The release of wireless-enabled rear speakers and amplifiers is a growing trend in the home theater marketplace. The past half-decade has seen remarkable growth in the sales of home theater products. However, the reality is that many consumers fail to connect their rear speakers because of problems connecting wiring across rooms.
In response to this, the largest low-end home theater manufacturers ?including Sony Corp and Pioneer Corp of Japan and Samsung Electronics and LG Electronics of Korea ?launched home theater products with wireless rear speakers in 2004. At the Consumer Electronics Show (CES) in January, Panasonic announced its own foray into wireless rear speakers, as an optional add-on to one of its most popular selling home theater products.
All of these releases were for 5.1-channel, low-end home theater systems, as a majority of modern entertainment content is encoded in this popular surround sound format. Now, many of these large manufacturers also have 6.1-channel and 7.1-channel wireless speakers and amplifier systems scheduled to be released in the next two years; however, developments from mid-sized and small manufacturers also bear some watching.
Chinese Developments
There is no greater concentration of wireless audio speaker development than in Hong Kong, Taiwan and mainland China. The most popular technology used for wireless transmission is RF, particularly 2.4GHz. Jazz Hipster Corp of Taiwan is a notable manufacturer of home theater using 2.4GHz technology. The company? J9618B and J9940R 5.1 digital wireless theaters offer built-in 5.1 Dolby Digital and DTS decoding, 180 watts total continuous power RMS and 8-channel RF 2.4GHz.
Telean Electronics Ltd, Nasaco Electronics Ltd, Coby Communications Ltd and TwinPro International Holdings Ltd, all of Hong Kong, use 2.4GHz for low-end rear speakers that can be used to augment 5.1-channel home theater systems. Pixa of Taiwan released its DVW-200 Easy Theater 7.1-channel system in January, one of the early entries in the 7.1 home theater field.
Avoiding Interference
There has been some debate on what kind of wireless transmission technology is most suitable for home theater. The 2.4GHz frequency band is also used by other common household devices, such as cordless phones and microwave ovens, and is therefore prone to interference. This is a major reason most 2.4GHz home theaters offer 8 preset frequency channels within the 2.4GHz range. The 2.4GHz frequency range provides more than enough transmission speed to comply with the two most popular surround sound formats, Dolby Digital (requiring 400Kbps) and DTS (which uses up to 448Kbps for a full 5.1 stream). It also is a proven technology that is cheap to produce compared to other wireless technologies.
Sony released its DAV-LF1 home theater late in 2004, which uses its Digital Infrared Audio Transmission System (DIAT) infrared wireless technology to deliver audio to a pair of rear speakers in the full 20Hz-20KHz range. The audio signal reaches the speakers through a separate IR transmitter on each of the front left and right rear speakers.
LG Electronics uses Bluetooth for the rear speakers in its DA-W6100 wireless home theater system. The system has DTS, Dolby Digital and Dolby Pro Logic II decoders, though the practical data transfer rate of Bluetooth, 433Kbps, may leave the system a bit slow for DTS decoding.
Firebird Sounds of the US makes a wireless amplifier that can be implemented into an existing 5.1, 6.1 or 7.1 home theater system or can be sold as a standalone solution for subwoofers or speakers. The amplifier uses 8-channel 2.4GHz RF and has a frequency response of 5Hz-25KHz (4&937; and 5Hz-50KHz (8&937; and distortion rates of 0.03% (8&937; 1KHz, 50 watts) and 0.05% (4&937; 1KHz, 50 watts).
In the long term, ultra wideband (UWB) may become a legitimate technology for wireless home theater systems. UWB - able to transmit 100Mbps within a 10 meter area at power levels as low as half a milliwatt - in principle offers a solution to the limitations of the current wireless technologies being used to send both power and audio signals to wireless speakers. But holdups with the IEEE standardization of UWB make this unlikely to happen anytime soon.
by Michael Thuresson
(May 2005 Issue, Nikkei Electronics Asia)
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