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Q I have an Onkyo TX NR1009 AV receiver that I operate in a 7.2 configuration. All is well when I watch a movie with a 7.1 soundtrack since my couch is inline with the back surround speakers. However, when I watch movies or TV with 5.1 sound the rear speakers go silent and I need to shift my position to be inline with the side surround speakers. Is it possible to have the receiver route the 5.1 signal so the back surround speakers remain active and I don’t have to change my seating position? —George Yeoh

A The nature of your question makes me wonder about your speaker setup. In a typical Dolby-recommended 7.1 configuration, surround speakers are situated directly to the left and right of the listening position and elevated above ear height. Back surround speakers, meanwhile, should be located behind the seating area and angled in toward the center (see diagram above).

With this setup, you shouldn’t have to shift your seating position to hear surround sound from 5.1 sources, even if the back surround speakers “go silent” in that mode. The experience won’t be as enveloping as it would be with a 7.1 source, but your side surround speakers still should be able to deliver an adequate surround effect.

Since 7.1-channel source material is in limited supply, you might want to consider tapping the processing modes on your Onkyo receiver to put those back surround speakers to continuous use. The NR1009’s Dolby Pro Logic IIx Movie mode extracts information from the discrete L/R surround channels in 5.1 soundtracks, routing it to the surround back speakers to create simulated 7.1 sound. Dolby PLIIx also works with stereo sources and features a Music mode that lets you adjust the balance of vocals coming out of your system’s center speaker as well as customize the width and depth of the soundfield to best fit your listening room.

Another processing mode on your Onkyo, THX Select2 Cinema, has an effect that’s similar to Dolby PLIIx Movie mode — you’ll want to experiment with both to determine which one sounds best with your setup. While we’re on the topic of THX, your seating position problem might also be lessened by using THX-type dipole surround speakers for the side surround channels. Dipole surrounds deliver a wider, more diffuse effect than direct-radiating designs, and are recommended by THX for use as side surround speakers even in 7.1-channel setups.