Loudspeakers with Powered Woofers
Some loudspeakers include integral power amplifiers to drive the woofers. Such speakers provide a range of bass-tuning options not possible with conventional passive loudspeakers. A speaker with a powered woofer can be equalized to extend its cut-off frequency, allowing a relatively small-footprint speaker to deliver response to 20Hz. You can also adjust the bass level to best match your room. The ability to adjust each speaker’s bass output independently is a huge benefit, particularly in asymmetrical rooms. For example, if one speaker is in a corner and one speaker has no sidewall next to it, you can dial down the bass level from the corner-located speaker to compensate for its greater room gain.
http://www.theabsolutesound.com/articles/a-guide-to-better-bass-tas-197-1/
Some loudspeakers include integral power amplifiers to drive the woofers. Such speakers provide a range of bass-tuning options not possible with conventional passive loudspeakers. A speaker with a powered woofer can be equalized to extend its cut-off frequency, allowing a relatively small-footprint speaker to deliver response to 20Hz. You can also adjust the bass level to best match your room. The ability to adjust each speaker’s bass output independently is a huge benefit, particularly in asymmetrical rooms. For example, if one speaker is in a corner and one speaker has no sidewall next to it, you can dial down the bass level from the corner-located speaker to compensate for its greater room gain.
http://www.theabsolutesound.com/articles/a-guide-to-better-bass-tas-197-1/