Lately a large number of wireless audio products have emerged 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 newest gadgets and technologies to find out how well they work and in which situations they work best.
Products can be categorized into products with built-in and those with optional wireless capability. Streaming audio products will often have a plug-in slot for adding a wireless LAN card. Latest generation iPods and cell phones already come with built-in WiFi and Bluetooth support.
The Bluetooth protocol is a fairly low-cost solution. However, its drawbacks have an impact on high-quality audio applications and are often overlooked.
1) Short range
Bluetooth normally only offers a 30 foot range. This is sufficient for single-room applications. However, this limitation does not allow multi-room streaming using Bluetooth.
2) Limited data transmission capacity
Bluetooth will apply audio compression since it does not reliably offer a high-enough data rate for uncompressed audio. Audio compression will degrade the audio quality to some extent. High-quality audio transmission typically does not tolerate this type of degradation. Therefore Bluetooth is normally not used in high-end audio products.
3) Audio latency
The signal transmitted via Bluetooth will undergo a slight delay of at least 10 ms. This is mostly due to the audio compression. While being uncritical for MP3 players, this delay may be a problem for video and other real-time applications.
4) Lacking multi-headphone support
Bluetooth does not support any number of headphones which may be a problem if you have a larger number of people who want to listen to headphones from a single transmitter device.
Uncompressed audio streaming is supported by WiFi. WiFi is a very common protocol. However, WiFi also has limitations in regard to simultaneous transmission to several receivers. Due to the high availability, WiFi is convenient for streaming audio from a PC. However, WiFi products have fairly high power consumption. For this reason wireless headphones typically do not use this technology.
While newest-generation wireless speakers and wireless amplifier products use proprietary digital technologies, entry-level products often still rely on FM transmission which is noisy and has high audio distortion and high susceptibility to radio interference.
More recent wireless audio protocols are based on digital transmission. This avoids audio degradation. Some protocols also incorporate error correction to deal with interference from other wireless devices.
Advanced wireless amplifier devices support uncompressed digital audio streaming to preserve the original audio quality. Some of these protocols allow streaming to an unlimited number of wireless amplifiers which is convenient for whole-house audio distribution. The audio latency ranges from below 1 ms to up to 20 ms. A small latency is important for wireless surround sound applications. These wireless audio transmitters typically work at 2.4 GHz. There are also some products such as Amphony's line of wireless audio products which work at 5.8 GHz. Products that operate at 5.8 GHz have less competition from other wireless devices than those using the crowded 2.4 GHz frequency band.
Wireless amplifiers are available with different levels of audio quality, power consumption and standby power. Having a high-quality low-distortion amplifier is vital for good sound quality. Digital Class-D amplifiers offer high power efficiency of at least 80%. They also have low standby power, typically less than 5 Watts. This reduces heat and keeps them cool during operation. Some digital amplifiers, however, have fairly high harmonic distortion. It is important to select a wireless amplifier with low audio distortion. This will ensure good sound quality. High-quality amplifiers have audio distortion of 0.05% or less.
Products can be categorized into products with built-in and those with optional wireless capability. Streaming audio products will often have a plug-in slot for adding a wireless LAN card. Latest generation iPods and cell phones already come with built-in WiFi and Bluetooth support.
The Bluetooth protocol is a fairly low-cost solution. However, its drawbacks have an impact on high-quality audio applications and are often overlooked.
1) Short range
Bluetooth normally only offers a 30 foot range. This is sufficient for single-room applications. However, this limitation does not allow multi-room streaming using Bluetooth.
2) Limited data transmission capacity
Bluetooth will apply audio compression since it does not reliably offer a high-enough data rate for uncompressed audio. Audio compression will degrade the audio quality to some extent. High-quality audio transmission typically does not tolerate this type of degradation. Therefore Bluetooth is normally not used in high-end audio products.
3) Audio latency
The signal transmitted via Bluetooth will undergo a slight delay of at least 10 ms. This is mostly due to the audio compression. While being uncritical for MP3 players, this delay may be a problem for video and other real-time applications.
4) Lacking multi-headphone support
Bluetooth does not support any number of headphones which may be a problem if you have a larger number of people who want to listen to headphones from a single transmitter device.
Uncompressed audio streaming is supported by WiFi. WiFi is a very common protocol. However, WiFi also has limitations in regard to simultaneous transmission to several receivers. Due to the high availability, WiFi is convenient for streaming audio from a PC. However, WiFi products have fairly high power consumption. For this reason wireless headphones typically do not use this technology.
While newest-generation wireless speakers and wireless amplifier products use proprietary digital technologies, entry-level products often still rely on FM transmission which is noisy and has high audio distortion and high susceptibility to radio interference.
More recent wireless audio protocols are based on digital transmission. This avoids audio degradation. Some protocols also incorporate error correction to deal with interference from other wireless devices.
Advanced wireless amplifier devices support uncompressed digital audio streaming to preserve the original audio quality. Some of these protocols allow streaming to an unlimited number of wireless amplifiers which is convenient for whole-house audio distribution. The audio latency ranges from below 1 ms to up to 20 ms. A small latency is important for wireless surround sound applications. These wireless audio transmitters typically work at 2.4 GHz. There are also some products such as Amphony's line of wireless audio products which work at 5.8 GHz. Products that operate at 5.8 GHz have less competition from other wireless devices than those using the crowded 2.4 GHz frequency band.
Wireless amplifiers are available with different levels of audio quality, power consumption and standby power. Having a high-quality low-distortion amplifier is vital for good sound quality. Digital Class-D amplifiers offer high power efficiency of at least 80%. They also have low standby power, typically less than 5 Watts. This reduces heat and keeps them cool during operation. Some digital amplifiers, however, have fairly high harmonic distortion. It is important to select a wireless amplifier with low audio distortion. This will ensure good sound quality. High-quality amplifiers have audio distortion of 0.05% or less.
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You can find further details regarding wireless audio products at Amphony's website.
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