Ignoring the room
There have been numerous attempts to bring live sound into our homes. Most have been collections of many speakers, a lot of processing, with mixed results. The most promising of the lot is perhaps Ralph Glasgal's Ambiophonics which addresses problems in stereo reproduction, but ignores the room. My friend Peter Moncrief, publisher of the IAR, claims a full immersion system with multiple speakers playing stereo music, recreating perfectly the hall itself. I cannot verify this, but am pretty certain it must take a great deal of skill, room volume and equipment. And finally, Soundminded, who frequents these posts, has built a multi-channel setup that on tracks recorded in large rooms fools the listener effectively. But all are complex, not for easy access and changes the fundamental playback system. I have been dreaming about a different approach, one that leaves the basic system alone and works on the room itself. I refer to this as Active Walls. How might this work? In its simplest form we would have a panel loudspeaker placed on each wall and the ceiling of our listening room. Attached to each panel, a microphone pointing outwards and into the room. Internally, a sophisticated electronic setup driving the loudspeakers. This arrangement would 'hear' any sound in the room and play that sound back with modifications designed to do two things: cancel existing wall reflections and introduce new ones of our choosing. Before I get into the whys and wherefores of this idea, let's take a step back and see the problem itself - the room. If you sit in the middle of your living room, close your eyes and concentrate on the sounds around you, you can tell the approximate size of the room. The smaller the room, the easier it is to judge distances to walls with closed eyes. We can all agree we have the ability to discern the differences between sitting in a bedroom and Carnegie Hall, even with our vision blocked. How is it we do this? By measuring room reflections. If you have ever been in an anechoic chamber, or a very dead room, you'll know just how true this statement is. The first time I walked into a reflection free chamber it freaked me out, and I got a sense of vertigo as my internal measuring system essentially shut down. Our ear/brain mechanisms can measure the time it takes for sound to reflect off walls and return. From this information we can make a good guess as to what the construction of the wall is, the size of the room, and the direction of the source. We're very good at it, as are most advanced mammals. We got good to keep us alive a few million years ago when we successfully competed for food in the wild. Unless your room is the size of a concert hall, you have reflections that help identify the size and restrictions of that room. Tomorrow we'll continue to understand what this means.
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