Recent wireless audio gadgets such as iPods,wireless headphones and cell phones support newest wireless protocols. These protocols are supposed to eliminate the cord and provide perfect high-fidelity audio. We will take a look at some of the newest devices to find out which applications they work for.
Products can be categorized into products with built-in and those with optional wireless capability. Streaming audio products will frequently have a plug-in slot for adding a wireless LAN card. Newest generation iPods and mobile phones already come with built-in WiFi and Bluetooth support.
The Bluetooth protocol is a fairly low-cost option. Yet,its pitfalls have an effect on high-quality audio applications and are often ignored.
1) Limited operating range
The range of Bluetooth devices is normally merely 30 ft. This excludes Bluetooth from multi-room applications.
2) Small data rate –audio compression
Bluetooth reliably supports data transmission rates of about 1 Mbps only which is not enough for uncompressed CD-quality audio. As a result Bluetooth applies audio compression. Audio compression will deteriorate the audio quality to some degree. High-quality audio transmission generally does not tolerate this kind of distortion. Consequently Bluetooth is normally not used in high-end audio products.
3) Signal latency
The signal broadcast via Bluetooth will bear a small delay of a minimum of 10 ms. This is mostly attributable to the audio compression. While being uncritical for MP3 players,this delay may be a problem for video and other real-time applications.
4) No multiple headphone support
Bluetooth cannot stream to multiple headphones at the same time. This might be a dilemma in cases where numerous people want to listen to the same Bluetooth transmitter.
Another common protocol is WiFi which supports uncompressed audio but also has problems simultaneously streaming to multiple receivers. Due to the high availability,WiFi is suitable for streaming audio from a PC. On the other hand,WiFi products have relatively high power consumption. For this reason wireless headphones normally do not use this technology.
Home wireless speaker devices and wireless amplifiers usually utilize proprietary protocols. These protocols are specifically engineered for real-time audio applications. On the other hand,low-cost wireless speakers and headphones still utilize FM transmission. FM transmission suffers from rather high audio distortion and noise / static.
More recent wireless audio protocols are based on digital transmission. This eliminates audio degradation. Some protocols also incorporate error correction to cope with interference from other wireless devices.
Sophisticated wireless amplifier devices support uncompressed digital audio streaming to preserve the original audio quality. A few of these protocols permit streaming to an infinite number of wireless amplifiers which is practical for whole-house audio distribution.
The audio latency ranges from below 1 ms to up to 20 ms. A small latency is key for wireless surround sound applications. Typically newer generation wireless audio transmitters will work at 2.4 GHz. Some transmitter devices,such as Amphony’s line of devices,work at the less crowded 5.8 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 essential for good sound quality. Digital amplifiers typically offer a power efficiency of no less than 80% and standby power consumption of less than 5 Watts which keeps them cool during operation and helps save energy. However,some Class-D amps have fairly high audio distortion. It is vital to choose a wireless amplifier with low audio distortion. This will make sure good sound quality. High-quality amplifiers have audio distortion of 0.05% or less.
