You need at least 5 speakers for real surround sound in a viewing room, but your brain can think you're surrounded by speakers when you aren't.

For example, the folks at Dolby Labs have a couple of systems (which you might find in some HDTVs' audio systems) that make two speakers sound like 5.1 or more! The two systems are Dolby Headphone, which reproduces surround sound for headphones, and Dolby Virtual Speaker, which does the same with two conventional speakers. These systems use computer horsepower to modify the sound going to your two speakers (or headphone transducers) by adding echoes and delays. These echoes and delays are designed to reach your listening position so that your brain is fooled into thinking that it hears more than two speakers.

Are these systems any good? Well, they sure aren't bad. Dolby Virtual Speaker and SRS Labs' TruSurround can do a good job of fooling you. If you aren't installing a real surround-sound system, look for an HDTV with a system like these.

You can't substitute these virtual surround-sound systems for even a small, inexpensive, real surround-sound system (such as a $200 Home Theater in a Box system). But if you don't have the room or budget for 5.1 speakers, give virtual surround sound a whirl and see what you think.