THX - It's Not a Format
THX is a set of equipment specifications, compatible with all surround formats, intended to standardize the performance of any theater system. It does not compete in any way with Dolby Digital, Pro Logic or any other surround format. Software (movies) certified by THX may be played on any Dolby surround system and conversely, THX hardware can play all Dolby surround movie software whether or not it is THX certified.
There are actually three parts to the THX standard: one covers the mastering of home videos, specifically laserdiscs and DVDs. All THX-certified software will work with any player, in any system. Part two is known as the Theater Certification Process, wherein a commercial movie theater can achieve THX status by complying with a series of hardware and setup guidelines. Part three deals with the gear consumers purchase for their home theaters, and is known as Home THX.
Home THX components are not necessarily better or worse than other products: they have simply earned THX approval by conforming to all THX-mandated specifications. Once the product has been submitted to Lucasfilm, LTD (the company that developed and licenses the THX standard) and passed a battery of tests, it can wear a "THX Approved" badge. In order to be a true THX system, all the audio components in that system--processor, amplifier, speakers and subwoofer--should be THX-approved. But that does not mean that THX and non THX components cannot be used together, they can.
And yet, although THX guarantees a certain, minimum standard of certain types of performance, many of the best products are not THX approved. Why? Audio manufacturers often choose to forego THX certification because either A) they believe THX specifications actually compromise performance (for example, many speaker manufacturers assert that THX-mandated dispersion patterns can negatively affect sound quality) or B) they decline to pay, and pass on to their customers, the licensing fees demanded by Lucasfilm.
So, should you buy THX-approved gear? That depends. For inexpensive, entry level gear, THX-approval guarantees a minimum standard of quality: a THX-approved receiver of amplifier will drive a variety of loudspeakers and, conversely, THX-approved speakers will work with most amps. So will most non-THX components! It would be foolish to ignore a product simply because it has or hasn't been THX certified. What's more, most high quality "high end" products are not THX-approved. If you need an "official seal of approval", THX might be worthwhile. But remember: you can build an excellent home theater independent of THX certification. When in doubt, trust your ears.
===================================================
This was copied from
here