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AES

Audio Engineering Society

24th International Conference on Multichannel Audio
June 26-28, 2003, Banff, Canada

 

SURROUND AMBIOPHONIC RECORDING AND REPRODUCTION

by Ralph Glasgal

2 CHANNEL AMBIOPHONIC RECORDING (fig. 3)

While for many people, with large CD collections, basic Ambiophonics will sound as good as they wish, others will find enjoyment in the improvement that can be achieved by making recordings specifically meant to be played back over Ambiophonic systems. The Ambiophone recording microphone assembly was designed to make this feasible. (fig. 2) The derivation of the Ambiophone has been described in detail in the earlier referenced papers. Basically it is a head shaped ball with two omnidirectional microphones mounted flush where the ear canals would be. The microphone is baffled. That is it faces forward and is shielded from sound originating from overhead, the rear or the extreme sides.

Fig. 2 Ambiophone prototype

The microphone is placed first to fifth row center depending on taste. The perspective one hears during reproduction is the same as if one were at the mic position during the recording session. The usual considerations of hall critical radius or ratios of direct to reverberant sound do not apply here since the mic is baffled. Since all hall ambience will be generated from this or other great hall impulse responses, it is not necessary to record hall reverb during the recording session. The Ambiophone must also collect horizontal frontal or proscenium ambience since this indirect sound should emerge from the Ambiopole with the direct stage sound. The head shape of the Ambiopole provides the Interaural Level Difference for sounds from the stage sides. Otherwise, the Ambiopole, being centered in front of the home listener, would not provide this. The Ambiophone captures both correct ILD and ITD (see Appendix) compared to coincident microphone techniques, spaced omnis, spot mic mixing, etc. The Schoeps KFM-6 turns out to be a good match for an Ambiophone, if baffled during use.

Figure 3 Two Channel Ambiophonic System

Where classical music, reproduced in the home environment is concerned, two channel Ambiophonic recording and reproduction should satisfy even the most golden-eared audiophiles. Ambiophonics appears to entirely swamp the digital sampling differences between 2 channel media such as CD, SACD and DVD-A. It would be an interesting double blind project to see if the different media can actually be distinguished when Ambiophonic conditions prevail during both recording and playback.

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