THX is a company best known for setting audio and ultimately video standards for companies which made cinema sound match and be more uniformed.
Founded by engineer Tom Holman, the THX name is reported to either be an abbreviation of Tom Holman's name and eXperiment or crossover (X-over), or after the name of co-founder George Lucas' first film (THX-1138).
THX became more famous than ever when the company was commissioned by many electronics companies to give their home theater products the same THX "badge" or blessing that the pro cinema sound companies got. By the 1990's receivers, amps and speaker systems were THX certified. Today video products like TVs and Blu-ray players along with complete car audio systems get the THX certification.
THX also offers calibration training classes similar to, though generally more extensive than what the Imaging Science Foundation offers.