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Audio Engineering Society
Convention Paper

Scalable Tri-play Recording for Stereo, ITU 5.1/6.1 2D, and Periphonic 3D (with Height) Compatible Surround Sound Reproduction - Page 7
Robert E. (Robin) Miller III, FilmakerStudios, Bethlehem, Pennsylvania 18018, USA

APPENDICES

Appendix A - family of Ambiophonics

PerAmbio 3D/2D belongs to the Ambiophonics family, championed by Ralph Glasgal, including: Ambiophonic 2D [ 16] - 2.0 channels to 2 or more speakers (+SW) with hall convolution (Fig. 15);

PanAmbio (panor-ambiophonic) 2D [ 12] - 4.0/4.1 channels to 4 or more speakers (+SW) (Fig. 16);

PerAmbio (periphonic ambiophonic) 3D [ 7] - 6.0/6.1 channels to 10 or more speakers (+SW).

Ambiophonics works with pinnaless binaural records but enhances almost all stereo releases, adding 3D ambience by hall convolution, and presenting a wide, accurate stage with no pinna confusion for central voices. Also compatible with 5.1/6.1, specially recorded PanAmbio (2D) and PerAmbio 3D/2D releases allow music lovers and audiophiles a greater level of listening precision.


Fig. 15.
 Ambiophonic 2.0 turns stereo ìinside-out, reproducing an up to 180° wide, accurate front stage. 3D ambience is added by convolution using hall impulse response.


Fig. 16.
 PanAmbio 4.1 duplicates the wide front stage in back.  4.0 recordings made with two Ambiophones play compatibly on 5.1/6.1 systems.

Because they are more binaural than stereo, Ambiophonic playback demands less from the listening room than 5.1 or 2.0 but does require:

  • Two Ambiodipoles, one front and one rear, driven by a crosstalk cancelling program similar to RACE.
  • Front and rear speaker pairs that are well matched in level and frequency response and axial response.
  • Computer or player with up to three output pairs.
  • Decoder if playing Tri-Play Media.
  • Surround speakers for either convolved or recorded hall ambience

Calibration of channels at listening position within 1dB using an SPL meter and pink noise is desirable.

Appendix B - WFS & Ambisonics

A development of Delft University [25] and IRT [26] is Wavefield Synthesis (WFS) - a 2D surround recreation of either plane wave (distant) or point sources even within the hundred or so speaker array. WFS has been installed in a special purpose theater and may be practical soon elsewhere, but it requires many speakers and channels. Since it is 2D (horizontal only), it cannot reproduce height, but a hybrid system is also possible.

Gerzon [17] approached wavefield synthesis in 1985 using an omni (W) and three bi-directional microphones aimed forward, leftward, and upward (X, Y, & Z). Four recording channels (B-format, 1st order) supply a unique hypercardioid signal to any number of speakers given their position in degrees

Ambisonics can be created by assignment, e.g. monaural dialogue or effects using a 3 dimensional pan pot, much as 5.1 can by a 2-dimensional one. 1st order B-format (4 channel) stems of music or ambient sound effects can be combined to form a 4 channel Ambisonic mix.

Neither Ambisonics nor WFS can do much to reproduce the existing library of LPs, CDs and even DVDs.  But WFS in particular, is the best 3D method for covering large audiences if new recordings specially made for them are available.

Hierarchical MLP [28] offers more discrete channels on DVD-A and AAC [29] offers more than five for broadcast. For current 6 channel media, Ambiophonics combined with Ambiophonics - PerAmbio 3D has envelopment + frontal imaging + spatial impression.

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