4 questions to ask when setting up your rear speakers

Getting the most from your home cinema surround sound set-up

Do I need rear speakers?

What do rear speakers do, exactly? Well, with the advent of discrete 5.1 surround sound in 1992, sound designers gained the ability to place specfic effects into either the left or right rear speaker. Unlike older systems that relied on a mono rear channel of sound, such as Dolby Surround, the rear channels are given more to do instead of the same signal being shared between multiple surround speakers. Sound steering was better as the sound matched what was on screen more precisely.

Should I use hif-fi speakers?

Positioning can be a bit awkward if you have a large rear speaker. Place it too close and a headache may ensue. Hide it in a corner and performance will be diminished. Hi-fi speakers are designed to create an audio image that places sonic elements within a focused soundstage. This direct pattern of sound reproduction is what sound engineers avoid with most rear speaker effects. It’s why, to avoid sound localisation, cinemas use multiple pairs of rear speakers along the sides and behind you.

How do I deal with localisation?

Negating the effect of localisation can be done in two ways: mounting a hi-fi style bookshelf or style speaker high on the wall, or buying a specialist rear speaker that’s either bipolar or dipolar in design. A bipolar design will use an opposingdriver arrangement which run in phase (unison). This gives good bass and helps fill the room. A dipolar design is similar, using opposing sets of drive units radiating into directions, one running out of phase with the other. This creates an out-of-box sound that’s hard to localise.

How loud should they be?

Whatever your speakers, watch the volume levels. It’s tempting to crank it up to make the rear speakers more audible but all that does is defeat their purpose: they’re not meant to draw attention to themselves. Too much rearfocused sound is unrealistic and, over long periods can become wearing for the listener, so don’t be tempted to select an artificially heavy rear bias. Even in 5.1 channel mixing, it’s common to use a mono effect at times. Effects such as rainfall are often rendered this way.