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Audio Engineering Society
Convention Paper

Spatial Definition and the PanAmbiophone microphone array
for 2D surround & 3D fully periphonic recording

Robert E. (Robin) Miller III ©2004
FilmakerStudios, Bethlehem, Pennsylvania 18018, USA

Presented at the 117th Convention
2004 October 28-31 San Francisco, CA

This convention paper has been reproduced from the author's advance manuscript, without editing, corrections, or consideration by the Review Board. The AES takes no responsibility for the contents. Additional papers may be obtained by sending request and remittance to Audio Engineering Society, 60 East 42nd Street, New York, New York 10165-2520, USA; also see www.aes.org. All rights reserved. Reproduction of this paper, or any portion thereof, is not permitted without direct permission from the Journal of the Audio Engineering Society.  For a PDF version of this paper (0.5 MG), click here.


More than just high definition in terms of higher sampling resolution, spatial definition calls attention of recording engineers to the need to address qualities that contribute to higher perceived reality: 1) Achieving more natural, lifelike audio reproduction both in 5.1 and other formats such as those of the Ambiophonic family. 2) Solving problems associated with phantom images, multiple uncorrelated spot microphones, and smeared temporal response of microphones and speakers. And 3) Raising the bar of audio reproduction to true 3D in order to approach live hearing. The ongoing pursuit of Ambiophonics is to achieve this higher spatial definition not just for critical music listeners, but for all listeners of music, movies, VR, and training simulation.

One flavor of Ambiophonics is 5.1- compatible PanAmbiophonic (“PanAmbio”) 2D surround (see Fig.2, Appendix). High spatial resolution/definition PanAmbio recordings that are compatible with 5.1 are made with an HRTF-based four-channel microphone array termed a “PanAmbiophone” intended:

  • For ITU 5.1 surround, stereo, or…
  • PanAmbiophonic (double stereo dipole)
  • Accurate 360° locating
  • Lifelike tonality
  • 5~30kHz frequency response, flat ~360°
  • 4.0 output (5.1/6.1 with processing)
  • Extensible to 5.1-compatible PerAmbio 3D

In addition to contributing to high spatial definition, the PanAmbiophone features ease of use, obviates need for spot microphones, and allows positioning farther from the source (e.g. an orchestra) than other main microphone approaches – even well beyond the critical radius, thereby more closely emulating human hearing in ideal positions in live venues (and helping to compensate for its size in sightlines and camera angles).

Discussed are the PanAmbiophone’s design evolution and measured performance from 5Hz to 30kHz, accurate localization around 360°, uncompromised impulse and phase response, choice of polar characteristics for outdoor or indoor use, and uncompromised SNR, along with compatibility considerations related to directionality for reproduction using either double stereo dipoles (PanAmbio), or ITU 5.1/6.1 speakers. Even placing the array farther from the source produces a wide (120°) front stage in PanAmbio with a natural balance of depth of front-andcenter sources to more distant ones without spot microphones. When replayed on 5.1 layouts, side and rear directionality and therefore tonality and spaciousness compare favorably with ITU-intended recordings (not meaning re-panned “multi-mono”). The Miller PanAmbiophone for 2D & 3D surround recording result in either system is a useful instrument for naturalsounding reproduction – high spatial definition to use along with high spectral resolution.

The directional PanAmbiophone is described as a tool for controlling indoor ceiling reflections and front-toback imaging for Ambiophonic, 5.1/6.1 and stereo downmix. Generally requiring no spot microphones, the PanAmbiophone is easier to use, and positioning of the array with regard to both recording angle and critical radius and the capability of balancing front and back stages in post-production are discussed. Applications are explored in typical venues for recording and broadcast and for classical, jazz, pop, and movie genres for 2D surround, for home theater use. VR and training simulation are other important applications that benefit from the PanAmbiophone’s localization accuracy.

For future value in multiple formats including 3D of sessions recorded today using the PanAmbiophone, PerAmbio 3D/2D uses a “mode” for decoderless 2D mapping chosen by the recording engineer, possibly changed in post-production, and selected upon replay by the user (automatically in metadata?). For monitoring and in home theaters, height and surround speakers may be flexibly positioned and their coordinates programmed in the decoder. Optionally, to enhance ambience, hall sound may be convolved from hall impulse responses, either by producer or user. Recorded using the PanAmbiophone in 5.1-compatible 2D or PerAmbio 3D, performances are preserved, and producer and user libraries will not become obsolete.

PanAmbio 2D surround, PerAmbio 3D/2D, and the PanAmbiophone have been realized, experimentally tested, and subjectively evaluated – ready for recording engineers for easy use, psycho-acoustic correctness, and investment in audio content intended to have greater future content prized for high spatial definition.


The author is grateful to Ralph Glasgal for his inspiration and wisdom and to the Ambiophonics Institute for support of the author’s work. Additional support is by the University of Parma with special thanks to Angelo Farina, Enrico Armelloni, and Anders Torger; Alex Khenkin of Earthworks; Geoff Houser, Craig Greenwood and Brad Frikkers for fabricating microphone prototypes; and the many musicians who performed for the test recordings. All trademarks are those of their owners.

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