Ed's AV Handbook.com
Home Theater & High Fidelity Stereo Audio


Chapter Six
The Room, Speaker, & TV

Page 5

Batting practice for the audio/video pro and a primer for the novice
 


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Determine the center speaker location
          Measure the distance from the listening position to the left or right front speaker.  This is the measurement for the distance from the listening position to the center speaker.
Center this speaker between the front left and right speakers.


Select surround speaker locations
          Dolby Labs specifies that the two rear channel speakers in a 5.1 surround system be positioned at 110 degrees left and right of the front center speaker.  Draw a circle through the front left, center, and right speaker positions with the “sweet spot” at the center.  Place the left and right rear speakers on the circle at the specified 110 degree positions.  Provide an unobstructed path to the listener’s ears.  This may require moving the speakers slightly above ear level.
          A 6.1 and 7.1 surround system adds additional rear speakers to the 5.1 speaker arrangement.  A 6.1 surround system places one additional rear speaker on the circle at 180 degrees from the front center speaker.  A 7.1 system adds two rear speakers to the 5.1 speaker arrangement.  They are placed on the circle at 150 degrees left and right of the front center speaker.
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Note for the smaller room
          If listening positions are near a room boundary, and consequently closer than specified to the rear speaker locations, then move the rear speakers well above or below ear level. Consider the option of above ear level on-wall dipole/bipole speakers placed at 90 degrees left and right of the front center speaker.  Each option is a compromise, but they may generate a more diffuse sound pattern that creates a farther-away effect.

Subwoofer placement
          There are two schools of thought on sub woofer choice and placement.  The first places a sub woofer in the corner of the room.  The corner is an acoustical pressure zone.  This type of corner placement acoustically stimulates and endeavors to manage and use low frequency room modes.  Closely follow the manufacturer’s instructions for exact placement and adjustment.
          The second school places the sub woofer at a position that avoids stimulating a primary room mode and its first, second and possibly third 
harmonic.  Therefore, place the sub woofer less than 25% but more than 10% from the dimension of any room boundary.
          An alternative to the second school is to temporarily place the sub woofer at the listening position.  While listening to a musical recording with good bass content, walk around the room.  Locate a position in the room where the sub woofer sounds musically balanced, then move the woofer to that position.
          Another option is to use two or more sub woofers.  This will increase decibel level, and improves dynamics.  Plus an additional sub woofer placed opposite the first woofer, can offset room mode problems.
          Finally, with any of the above methods: Set the sub woofer volume to its minimum level and open the crossover to its highest position.  With a reference system volume level of 85 decibels, a sound pressure level meter (C-weighted), and white noise as a source; adjust the sub woofer to a level that is equal and balanced to each of the other speakers.  Then, using a musical source, adjust the sub woofer’s crossover setting and fine tune the volume level until it sounds musically balanced with the main speaker system.

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Ed's AV Handbook.com
Batting Practice for the AV Pro and a Primer for the Novice.
Copyright 2007 Txu1-598-288   Revised 2018