Although nothing in the audio reproduction chain affects the sound that we hear more than the quality and accuracy of the loudspeaker, listening rooms play a large role too. Speakers operate within rooms, and the speaker and the room together make up an electro-mechano-acoustical system that takes the amplifiers electrical signal and converts it into the sounds that reach our ears.

Speaker placement affects many things, including sonic imaging or where the sounds appear to be coming from, the speakers frequency response, and what room resonancesoften called standing waves or room modesare activated, and by how much.

The first step is to examine the choice of listening position, which often determines speaker placement. One configuration to avoid is placing the listener near the back wall, where the pressure maximum for several of the rooms low-frequency resonant modes are located, creating boomy, over-accentuated bass with cancellations or near-cancellations at other frequencies.

The money seat should be centered laterally, with the left-front, center, and right-front (LCR) speakers also centered laterally, so that the left speakers spacing from the left wall mirrors that of the right speakers spacing from the right wall. Such symmetrical placement ensures that the influence of wall reflections on the speakers timbre will be the same left and right. Putting the preferred listening position on the centerline of the LCR array optimizes imaging, as the speaker-to-listener distance for the left-front speaker matches that for the right speaker, thus sound arrives from both channels simultaneously.

Its also best to avoid putting the listening position in the exact center of the room, as this will reinforce certain undesired room resonances. A position about two-thirds of the room depth back from the front wall is a good spot. In fact, as a general rule, thinking about placements that involve thirds or fifths of a room dimension is a good plan, as it helps avoid resonances caused by reflections from one wall reinforcing those from the opposite wall. Since we cant always avoid reflections and their impacts on certain frequencies, we strive to spread out their effects evenly across the frequency range. Before getting too involved in placement issues, take into consideration what recommendations the loudspeaker manufacturer has provided for its speakers. Some atypical designs may have atypical placement requirements.

Richard Rives Bird, president of acoustical consultancy Rives Audio, suggests to always start by getting the two main channels right. If you get the left and right channels done very wellvery good stereo imaging for musical programming materialyouve accomplished 90 percent of the battle. The next thing is to get the center channel right. The center speaker carries virtually all of the on-screen dialog for movies, and as such is hugely important to any home theater.

A speakers placement relative to nearby room surfaces affects its fre...

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