AES Journal Forum

It is about time that the audio industry and academia address the loudspeaker and room compatibility issue for domestic size reverberant spaces and recognize it as just one more problem area in the transmission path from microphone membrane to eardrum. The brain takes over behind the ear drums, creating the perception of an acoustic event in some form of 3D space. The perceived scene is spatially distorted due to the directional characteristics of microphones and their distances to sound sources, and due to the directional characteristics of loudspeakers and their distance and azimuth to the listener. The microphone output signals contain a limited and specific view of the original acoustic scene. On playback the loudspeakers illuminate the listening room. The resulting eardrum signals consist of superimposed streams of air pressure variations arriving from different directions.  With two ears, a movable head, a brain and a mind, evolution has formed a superbly capable perceptual apparatus, which automatically sorts a plurality of sound streams for direction, distance, meaning and for focusing attention.  Loudspeakers and room (also the room behind the speaker membrane) must not provide misleading cues to a listener's brain in order to fully hear the information contained in the microphone signal streams and to instinctively withdraw attention from loudspeakers and listening room. The result is a convincing auditory illusion.

Bob.  RCA in the '40s.  I can only imagine you are talking about the legendary Harry Olson - any relation, the names are remarkably similar?  Yes, Harry contributed a lot of solid engineering, good sense and logical thought to the audio industry, much of it ignored or  forgotten it seems.  I am frequently humbled by the insights of our predecessors, who lacked the high technology measurements and analytical tools we have.  There is a lot of old fashioned folklore that needs to be purged from our industry.  Science is hard work, opinions come easily.  Thanks for your comment.

Flat walls don’t necessarily reflect a flat response and can cause flutter-echo which is a distraction. Acoustical treatment and diffusion can be used to flatten the reflection response.

There might be flutter echo if you were doing it in a bare room, but not in a room designed for audio - either production or reproduction. For example, my room is 20 ft wide by 30 ft long and has some diffusers in the back half on the side walls, plus absorbent furniture at the listening position and plush throw rugs on all floors, and a cathedral ceiling. The RT60 is about 500 ms, about right for this size room. The walls near the speakers at the front of the room are flat wallboard done purposely to create a huge lattice of direct and reflected image sources. What all this means is that the first reflections are specular and occur only once, then are absorbed normally, the same as any other system. All that changes is the spatial characteristic, leaving the temporal unaffected except for what is contained in the recording. Doing the spatial by reflection like this is the only way to be able to adjust the direct to reflected ratio and make it more like the live model. It's a whole different universe with different rules. Paper to follow - hopefully!