High definition sound


Adding surround

The high definition standard allows for Dolby Digital 5.1, the six-channel surround format used on DVDs, but most broadcasters transmit Dolby Surround, a four-channel format that creates a similar effect. To hear all the elements of a multichannel soundtrack – the delicate rustling of leaves behind you, the helicopter that pans from left to right in front of you, or the dinosaur footfalls that rattle the ornaments on the mantelpiece and vibrate the sofa ? you need a surround system, and this means five speakers, a subwoofer, and home theatre receiver.

Projectors, LCD and plasma panels typically have only two speakers, so there?s no surround from these alone. Some high definition rear projection televisions incorporate surround sound decoders and provide either extra speakers or sockets for connecting additional speakers, but given the size and quality of the speakers, the surround experience won?t have the impact you?d expect from a high definition home theatre.

When it comes to surround, then, you?re better off matching your HD television with an audio setup that is equal in quality. There are a couple of options here, from the instant home theatre in a box solution, to a system comprising a home theatre receiver and a suite of speakers.

Most televisions have only two speakers, which means you won?t be able to hear the 5.1 surround sound soundtrack on DVDs and HDTV broadcasts, such as the AFL on Channel Ten. For this, you need up to six speakers placed around the room.

Surround sound and HD

In the beginning, the sound from television was one channel, or mono, only. Stereo added a second channel to the mix and, today, formats providing three, four, six and up to eight separate channels of sound do an even better job of replicating the way we hear the world around us.

Dolby Digital 5.1, Dolby Pro-Logic and Dolby Surround are the formats common to HD broadcasts, and all require five speakers and a subwoofer, which is dedicated to reproducing the bass in a soundtrack. The subwoofer channel is referred to as the Low Frequency Effects (LFE) channel and, because it handles only a limited range of sound, is the ?.1? in Dolby Digital 5.1.

The five speakers comprise front left/right, centre and rear left/right. The front pair are placed either side of the TV screen, while the centre is placed above or below the screen to ?fix? dialogue to the onscreen action. The surround speakers are placed one on each side of the seated audience ? around a metre above ear height ? and either mounted on the wall or fixed to stands (see picture below).