What Is a Surround Sound Subwoofer?

Lori Kilchermann

A surround sound subwoofer is a large speaker that is typically positioned in the center of the front or rear wall of the home theater or viewing room. The purpose of the surround sound subwoofer is to emit the low-frequency sounds of the program or sound track that is being broadcast over the home surround sound system. A common misconception that is often held regarding the surround sound subwoofer is that it is used only to voice the bass sound from the low-frequency effects (LFE) channel. In reality, the main speakers also direct a portion of the low-frequency sound waves to the subwoofers in a surround sound system.

Subwoofers are designed to reproduce bass sounds with more clarity than full range speakers.
Subwoofers are designed to reproduce bass sounds with more clarity than full range speakers.

In most modern surround sound systems, the bass is not limited to only the surround sound subwoofer channel. Much of the bass signal is sent to the main loud-speaker channels of the system. In most surround sound applications, the LFE channel is separate and distinct from the bass channel, thus a surround sound subwoofer is required for the LFE as well as for the bass channel in order to produce the best sound. The bass from any channel in the system is able to send a signal to the surround sound subwoofer. This is not limited to the bass from a LFE channel.

Subwoofers may be featured in home theater systems.
Subwoofers may be featured in home theater systems.

The low-frequency sounds of any sound track are much stronger acoustically than other notes, such as a mid-range or high note, making the positioning of the surround sound subwoofer critical in producing an evenly moderated sound. The subwoofer allows the low frequency sounds to be directed towards the floor where the sound is easily directed to all parts of the room. The actions of the human ear attempting to isolate the low-frequency sounds from the high-range and mid-range sounds is what creates the surround action of the sound.

By placing the low, rumbling tones near to the floor, the subwoofer creates a feeling of motion as the sound waves contact the lower extremities. This adds realism to earthquakes, explosions and crash scenes as the mind is tricked into feeling the sound. Low-frequency sound is also much easier for the human ear to detect at low volume and it spreads out wider than other tones. The placement of the subwoofer in the center of a wall directly in front or in back of the viewer forces the ear to focus on a central location. Side-mounted loud speakers draw attention both to the side and above, allowing the sound to sweep in and carry the listener away.

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