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Recording with height 

Systems and Techniques 

for 3D recording 

Helmut Wittek, 

SCHOEPS GmbH 

wittek@schoeps.de 

H.Wittek: Systems and techniques for 3D recording Slide 1

Outline 

• What is 3D Audio? 

– 3D Video 3D Audio 

– 3D Audio-Formats 

• Physical/Perceptual effect of the height loudspeakers 

• Spatial properties (Direction, Distance, Room) of 3D audio 

• Consequences for microphone recording 


What is 3D-Audio? 

• What is 3D-Audio? 

• 2D Video: 

– no real depth, but width + height 

3D Video adds the real depth 

dimension 

• 2D Audio: 

– no height, but width + depth 

3D Audio adds the height dimension 

• One example for 3D Audio is Multichannel Stereo + height … 


Multichannel + height 

• 5.1 Surround + n height channels 

– one of the proposals: “Auro3D 9.1” = 5.1 Surround + 4 height channels 

= X = X 

30° 

= X 

= X 

= X 

ITU 5.1 


Potential 3D Audio formats 

Sound field synthesis 

Reconstruction of the original 

wave field at the listener’s ears 

WFS / 

Derivatives 

+ height 

Ambisonics / 

HOA 

Binaural 

Stereo + height 

Stereophony 

Creation of a quasi-natural 

acoustical perception 


Effect of the height loudspeakers 

• 4 main physical changes of the sound field after adding 

height loudspeakers: 

1. More possible directions for 

discrete sources 

2. More possible directions for 

reflections 

2.0: 

5.1: 

RS 

R 

R C 

3. Lower source/reflection 

density 

RS h 

R h 

4. Higher diffuseness of the 

diffuse portions, more evenly 

Auro-3D: 

RS 

R C 

distributed diffuse field 


Effect of the height loudspeakers 

• Hypothesis: 4 main perceptual changes of the sound field after 

adding height loudspeakers: 

1. Enhanced distribution of 

sound sources 

2. More natural perception of 

distance/depth 

3. Less coloration 

R 

2.0: 

RS 

R C 

5.1: 

RS h 

R h 

4. More natural spatial 

impression; larger diffuse field 

Auro-3D: 

RS 

R C 

sweet spot 


Properties of 3D Audio 

1. Directional Imaging: 

• Discrete sources in the height loudspeakers are possible 

• Elevation is hardly possible or unstable, coloration is likely 

• Up/Down Panning can be used, but it does not create stable phantom 

sources, coloration is likely? 

• “Filling the area” is possible a/b technique 

• Sufficient channel separation is mandatory for directional imaging 

∆t 

2,2 ms 

1,7 ms 

1,2 ms 

0,7 ms 

0,2 ms 

3 m 0,6 m 


Properties of 3D Audio 

2. Distance/Depth: 

– More natural distance/depth perception? 

– Less coloration due to lower reflection density? 

3. Spatial impression/Envelopment: 

- More natural spatial impression? 

- Larger diffuse field sweet spot? 


Recording for 3D Audio 

• Consequences for the recording technique: 

– Directional Imaging: 

• Stereophonic rules (∆L, ∆t) apply in general for all loudspeaker pairs, 

height loudspeakers are potentially displaced by 1-2 ms! 

– Channel separation: 

• discrete signals: one signal on more than two loudspeakers leads to 

coloration 

• diffuse signals: the more de-correlated diffuse sources, the more 

diffuse is the resulting sound field 


Two examples for Auro3D recording techniques 

• ORTF-like recording techniques, e.g. “OCT 9” 

– Closely spaced, directive microphones 

– Typical properties: 

• proportional and clear directional imaging 

• natural spatial impression 

– Application: chamber music, drama, sports, ambience 

• Wide a/b-like recording techniques 

– Widely spaced, omni-directional microphones 

– Typical properties: 

• stable, but not proportional directional imaging 

• enhanced spatial impression 

– Application: music, film music 



OCT 70 + 4 super-cardioids pointing upwards 

Largely-spaced 9-channel A/B setup 

ms 

Reflection patterns in the “Sweet Spot” of an Auro-3D speaker array, 

generated using 2 different microphone arrays. 

The microphone arrays record the same source. A shoebox-shaped 

recording room was produced for emulation purposes. The source produces 

a Dirac impulse. 

Each peak color corresponds to a (1st order) image source. 

ms 



„OCT 9“: 

lower plane: OCT Surround 

upper plane: height + 100cm, 4 Supercardioids pointing upwards 

C 

L h R 

Lh 

b 

Rh 

40 cm 

LS 

b + 20 cm 

RS 

LSh 

RSh 



Wide a/b: 

spacings > 0.5-2 m, 

upper plane: height + > 1 m 

C 

L 

L 

R 

R 

LS 

LS 

RS 

RS 


Test recordings Galaxy Studio 

• Test recordings in Galaxy Studios and HfM Detmold(ICSA): 

– OCT 9 

– Omni array 

Listen to a/b 

comparisons - 

without/with height 

- OCT/Omnis 

Workshop WC 5 

Today, 14h in the 

“großer 

Seminarraum” 

Thank you! 

Questions and corrections are 

welcome

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