I reckon us Aussies enjoy experiencing movies at home. I used the word “experiencing” and not “watching” as movies are both a visual and audio event. Elementary examples of this include speech, without which one cannot follow the story at all, music, which is important for establishing  a scene, via mood and environmental cues and sound effects through which the unveiling of large objects in shadows are achieved mainly by rumbles. In a lot of homes, there is some sort of surround sound system used to experience movies. So the next time you upgrade your picture (TV, projector, etc…) also think about the other half of the equation - sound.


The original industry standard for home surround sound system design is the venerable 5.1 setup consisting of a pair of main stereo front speakers (L, R), a centre speech speaker (C), a pair surround effects/ambience speakers (SL, SR) and a subwoofer for the low frequency portion of the soundtrack. This is currently the case simply because a bunch of sound experts (from Dolby, THX, DTS, etc…) developed the layout about 20 years ago and convinced all directors from then onwards to mix their soundtracks this way on DVDs for home consumption. Therefore - one must setup such a layout at home in order to experience what the director intended to communicate to the audience. Lets spend a few minutes understanding what this layout is and why it is this way.

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In the diagram above, we have what is about the ideal 5.1 layout, with the centre speaker placed near the location movie characters would appear onscreen, and the surround speakers on either side of the seating (note - the designated seating position is the 3 seater couch only - not the extra individual diagonal single seaters). What is not shown is the fact that the while the main L, C and R speakers aim at the listener, the SL and SR speakers do not, they are actually intended to disperse sound above the listener, as shown below:

 

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The reason for this is that humans naturally react to sound by looking towards the direction they came from (an evolutionary trait from the time when we had to be aware of predators, falling rocks, etc… these days it still helps us avoid getting hit by trucks when crossing the road). With surround speakers, there is nothing but a war to stare at - so it's better if we do not feel like looking at the speaker at all, and to achieve this, the surround speaker is designed to release sound in a wide arc above the listener so that we do not feel the sound coming from a specific direction.


The reason why we have a centre speaker and a subwoofer is actually to do with efficiency. The act of reproducing sound through speakers requires power from the amplifier/AVR. This power is not free, and I am not talking about the electricity bill - which is actually only about 20c a day - I am talking about the power supply capacity of the AVR - which is very limited and precious. In the case of the centre speaker, the same result can be achieved by just playing the same audio content on both the L and R speakers. However, this would mean the AVR is wasting twice the power then it would have if we had a centre speaker just for the speech that should come from the middle. The efficiency effect is even more pronounced with the subwoofer, without which the low frequencies would need to be played to all the speakers, at 5 times the power cost of just letting the subwoofer handle it. It is also fortunate that because humans are distinguishing the direction of low frequencies below 80hz, the subwoofer can be placed anywhere around the front or sides of the room, as long as it's not too close to the seats.