point 
  • Rear microphones positioned about one meter from the base point 
  • Side channels for 7.1.4 using side-facing supercardioids 

 

For the PCMA-3D Version 1, the height channels use a coincident technique with supercardioid microphones (typically Schoeps CCM 41 or MK 41) pointing directly at the ceiling, arranged coincidentally with the main microphones. "The advantage of this is it's super easy to fold it down to 5.1 or stereo. You don't actually add any tonal coloration other than the reverb just added to the signals," says Hyunkook. 

 

 

For the PCMA-3D Version 2, which Hyunkook used for organ recordings, he introduces some spacing between the main layer and the height layer. "When I did the organ recording, I added a little bit of spacing because it's all about harmonic reconstruction, because the organ is such a large instrument," Hyunkook explains. This spacing creates a different tonality because with such a large instrument, "it's not about ambience anymore because you capture direct sound from the organ." 

This variation employs wide cardioid capsules (e.g. Schoeps MK 21) or diffuse field equalized omnis (e.g. Schoeps MK 2H) for LCR. 

 

 

The choice of microphone capsules also varies depending on the source material. For orchestral recordings, Hyunkook recommends omni capsules like the Schoeps MK 2H diffuse field equalized omni capsule to capture more low-end. However, even with omni main microphones, he emphasizes that "for the height layer, supercardioid works just perfectly." 

Why Schoeps Microphones? 

Both engineers emphatically explain why Schoeps microphones are essential to their immersive recording setup. 

"The most important thing about Schoeps mics is the tonality," Hyunkook states. "The tonal balance doesn't sound overly bassy or dull. It's just spot on. It has that musical sound, and I don't have to EQ anything. Usually, I just use the original signals without even a high-pass filter. It's a very pure, neutral sound, which I like." 

Andrew emphasizes the crucial consistency across the Schoeps range: "Even as you change patterns, the tonality of the capsules is so consistent. That is huge, because you don't want anything that you're going to have to compensate for. As soon as you start messing with it, all of this coherence goes away, and a lot of the benefit of the mic technique itself goes out the window." 

The natural sound of Schoeps microphones has become a cornerstone of Andrew's workflow. "I have yet to EQ anything I've recorded with them," he explains. "It just sounds like you're in the room." He's quick to address a common misconception about neutral-sounding microphones: "You could say, 'oh, well, maybe it's a boring sound.' It isn't. It's actually a very exciting sound, but it's very present." 

Andrew contrasts this with iconic but heavily colored setups: "If you do a Decca tree with old tube microphones, M49s and M50s, it's a beautiful sound that we've heard before, but it's a very, very affected sound. People think of it as being very natural. It's nothing like what you hear in the room." With Schoeps, he says, "I feel like you have this starting point that's easy to get, that you could do anything with, but as of yet, I haven't had to do anything. It fits in perfectly with every track I've used it on." 

Practical Benefits: Portability and Flexibility 

Beyond sound quality, both engineers highlighted the practical advantages of Schoeps' Colette microphone series for immersive setups: 

"Just on the practical side, especially with the Colette series, they're tiny," Andrew notes. "I have what basically looks like a pencil bag that has all 11 microphones in it. So it's very portable, which is big for me. I need to be able to set up quickly and in places that would be a problem with other microphones." 

Hyunkook adds: "When Schoeps introduced the CMC 1, that was a real lifesaver. I do a lot of location recordings where sometimes you have to hang the microphone from a balcony or ceiling. The microphone should be small enough, otherwise video guys hate it." 

The modular nature of Schoeps microphones provides exceptional flexibility. "Once you have a set of MK capsules and CMC bodies, you can just swap the capsules," Hyunkook explains. "I can vary the combinations—use CMC 1 with the MK 4, or CMC 6 with other capsules. It's super flexible." 

Creative Applications Beyond Classical Recording 

While microphone arrays have traditionally been applied to classical and orchestral recording, both Hyunkook and Andrew are excited about expanding these approaches to pop and rock productions. 

"These string quartet recordings I've done are for a very traditional band," Andrew notes, referring to his work with the atmospheric indie rock band Low Roar on their album "House in the Woods" (The production has since been released) and the track "None of Your Business" showcases how seamlessly the immersive string quartet recording integrates with conventional elements. "There's nothing immersive about the production other than the recording of the string quartet, and it fits in perfectly with the rest of the recording [which was done in 2.0]. There's no compromise or anything like that."

Hyunkook adds: "Now that there is more interest in immersive recording in pop and rock, I think there are a lot of opportunities we can create. Different configurations might work for drum recordings. The same vertically coincident array concept can be used for drum overheads, but spaced. Just like conventional cardioids pointing down to the cymbals, but you add two more microphones upwards." 

Unexpected Creative Possibilities 

The flexibility of immersive recording techniques opened up surprising creative options for Andrew: "I would have the front microphones to use for the stereo version of the song, and the rest of the microphones to bring in for the immersive version. Instead, I found that the height microphones on their own create an amazing ethereal sound for parts of the arrangement with harmonics." 

This discovery meant that Andrew could make creative decisions even in stereo mixes: "I could actually make decisions in the stereo mix about how ambient I wanted things to be, just by mixing and matching microphone signals. It was really extraordinary and never even occurred to me that that's what I would be doing." 

Looking to the Future 

Both express tremendous enthusiasm for continuing their work with immersive recording techniques and Schoeps microphones. 

"I just want to record more stuff," Andrew exclaims. "I've been doing this for a long time, and some of it isn't new or exciting in the same way. But I cannot wait to record more with this technique. It's amazing." 

Hyunkook concludes: "I really value that scientists and artists work together. That's how we can actually make something new and push the boundary. Scientists need to understand what artists need, and artists can benefit from scientific research. We can make something together." 

Learn more about Professor Hyunkook Lee's research at the Applied Psychoacoustics Lab, University of Huddersfield. 

Andrew Scheps is a Grammy-winning producer, mixer, and engineer whose credits include Adele, Red Hot Chili Peppers, and Metallica. 

Decca-Tree 3D Set

Recording technology for immersive audio

CCM 41

SUPERCARDIOID COMPACT MICROPHONE

CCM 2H

Compact Microphone

MK 41

MICROPHONE CAPSULE

MK 4

MICROPHONE CAPSULE

MK 21

Mikrofonkapsel

CMC 1 U

miniature Colette microphone amplifier

CMC 6

MICROPHONE AMPLIFIER

ORTF-3D

Setup for 3D Audio