Acústica: cómo posicionar los parlantes en una habitación

Understanding Room Acoustics and Speaker Placement By Floyd E. Toole, Vice President Acoustical Engineering Harman International Industries, Inc.
The room is the final audio component and, as such, it can make or break a truly satisfying listening experience. All rooms are different, so a truly guaranteed recipe for success doesn’t exist. We all hope for good luck but, most often, things needhelp to ensure a really successful marriage of loudspeakers and room acoustics. To keep things simple, let us separate the acoustical issues. First, is the shape of the room. Rectangular rooms are fine. Splayed walls, or other exotic shapes are not necessary for good sound. L-shaped rooms and three-sided rooms force us to be more creative, but can also work well. A diagonal arrangement, with the TVin a corner, is superb, which is fortunate, as it is often forced on us by windows, doors, fireplaces, etc. Note that the surround speakers are to the sides of the listeners, not behind them.

Two rooms arranged correctly for multichannel reproduction of movies and music. Both work superbly. The white speakers at the back of each room are for systems capable of seven-channel operation, arecommended option. In the arrangement at the right, the space behind the TV is perfect for a subwoofer. The seating is also much more sociable than the formal “theater” seating. Now that we have a basic layout in mind, let’s take a look at room acoustics. At some time in our lives, we have all been in a totally empty room, an experience in “untamed” acoustics. Sounds are extremely “live” they reflectand reverberate. Clap your hands and the impact is repeated hundreds of times, as the sound is reflected among the hard flat room boundaries. Talk, and voices take on an artificial “richness” in the lower frequencies, and intelligibility is reduced because each utterance is prolonged by overactive reverberation. Put some carpet down, and things improve dramatically. Add drapes, some furniture, andthe room is transformed into a much more pleasant space in which to live, converse, and listen to music and movies. Fill the room with too much “stuff”, including lots of upholstery, cushions, heavy drapes, etc. and the place can become overly dead and stuffy. If we really want to optimize the room acoustics for the best possible sound quality, we have to be prepared to modify the décor. The goalis to make the room neither too live nor too dead. A happy medium is the objective.

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Makes a Room More “Live” Hardwood or tile floor with small area rugs Thin low-pile or looped-pile carpet Light, “Scandinavian”, furnishing, leather upholstered chairs and sofas. Lightweight curtains and drapes. You can see between the fibers, and blow through the fabric easily. Flat unobstructed walls thatact like big acoustic mirrors.

Makes a Room More “Dead” Wall-to-wall carpet Thick, clipped-pile carpet with a felt or porous foam underlay. Bulky, fabric upholstered chairs and sofas, with cushions. Heavy, dense weave, velour or velvet drapes. Fabrics that are more opaque, and that offer moderate resistance to blowing. Walls that are broken up with irregularities, such as fireplaces, bookcases(excellent!), paintings, display cases, etc. to add diffusion.

If you are partial to hardwood floors, more attention must be paid to deadening the room with drapes and the type of furnishing. If you are partial to the stylish wood and leather “Scandinavian” style of furniture, then better think about heavy wall-to-wall carpeting. A combination of hardwood flooring with the light furnishingsyields a stylish, but acoustically hostile environment for good sound. Thanks to the built-in ambience of multichannel sound, the error that is easiest to live with is for the room to be too “dead”. Some styles, cultures and climates encourage hard, lively, rooms, with wood or tile floors, and even plaster or masonry walls to compound the situation. Others encourage the “cozy” surroundings of heavy...