Home Theater Speaker Systems Basics

Irrespective of the audio format, surround sound always use multiple speakers that surround the audience to generate an expansive soundfield.

Thus, while a stereo speaker system consists of the front speakers only, in surround sound, there are additional speakers apart from the two fronts placed at specific positions within the room.

These include a center channel speaker placed above, below, or behind the screen to carry the on-screen dialogue; it is used mainly to 'pin' the dialogue to the screen. Equally important is the role of a number of surround speakers placed towards the rear of the room to create the enveloping effect. 

Sound from all these speakers should arrive at the listening position in a timely and co-ordinate manner. Failure in this respect leads to an unrealistic, disjointed soundfield

Surround Speakers Systems: Number of speakers and playback channels

Earlier on in our introduction, we indicated that the number of surround speakers in a multi-channel speaker system setup depends on both the number of playback channels supported by your audio setup as well as the sound format in question.

This leads to an added complexity with surround sound - namely that the number of speakers in use does not necessarily have to match the number of audio signals supported by the surround format.

This explains why a four-channel sound format like Dolby Surround, is played over a five-channel playback speaker system. In this case, each of the surround speakers is actually playing the same identical sound. Similarly, despite that Dolby Digital EX is a six-channel surround sound format, yet it can be played over a 7.1 playback speaker system with the two back surround speakers playing the same identical sound signal.

And inasmuch as it is possible to play a multi-channel audio format over a larger number of speaker channels, it is equally possible to play multi-channel audio over a reduced number of speakers. Thus, it is possible to setup a multi-channel speaker system without the center channel speaker; all you have to do is to run the surround processor or AV receiver in phantom center-channel mode. This sends the signal intended for the center speaker equally over the front left and front right speakers.

Admittedly, such a set-up would not lead to the best listening results; the center channel speaker is one of the most important channels in a surround speaker system setup. But with a properly setup speaker system in a small room and with the viewer seated at the best spot, it is still possible to enjoy a good sound stage even without the center channel speaker.

At this point, it is important to understand that when we refer to the maximum number of speakers in an audio setup, e.g. 2.0, 5.1, etc., we are referring to the number of front and rear speakers that the respective playback speaker system use.

The .1 in any surround sound playback system refers to the low frequency effects (LFE) channel, also referred to as the subwoofer channel.

Strictly speaking, a dedicated subwoofer is optional; if you are making use of full range floor-standing tower speakers with multiple 8-inch or 10-inch subwoofers for the front left and right speakers, then you might either pass all low frequencies to them, or to both your LFE channel and the front speakers. This depends on the bass management features supported by your home theater receiver or AV amplifier.

Speaker Systems setups for multi-channel audio formats These diagrams depict the different speaker system layouts for 5.1, 6.1, and 7.1 surround sound playback setups. The 5.1 speaker system setup is the most common and is the one most suitable for the small to medium size room. The reason is that it would be hard to benefit from the added one or two extra speaker channels supported by 6.1 and 7.1 playback setups in the small room environment. 6.1 and 7.1/7.2 speaker systems add additional surround speakers at the back of the room. In a medium to large home theater environments, these extra speaker channels help deliver a more realistic surround soundfield.
But to enjoy the full benefit of a 6.1 or 7.1 or even 7.2 surround sound playback speaker system, your prime listening position should not be located near a wall. For additional information on home theater speakers - from speaker choice, to buying tips, speaker placement, and speaker specs, please refer to the additional home speaker guides appearing under this section.

Additional Guides to Home Theater Speaker Systems appearing under this section: