Are Early Reflections desirable for late reverberation?

Griesinger found a static pattern of ER is likely perceiced as disturbing in a stereo setup (Griesinger, Lexicon 480L manual). This is also my observation. Three factors may contribute to this finding: summing location, insufficient number of speakers for reproduction and failure to model source characteristics.

There is also an aestetic dimension whether to focus on one of three auditory streams: spacial impression, envelopment or hall. Hall ist the most obvious and conciously perceived attribute.

0.1 Summing location

Summing location is the acoustic equivalent of stereo photography. Our brain constructs a 3-D auditory image from two loudspeaker signals. Salient Early Reflections seem to disturb the process as they represent a different approach to 3-D information: summing location involves inhibiting the comb filter effect — thereby ER might be (falsely) processed as part of a stereo signal by our brain. At least the auditory signal contains contradicting types of information in this case. The solution is to use different speakers for stereo imaging and salient reflections. Or prominently featuring a omni source in the center speaker if that is feasable.

0.2 Insufficient number of speakers for reproduction

Obviously, late reflections originating from side and rear walls should be reproduced by speakers in that direction. Misrepresentation of ER by five or less speakers prompts focus on envelopment and hall. Sometimes omitting these reflections is preferable. Headphones may offer salvation via HRTFs. Viable is also modeling close distances with strong focus on ambience and less focus on envelopment and hall.

0.3 Failure to model source characteristics

Source characteristics include - but are not limited to - directivity of music instruments and movement on stage. The most important finding of my research is that modeling these two characteristics alleviates much of the previously described limitations.

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