Here on the Home Theater Installation Orange County blog, we’re in the middle of a series explaining the various aspects of home theater sound. There are so many types and technologies that it can be hard for many people to keep up. We’re here to help with this multi-part guide.

Last week we looked at the two main 7.1-channel formats, Dolby TrueHD and DTS-HD Master Audio. We also covered what makes 7.1 different than 5.1: the two additional rear surround speakers, for a total of 7 channels plus a subwoofer.

This week we’re rounding out the 7.1 category with three other sound types.

Dolby Pro Logic IIx

If you remember back a couple weeks, we talked about some formats that do something called upmixing. These formats take a stereo signal and upmix it to take advantage of all 5.1 channels. Well, Dolby Pro Logis IIx is the next iteration of upmixing. Systems equipped with this codec can take audio content that’s encoded as stereo or as 5.1 and distribute that sound across all 7.1 channels.

This format is useful when playing older media or stereo-encoded audio CDs.

Dolby Digital Plus

This format is the successor to Dolby Digital 5.1. It does what Dolby Digital does, but over all 7.1 channels. It’s slightly inferior to Dolby TrueHD in that Dolby Digital Plus is lossy. (Though again, if you have average ears and average equipment, you’ll rarely notice a difference.)


This technology is DTS’s answer to Dolby Digital Plus. It’s a 7.1-channel upgrade to DTS’s 5.1-channel technology. It, too, is lossier than its fancier sibling, DTS-HD Master.


When selecting new 7.1-channel audio equipment, the smart play is to go for equipment that can process all of these formats. The media you want to play will be encoded various ways, and you don’t want to be held back by an unsupported format.

Talk to one of our specialists today to make sure you’re getting everything you need for your new system.


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