Where to place Loudspeakers in a 5.1 Setup - Tip 8There are recommendations from various organizations on the correct placement of loudspeakers for a 5.1 surround sound installation. In general, they all agree on the following positioning in the horizontal plane:
- The front left and right loudspeaker angles can be pushed out slightly (5° max) as there is a real source (centre channel) and not a phantom image formed by a stereo pair. However 30° is the preferred angle.
- The rear loudspeakers can be position will less restriction as human source positional perception is not so good to the rear.
The rear channel angles can be raised by more than the front monitors as humans have poor positional perception of sounds from the rear but the standards do not agree with one another on this: 15º is perhaps sensible maximum here.
In all cases the acoustical axis of the monitor must be angled both horizontally and vertically towards the listening position to give the best on axis frequency response.
Finally, all of the monitors should be positioned the same distance from the listening position, i.e. the monitors should be placed in a circle with the listening position at the centre of the circle. Where this is not possible time delays must be used to ensure that sound from each of the channels arrives at the same time. Approximately 1ms is required for every 30 cm positional difference so a delay unit with a 10 µsec resolution is the minimum requirement to give a 3 mm positional resolution accuracy. If the rear monitors are further away from the listening position then all 3 front channels must be delayed by the same amount. If the centre monitor is closer to the listening position then only a single channel delay unit is required. If the monitors are not aligned properly so that the sound arrives at the same time then ripples will be experienced in the midrange range at the listening position.
Multichannel stereophonic sound system with and without accompanying picture (Geneva, 1992-94)