July 27th, 2010 
guestexpert 
Tags: Multi-channel audio has become mainstream and vendors have come up with many types of basic and more sophisticated technologies including wireless surround speakers, virtual surround sound to simplify the setup of home theater products. I will review the latest trends to determine which products actually work. I will also give some guidance for selecting the best components.
The majority of today’s TVs will be set up as a multi-channel audio system. As traditionally TVs would contain built-in stereo loudspeakers, today a number of external speakers are used to let the viewer experience surround sound. In case of 5.1 surround, 6 speakers are utilized: center, left and right front, left and right rear and a subwoofer. More recent 7.1 systems require a total amount of 8 speakers by adding 2 additional side speakers.
For that reason, home theater setups have turn out to be relatively difficult. Running cables to remote speakers also is often undesirable because of aesthetic reasons. Suppliers have recently released new devices and technologies. These products were developed to help simplify the setup of home theater products.
The first option is building so-called virtual speakers by applying signal-processing to the sound and introducing phase shifts and special cues to those audio parts that would usually be sent by the remote speakers. The signal processing is designed according to how the human hearing determines the location of a sound. The sound signal is then sent through the front speakers. The viewer is in effect tricked into assuming the sound is originating from a location other than the front speakers.
This technology minimizes the number of required speakers and eliminates long speaker cables but each person will process sound somewhat differently because of the form of the ear. Because the signal processing is based on a standard human ear model, virtual surround will not function equally well for everyone dependant upon how much the viewer differs from the standard model.
Wireless surround sound devices are another solution for simplifying home speaker setups and usually come with a transmitter component which connects to the source in addition to wireless amplifiers which will connect to the remote loudspeakers. Usually the transmitter component will include amplified speaker inputs and line-level inputs. This provides freedom to connect to each kind of source. A transmitter volume control helps take full advantage of the dynamic range and eliminates clipping of the sound inside the transmitter.
Several wireless kits come with wireless amplifiers that connect to two loudspeakers. This still requires cable runs between the two speakers. Other products offer separate wireless amplifiers for each speaker. Entry-level wireless devices utilize FM broadcast or audio compression which will degrade the audio quality to some degree. More advanced wireless systems employ uncompressed digital audio transmission. Be certain that you pick a wireless system with a low audio latency, at most several milliseconds. This will ensure that the audio from all loudspeakers, including the non-wireless speakers, is in sync. Low latency is also vital for good sync with the video. A large latency would lead to an echo effect. This effect would degrade the surround effect. Many wireless devices operate in the 900 MHz and 2.4 GHz frequency bands. Some products use the less crowded 5.8 GHz frequency band and as a result have less competition from other wireless products.
Another option are side-reflecting loudspeakers. These systems are also known as sound bars. In this case the sound for the remote loudspeakers will be broadcast by individual speakers positioned at the front at an angle and reflected by walls as to seem to be coming from besides or behind the viewer. The result heavily is dependent upon the interior, particularly the shape of the room and the decoration. It will work well for square rooms with no obstacles and sound reflecting walls. Then again, realistic scenarios often will be different from this ideal and reduce the effect of this approach.
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