Harman Kardon AVR 247 Owner's Manual page 22

SPEAKER PLACEMENT
Left Speaker Output. You will then need to follow the directions
in the Advanced Features section for manual setup of the sur-
round back speaker.
Subwoofer Placement
The subwoofer's location is less critical, since low-frequency sounds are
omnidirectional. Placing the subwoofer close to a wall or in a corner will
reinforce the low frequencies, and may create a "boomy" sound. You
may wish to experiment over time by placing the subwoofer where the
listener normally sits and then walking around the room until the low
frequencies sound best. Place the subwoofer in that spot.
NOTE: Your receiver will sound its best when the same model
loudspeaker is used for all positions (other than the subwoofer).
If that isn't possible, try to use speakers made by the same
manufacturer.
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