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A Look At Some Of The Most Recent Wireless Toys

Recent wireless audio gizmos such as iPods, wireless headphones and cell phones support new wireless protocols. These protocols are supposed to eliminate the cord and deliver perfect high-fidelity audio. I will examine whether these products keep their promise to deliver perfect-quality audio. In addition, I will examine the underlying technologies.

These products fall into 2 categories. The first category of products already has wireless built in. Second-category products, including a number of streaming audio products, have optional wireless ability. Normally they have a slot to add a wireless LAN card. 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 limitations which are frequently ignored.

1) Short range

Bluetooth generally just provides a 30 foot range. This is adequate for single-room applications. However, this limitation does not allow multi-room streaming utilizing Bluetooth.

2) Inadequate data transmission capacity

Bluetooth provides a maximum reliable data rate of around 1 Mbps only. This rate is not large enough to send uncompressed CD-quality audio. Therefore Bluetooth wireless devices use audio compression. Audio compression will deteriorate the audio quality to some degree. High-quality audio transmission normally does not tolerate this sort of degradation. Therefore Bluetooth is usually not used in high-end audio products.

3) Audio latency

Because of audio compression, Bluetooth will introduce a signal delay of not less than 10 ms which will cause the audio to be slightly out of sync in case of video and real-time applications. This is again less of a dilemma for MP3 players.

4) No multiple headphone support

Bluetooth does not support any number of headphones which might be a dilemma if you have a larger number of people who want to listen to headphones from a single transmitter device.

WiFi is another widely used wireless protocol that is also suitable for audio streaming. WiFi does support uncompressed audio but will have problems transmitting to a large number of wireless receivers at the same time. Due to the fairly high power consumption it is hardly ever used in wireless headphones however. WiFi is practical for streaming audio from a PC however because nearly all PCs have WiFi access.

Home wireless speaker devices and wireless amplifiers generally employ proprietary protocols. These protocols are specially engineered for real-time audio applications. On the other hand, entry-level wireless speakers and headphones still employ FM transmission. FM transmission suffers from fairly high audio distortion and hiss / static.

More advanced wireless protocols are based on digital formats which avoid audio degradation and incorporate sophisticated features such as error correction to cope with interference from competing wireless devices.

Newest-generation wireless amplifiers permit streaming to an infinite number of receivers and support uncompressed audio transmission.

Some of these protocols support low-latency audio transmission which ensures that the audio of all speakers will be in sync in a multi-channel application. Wireless audio transmitter devices usually operate at 2.4 GHz or sometimes in the less crowded 5.8 GHz frequency band such as Amphony’s wireless audio devices.

Wireless amplifiers are available with different levels of audio quality, power consumption and standby power. Getting a high-quality low-distortion amplifier is critical for good sound quality. Digital Class-D amplifiers offer high power efficiency of a minimum of 80%. They also have low standby power, typically less than 5 Watts. This minimizes heat and keeps them cool during operation. Some digital amplifiers, however, have relatively high harmonic distortion. Audiophile wireless amplifiers offer an audio distortion of 0.05% or less.