CX (audio)
CX is a noise reduction system for recorded analog audio. It was developed by CBS Laboratories (a division of CBS) in the 1970s as a competitor to other noise reduction (NR) systems such as Dolby and dbx. The name CX was derived from "Compatible eXpansion," a feature of the technique.
CX was originally designed by CBS as a noise-reduction technology for vinyl LP records. CX required a special decoder connected to a stereo system, in order to fully reproduce the CX encoded sound on the LP. However, CX-encoded records could also be played without a decoder, with a resulting (claimed acceptable) amount of dynamic range compression. Relatively few hardware decoder boxes were sold.
The project was led by CBS Records group vice president Bob Jamieson. The label predicted that CX encoding would become standard on all new LP releases but this did not happen. CBS struggled to gain support for the system from other record companies. The process was controversial among CBS executives and unpopular with some artists. Classical guitarist Liona Boyd demanded that the CX encoded version of one of her albums be withdrawn because of perceived shortcomings, even though Jamieson claimed that CBS had the technical means to overcome such objections.[1]
Approximately 70 CX encoded LP titles were released by CBS in 1982 in the United States. In Europe many CX discs were manufactured in Holland with the catalog number prefix "CBSCX". The albums in this series also came in standard, non CX encoded versions. While the implementation of CX with LP's was quite unsuccessful and short-lived, CX would later see success as the NR used for the stereo analog audio tracks on laserdiscs. It was also used for the audio tracks on discs of the RCA SelectaVision CED videodisc system.
Almost all laserdisc (and stereophonic CED) players manufactured since the early-1980s had CX NR capability as a standard feature, with almost all commercial laserdisc releases having CX encoding on their analog tracks as well. For the LaserDisc system, the CX companding specifications were changed, from 20db of noise reduction to 14db, along with moving the 'threshold' where compression/expansion changes from 2:1 to 1:1 from -40db to -28db - other minor changes were made as well. In addition, some of the LD's FM audio encoding specs were changed too, allowing more headroom and better high frequency response at high levels. These changes were made because, at the time of CX's adoption on LD (1981), the vast majority of program sources for mastering, such as 35mm optical and mag film soundtracks, as well as the IVC-9000 and the 1-inch C-Type video tape formats used for LD mastering, had S/N ratios such that undecoded playback would accentuate their noise to unacceptable levels. By lowering the total amount noise reduction achieved, undecoded playback compatibility was increased. Audible pumping and breathing effects during CX decoded playback were reduced as well.[2]
For the CED VideoDisc, CX companding specifications were unchanged from those of the LP system because the CED system had much higher overall noise levels than the LD format, requiring the full 20db of noise reduction achieved with the unmodified system. The names given by CBS to the two different versions of CX were "CX-20" and "CX-14".[3]
The theory of operation is described in U.S. Patent 4,376,916.
Contents |
[edit] Partial List of CX encoded LP's released by CBS
- The Clash - Sandinista! - Epic Records - 1980
- The Clash - Combat Rock - Epic Records - 1982
- Aaron Copland - Copeland Conducts Copeland - Columbia Records 33586
- Lacy J. Dalton - 16th Avenue - Columbia Records 37975
- Bob Dylan - Blood on the Tracks - Columbia Records - (1982 re-issue)
- Terumasa Hino - Double Rainbow - Columbia CX 37420
- Billy Joel - Glass Houses - Columbia Records 36384
- Charly McClain - Too Good To Hurry - Epic Records 38064 - 1982
- Frank Marino - Juggernaut - Columbia CXAL 38023
- Johnny Mathis - First 25 Years: Silver Anniversary Album - Columbia Records - (1981)
- Men at Work - Cargo - Columbia Records 38660
- Randy Meisner - Randy Meisner - Epic Records - 1982
- Orchestral Manoeuvres in the Dark - Orchestral Manoeuvres in the Dark - DinDisc Limited/Epic Records - 1981
- Pink Floyd - The Wall - Columbia Records 36183
- Freddie Salem & The Wildcats - Cat Dance - Epic Records 38018 - 1982
- Santana - Zebop! - Columbia CX PC 37158 - 1981
- Saxon - Strong Arm of the Law - Carrere CXBL 537679
- Saxon - Denim and Leather - Carrere CXAL 537685
- Simon & Garfunkel - Simon and Garfunkel's Greatest Hits - Columbia Records 31350
- The Sinceros - Pet Rock - 1981
- T.V. Smith's Explorers - The Last Words of the Great Explorer - Epic BL 37432 - 1981
- Translator - Heartbeats And Triggers - 415 Records/Columbia Records - 1982
- Deniece Williams - I'm So Proud - Columbia Records - 1983
[edit] See also
[edit] References
- ^ "Slow Progress Seen in CBS' CX Campaign", Billboard Magazine, February 20, 1982, pg. 3
- ^ The Audio Side Of The Laser Videodisc. Authors: Badger, Greg; Allen, Richard Affiliation: Pioneer Video, Inc., Costa Mesa, CA AES Convention:72 (October 1982) Paper Number:1935
- ^ The Audio Side Of The Laser Videodisc. Authors: Badger, Greg; Allen, Richard Affiliation: Pioneer Video, Inc., Costa Mesa, CA AES Convention:72 (October 1982) Paper Number:1935
