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THX Ultra 2 Surround modes


Standard Member

Sorry if this is an old question....

On a THX Ultra 2 spec amp, could someone explain the difference between THX Ultra 2 Cinema mode and THX Surround EX?

Also what is the treatment when feeding my amp with regular 5.1, 5.1 EX and 5.1 discrete and 7.1 PCM (discrete) if such a release exists yet

Am trying to work out the best settings. Assume it might default to one or the other if the correct flag is detected?

Many thanks



Distinguished Member
THX Ultra2 modes will give you pseudo stereo surround backs (7.1) from a 5.1 source. THX Surround EX works like Dolby EX and will give you 6.1 (if you have a 7.1 setup then each of the surround backs will be getting a dual mono signal).

Your best bet is to just play around with each different mode to see which you prefer. I'd leave the Auto Flag Detect Mode off (assuming your Amp has that option).

Personally, I use either THX Ultra2 Cine or Dolby Digital/DTS + PLIIxC depending on my mood. :)


Distinguished Member
THX Ultra 2 is a specification with a set of required technologies and performance figures that exceed those of THX Surround Ex. For basic information, try the THX web site technologies section.

Although often considered a 7.1 spec (since THX Ultra was a 5.1 spec), the ability to use 7 speakers from 5.1 input is only a very minor part of the THX Ultra 2 spec and THX Surround EX is also a 6.1 format that will play through 7 speakers.

On your amp, the THX Ultra 2 Cinema mode will enable additional Ultra 2 features, and so should sound better in a larger room (you'll need to configure these correctly first though).

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