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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

PANORAMBIOPHONICS (Fig. 5)

If a four channel medium such as SACD, DVD, or DTS-CD is available then it is possible to record direct sound sources over 360-degrees in the horizontal plane. A special microphone assembly which we have called a Panorambiophone (or Panambiophone and Panambio for short) is used to capture signals appropriate for reproduction via one front Ambiopole and one rear Ambiopole. Front and rear Ambiopoles do merge seamlessly. We have already demonstrated to hundreds of visitors that the combination of the Panambiophone and the two Ambiopoles does indeed allow normal binaural localization over the full circle including the 90- degree positions at the extreme sides. This localization is possible for most individuals even if their heads are fixed. But it is also true that slight head movements focus the azimuth for some individuals at some problem angles mostly to the rear.

Fig. 5  Panorambiophonics Delivers Full Circle Localization via 4 Channels and Speakers

The Panambiophone consists of two Ambiophones placed one behind the other but still both facing in the forward direction.  The two head shaped balls must be placed nose to baffle to nape since if there is too much separation the differential delay of slightly off 90-degree direct sound sources will cause comb filtering when reproduced.  A baffle between the two Ambiophones insures that the front stage is picked up mainly by the front ball and the rear stage is mainly heard by the rear ball.  For concert music both balls should be protected from overhead reflections.  The Panambiophone, like the Ambiophone is placed at the best seat in the house or at the center of the sonic action.

In reproduction, two crosstalk cancellers fed two Ambiopoles and listeners should sit, stand, or recline on the line between them for best effect. Off line seating still yields interesting front/back localization but the exact angles are unpredictable. During symphonic recording, the rear Ambiophone picks up the rear half horizontal hall ambience while the front Ambiophone automatically captures the front half direct and ambient sound. Thus, one can have a reasonable you-are-there 360 degree ambience sound experience with just four speakers if the recording venue was not just a studio or an auralization computer. This methodology should be compared with the random difficulties encountered using other ambience pickup microphone arrangements such as IRT, Fukada, Williams, Decca, etc.

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