All loudspeakers characteristically exhibit trade-offs between frequency response and response time (transient response) depending on the characteristics of the voice coil, properties of the magnetic motor, the cone mass, and the nature of the enclosure. While cone size and voice coil inductance are major factors, a recent study indicates that the role of inductance is more important than was previously believed. The effects of the cone mass are not significant at sub-bass frequencies.
With the advent of the CD, the demand to reproduce deep, clean, loud bass increased, and had increased again with the introduction of digital audio Surround sound formats like Dolby Digital and DTS, which make extensive use of subwoofers for special effects. In modern music, the subwoofer 'channel' is often used aggressively by producers to enhance the listening experience.
Subwoofers are available in several formats, including bass reflex, acoustic suspension, infinite baffle, horn loaded, tapped horn and bandpass types. Each enclosure topology design has advantages and disadvantages in efficiency, bass extension, and cabinet size. Bass-reflex enclosures are the most common type in domestic hi-fi and professional sound.
The fundamental difficulty for subwoofers is to couple the motion of the cone to the listening environment, while limiting cone excursion to safe levels, cooling of the voice coil, while minimizing distortion, and maximizing output. Since the human ear is increasingly insensitive as frequencies decrease, these requirements are hard to meet simultaneously.