THX's technology is described as enhancing sound quality through speaker units attached to users devices such as flat-screen televisions or computers.
According to the compaint, Apple knowingly infringed upon THX's U.S. Patent No. 7,433,483 that claims features such as the output aperture, also known as the speaker duct, being relatively more narrow than the speaker face.
The audio technology company claim, according to Bloomberg, that the alleged violation has caused "monetary damage and irreparable harm." This has led them to seek royalties or damages as compensation for lost profit.
The company, founded in 2002 as part of Lucasfilm Ltd. holds several patents for various sound standards and certification systems used for cinemas and home entertainment.
Apple also hold several speaker-centric patents, it's most recent 'No. 8,385,568' for "Low-profile speaker arrangements for compact electronic devices" was filed for in 2010 but was not granted until Feburary 2013.
Apple Insider states that Apple have until May 14 to dsicsuss initial disclosure, an early settlement and other stipulations.
Source: Apple Insider