Lately a great number of wireless surround sound kits have appeared such as latest-generation wireless headphones, iPods, cell phones and wireless amplifier products which promise to cut the cord. I will take a look at some of the latest devices and technologies to see how well they operate and in which conditions they work best.
These products fall into 2 categories. The first sort of products already has wireless built in. Second-category products, including some streaming audio products, have optional wireless capability. Normally they have a slot to insert a wireless LAN card. Newest generation iPods and mobile phones already come with built-in WiFi and Bluetooth support.
Bluetooth is fairly common as a low-cost wireless option. Nonetheless, Bluetooth does have some pitfalls. These weaknesses are often overlooked but will have an effect on high-quality audio applications.
1) Inadequate range
Bluetooth normally only provides a 30 foot range. This is adequate for single-room applications. However, this limiting factor does not permit multi-room streaming utilizing Bluetooth.
2) Limited data transmission capacity
Bluetooth reliably supports data transmission rates of roughly 1 Mbps only which is not sufficient for uncompressed CD-quality audio. Therefore Bluetooth utilizes audio compression. Audio compression will deteriorate the audio quality to some extent. High-quality audio transmission normally does not tolerate this type of degradation. Therefore Bluetooth is typically not used in high-end audio devices.
3) Audio latency
Because of audio compression, Bluetooth will introduce a signal delay of at least 10 ms which will cause the audio to be to some extent out of sync in case of video and real-time applications. This is again less of a setback for MP3 players.
4) Lacking multi-headphone support
Bluetooth can't stream to multiple headphones at the same time. This may be a dilemma in cases where numerous people want to listen to the same Bluetooth transmitter.
WiFi is one more commonly used wireless protocol that is also suitable for audio streaming. WiFi does support uncompressed audio but will have problems transmitting to a high number of wireless receivers simultaneously. As a result of the relatively high power consumption it is rarely utilized in wireless headphones though. WiFi is convenient for streaming audio from a PC however since nearly all PCs have WiFi access.
Home wireless speaker devices and wireless amplifiers typically employ proprietary protocols. These protocols are specially engineered for real-time audio applications. However, entry-level wireless speakers and headphones still use FM transmission. FM transmission suffers from rather high audio deterioration and hiss / static.
More advanced wireless protocols are based on digital formats which get rid of audio distortion and incorporate advanced features including error correction to cope with interference from competing wireless devices.
Sophisticated wireless amplifier products support uncompressed digital audio streaming to maintain the original audio quality. A number of of these protocols permit streaming to an infinite number of wireless amplifiers which is practical for whole-house audio distribution.
The audio latency of these wireless amplifiers is typically between 1 ms and 20 ms. A small-latency amplifier is essential for home theater audio. This ensures that all speakers will be in sync. These wireless audio transmitters typically work at 2.4 GHz. There are also some devices such as Amphony's line of wireless audio products that work at 5.8 GHz. Products that operate at 5.8 GHz have less competition from other wireless products than those utilizing the crowded 2.4 GHz frequency band.
Wireless amplifiers offer different levels of audio quality, output power and standby power. Digital Class-D amplifiers offer high power efficiency of not less than 80%. They also have low standby power, generally less than 5 Watts. This reduces heat and keeps them cool during operation. Some digital amplifiers, on the other hand, have relatively high harmonic distortion. Audiophile wireless amplifiers offer an audio distortion of 0.05% or less.
These products fall into 2 categories. The first sort of products already has wireless built in. Second-category products, including some streaming audio products, have optional wireless capability. Normally they have a slot to insert a wireless LAN card. Newest generation iPods and mobile phones already come with built-in WiFi and Bluetooth support.
Bluetooth is fairly common as a low-cost wireless option. Nonetheless, Bluetooth does have some pitfalls. These weaknesses are often overlooked but will have an effect on high-quality audio applications.
1) Inadequate range
Bluetooth normally only provides a 30 foot range. This is adequate for single-room applications. However, this limiting factor does not permit multi-room streaming utilizing Bluetooth.
2) Limited data transmission capacity
Bluetooth reliably supports data transmission rates of roughly 1 Mbps only which is not sufficient for uncompressed CD-quality audio. Therefore Bluetooth utilizes audio compression. Audio compression will deteriorate the audio quality to some extent. High-quality audio transmission normally does not tolerate this type of degradation. Therefore Bluetooth is typically not used in high-end audio devices.
3) Audio latency
Because of audio compression, Bluetooth will introduce a signal delay of at least 10 ms which will cause the audio to be to some extent out of sync in case of video and real-time applications. This is again less of a setback for MP3 players.
4) Lacking multi-headphone support
Bluetooth can't stream to multiple headphones at the same time. This may be a dilemma in cases where numerous people want to listen to the same Bluetooth transmitter.
WiFi is one more commonly used wireless protocol that is also suitable for audio streaming. WiFi does support uncompressed audio but will have problems transmitting to a high number of wireless receivers simultaneously. As a result of the relatively high power consumption it is rarely utilized in wireless headphones though. WiFi is convenient for streaming audio from a PC however since nearly all PCs have WiFi access.
Home wireless speaker devices and wireless amplifiers typically employ proprietary protocols. These protocols are specially engineered for real-time audio applications. However, entry-level wireless speakers and headphones still use FM transmission. FM transmission suffers from rather high audio deterioration and hiss / static.
More advanced wireless protocols are based on digital formats which get rid of audio distortion and incorporate advanced features including error correction to cope with interference from competing wireless devices.
Sophisticated wireless amplifier products support uncompressed digital audio streaming to maintain the original audio quality. A number of of these protocols permit streaming to an infinite number of wireless amplifiers which is practical for whole-house audio distribution.
The audio latency of these wireless amplifiers is typically between 1 ms and 20 ms. A small-latency amplifier is essential for home theater audio. This ensures that all speakers will be in sync. These wireless audio transmitters typically work at 2.4 GHz. There are also some devices such as Amphony's line of wireless audio products that work at 5.8 GHz. Products that operate at 5.8 GHz have less competition from other wireless products than those utilizing the crowded 2.4 GHz frequency band.
Wireless amplifiers offer different levels of audio quality, output power and standby power. Digital Class-D amplifiers offer high power efficiency of not less than 80%. They also have low standby power, generally less than 5 Watts. This reduces heat and keeps them cool during operation. Some digital amplifiers, on the other hand, have relatively high harmonic distortion. Audiophile wireless amplifiers offer an audio distortion of 0.05% or less.
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You can find further details concerning wireless surround sound models from Amphony's web page.
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