Tuesday, September 6, 2011

Optimal speaker placement

The trick was to establish a baseline for what sounded best, and there was no guidebook. So Dr. Kyriakakis and his students went to Boston Symphony Hall in 1998 to conduct a series of sound tests and to record the “Messiah.”

At that time, acousticians had long known that a shoebox-shaped concert hall like Boston’s offered the best sound, but what was important for Dr. Kyriakakis was to know why the human ear and the human brain that processed the signal felt that way.

Back in Los Angeles, his team began a series of simple experiments. Listeners were invited into the labs to hear the Boston tests and music and to rate the sound, using a scale of 1 to 5. Researchers shifted the sound to different combinations of speakers around the room.
Statistics showed that speakers directly ahead, combined with speakers 55 degrees to either side of the listener, provided the most attractive soundstage. The “wide” speakers mimicked the reflection from the side walls of the concert hall by causing the sound to arrive at the listener’s ears milliseconds after the sound from the front. Sound from other angles did not have as great an effect.

Next, the team asked listeners what combination of speakers gave the best impression of “depth of stage.” Here again, statistics showed a clear preference for speakers in front of listeners and high above them. This sound — also slightly delayed — gave the ear and the human brain a sense of where the different instruments were on a bandstand.
--Guy Gugliotta, NYT, on what makes sound pleasing