Extended Frequency Response

• Subwoofers excel at providing extreme low frequency sound information. Two- and three-way bookshelf speakers have compromises to low frequency levels in the interest of overall balance of sound across the audible spectrum. Everything about a subwoofer is done with the goal of creating bass, and so all of their technology is focused on that. Cabinet design, crossovers and integrated amplifiers are devoted to bottom-end sound reproduction.
  
  

Increased Amplifier Overhead

• Many subwoofers are of an active design, that is, amplifiers are incorporated with the sole purpose of driving the subwoofer. Because of the long waveforms of low frequency sound, more power is required to create and project these than the rest of the audible range. In a two-speaker system, the most typical compensations include boosting bass EQ and turning the volume up. With the subwoofer handling the low frequency chores, theses changes are unnecessary, and neither stereo amp nor main speakers need to strain.
  
  

Reduced Distortion

• Distortion goes hand-in-hand with amplifier overhead. When the main speakers are not being pushed, their signal remains true to the amp output. When an amp is not providing bass boosts and excess volume, its output remains faithful to the input. Part of subwoofer design has to do with controlling distortion in the low frequency range. If the speaker movement does not match the input signal, distortion occurs, and microelectronics are now used to adapt amplifier output to match speaker behavior, resulting in low distortion.
  
  

Style Reproduction

• Fans of hip hop and dance music have a greater need, based on the style of music they enjoy, for extended low frequency response. The sound of the music would simply not be satisfying coming from a small pair of bookshelf speakers. Subwoofers allow full enjoyment of the hyper-extended nature of bass frequencies that are an integral part of certain styles of music. Well-tuned subs, when used on styles that don't require such extension, can add a subtle element of immediacy to the stereo main speakers.