Subwoofer

A subwoofer (or sub) is a loudspeaker designed to reproduce low-pitched audio frequencies known as bass and sub-bass, lower in frequency than those which can be (optimally) generated by a woofer. The typical frequency range for a subwoofer is about 100–200 Hz for consumer products, below 100 Hz for professional live sound, and below 80 Hz in THX-approved systems. Subwoofers are never used alone, as they are intended to augment the low frequency range of loudspeakers that cover the higher frequency bands. While the term 'subwoofer' technically only refers to the speaker driver, in common parlance, the term often refers to a subwoofer driver mounted in a speaker enclosure (cabinet), often with a built-in amplifier. A subwoofer (or sub) is a loudspeaker designed to reproduce low-pitched audio frequencies known as bass and sub-bass, lower in frequency than those which can be (optimally) generated by a woofer. The typical frequency range for a subwoofer is about 100–200 Hz for consumer products, below 100 Hz for professional live sound, and below 80 Hz in THX-approved systems. Subwoofers are never used alone, as they are intended to augment the low frequency range of loudspeakers that cover the higher frequency bands. While the term 'subwoofer' technically only refers to the speaker driver, in common parlance, the term often refers to a subwoofer driver mounted in a speaker enclosure (cabinet), often with a built-in amplifier. Subwoofers are made up of one or more woofers mounted in a loudspeaker enclosure—often made of wood—capable of withstanding air pressure while resisting deformation. Subwoofer enclosures come in a variety of designs, including bass reflex (with a port or vent), using a subwoofer and one or more passive radiator speakers in the enclosure, acoustic suspension (sealed enclosure), infinite baffle, horn-loaded, and bandpass designs, representing unique trade-offs with respect to efficiency, low frequency range, cabinet size and cost. Passive subwoofers have a subwoofer driver and enclosure and they are powered by an external amplifier. Active subwoofers include a built-in amplifier. The first subwoofers were developed in the 1960s to add bass response to home stereo systems. Subwoofers came into greater popular consciousness in the 1970s with the introduction of Sensurround in movies such as Earthquake, which produced loud low-frequency sounds through large subwoofers. With the advent of the compact cassette and the compact disc in the 1980s, the easy reproduction of deep and loud bass was no longer limited by the ability of a phonograph record stylus to track a groove, and producers could add more low frequency content to recordings. As well, during the 1990s, DVDs were increasingly recorded with 'surround sound' processes that included a low-frequency effects (LFE) channel, which could be heard using the subwoofer in home theater systems. During the 1990s, subwoofers also became increasingly popular in home stereo systems, custom car audio installations, and in PA systems. By the 2000s, subwoofers became almost universal in sound reinforcement systems in nightclubs and concert venues. From about 1900 to the 1950s, the 'lowest frequency in practical use' in recordings, broadcasting and music playback was 100 Hz. When sound was developed for motion pictures, the basic RCA sound system was a single 8' speaker mounted in straight horn, an approach which was deemed unsatisfactory by Hollywood decisionmakers, who hired Western Electric engineers to develop a better speaker system. The early Western Electric experiments added a set of 18' drivers for the low end in a large, open-backed baffle (extending the range down to 50 Hz) and a high-frequency unit, but MGM was not pleased with the sound of the three-way system, as they had concerns about the delay between the different drivers. In 1933, the head of MGM's sound department, Douglas Shearer, worked with John Hilliard and James B. Lansing (who would later found Altec Lansing in 1941 and JBL in 1946) to develop a new speaker system that used a two-way enclosure with a W-shaped bass horn that could go as low as 40 Hz. The Shearing-Lansing 500-A ended up being used in 'screening rooms, dubbing theaters, and early sound reinforcement'. In the late 1930s, Lansing created a smaller two-way speaker with a 15' woofer in a vented enclosure, which he called the Iconic system; it was used as a studio monitor and in high-end home hi-fi set-ups. During the 1940s swing era, to get deeper bass, 'pipelike opening' were cut into speaker enclosures, creating bass reflex enclosures, as it was found that even a fairly inexpensive speaker enclosure, once modified in this way, could 'transmit the driving power of a heavy...drumbeat—and sometimes not much else—to a crowded dancefloor.' Prior to the development of the first subwoofers, woofers were used to reproduce bass frequencies, usually with a crossover point set at 500 Hz and a 15' loudspeaker in an infinite baffle or in professional sound applications, a 'hybrid horn-loaded' bass reflex enclosure (such as the 15' Altec Lansing A-7 enclosure nicknamed the 'Voice of the Theater', which was introduced in 1946). In the mid-1950s, the Academy of Motion Picture Arts and Sciences selected the 'big, boxy' Altec A-7 as the industry standard for movie sound reproduction in theaters. In September 1964, Raymon Dones, of El Cerrito, California, received the first patent for a subwoofer specifically designed to augment omni-directionally the low frequency range of modern stereo systems (US patent 3150739). Able to reproduce distortion-free low frequencies down to 15 cycles per second (15 Hz), a specific objective of Dones's invention was to provide portable sound enclosures capable of high fidelity reproduction of low frequency sound waves without giving an audible indication of the direction from which they emanated. Dones's loudspeaker was marketed in the US under the trade name 'The Octavium' from the early 1960s to the mid-1970s. The Octavium was utilized by several recording artists of that era, most notably the Grateful Dead, bassist Monk Montgomery, bassist Nathan East, and the Pointer Sisters. The Octavium speaker and Dones's subwoofer technology were also utilized, in a few select theaters, to reproduce low pitch frequencies for the 1974 blockbuster movie Earthquake. During the late 1960s, Dones's Octavium was favorably reviewed by audiophile publications including Hi-Fi News and Audio Magazine. Another early subwoofer enclosure made for home and studio use was the separate bass speaker for the Servo Statik 1 by New Technology Enterprises. Designed as a prototype in 1966 by physicist Arnold Nudell and airline pilot Cary Christie in Nudell's garage, it used a second winding around a custom Cerwin Vega 18-inch (45 cm) driver to provide servo control information to the amplifier, and it was offered for sale at $1795, some 40% more expensive than any other complete loudspeaker listed at Stereo Review. In 1968, the two found outside investors and reorganized as Infinity. The subwoofer was reviewed positively in Stereophile magazine's winter 1968 issue as the SS-1 by Infinity. The SS-1 received very good reviews in 1970 from High Fidelity magazine. Another of the early subwoofers was developed during the late 1960s by Ken Kreisel, the former president of the Miller & Kreisel Sound Corporation in Los Angeles. When Kreisel's business partner, Jonas Miller, who owned a high-end audio store in Los Angeles, told Kreisel that some purchasers of the store's high-end electrostatic speakers had complained about a lack of bass response in the electrostatics, Kreisel designed a powered woofer that would reproduce only those frequencies that were too low for the electrostatic speakers to convey. Infinity's full range electrostatic speaker system that was developed during the 1960s also used a woofer to cover the lower frequency range that its electrostatic arrays did not handle adequately.