# 5.1 content with 7.1 speaker setup



## TCinGA

When playing 5.1 content into a system using a 7.1 speaker arrangement what content is sent to the rear surrounds ?

Is this a set up function on the receiver ? Is upmixing the right term for what happens ?

I'm using an Onkyo 806 and am about to install the rear surrounds but it got me thinking about what actaully plays through those speakers when most content is 5.1 ?

Thanks for any inputs.


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## eugovector

The processor built into your AVR can matrix the back channels from the 2-5 discrete channels. Matrixing is the right term.

With your Onkyo, set it for 7 speakers and use a processing mode like Dolby Pro Logic II movie if you want sound from all 7 speakers.


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## koyaan

When playing regular 5.1 material on a 7.1 system, no information goes to the rear speakers unless you " create " rear channel sound by use of a program like Dolby PLIIx or DTS NEO:6. These will matrix out rear channel signals from the surround information.


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## TCinGA

Thanks. These go into the "learn something new everyday" folder. That was an easy one 

Thanks. Any reccomendations on which processor mode to use ? Does it just come down to personal preference ?


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## tonyvdb

TCinGA said:


> Any reccomendations on which processor mode to use ? Does it just come down to personal preference ?


I personally like the THX cinema or THX Ultra movie I believe your 806 has those modes.


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## koyaan

It's just personal prefrence. I haven't tried the THX processing, but I find I generally like PLIIx for movies and DTS NEO:6 for most music. The PLIIx seems to put more information in the center channel, while NEO:6 seems to use the main speakers more.


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## doublejroc

I definitely agree it's personal preference. You're the one listening to the music or soundtrack, right?
My preference for movies is thx cinema, and I'll hop between direct and stereo for 2ch music. I'm running the 706 model. Enjoy that 806!


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## Mark Techer

Use the THX mode for all your movies, not just the ones with THX on the cover.

Matrix decoding works for the surround of 5.1 because there will be signal in both the SL and RL that are both in phase and at the same level. If you were to play these sound through a good 2CH system, you would hear a phantom image between the speakers. The matrix decoder simply looks for these sounds and steers them to the back surrounds. THX modes go a step further by altering the phase time relationship between the two signals to create a much more enveloping sound field.


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## ojojunkie

Mark Techer said:


> Use the THX mode for all your movies, not just the ones with THX on the cover.
> 
> Matrix decoding works for the surround of 5.1 because there will be signal in both the SL and RL that are both in phase and at the same level. If you were to play these sound through a good 2CH system, you would hear a phantom image between the speakers. The matrix decoder simply looks for these sounds and steers them to the back surrounds. THX modes go a step further by altering the phase time relationship between the two signals to create a much more enveloping sound field.


Yes, I agree. Since my pre/pro is THX Ultra 2 I take advantage of this feature in all movies. The sound is amazing. :unbelievable: Just not sure if same decoding function on receivers. :dontknow:


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## Mark Techer

ojojunkie said:


> Yes, I agree. Since my pre/pro is THX Ultra 2 I take advantage of this feature in all movies. The sound is amazing. :unbelievable: Just not sure if same decoding function on receivers. :dontknow:


The processing for THX Ultra and Select are essentially the same. The major difference I have found between high end gear and cost effect AVRs that are THX certified is that the high end gear usually has a few more options such as Room Boundary Compensation or might ask if your SUB is THX certified.

The THX Cinema 2 mode is found on both levels that run 7.1 speaker configurations. I would have to say that this surround mode is by far the most enveloping surround sound I've heard.


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