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Transmission Developments Limited (TDL) was founded in the 1970s by John Wright in High Wycombe, Buckinghamshire, UK, along with business partners John Hayes and later David Brown. The company pioneered transmission line loudspeaker technology for over 30 years, becoming one of the UK's most respected manufacturers of transmission line speakers. Wright, also a leading equipment reviewer and Stereophile contributor, was described as a 'fanatical' pursuer of quality. TDL's innovative designs achieved frequency responses as low as 17 Hz without subwoofers. The company was later part of ELAC and after Harman purchased ELAC in 1989, Wright organized a management buyout of the TDL brand. Following Wright's death in 1999, TDL disbanded. The brand was subsequently acquired by Richer Sounds and later The Audio Partnership, though current products differ significantly from the original transmission line designs.