cinema subwoofer model tuned to around 20 Hz: the 8182. Starting in 1983, THX certification of the cinema sound experience quantified the parameters of good audio for watching films, including requirements for subwoofer performance levels and enough isolation from outside sounds so that noise did not interfere with the listening experience. This helped provide guidelines for multiplex cinema owners who wanted to isolate each individual cinema from its neighbors, even as louder subwoofers were making isolation more difficult. Specific cinema subwoofer models appeared from JBL, Electro-Voice, Eastern Acoustic Works, Kintek, Meyer Sound Laboratories and BGW Systems in the early 1990s. In 1992, Dolby Digital's six-channel film sound format incorporated a single LFE channel, the "point one" in 5.1 surround sound systems. Tom Horral, a Boston-based acoustician, blames complaints about modern movies being too loud on subwoofers. He says that before subwoofers made it possible to have loud, relatively undistorted bass, movie sound levels were limited by the distortion in less capable systems at low frequency and high levels. Sound reinforcement Professional audio subwoofers used in rock concerts in stadia, DJ performances at dance music venues (e.g., electronic dance music) and similar events must be capable of very high bass output levels, at very low frequencies, with low distortion. This is reflected in the design attention given in the 2010s to the subwoofer applications for sound reinforcement, public address systems, dance club systems and concert systems. Cerwin-Vega states that when a subwoofer cabinet is added to an existing full-range speaker system, this is advantageous, as it moves the "...lowest frequencies from your main [full-range] PA speakers" thus "...eliminat[ing] a large amount of the excess work that your main top [full-range] box was trying to reproduce. As a result, your main [full-range] cabinets will run more efficiently and at higher volumes." A different argument for adding subwoofer cabinets is that they may increase the "level of clarity" and "perceived loudness" of an overall PA system, even if the SPL is not actually increased. Sound on Sound states that adding a subwoofer enclosure to a full-range system will reduce "cone excursion", thus lowering distortion, leading to an overall cleaner sound. Consumer applications (as in home use) are considerably less demanding due to much smaller listening space and lower playback levels. Subwoofers are now almost universal in professional sound applications such as live concert sound, churches, nightclubs, and theme parks. Movie theatres certified to