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Topic: Loudspeaker Holophony (Read 2130 times) previous topic - next topic
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Loudspeaker Holophony

Hello,
the German Fraunhofer Institute has develop flat loudspeakers on base of the Wave Field Principle:

http://www.scientificblogging.com/science_...d#comment-22251

That let me hope, my more as fife years old procedure for loudspeaker Holophony becomes practicable in some years. I have improved the introduction on my http://www.holophony.net website now. Is this short descripton more understandable now? 
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The animation depicts the propagation of the (black drawn) direct acoustic wave and its first reflections in the (large outer) recording room. Their spatial structures mainly determine our spatial perception of the sound event. All conventional loudspeaker reproduction procedures cannot reproduce such complex spatial and temporal structure, the reduction onto a few transmission channels inevitably causes significant loss of spatial information.
This page describes a different way. Just like the recording room creates all reflections from the pure audio signal of the source, a sound field synthesis provides a virtual 3D copy of the genuine sound field. Such “Holophony” approach relies on the principle of Wave Field Synthesis, which was describe by Berkhout on the University of Delft in the eighties of last century. The underlying Kirchhoff- Helmholtz- Integral prove the possibility for restore the genuine sound field completely in theory, but practically constrains make unfeasible that goal until today.
A number of scientific institutes realise the procedure on practise, but reduced onto one single horizontal loudspeaker row around the listener. That limits the principle upon the horizontal plane of the listener. The “Holophony”- solution based on a large-scale frontal WFS Loudspeaker screen, depict magenta in the animation. Such arrangement can work in truly in all three room dimensions. Over and above in the near field of such huge resulting diaphragm, the playback room acoustics become subordinate matter. Its reflections no longer must eliminate by strongly damping, but become purposefully include in the synthesis. The loudspeaker screen aligns the direct wave and its first reflexions in the playback room for fake the recording room reflections in time, level and direction. They arrive by the listener’s ear in the same manner as by the ears of a virtual listener in the recording room.
In this respect the described procedure differs fundamentally from the realised WFS Approach of the scientific institutes, which transmitting chain doesn’t end by the listener’s ear, but by the loudspeakers. Yet all delay times and level changes of the first reflections in the playback room may subtract during the synthesis if the procedure aimed for congruent signals on the dedicated virtual listener point in the recording room and the listener at home. The (virtually) same starting points of the reflections cause the same comb filter effects, the individual filter system of our head and pinna provide correct amplitude changes from the correct direction of the wave fronts.
If changed the point of reference in the recording room, accordingly change all positions of the virtual sound sources in the model based approach. So the listener can acoustically walk and turn in the near field of the WFS- Loudspeaker screen at home across the recording room by means of his remote….
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Kind Regards

Helmut
P.S.:advices for faults in by bad english are welcome