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A Look At A Few Of The Latest Wireless Devices
Lately a large number of wireless audio products have emerged such as latest-generation wireless headphones, iPods, cell phones and wireless amplifier devices which claim to eliminate the cable. We will take a look at some of the most recent devices to learn which applications they work for.
Several products come with wireless already built in while some others, specifically streaming audio products, frequently have optional wireless capability. Modern cell phones and MP3 players already come with support for wireless. iPhones and touch-screen iPods, for instance, have Bluetooth and WiFi.
Bluetooth is a relatively low-cost solution but has some pitfalls which are frequently overlooked.
1) Limited range
The range of Bluetooth devices is normally merely 30 ft. This excludes Bluetooth from multi-room applications.
2) Limited data transmission capacity
Bluetooth provides a maximum reliable data rate of roughly 1 Mbps only. This rate is not high enough to send uncompressed CD-quality audio. Therefore Bluetooth wireless devices use audio compression. The audio will be degraded to some extent because of the audio compression. For this reason higher-end audio equipment normally does not use Bluetooth wireless audio.
3) Signal latency
Because of audio compression, Bluetooth will cause a signal delay of at least 10 ms which will cause the audio to be somewhat out of sync in case of video and real-time applications. This is again less of a problem for MP3 players.
4) No multiple headphone support
Bluetooth does not support any quantity of headphones which may be a dilemma 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 widespread protocol. On the other hand, WiFi also has drawbacks in terms of simultaneous transmission to a number of receivers. Because of the relatively high power consumption it is hardly ever used in wireless headphones though. WiFi is practical for streaming audio from a PC however because nearly all PCs have WiFi access.
Wireless speakers and wireless amplifier products for home theater speakers normally utilize their own proprietary protocol. Entry-level wireless headphones and speakers generally still use FM transmission which offers low cost but is prone to noise and audio distortion.
More recent wireless audio protocols are based on digital transmission. This prevents audio degradation. A number of protocols also incorporate error correction to deal with interference from other wireless products.
Latest-generation wireless amplifiers employ uncompressed audio transmission. New protocols also allow streaming to an infinite number of receivers. This enables whole-house audio distribution.
The audio latency of these wireless amplifiers is typically between 1 ms and 20 ms. A small-latency amplifier is critical for home theater audio. This ensures that all speakers will be in sync. These wireless audio transmitters generally work at 2.4 GHz. There are also some devices such as Amphony’s line of wireless audio products which operate at 5.8 GHz. Products that work 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 fundamental for good sound quality. Wireless Class-D amplifiers typically have standby power of 5 Watts or less and a power efficiency of larger than 80% but sometimes high audio distortion. Audiophile wireless amplifiers offer an audio distortion of 0.05% or less.
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